Los Altos City Council
June 23, 2026

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future expansion of natural habitat, help to maintain site hydrology, and in some areas allow for runoff to be treated (e.g., by flowing through vegetated areas) before it enters the stream. In addition, vegetative communities within stream buffers may provide important refugia for animals associated with wetland and riparian habitats along the creek during flood events, when little to no such refugia may be present within the banks of the creek itself. In general, larger buffers protect more of the ecological functions and values of the stream than smaller buffers.

As discussed in Section 3.3.2 above, the City’s Watercourse Protection Regulations state that a protected stream setback is present along Adobe Creek, and extends a horizontal distance of 80 feet measured from the top of bank. This setback overlaps the project site, as shown on Figure 3. In our opinion, based on the moderate quality of the riparian habitat along Adobe Creek and the wildlife community present at this location (discussed in Section 4.3 above), the City’s specified 80-foot-wide setback measured from the top of bank is an appropriate buffer distance between new construction and Adobe Creek to maintain suitable riparian functions and values.

Under the proposed project, certain areas within the setback on the project site would be modified in some way. Currently, the setback area on the project site consists predominantly of developed areas, with 243 square feet of coast live oak woodland (Figure 3). The project would permanently remove the Halsey House building from the setback, and some trees within the setback may be removed or modified to accommodate the project.

The demolition of Halsey House and the removal of 243 square feet of coast live oak woodland within the setback would require a setback exception from the City, because vegetation would be removed and grading would occur. However, it is our understanding that the City will grant an exception for all project activities within the 80-foot setback along Adobe Creek. Thus, project impacts due to conflicts with the City’s Watercourse Protection Regulations are less than significant.

Further, the removal of the Halsey House building is expected to provide at least a minor improvement in habitat conditions within the setback. Removal of the building may provide animals in the riparian corridor with less of a sense that they are “hemmed in” by adjacent development, and the building footprint will become ruderal habitat that will provide some habitat value (e.g., as foraging habitat) for animals associated with the creek corridor. Although up to 243 square feet of coast live oak woodland habitat may be removed or trimmed, these impact areas will be reseeded or replanted, and the net effect of the project will be ecologically beneficial due to removal of the building. Therefore, the project’s encroachment into the stream corridor (consisting of removal of Halsey House, converting 243 square feet of coast live oak woodland to developed areas, and reseeding or planting impacted areas) would not be considered a significant biological impact under CEQA.

6.6 Impacts due to Conflicts with an Adopted Habitat Conservation Plan: Conflict with the provisions of an adopted habitat conservation plan,

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natural community conservation plan, or other approved local, regional, or state habitat conservation plan (No Impact)
The project site is not located within an area covered by an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan. Therefore, the project would not conflict with any such plans.

6.7 Cumulative Impacts (Less than Significant)
Cumulative impacts arise due to the linking of impacts from past, current, and reasonably foreseeable future projects in the region. Future development activities in Los Altos will result in impacts on the same habitat types and species that will be affected by the proposed project. The proposed project, in combination with other projects in the area and other activities that impact the species that are affected under the project, could contribute to cumulative effects on special-status species. Other projects in the area include both development and maintenance projects that could adversely affect these species and restoration projects that will benefit these species.

The cumulative impact on biological resources resulting from the project in combination with other projects in the larger region would be dependent on the relative magnitude of adverse effects of these projects on biological resources compared to the relative benefit of impact avoidance and minimization efforts prescribed by planning documents, CEQA mitigation measures, and permit requirements for each project; and compensatory mitigation and proactive conservation measures associated with each project. In the absence of such avoidance, minimization, compensatory mitigation, and conservation measures, cumulatively significant impacts on biological resources would occur.

However, many projects in the region that impact resources similar to those impacted by the project will be subject to CEQA requirements. It is expected that such projects will mitigate their impacts on sensitive habitats and special-status species through the incorporation of mitigation measures and compliance with permit conditions.

Regardless of the magnitude and significance of cumulative impacts that result from other projects, the proposed project is not expected to have a substantial effect on biological resources, and would implement the mitigation measure described above to reduce impacts under CEQA to less than significant levels. Thus, provided that this project successfully incorporates the mitigation measure described in this biological resources report, the project will not have a cumulatively considerable contribution to cumulative effects on biological resources.

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Section 7. Compliance with Additional Laws and
Regulations for Nesting Birds
Several species of common native birds protected by the MBTA and California Fish and Game Code may nest in trees and shrubs on the site or immediately adjacent to the site. It is also possible that protected native birds could nest on the buildings on the site. The removal of vegetation or demolition of buildings supporting active nests may cause the direct loss of eggs or young, while construction-related activities located near an active nest may cause adults to abandon their eggs or young. This type of impact would not be significant under CEQA, in our opinion, because of the local and regional abundances of the species that could potentially nest on the site and the very low magnitude of the potential impact of development on these species (i.e., the project is expected to impact only a few pairs of these species, which is not a substantial impact on their regional populations). However, the following measures should be implemented to ensure that project activities do not violate the MBTA and California Fish and Game Code:

Measure 1. Avoidance of the Nesting Season. To the extent feasible, the initiation of commencement of demolition and construction activities should be scheduled to avoid the nesting season. If demolition and construction activities are initiated outside the nesting season, all potential demolition/construction impacts on nesting birds protected under the MBTA and California Fish and Game Code will be avoided. The nesting season for most birds in San Mateo County extends from February 1 through August 31.

Measure 2. Pre-Activity/Pre-Disturbance Surveys. If it is not possible to schedule the initiation of demolition and construction activities between September 1 and January 31, then pre-activity surveys for nesting birds should be conducted by a qualified ornithologist to ensure that no nests will be disturbed during project implementation. We recommend that these surveys be conducted no more than seven days prior to the initiation of demolition or construction activities. During this survey, the ornithologist will inspect all trees and other potential nesting habitats (e.g., trees, shrubs, and buildings) in and immediately adjacent to the impact areas for nests.

Measure 3. Non-Disturbance Buffers. If an active nest is found sufficiently close to work areas to be disturbed by these activities, the ornithologist will determine the extent of a construction-free buffer zone to be established around the nest (typically 300 feet for raptors and 100 feet for other species), to ensure that no nests of species protected by the MBTA and California Fish and Game Code will be disturbed during project implementation.

Measure 4. Nesting Deterrence. If construction activities will not be initiated until after the start of the nesting season, all potential nesting substrates (e.g., bushes, trees, grasses, and other vegetation) that are scheduled to be removed by the project may be removed prior to the start of the nesting season (e.g., prior to February 1). This will preclude the initiation of nests in this vegetation, and minimize the potential delay of the project due to the presence of active nests in these substrates.

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Section 8. References
Barry, S. 1994. The distribution, habitat, and evolution of the San Francisco garter snake, Thamnophis sirtalis tetrataenia. Unpublished Masters Dissertation, UC Davis, 143 pages.

Bay Area Puma Project. 2024. Signtings Map. Accessed through July 2024 from https://bapp.org/meetpuma/sightings.

Bousman, W.G. 2007a. Olive-Sided Flycatcher, Contopus cooperi. Pages 272-273 in W. G. Bousman, editor.

Breeding Bird Atlas of Santa Clara County. Santa Clara Valley Audubon Society, Cupertino, California.

Bousman, W. G. 2007b. Loggerhead shrike Lanius ludovicianus. Pages 288-289 in W. G. Bousman, editor.

Breeding bird atlas of Santa Clara County. Santa Clara Valley Audubon Society, Cupertino, California.

Bumble Bee Watch. 2024. Bumble Bee Sightings Map. Accessed through July 2024 from https://www.bumblebeewatch.org/app/#/bees/map.

Calflora. 2024. Calflora: Information on California Plants for Education, Research and Conservation. The Calflora Database, Berkeley, California. Accessed through July 2024 from https://www.calflora.org/. [Cal-IPC] California Invasive Plant Council. 2024. California Invasive Plant Inventory Database. Accessed through July 2024 from http://www.cal-ipc.org/paf/.
[CDFW] California Department of Fish and Wildlife. 2019. Report to the Fish and Game Commission.

Evaluation of the petition from the Xerces Society, Defenders of Wildlife, and the Center for Food Safety to list four species of bumble bees as endangered under the California Endangered Species Act.

April 4.
[CDFW] California Department of Fish and Wildlife. 2024. Vegetation Classification and Mapping Program:

Natural Communities List. Accessed through July 2024 from https://www.wildlife.ca.gov/Data/VegCAMP/Natural-Communities. [CNDDB] California Natural Diversity Database. 2024. Rarefind 5.0. California Department of Fish and Wildlife. Accessed July 2024 from http://www.dfg.ca.gov/biogeodata/cnddb/ mapsanddata.asp.
[CNPS] California Native Plant Society. 2024. Inventory of Rare and Endangered Plants (online edition, v8-03

0.39). Accessed May 2024 from http://www.cnps.org/inventory.

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Cornell Lab of Ornithology. 2024. eBird. Accessed through July 2024 from http://www.ebird.org/.

Faber-Langendoen, D., J. Nichols, L. Master, K. Snow, A. Tomaino, R. Bittman, G. Hammerson, B. Heidel, L.

Ramsay, A. Teucher, and B. Young. 2012. NatureServe Conservation Status Assessments:

Methodology for Assigning Ranks. NatureServe, Arlington, VA.

Google Inc. 2024. Google Earth Pro (version 7.3.2.5776) [Software]. Available from earth.google.com. iNaturalist. 2024. Accessed through July 2024 from: https://www.inaturalist.org/observations.

Leidy, R. A. 2007. Ecology, assemblage structure, distribution, and status of fishes in streams tributary to the San Francisco Estuary, California. San Francisco Estuary Institute Contribution No. 530.

Leidy, R. A., G. Becker, and B. N. Harvey. 2005. Historical status of Coho salmon in streams of the urbanized San Francisco Estuary, California. California Fish and Game 91:219-254. [NRCS] Natural Resource Conservation Service. 2024. Web Soil Survey. U.S. Department of Agriculture.

Accessed July 2024 from: http://websoilsurvey.nrcs.usda.gov.

National Wetlands Inventory. 2024. Wetlands Mapper. U.S. Fish and Wildlife Service. Accessed July 2024 from https://www.fws.gov/program/national-wetlands-inventory/wetlands-mapper.

Peninsula-Birding List Serve. 2024. https://groups.io/g/peninsula-birding. Accessed through July 2024.

PRISM Climate Group. 2024. Online PRISM Data Explorer. Oregon State University, Corvallis, OR. Accessed July 2024 from: http://www.prism.oregonstate.edu/.

Rottenborn, S. C. 2007a. Tricolored blackbird Agelaius tricolor. Pages 426-427 in W. G. Bousman, editor.

Breeding Bird Atlas of Santa Clara County. Santa Clara Valley Audubon Society, Cupertino, California.

Rottenborn, S.C. 2007b. Vaux's Swift, Chaetura vauxi. Pages 244-245 in W. G. Bousman, editor. Breeding Bird Atlas of Santa Clara County. Santa Clara Valley Audubon Society, Cupertino, California.

Sawyer, J. O., T. Keeler-Wolf and J. M. Evens. 2009. A Manual of California Vegetation [online]. Second Edition. California Native Plant Society.

Sequoia Audubon Society. 2001. San Mateo County Breeding Bird Atlas. May.

Xerces Society. 2024. Western Monarch Overwintering Site Viewer. Accessed July 2024 from https://www.westernmonarchcount.org/map-of-overwintering-sites/.

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Appendix A. Plants Observed
Family Scientific Name Common Name Cal-IPC Rank1
Lauraceae Umbellularia californica California bay
Anacardiaceae Schinus molle* pepper tree Limited
Anacardiaceae Toxicodendron diversilobum poison oak
Apiaceae Torilis arvensis* tall sock-destroyer Moderate Apocynaceae Vinca major* greater periwinkle Moderate
Araliaceae Hederal helix* English ivy High
Asteraceae Artemisia californica California sagebrush
Asteraceae Carduus pycnocephalus ssp.
pycnocephalus* Italian thistle Moderate
Cucurbitaceae Marah fabacean California man-root
Fabaceae Genista monspessulana* French broom High
Fabaceae Medicago polymorpha* variable burclover Limited Fabaceae Trifolium hirtum* Rose clover Moderate
Fagaceae Quercus agrifolia coast live oak
Fagaceae Quercus lobata valley oak
Grossulariaceae Ribes californicum Hillside gooseberry
Lamiaceae Monardella villosa ssp. villosa coyote-mint
Lamiaceae Salvia leucophylla purple sage
Lamiaceae Salvia mellifera black sage
Lamiaceae
Salvia spathacea
California hummingbird
sage
Montiaceae
Claytonia parviflora
small-flowered
claytonia
Oleaceae Ligustrum sp.* privet
Papaveraceae Eschscholzia californica California poppy
Polygonaceae Rumex crispus* curly dock Limited
Ranunculaceae Ranunculus californicus California buttercup Rhamnaceae Frangula californica California coffee berry Rosaceae Fragaria vesca wood strawberry
Rosaceae Heteromeles arbutifolia toyon
Rosaceae Rubus ursinus California blackberry
Rubiaceae Galium aparine goose grass
Sapindaceae Aesculus californica California buckeye
Simaroubaceae Ailanthus altissima* tree of heaven Moderate

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Viburnaceae Sambucus mexicana blue elderberry
Iridaceae Iris douglasiana Douglas iris
Poaceae Bromus diandrus* ripgut brome Moderate
Poaceae Bromus hordeaceus* soft chess Limited
Poaceae Hordeum murinum* foxtail barley Moderate
Poeceae Poa annua* annual blue grass
1Cal-IPC Ranks (Cal-IPC 2024):
• Watch List – These species are predicted to become invasive if no further actions are taken.

Distribution may range from limited to widespread in specific regions. • Limited – These species are invasive, but their ecological impacts are minor on a statewide level.

They have low to moderate rates of colonization. Although their distribution is generally limited, these species may be locally persistent and problematic. • Moderate – These species have substantial and apparent—but generally not severe—ecological impacts on the surrounding habitat. They have moderate to high rates of dispersal. Distribution may range from limited to widespread.
• High – These species have severe ecological impacts on the surrounding habitat. They have moderate to high rates of dispersal and establishment, and most are widely distributed. *Nonnative or invasive species

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Appendix B. Special-Status Plants Considered but Rejected for Occurrence
Common Name Scientific Name
No Suitable Habitat
Edaphic Conditions
Absent
Outside the
Elevation Range
Outside of Known
Geographic
Range/No Nearby
Extant Records
San Mateo thorn-mint Acanthomintha duttonii X X
Franciscan onion Allium peninsulare var.
franciscanum X
California androsace Androsace elongata ssp. acuta X
slender silver moss Anomobryum julaceum X X
coast rockcress Arabis blepharophylla X
Anderson's manzanita Arctostaphylos andersonii X
Schreiber’s manzanita Arctostaphylos glutinosa X X
Ohlone manzanita Arctostaphylos ohloneana X X X
Kings Mountain manzanita Arctostaphylos regismontana X X X Bonny Doon manzanita Arctostaphylos silvicola X X X
Humboldt County milkvetchAstragalus agnicidus X
alkali milk-vetch Astragalus tener var. tener X X X
Brittlescale Atriplex depressa X X
lesser saltscale Atriplex minuscula X X
Brewer's calandrinia Calandrinia breweri X X
Santa Cruz Mountains
pussypaws
Calyptridium parryi var. hessae X X
Congdon's tarplant Centromadia parryi ssp.
congdonii X X
Point Reyes salty bird'sbeakChloropyron maritimum ssp. palustre X X X
Ben Lomond spineflower Chorizanthe pungens var.
hartwegiana X X
robust spineflower Chorizanthe robusta var. robusta X X

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Common Name Scientific Name
No Suitable Habitat
Edaphic Conditions
Absent
Outside the
Elevation Range
Outside of Known
Geographic
Range/No Nearby
Extant Records
Mt. Hamilton thistle Circium fontinale var. fontinale X X fountain thistle Cirsium fontinale var. campylon X X
lost thistle Cirsium praeteriens X X X
Brewer’s clarkia Clarkia breweri X X
Santa Clara red ribbons Clarkia concinna ssp. automixa X Lewis clarkia Clarkia lewisii X X
round-headed ChinesehousesCollinsia corymbosa X X X
San Francisco collinsia Collinsia multicolor X X
clustered lady's-slipper Cypripedium fasciculatum X X X western leatherwood Dirca occidentalis X
Santa Clara Valley dudleya Dudleya abramsii ssp. setchellii X X small spikerush Eleocharis parvula X X
San Mateo woolly
sunflower
Eriophyllum latilobum X X
Hoover's button-celery Eryngium aristulatum var. hooveri X X X Jepson's coyote-thistle Eryngium jepsonii X X
San Francisco wallflower Erysimum fanciscanum X X
San Joaquin spearscale Extriplex joaquinana X X X
minute pocket moss Fissidens pauperculus X
fragrant fritillary Fritillaria liliacea X
phlox leaf serpentine
bedstraw
Galium andrewsii ssp. gatense X X
Toren’s grimmia Grimmia torenii X X
vaginulate grimmia Grimmia vaginulata X X
San Francisco gumplant Grindelia hirsutula var. martitima X X short-leaved evax Hesperevax sparsiflora var.
brevifolia X X
Santa Cruz cypress Hesperocyparis abramsiana var.
abramsiana X X X
Butano Ridge cypress Hesperocyparis abramsiana var.
butanoensis X X X
Marin western flax Hesperolinon congestum X X
Loma Prieta hoita Hoita strobilina X X X

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Common Name Scientific Name
No Suitable Habitat
Edaphic Conditions
Absent
Outside the
Elevation Range
Outside of Known
Geographic
Range/No Nearby
Extant Records
harlequin lotus Hosackia gracilis X
coast iris Iris longipetala X
Contra Costa goldfields Lasthenia conjugens X X
legenere Legenere limosa X X
serpentine leptosiphon Leptosiphon ambiguus X
bristly leptosiphon Leptosiphon aureus X
large-flowered leptosiphon Leptosiphon grandiflorus X
broad-lobed leptosiphon Leptosiphon latisectus X X
woolly-headed lessingia Lessingia hololeuca X X
smooth lessingia Lessingia micradenia var.
glabrata X X
spring lessingia Lessingia tenuis X
Hall’s bushmallow Malacothamnus hallii X
Woodland woollythreads Monolopia gracilens X X
Prostrate vernal pool
navarretia
Navarretia prostrata X X
Kellman’s bristle moss Orthotrichum kellmanii X X
Dudley’s lousewort Pedicularis dudleyi X X
Santa Cruz Mountains
beardtongue
Penstemon rattanii var. kleei X X X
white-rayed pentachaeta Pentachaeta bellidiflora X X
white-flowered rein orchid Piperia candida X X
Michael's rein orchid Piperia michaelii X X
Choris' popcornflower Plagiobothrys chorisianus var.
chorisianus X X
Hickman's popcornflower Plagiobothrys chorisianus var.
hickmanii X
hairless popcornflower Plagiobothrys glaber X X
California alkali grass Puccinellia simplex X X
Lobb's aquatic buttercup Ranunculus lobbii X
Sanford's arrowhead Sagittaria sanfordii X
Hoffmann's sanicle Sanicula hoffmannii X X
rock sanicle Sanicula saxatilis X X

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Common Name Scientific Name
No Suitable Habitat
Edaphic Conditions
Absent
Outside the
Elevation Range
Outside of Known
Geographic
Range/No Nearby
Extant Records
chaparral ragwort Senecio aphanactis X X
Santa Cruz microseris Stebbinsoseris decipiens X X
most beautiful jewelflower Streptanthus albidus ssp.
peramoenus
X X
northern slender
pondweed
Stuckenia filiformis ssp. alpina X X X
California seablite Suaeda californica X X X
two-fork clover Trifolium amoenum X X
Santa Cruz clover Trifolium buckwestiorum X X
saline clover Trifolium hydrophilum X X
Pacific Grove clover Trifolium polyodon X X
Methuselah's beard lichen Usnea longissima X X

HALSEY HOUSE

HISTORIC RESOURCE EVALUATION

LOS ALTOS, CALIFORNIA
[21130]

PREPARED FOR THE CITY OF LOS ALTOS
August 30, 2021
Attachment 5 - Appendix D

Cover image: Theodore and Emma Halsey in the rear courtyard of Halsey House, circa 1924. Source: Los Altos History Museum Collections.

Historic Resource Evaluation Halsey House
Project Number 21130 Los Altos, CA

TABLE OF CONTENTS
I. INTRODUCTION........................................................................................................................................1 Methodology ..........................................................................................................................................1 Summary of Findings ............................................................................................................................2 II. EXISTING HISTORIC STATUS...................................................................................................................4 National Register of Historic Places ....................................................................................................4 California Register of Historical Resources ........................................................................................4 California Historical Resource Status Codes ......................................................................................4 City of Los Altos Historic Resource Inventory (HRI)...........................................................................5 III. ARCHITECTURAL DESCRIPTION ............................................................................................................7 IV. HISTORIC CONTEXT .............................................................................................................................16 Brief History of Los Altos ....................................................................................................................16 V. SITE HISTORY.........................................................................................................................................19 Site Development................................................................................................................................19 Construction Chronology of the Halsey House................................................................................19 Development of the Redwood Grove Landscape and Site .............................................................27 Ownership and Occupancy History...................................................................................................30 Select Owner and Occupant Biographies............................................................................................34 The Design of the Halsey House ........................................................................................................36 VI. EVALUATION.........................................................................................................................................39 California Register of Historical Resources ......................................................................................39 Criterion 1 (Events) .................................................................................................................................39 Criterion 2 (Persons)...............................................................................................................................40 Criterion 3 (Design/Architecture)..........................................................................................................42 Criterion 4 (Information Potential) .......................................................................................................43 Integrity ................................................................................................................................................43 Character-Defining Features..............................................................................................................46 Los Altos Historic Landmark and Historic Resource Criteria .........................................................48 Halsey House as a Designated Historic Landmark...........................................................................48 Halsey House as a Contributor to a Possible Historic District........................................................49 VII. CONCLUSION ......................................................................................................................................51 VIII. REFERENCES .......................................................................................................................................52 IX. APPENDIX .............................................................................................................................................55 Significance and Chronology Diagrams of the Halsey House ........................................................55

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I. INTRODUCTION
This Historic Resource Evaluation (HRE) has been prepared at the request of the City of Los Altos for the building at 482 University Avenue (located within APN 175-30-021), historically called the Halsey House. The Halsey House, which is located in the approximately six-acre Redwood Grove, is owned by the City of Los Altos. The property is located along the city boundary of Los Altos and Los Altos Hills to the west. It is reached via an access road on the west side of University Avenue (Figure 1).

Built in 1923 for Theodore Vail Halsey and Emma Wright Halsey by an unknown architect, the Halsey House was used as a single-family residence until 1945. In 1945, the property was sold to the Besseys and was converted into two residential units soon after. In 1974, the property was purchased by the City of Los Altos to serve as a park. At that time, the building was converted to a nature center for educational and recreational programming. In 2008, the building was closed to the public, and since 2008, the Halsey House has been vacant.

Figure 1: The location of the subject property (shaded blue), with the Halsey House identified by the dashed red circle. The larger area of Redwood Grove and the approximate boundary of the historic property of Halsey House is shown with a dashed yellow line. Source: Santa Clara County SCC Map.

Methodology
This report follows a standard outline for Historic Resource Evaluations (HREs) and provides a summary of the building’s current historic status, an architectural description, a historic context for

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the development of the Halsey House and Los Altos, and a narrative description of the subsequent changes to the Halsey House since its construction in 1923. This report includes an evaluation of the property’s eligibility for listing in the California Register of Historical Resources and includes an updated evaluation of the property according to the Los Altos Historic Resource Inventory Criteria for Evaluation.

Page & Turnbull prepared this report using research provided by the City of Los Altos and the Los Altos History Museum, as well as various online sources including Ancestry.com, the California Digital Newspaper Collection, and Newspapers.com. Key primary sources consulted and cited in this report include Sanborn Map Company fire insurance maps, City of Los Altos records, historical newspapers, a 2001 oral history with Eugenia Halsey Buss in the collection of the Los Altos History Museum, and historic photographs provided by the Los Altos History Museum and Katherine Halsey Buss. Page & Turnbull also reviewed secondary source material including the Halsey House Historic Structures Report completed by Architectural Resources Group (ARG) in 2019, as well as additional reports on the building’s material and structural condition, and studies on its reuse.

Page & Turnbull staff conducted a site visit to the Halsey House on June 22, 2021. All photographs within this report were taken at that time, unless otherwise noted.

Summary of Findings
This Historic Resource Evaluation finds that the Halsey House is eligible for the California Register under Criterion 1 (Events) at the state level of significance as an excellent example of the residential development patterns of Los Altos and for the establishment of the Redwood Grove, which is a unique property developed by Emma Halsey and her Japanese gardener, Mori, in the 1920s. Page & Turnbull did not find the property significant under Criterion 2 (Persons), Criterion 3 (Design/Architecture), or Criterion 4 (Information Potential).

Additionally, Page & Turnbull reviewed the Halsey House’s existing historic status as a City of Los Altos Historic Landmark and found that the building continues to meet the necessary criteria for age and physical integrity, despite the ongoing issues of the building’s condition. While Page & Turnbull found the property to be eligible for the California Register under different criteria than it was listed under as a local landmark, Page & Turnbull agrees that the property is a rare or unique example and remains eligible as a Historic Landmark of Los Altos.

The Halsey House was additionally identified as a possible contributor to the University/Orange Historic District during the 1990 architectural survey. This district has never been formally adopted.

From an initial review of the University/Orange Historic District, Page & Turnbull believes that the

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Halsey House does not fit the overall character of the eligible district due to its secluded location far removed from the street and its unique wooded and semi-rural setting.

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II. EXISTING HISTORIC STATUS
The following section examines the national, state, and local historic status currently assigned to the Halsey House.

National Register of Historic Places
The National Register of Historic Places (National Register) is the nation’s most comprehensive inventory of historic resources. The National Register is administered by the National Park Service and includes buildings, structures, sites, objects, and districts that possess historic, architectural, engineering, archaeological, or cultural significance at the national, state, or local level.

The subject property is not currently listed on the National Register.

California Register of Historical Resources
The California Register of Historical Resources (California Register) is an inventory of significant architectural, archaeological, and historical resources in the State of California. Resources can be listed in the California Register through a number of methods. State Historical Landmarks and National Register-listed properties are automatically listed in the California Register. Properties can also be nominated to the California Register by local governments, private organizations, or citizens.

The evaluative criteria used by the California Register for determining eligibility are closely based on those developed by the National Park Service for the National Register of Historic Places.

The subject property is not currently listed on the California Register.

California Historical Resource Status Codes
Properties listed or under review by the State of California Office of Historic Preservation are listed within the Built Environment Resource Directory (BERD) and are assigned a California Historical Resource Status Code (Status Code) of “1” to “7” to establish their historical significance in relation to the National Register of Historic Places (National Register) or California Register of Historical Resources (California Register).1 Properties with a Status Code of “1” or “2” are either eligible for listing in the California Register or the National Register, or are already listed in one or both of the registers. Properties assigned Status Codes of “3” or “4” appear to be eligible for listing in either register, but normally require more research to support this rating. Properties assigned a Status Code of “5” have typically been determined to be locally significant or to have contextual 1 California State Office of Historic Preservation, Built Environment Resource Directory (BERD), Santa Clara County, updated March 2020.

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importance. Properties with a Status Code of “6” are not eligible for listing in either register. Finally, a Status Code of “7” means that the resource has not been evaluated for the National Register or the California Register, or needs reevaluation.

The subject property is listed in the BERD database for Santa Clara County with a status code of “7N1,” assigned during the 1990 survey that led to the establishment of the Los Altos Historic Resource Inventory in 1997.
2 A 7N1 status code means that the property “Needs to be reevaluated (former status code 4) - may become NR eligible with restoration or other specific conditions.”3 The most recent update to the BERD database was in March 2020.

City of Los Altos Historic Resource Inventory (HRI)
The City of Los Altos maintains a Historic Resource Inventory (HRI) that serves as an official list of Historic Resources, designated Historic Landmarks, and designated historic district contributors. For the City of Los Altos, a Historic Resource is defined as “a property or structure that has been determined to be over 50 years old, retains its physical integrity, has historical, architectural, cultural, and/or aesthetic value, and is listed on the HRI.”4 A City of Los Altos Historic Landmark is a Historic Resource that has a higher level of significance (i.e. an outstanding example of design or construction, the first, last or only example of its type, or the location of a highly significant event of local, statewide, or national significance).5 While the definition of Historic Resources is limited to buildings or structures, Historic Landmarks can also include improvements, natural features, and sites or areas of land, under single or common ownership. 6 When the Los Altos HRI was first established in 1997, the HRI used the Kalman Scale, a “numerical evaluation system derived from The Evaluation of Historic Buildings by Harold Kalman,” to quantitatively analyze and rank the significance of potential historic resources.7 Los Altos used the Kalman scale through 2010.8
2 While the BERD database does not supply the date of the survey, however, it appears to have been the 1990s Los Altos architectural survey due to the information included in the individual building records in the database. The Department of Parks and Recreation Primary Record form (DPR 523A form) and Department of Parks and Recreation Building, Structure, and Object forms (DPR 523B form) completed in 1997 for the HRI stated that the building is a good example of the Spanish Colonial Revival style, but did not provide a status code for the property. 3 For the status code assigned to the Halsey House refer to: California State Office of Historic Preservation, Built Environment Resource Directory (BERD), Santa Clara County, updated March 2020; for the meaning of a 7N1 status code, refer to:

California State Office of Historic Preservation, “California Historical Resource Status Codes,” updated March 2020, 3. 4 CIRCA: Historic Property Development, City of Los Altos Historic Resource Inventory, (October 2012), I-4. 5 Ibid., I-14. 6 Ibid. 7 Adaptations of the method used by Kalman was a common evaluation approach widely used in the late 1970s, prior to the establishment and standardized use of the National Register and California Register criteria for the evaluation of potential historic resources. Ibid., I-2. 8 Ibid., I-5.

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In 2012, the HRI was revised and the criteria for evaluation were aligned with the existing evaluation criteria for both the National Register and California Register. Today, a historic resource for the City of Los Altos is determined through establishing that it meets the age threshold of fifty years, retains its physical integrity, and meets one or more of the criteria for historic significance. 9 The Halsey House and the larger property of Redwood Grove was listed as a City of Los Altos Historic Landmark in May 1981 and was listed as a Historic Landmark in the HRI when it was established in 1997. During a 1990 historic property survey of Los Altos’ historic resources, the Halsey House was analyzed with the Kalman Scale and was given a rating of 95 out of 100 points.

Updated Department of Parks and Recreation Primary Record form (DPR 523A form) and Department of Parks and Recreation Building, Structure, and Object forms (DPR 523B form) were completed for the Halsey House in July 2011 as part of the effort to update the HRI. These DPR forms state that the Halsey House was significant for its association with the Halsey family as an important early Los Altos family and as a fine example of the Spanish Eclectic style. 10 The building
was also identified as a possible contributor to a proposed University/Orange Historic District. The Halsey House was given an updated Kalman Scale score of 73 and assigned the California Resources Historical Resources Status Codes of 5S1 and 5D2.11 These status codes mean that the resource is “Individually listed or designated locally” and a “contributor to a multi-component resource that is eligible for local listing or designation,” respectively.12 While the 2011 DPR forms were completed for the building and not the larger property, despite their listing as a single Historic Landmark, the evaluation included mention of the Redwood Grove as “a notable natural landmark within the City of Los Altos.”13
As noted in the section above (refer to Existing Historic Status: California Historical Resource Status Codes), the building currently has a status code of 7N1 in the BERD database that appears to date from the 1990 architectural survey. It appears that the 5S1 and 5D2 status codes from the 2011 HRI update were never submitted to the Northwest Information Center to be recorded in the BERD database.
9 Ibid., I-11 to I-14. 10 Circa: Historic Property Development. “Halsey House (Redwood Grove Park). State of California DPR 523A and 523B forms.

Completed March 2009.
11 Although an updated Kalman Scale score was listed on the 2011 DPR forms, the breakdown of the numbers assigned within each category was not included and staff at the City of Los Altos were unable to located this revised Kalman Score analysis at this time.
12 California State Office of Historic Preservation, “California Historical Resource Status Codes,” updated March 2020, 2. 13 Circa: Historic Property Development. “Halsey House (Redwood Grove Park). State of California DPR 523A and 523B forms.

Completed March 2009, 3.

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III. ARCHITECTURAL DESCRIPTION
The Halsey House is currently vacant and has been boarded up and encircled by chain link fencing.

The following description is based on a site visit that included access to the interior of the building to investigate existing windows and doors, a partial tour of the exterior of the building’s perimeter wall within the chain-link fencing, as accessible, a view of the rear courtyard from over the south courtyard wall, and a walk of the perimeter of the building outside the chain-link fencing. Historic photographs from the Los Altos History Museum, various plans of the building provided by the City of Los Altos, information included in the 2019 Historic Structure Report by ARG, and photographs from 2003 and circa 2009 that were supplied by the City of Los Altos, were used to verify the building’s design and the presence of features that are not currently visible from the exterior.

Figure 2: Bird's-eye view of the Halsey House. Source: Google Maps, 2021.

The Halsey House is a one-story stucco-clad building with a clay tile hipped roof (Figure 2). The building is generally U-shaped and is arranged around a rear courtyard with a courtyard wall that spans the south ends of the east and west wings. Extant original windows consist of a variety of multi-lite wood windows that include asymmetrically divided three-over-one double-hung sash, sixlite casement windows, small four-lite casement windows, some one-over-one double-hung windows, and two pairs of six-lite slider windows (one set of which is now missing). The asymmetrically divided three-over-one double-hung sash are the primary window type of the residence and will be referred to as “typical double-hung windows” throughout this report. Nonhistoric windows consist of a jalousie window and some fixed single-lite windows. Some of the

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existing one-over-one double-hung sash are windows that replaced original three-over-one windows. The building also retains a number of original wood-frame doors that include paired tenlite fully glazed French doors, which will be referred to as “typical French doors” within this report.

These typical French doors are often paired with multi-lite sidelights in either a five-lite or ten-lite configuration.

Primary (North) Façade
The primary façade consists of an entrance porch at the east corner with north- and east-facing walls, the main length of the building along its north side, and the north- and east-facing walls of the 1928-addition located at the west corner of the north façade (Figure 3). 14 Figure 3: Primary (north) façade of the Halsey House, largely hidden by chain-link fencing. Looking slightly southeast.

The entrance porch at the northeast corner of the building is reached via low concrete steps that are tinted a warm red color and rise to a concrete landing that is square in shape. Within the northfacing wall of the entrance porch are typical French doors with 10-lite sidelights (Figure 4). The eastfacing wall contains the primary entrance to the residence that consists of a 15-lite fully glazed, single-leaf door with five-lite sidelights. This entrance door and surround retains its historic hardware including a doorknob, door lock, and doorbell. An original metal wall-mounted lamp is located to the south (left) of the entrance surround, and a small four-lite casement window is located at the south edge of the east-facing wall. A historic wood pergola is located over the 14 The Halsey House is oriented west of true north, but this report refers to the primary façade as facing north, the rear façade as facing south, etc. In actuality, the entrance porch is aligned to true north.

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entrance porch and features decorative profiled ends (Figure 5). Non-historic corrugated plastic is located over the pergola to serve as a roof.

Figure 4: Entrance porch at northeast corner of
building. Looking southwest.

Figure 5: Wood pergola and plastic roof over
entrance porch at north façade. Looking southwest.

Figure 6: Interior view of French doors that open to north patio along north façade. Looking slightly northwest.

Figure 7: Extant original wall-mounted
lamp between French doors at north
façade. Looking slightly southwest.

The main length of the north façade features three evenly spaced typical French doors without sidelights that open onto the concrete north patio (Figure 6). Two original wall-mounted lamps (missing their glass covers) are located to either side of the center pair of French doors (Figure 7).

Two sets of three windows are located along the west (right) portion of the façade. The east (left) set of three windows consists of replacement windows with fixed glass flanking a center jalousie window, while the west (right) window arrangement consists of three historic six-lite windows that were installed during the erection of the 1928 addition (Figure 8).

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The east facing wall of the 1928 addition has a secondary entrance with a non-historic single-leaf wood replacement door reached by three tinted concrete steps that match the north patio (Figure 9). The north-facing wall of the addition features three typical double-hung windows.

Figure 8: Interior view of jalousie and fixed windows
along primary façade. Looking northeast.

Figure 9: Secondary entrance to 1928 addition at
west end of primary façade. Looking northwest.

East Façade
The east façade features several window types and one set of doors. From left to right (south to north), openings consist of paired six-lite slider windows, typical French doors, one typical doublehung window, two smaller replacement one-over-one double-hung windows (note, Figure 10 shows the original three-over-one windows at this location in 2003), two typical double-hung windows, and a group of four typical double-hung windows (Figure 10).

Figure 10: East façade of Halsey House in 2003. Source: City of Los Altos.

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West Façade
The west façade contains the west- and south-facing walls of the 1928 northwest addition and the west-facing wall of the original portion of the residence (Figure 11 and Figure 12). Along the westfacing wall of the addition, the building features a brick exterior chimney that is centered on the wall and two paired typical double-hung windows to the north (left) of the chimney. The south-facing wall of the addition consists of a single typical double-hung window at its west (left) side, a wood infilled window opening with a wood frame, and a rectilinear horizontal fixed window.

Figure 11: South-facing wall of 1928
addition. Looking north. Source: Halsey
House HSR by ARG, taken in May 2019.

Figure 12: West façade of original section of residence. Looking slightly southeast. Source: Halsey House HSR by ARG, taken in May 2019.

The length of the original section of the building features a number of openings, including one door.

From left to right (north to south), these openings consist of a group of three typical double-hung windows, one typical double-hung window, a single-leaf partially glazed wood panel door, a group of three typical double-hung windows, one small four-lite casement window, one typical double-hung window, and two typical double-hung windows.

Rear (South) Façade
The south façade of the Halsey House features the south-facing walls of the east and west wings of the building and the rear wall of the courtyard that spans these two wings (Figure 13). The south facade of the west wing contains a group of three typical double-hung windows centered along this wall (Figure 14). The south wall of the courtyard consists of a tall stucco-clad wall that features one round-arched opening with a wood plank door that is located near the east wing. Along the exterior of this courtyard gate are three semi-circular stone steps that descend to the height of the rear

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courtyard, which is slightly below the grade of the property to the rear (Figure 15). The south façade of the east wing features an asymmetrically placed opening that originally featured paired six-lite sliding windows that have since been removed due to damage.

Figure 13: South façade with rear courtyard wall. Looking slightly northwest. Source: HSR by ARG, taken in May 2019.

Figure 14: Interior view of three grouped typical
double-hung windows along south façade of west
wing. Looking southeast.

Figure 15: Semi-circular steps to gate in south
façade of courtyard wall. Looking down and slightly
northwest.

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Rear Courtyard
The rear courtyard is surrounded by the residence on three sides (north, east, and west) and is enclosed along its south side by a stucco-clad wall with a round-arched gate (refer to description of the Rear (South) Façade, above).

Figure 16: View of rear courtyard, looking north. Red dashed outline shows original patio. Yellow dashed outline shows area of concrete infill.

Figure 17: View of original stone paving,
fountain, and seating. Looking down
and west from top of courtyard wall.

The courtyard features a tinted cement patio at its north end that matches the design of the north patio. The center portion of the courtyard has been infilled with concrete with small planting areas along both the east and west sides (Figure 16). The south portion of the courtyard retains its original stone and concrete paving with low steps and lined planting beds. A small fountain is attached to the south courtyard wall and is flanked by two curved buttresses that are designed to double as benches (Figure 17).

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Figure 18: West side of courtyard (east-facing wall), looking northwest.

Figure 19: North and east sides of rear
courtyard (south- and west-facing wall).

Looking north over rear courtyard wall.

Along the west side of the courtyard, the east-facing wall of the Halsey House features, from south to north (left to right): one typical double-hung window, one ten-lite single-leaf fully glazed door that opens onto a small concrete landing with three steps and a metal railing, two small four-lite casement windows, three separate typical double-hung windows, and a pair of typical French doors that open to a small non-historic concrete landing with three steps (Figure 18).

Along the north side of the courtyard, the south-facing wall of the Halsey House features a centered exterior chimney that is clad in stucco to match the finish of the residence (Figure 19). Two typical French doors with five-lite sidelights are located to either side of the chimney.

Along the east side of the courtyard, the west-facing wall of the Halsey House features, from north to south (left to right): two sets of typical French doors, paired typical double-hung windows, paired one-over-one double-hung windows, one slightly shorter three-over-one double-hung window, and one one-over-one double-hung window (Figure 19).

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Site
The Halsey House is located to the south of Adobe Creek and is reached via an access road along the south side of University Avenue (Figure 20). The surrounding property of Redwood Grove Park is marked by mature trees primarily consisting of redwoods and oaks.

Figure 20: Access road at south side of University
Avenue. Looking east into the Redwood Grove.

Figure 21: Caretaker’s cottage within Redwood Grove
Park. Looking northeast.

The only other building on the property is the caretaker’s cottage that is located to the northeast of the Halsey House near the access road from University Avenue (Figure 21). A wood flagpole, which appears historic but was installed at an unknown date, is located to the east of the Halsey House (Figure 22). Contemporary benches, picnic tables, trash cans, signage, and non-historic concrete paving have been installed since the property became a city park (Figure 23). A non-historic wood bridge was installed recently over Adobe Creek.

Figure 22: Wood flagpole to the east
of Halsey House. Looking south.

Figure 23: Looking south within Redwood Grove Park. Caretaker’s cottage at right; non-historic paving and signage visible.

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IV. HISTORIC CONTEXT
Brief History of Los Altos
Prior to European settlement of the Santa Clara Valley, the area of modern Los Altos was inhabited by the Ohlone peoples. As many as 40 permanent villages rimmed the San Francisco Bay, and remnants of an Ohlone village and burial ground have been found in Los Altos through archeological investigation.
15 European settlement of the Santa Clara Valley began with the establishment of the Franciscan Mission of Santa Clara de Asís in 1777. Spanish colonizers and Franciscan friars established Mission Santa Clara and 20 other California missions to convert local indigenous peoples to Catholicism, expand the Spanish colonial sphere of influence, and establish a colonial society through the mission system. While the system claimed to be based on the voluntary conversion of neophytes, large numbers of Native Americans were forcibly relocated to support the missions, devastating cultural continuity for many communities, and decimating indigenous populations through exposure to disease.16 Following the Secularization Act of 1833, the missions and the Franciscan order were stripped of their extensive land holdings throughout the state, and the land was awarded by the Mexican government to a number of individuals as rewards for their political or military service, or as personal favors. Two of these land grants, Rancho La Purisima Concepcion and Rancho San Antonio, later became part of the Fremont Township within Santa Clara County in 1851 and include the area of modern Los Altos.17
The following brief history of Los Altos’ early ranching, orchard, and residential development is excerpted from the Historic Context within the City of Los Altos Historic Resource Inventory as revised in April 2011:

In the early rancho days, much of the Santa Clara Valley was used for cattle grazing.

This activity later gave way to wheat and grain fields in the 1860s and 1870s.

Mountain View was the principal settlement in the area and grew primarily as a result of the old Mountain View Station, a stage stop located along the San FranciscoSan Jose Stage Road. This route today is known as El Camino Real. 15 The brief development history of Los Altos has largely been summarized from the following source: Circa: Historic Property Development, City of Los Altos Historic Resources Inventory Report, completed for the City of Los Altos, April 2011. 16 Robert Archibald, “Indian Labor at the California Missions,” The Journal of San Diego History, Spring 1978, v. 24, no. 2, accessed July 2021, https://sandiegohistory.org/journal/1978/april/labor/; Charles Wollenberg, Golden Gate Metropolis:

Perspectives on Bay Area History (Berkeley, California: Institute of Governmental Studies, University of California, Berkeley, 1985), 44-48. 17 Shirley Eastman, “History of the Los Altos Area” in Memories of Los Altos, ed. Joe Salameda (Los Altos: Los Altos Historical Society, 1982).

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When the Southern Pacific railroad came through in 1864, the line was located about a mile from Mountain View Station, bypassing what was known as Old Mountain View (near present day Calderon). The “New Mountain View” was officially laid out in 1865 at the present downtown area along Castro Street. Settlement in and around Los Altos area grew as a result of the railroad and Mountain View was the center for all business activity for these early residents. [….]
Many believe that the real beginning of Los Altos start[ed] with the Altos Land Company and acquisition of Sarah Winchester’s 100 acres in 1906. This land became what is known today as the downtown triangle.

The earliest account, date[d] August 2, 1906, was found in the Palo Alto Times in an article describing the purchase of the 100 acres mentioned above by the Interurban Electrical Railway for a right-of-way. It mentioned the creation of a new town-site to be called “Banks and Braes.” Just when the name was changed to Los Altos is unknown, but we do know that the Altos Land Company and the University Land Company were formed in 1907. An October 2, 1913 issue of the Mayfield News, however, describes the townsite as being sold again and placed solely into the hands of Paul Shoup and George Herbert, a San Jose fruit packer. The deal is described as one of the most important real estate transactions in Santa Clara County.

With the establishment of the town in 1907 came the beginnings of subdivisions (although a few earlier subdivisions were recorded prior to 1907). [….] The original town contains the University Avenue neighborhood. This early and very elite neighborhood contains a variety of architectural house types which are unified mainly by the street layout and alleyways. The lot sizes and scales of these homes vary in size greatly; yet there is a continuity of form in the streetscape in most cases.

Dates in this area range from 1908 to the 1930s and buildings in many cases are probably architect-designed judging from the styles found, and the social status of people who occupied these buildings. Many of the homes in the district began as summer homes for prominent San Francisco businessmen and their families while others remained year-round living quarters for businessmen who commuted on the train.
[….] By 1911, according to Eastman’s history of the town, Los Altos had only fifty homes; by 1913, only thirty-two telephones had been connected. The majority of

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properties in the residential context are homes built in the 1920s and 30s, reflecting the growth of the area.18
Although the residential areas of Los Altos continued to grow, particularly as the automobile provided more independent travel options between the towns and rural areas of the Peninsula and the surrounding cities of the Bay Area, the area of Los Altos remained home to a flourishing orchard industry until the post-World War II period. After the war, due to the extreme demand for housing, land became more valuable for development than farming and many of the orchards were closed, sold, and subdivided for residential development. As described by the City of Los Altos in a brief history:

The town's name gradually spread informally to identify a much larger unincorporated area served by the Los Altos School District formed in 1910, including what is today Los Altos Hills and portions of other neighboring towns.

This larger community's population exploded after World War II, and on December 1, 1952, an expanded Los Altos became the eleventh city in Santa Clara County. As a result of decreased interest in train travel due to the wide adoption of the automobile, the Southern Pacific Railroad, an essential part of the town's founding, ceased operation here in 1964, and its right-of-way became Foothill Expressway.19 18 Circa: Historic Property Development, City of Los Altos Historic Resources Inventory Report, completed for the City of Los Altos, April 2011, II-4 to II-8. 19 “History of Los Altos,” City of Los Altos, Accessed July 2021, https://www.losaltosca.gov/community/page/history-los-altos

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V. SITE HISTORY
Site Development
Prior to the construction of the Halsey House in 1923, the approximately six acres of land of the future Redwood Grove was the site of a two-bedroom summer cottage owned by William H. and Myra E. Wright, the parents of Emma Wright Halsey. The location, according to Halsey family lore, was found by Emma for her parents, who were looking for a summer get-away along the Peninsula.

The Wrights purchased the property in 1912 and constructed a summer cottage, to be used seasonally as “a place in the sunshine” to escape the summer fog of San Francisco.

When Emma Wright married Theodore Vail Halsey in 1915, their marriage took place on the grounds of the Wrights’ summer retreat, and the property was given to the newlyweds as a wedding present.20 The Halseys initially continued to use the Los Altos property seasonally while living in San Francisco, but in 1923 they decided to live in Los Altos permanently and had the existing summer cottage demolished and the Halsey House constructed.

Construction Chronology of the Halsey House
The Halsey House was constructed in 1923 by an unidentified architect or builder. The 1926 fire insurance map by the Sanborn Map Company is the first map to show the original footprint of the residence. As constructed, the residence was U-shaped with the east wing slightly shorter in length than the west wing; the extant northwest addition that was constructed in 1928 for Myra Wright was not yet present (Figure 24). Early Halsey family photographs show the north façade of the residence prior to the construction of the addition and confirm that the north façade originally included the three pairs of French doors and three eight-lite casement windows (now replaced with a jalousie window and two fixed windows) (Figure 25).
20 “Eugenia Halsey Buss Interview, August 23, 2001,” transcribed interview of Eugenia Halsey Buss (and Robert Buss) by Don McDonald, Los Altos History Museum, Oral History Program.

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Figure 24: Sanborn Map Company fire insurance map from 1926 showing the subject building’s original footprint, circled in red. Source: San Francisco Public Library. Edited by Page & Turnbull.

Figure 25: Two photographs of the Halsey House prior to 1928, showing the original full length of the primary (north) façade which ended just west of the three grouped eight-lite casement windows. Source: Los Altos History Museum Collections, courtesy of Katherine Halsey Buss.

In 1928, the northwest addition was constructed to provide a separate apartment with a separate entrance for Emma’s mother, Myra Wright.

At some time in the 1930s, an addition was made to the east wing, extending it to be equal in length to the west wing. Early photographs of the rear courtyard show the shorter east wing and the original location of the courtyard gate in the east wall of the courtyard, prior to its relocation to the south wall of the courtyard (Figure 26 and Figure 27). The extension of the east wing added an additional bedroom and bathroom to the residence that were used to house a live-in servant,

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variously a maid or a cook.
21 While none of the available photographs of the Halsey House during the Halseys’ residency show this addition as completed, it is mentioned within the oral history with Eugenia Buss and in other communications with Halsey descendants.

Figure 26: Historic photograph of the courtyard in the late 1920s or early 1930s, showing the original configuration of the east wing and the courtyard wall. The red dashed line indicates the original end of the east wing prior to the construction of an addition at an unknown date likely in the 1930s. Today the round-arched courtyard door is located in the south wall, just left of the bench in this photograph. Source: Los Altos History Museum Collections. Edited by Page & Turnbull.

One other alteration known to have been completed during the ownership of the Halsey family is the construction of the wood pergola structure over the entrance porch at the east end of the primary façade. While the entrance porch originally featured a small shed roof over the primary entrance (visible in the left photograph at Figure 25), a photograph from the late 1930s or early 1940s shows the addition of a wood post at the northeast corner of the entrance porch that 21 Email communication between Katherine Buss and staff of ARG, May 30, 2019. Based on her memories of Halsey family history, Katherine Buss recalls that the family had a live-in cook.

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indicates that the pergola was present at this time (Figure 28). 22 The plastic corrugated roofing was
added later and is not historic.

Figure 27: Emma Halsey, in the 1920s, at
the open courtyard gate in its original
location along the east courtyard wall.

Looking east into the larger property.

Source: Los Altos History Museum
Collections.

Figure 28: Portrait of unidentified women, taken near the creek in front of Halsey House in the late 1930s or early 1940s. The entrance porch of Halsey House is just visible in the background at the far right. Source: Los Altos History Museum Collections.

Courtesy of Katherine Halsey Buss.

Photographs of the Halsey House’s courtyard in the 1920s through the 1940s illustrate the extensive planting of the courtyard completed by Emma Halsey with assistance from her two gardeners, Mori and Yoshio Hongo (Figure 29, Figure 30, and Figure 31). The courtyard retains its original tinted concrete patio at its north end and some of the original stone paving and lining of planting beds at its south end. The benches and a portion of the original fountain are extant along the south courtyard wall. The central circular planting bed and a freestanding fountain that was added during the Halseys’ residency have been removed, and a concrete patio was installed in the center of the courtyard prior to 1983.
23 22 Date of the photograph is assumed to be the late 1930s to early 1940s based on the clothing of the women in the photograph.
23 Photographs of planting within the courtyard and painting of the building’s courtyard-facing facades in 1983 were provided by Marie Backs to the author.

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Figure 29: Theodore and Emma Halsey within rear courtyard of Halsey House in the 1920s. Source: Los Altos History Museum Collections.

Figure 30: Photograph of the Halsey family and guests on the rear patio of the courtyard, in 1924. Looking north. Note the original balconette at the far left that is no longer extant. Source: Los Altos History Museum Collections.

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Figure 31: Rear courtyard of Halsey House in the late 1930s or early 1940s, showing growth of the garden.

Looking slightly northeast. Source: Los Altos History Museum Collections. Courtesy of Katherine Halsey Buss.

Alterations that have occurred since Emma Halsey sold the property in 1945 include alterations to the interior and exterior of the Halsey House, as well as changes to the larger property. At some time during the Busseys’ ownership, the Halsey House was subdivided into two units and rented out.

In 1970, when the property was purchased by Meredith Pearson, each wing of the Halsey House was a separate unit with its own kitchen, and the original living room along the north side of the building was a shared living area for both units.24 A number of interior alterations had been made prior to 1970, including the installation of a second kitchen and the erection of non-historic partitions in the original living room, entrance hall, and the dining room.

Exterior alterations have been established through observation and a review of historic photographs. These alterations have not changed the existing footprint of the building and are largely limited to the replacement of doors and windows. These alterations include:
• Primary (north) façade:
o Two fixed windows flanking a metal frame jalousie window were installed to replace three original eight-lite casement windows
24 Phone conversation between Meredith (Pearson) Phillips and the author on July 22, 2021.

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o Replacement wood frame single-leaf door were installed at the entrance to the 1928 addition
• East façade:
o Two one-over-one double hung windows were installed to replace original threeover-one windows after 2003 (refer to Figure 10) • West façade:
o Single-leaf door was installed at original window location o Brick chimney at the west-facing wall of the northwest addition appears to have been reconstructed with contemporary brick
o Along the south-facing wall of the northwest addition, one original window opening was infilled (frame and sill remain along exterior)
o Along the south-facing wall of the northwest addition, the easternmost window was replaced with a fixed window
• Courtyard façades:
o East-facing façade:
 Original wrought-iron balconette outside French doors was removed and replaced with concrete steps and landing (refer to Figure 30, original balconette visible at far left of photograph)
• Within the courtyard:
o A non-historic concrete patio was installed prior to 198325 o The bowl of the fountain at the south courtyard wall was removed prior to 198326 Several non-original partitions are known to have been constructed within the Halsey House prior to 1970. When the City of Los Altos acquired the property in 1974, some non-historic partitions were removed, and others were installed. A comparison between floor plans of the Halsey House by city staff in 1978 show some of these interior changes (Figure 32 and Figure 33). The installation of the acoustic tile and drop ceilings in the original living room appear to have been undertaken after 1974. 25 Photographs of planting within the courtyard and painting of the building’s courtyard-facing facades in 1983 were provided by Marie Backs to the author. 26 Ibid.

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Figure 32: Floor plan of Halsey
House circa 1974 through
1978, showing partitions in
place at that time. Drawing
dated April 1978. Blue dashed
line shows additional nonhistoric partition wall that is known to have been removed
between 1974 and 1978 by the
City of Los Altos. Red dashed
lines show walls that were
removed circa 1978 (refer to
Figure 33). Source: City of Los
Altos.

Figure 33: Floor plan of Halsey
House, dated April 1978.

Shows proposed floor plan
after the removal of some
partitions (refer to Figure 32).

This floor plan is largely
accurate to the current floor
plan of the building with minor
exceptions. Source: City of Los
Altos.

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Development of the Redwood Grove Landscape and Site
Along with the construction of the Halsey House, in the 1920s the property underwent significant change under the care of Emma Halsey and her gardeners, Mori and Yoshio “Frank” Hongo.27 The eponymous redwoods of Redwood Grove were transplanted as saplings to the site by Emma and Mori from Emma’s paternal grandfather’s property along Summit Road in the Santa Cruz Mountains in the early 1920s.28
The property was extensively landscaped through the planting of the redwoods, a variety of fruit trees – including apple, pear, apricot, cherry, almond, persimmon, and walnut trees – and the establishment of gardens that included ferns, azaleas, camellias, roses, irises, lavender, wisteria, and rhododendrons.29 Many of the flowering plants were located either within the rear courtyard or near the Halsey House, while the larger property remained wooded. The areas directly south and west of the house were planted with fruit trees to create a small orchard (Figure 34).

Figure 34: View of the west façade of the residence showing the small orchard at this location, circa 1924. Looking east. Source: Los Altos History Museum Collections.

Figure 35: Undated photograph
showing one of the small wood
bridges that crossed the creek.

Source: Los Altos History
Museum Collections.
27 Mori is called “Omori” in the oral history with Eugenia Halsey Buss from 2001 but is listed as M. Mori in census records. For the purposes of consistency within this report “Mori” will be used. 28 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 2. 29 Ibid, 4.; Helen Buss Halsey, “Map of the Garden and House,” provided to staff at ARG via email from Katherine Buss, May 2019.

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Other improvements that were made during the Halseys’ residence include the construction of a few small wood bridges that crossed over Adobe Creek, which winds through the property, as well as the construction of benches, the lining of planting areas with stone borders, and the construction of a croquet court that was converted into a fenced tennis court at an unknown date (Figure 35). 30 Figure 36: Sanborn Map Company fire insurance map from 1926 showing the approximate boundary of the Halsey property based on the modern property line and the shape of Adobe Creek, shown with a dashed red line. The property continues to the south and west of the area shown. The Halsey House is circled in red.

Source: San Francisco Public Library. Edited by Page & Turnbull. 30 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 4.

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Historic photographs of the property show a wood-frame garage building that may have been the automobile garage (no longer extant) located slightly southeast of the residence on the Sanborn Map Company map of 1926 and 1932. The other buildings shown on the 1926 map include the caretaker’s cottage (extant though altered), a small dwelling to the west of the Halsey House that may have been used as a cottage for guests (no longer extant), two small buildings with an unidentified use (no longer extant), and an additional garage building (no longer extant) located near the caretaker’s cottage (Figure 36).
31 The caretaker’s cottage survives today but has been altered through at least two additions, the replacement of its windows and doors, and other alterations to its original design. An evaluation of the caretaker’s cottage is outside the scope of this report.

Figure 37: 1963 aerial photograph. Red circle shows location of Halsey House; blue circle shows the location of the extant caretaker’s cottage; yellow dashed line shows the access road from University Avenue. Flight: CASSCL, Frame: 5-37. Source: UC Santa Barbara, Frame Finder. Edited by Page & Turnbull.

Significant changes to the landscape occurred during the ownership of the Besseys from 1945 until 1970. The Besseys constructed between six and ten additional cottages on the property to meet the 31 Mention of the additional cottage is limited to an annotation on a map of the house and garden as drawn by Helen Buss Halsey. On this hand drawn map, a “small cottage where Aunt Carrie stayed” is marked as having been located west of the Halsey House. Helen Buss Halsey, “Map of the Garden and House,” provided to staff at ARG via email from Katherine Buss, May 2019.; Due to the inaccuracy of distances in Sanborn maps and that the property line as shown has been approximated based on the modern property line and the shape of Adobe Creek, the second garage building may be improperly located on the map and associated with the residence located just north of the property line.

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needs of the post-World War II housing shortage.32 Some of these structures are visible in a 1963 aerial photograph of the property (Figure 37).

At the time of Meredith Pearson’s purchase of the Redwood Grove and Halsey House, these various cottages and buildings were extant. During the city’s ownership of the property and as part of the Redwood Grove’s conversion to a public park, the additional cottages constructed by Bessey were removed and only the Halsey House and the caretaker’s cottage were retained.

Today, few of the original plantings by Emma Halsey, Mori, and Yoshio Hongo survive, with the exception of the redwood trees planted in the early 1920s. Some individual specimens of fruit trees, flowering trees, and other plants may survive, but the overall impact of the formal landscape has been obscured through the alterations to the property since 1945.

Ownership and Occupancy History
The following tables provide a summary of the ownership and occupancy history of the Halsey House beginning with the year of construction of the residence in 1923. This does not include the purchase of the property in 1912 by William and Myra Wright, or the transfer of ownership between the Wrights and the Halseys in 1915, which predate the construction of the Halsey House.

The owner and occupancy histories were compiled from newspaper articles, city directories, oral histories, and existing documentation for the Halsey House. The County of Santa Clara Office of the Assessor was closed to researchers at the time of this report, and a full history of the deeds of the property was not completed at this time.
32 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 18. 33 The Bessey family are named as the purchasers of the property in all written and oral histories of the Halsey House. Bessey appears to refer to Edward Cushing Bessey and his wife Rachel Miller Shaw Bessey. As the Assessor’s office was closed at the time of this report, Page & Turnbull was unable to verify these names through the property’s deed records.

Table 2. Owner History for the Halsey House
Date(s) Owner(s) Occupation
1923-1943 Theodore Vail Halsey
Emma Wright Halsey
Executive, SF Pacific Telephone & Telegraph Company
Housewife
1943-1945 Emma Wright Halsey
1945-1970
Edward C. Bessey33
Rachel M. S. Bessey
1970-1974 Meredith Pearson
1974-present City of Los Altos

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Theodore and Emma Halsey received the property as a wedding gift in 1915 from Emma’s parents.

As described previously (refer to the section, Site Development, above), the property was used as a summer home by the Halseys and the Wrights prior to the construction of the Halsey House in 1923.

In 1923, the Halseys moved to Los Altos permanently with their two children, Theodore Vail, Jr. and Myra Eugenia (who went by Eugenia as an adult).
34 As stated previously, Mori is spelled “Omori” in the transcribed oral history with Eugenia Halsey Buss from 2001 but is listed as M. Mori in census records. For the purposes of consistency within this report “Mori” will be used. Exact dates of Mori’s residence at Halsey House or on the larger property are unknown, but it is likely that he resided on the property from the early 1920s through the mid- to late-1930s. 35 Myra Halsey married in 1939 and was not living at the Halsey House by 1940. 36 Email correspondence between Meredith Phillips and Marie Backs, supplied to the author by Phillips on July 22, 2021.; Phone conversation between Meredith (Pearson) Phillips and the author on July 22, 2021. Other family members residing at the property during this period prefer to remain unnamed. 37 Ibid.

Table 3. Occupant History for the Halsey House
Date(s) Occupant(s) Occupation
1923-1928
Theodore Vail Halsey
Emma Wright Halsey
Myra Eugenia Halsey (later Buss)
Theodore Vail Halsey, Jr.

Mori34
Executive, SF Pacific Telephone & Telegraph Company
Housewife
Student
Student
Gardener
1928-1943
Theodore Vail Halsey
Emma Wright Halsey
Myra E. Halsey (1928-1939)35
Theodore Vail Halsey, Jr.

Myra E. Wright
Mori (1930)
Katie Laetinen (1930)
Vivian Peterson (1940)
Executive, telephone company (various)
Housewife
Student
Student
None
Gardener
Cook
Maid
1943-1945 Emma Wright Halsey
Myra E. Wright
None
None
1945-1970 Unknown [various renters] N/A
Summer 1970
Meredith Pearson
[Pearson family and various
renters]36
Unknown
1970–1974 [Pearson family and various
renters]37 Unknown

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The Halseys’ gardener Mori, a Japanese immigrant who arrived in the United States in 1913, was also a resident on the property in the early 1920s through at least 1930. 38 Mori assisted Emma in the
planting of the redwood saplings and the general landscaping of the Halsey property.

In 1928, the Halseys were joined by Emma’s mother, Myra Wright, following the death of Emma’s father. At the time of the 1930 Federal Census, both Mori and a maid, Katie Laetinen, were listed at the Halsey residence in addition to the Halseys and Myra Wright. 39 It is unclear whether Mori was
residing in the caretaker’s cottage, as suggested in the oral history, as neither Mori nor Katie Laetinen were listed under a separate dwelling number.40 By the time of the 1940 Federal Census, Mori had left the United States to return to Japan and a new gardener, Yoshio (Frank) Hongo, had been hired to work with Emma at the Halsey property.41 According to the 2001 oral history with Eugenia Halsey Buss, Mori and Yoshio were well acquainted – Yoshio was a gardener at another Los Altos property – and Mori recommended Yoshio to be his replacement.42
Yoshio and his wife, Takiyo, lived in the caretaker’s cottage with their four children: Yuta, Fumiye, Kazuye, and Hisaye.43 Yoshio immigrated from Japan in 1912 and returned to Japan to marry Takiyo in 1918. 44 Takiyo came to the United States in 1919. Their four children were born in California. In 1942, the Hongo family was sent to Heart Mountain Relocation Center in Wyoming due to the forced internment of Japanese Americans under Executive Order 9066, issued in February 1942.

In 1943, Theodore Halsey passed away. From 1943 until 1945, Emma Halsey and Myra Wright lived at the Halsey House until it was sold to the Bessey family in 1945.45 38 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 1.; United States Federal Census, Santa Clara County, Fremont Township, Precinct 1, 1930. 39 United States Federal Census, Santa Clara County, Fremont Township, Precinct 1, 1930. 40 As neither was listed under a separate “dwelling number” within the census records, both have been included in the occupancy table above. The 2001 oral history implies that Mori resided in the caretaker’s cottage, which was then “fixed up” for the Hongo family.
41 Yoshio Hongo went by Frank Hongo and is referred to as Frank within the Eugenia Halsey Buss oral history. “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 3-4. 42 Ibid.; United States Federal Census, Santa Clara County, Fremont Township, 1930. Yoshio was listed as a gardener in Los Altos in the 1930 census.
43 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program, 3-4. 44 “Petition for Naturalization, Yoshio Hongo,” July 1953, Accessed via Ancestry.com. 45 Emma Halsey and Myra Wright moved to Palo Alto in 1945.

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The Bessey family appears to refer to Edward C. Bessey and Rachel Miller Shaw Bessey. 46 The
Besseys do not appear to have ever resided at the subject property and purchased it as a rental property and development opportunity. Prior to moving to the San Francisco Bay Area, the Besseys resided in San Diego, and Edward Bessey was employed as a pilot for the Trans Ocean airlines. 47 In
1949, Bessey force landed a passenger plane in the Atlantic Ocean just beyond the Shannon, Ireland Airport.48 During the news coverage of this incident, including the subsequent libel suit brought by Bessey against the airline, Edward Bessey’s address was listed variously as Westersfield, Connecticut and Los Altos, California. It appears that Bessey left the airline industry and became an automobile salesman in San Jose in the 1950s and transitioned into real estate by 1962.49 The Besseys lived in San Jose, Palo Alto, Mountain View, Los Altos, and Los Altos Hills, but are not known to have ever resided at the Halsey House.

During the Besseys’ ownership, the Halsey house was subdivided into two units and several cottages (numbering from six to ten) were constructed on the property in the postwar period and rented out.

The identities of individuals who resided at the property during this period have not been identified.50
In 1970, the property was purchased by Meredith Pearson (now Phillips), who briefly resided in the Halsey House during the summer of 1970. Pearson’s intention for the property was both to save the Redwood Grove from possible development, which was proposed by a developer interested in the property, and to establish a property for communal living with family and friends.51 Pearson relocated to Palo Alto in late 1970, but during her ownership of the property, several family members and friends continued to reside at the Halsey House and rented the other buildings on the property.
52 Pearson owned the property until it was sold to the City of Los Altos in 1974.

From 1974 until 2008, the Halsey House was open to the public for various public programs including as a small museum and an educational center. Since 2008, the building has been vacant 46 “Rachel Miller Shaw Bessey,” Los Altos Town Crier, February 8, 2012, Accessed July 27, 2021, https://www.losaltosonline.com/people/obituaries/rachel-miller-shaw-bessey/article_0f19701f-f092-59ac-b987- a91c08119d8c.html
47 City Directories, San Diego and Coronado.; Arriving Passenger and Crew Lists, various, 1947-1949. Accessed via Ancestry.com.
48 The plane had reportedly run out of gas due to a number of mistakes made by the navigator of the flight. “Atlantic Airliner Toll Drops to 8,” The Fresno Bee, August 17, 1949.; “Air Lines Sued for $200,000 by Pilot in Crash,” Oakland Tribune, April 12, 1950.
49 Various city directories from 1952 to 1968, including San Jose, Palo Alto, and Mountain View. 50 City and county directories are unavailable for this period. Initial research was not able to establish the residents of either the cottages (all demolished) or the main house.
51 Email correspondence between Meredith Phillips and Marie Backs, supplied to the author by Phillips on July 22, 2021. 52 Phone conversation between Meredith (Pearson) Phillips and the author on July 22, 2021.

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and closed to the public due to health and safety concerns. Today, the building is boarded up and encircled by fencing in an effort to keep out vandals.

SELECT OWNER AND OCCUPANT BIOGRAPHIES
Theodore Vail Halsey (1873–1943)
Theodore Vail Halsey was born in 1873 in Minnesota. His family moved to California in 1882 and resided in San Jose. Various family members of Theodore Halsey were involved in the development and implementation of the telephone and telegraph systems, and Halsey pursued a career in the telephone and telegraph industries.

For many years, Halsey was an executive of the Pacific Telephone and Telegraph Company of San Francisco and was charged with bribery in a large graft case against telephone company executives.

After a series of guilty verdicts for other executives charged in the case, Halsey was acquitted and was widely believed by the press to have been used as a scapegoat by “higher-ups” in their attempt to escape prosecution.53 The various court cases lasted from 1907 to 1912.

Halsey was an executive of the Telephone Investment Company and was also the first president of the Philippine Long Distance Telephone Company beginning in 1928. Halsey had been involved with introducing and developing the telephone system in the Philippines as early as 1906. Halsey did have a personal office/library within the residence (located in the original northwest corner of the building), however, Halsey family history does not indicate that he held important meetings or used this office to conduct significant business that related to his professional accomplishments.54 In the 1930s, Halsey established Delta Properties Inc. to farm and improve tracts held in the area of the Sacramento–San Joaquin Delta. Halsey was later joined by his son, Theodore Halsey, Jr., in this business venture.

Halsey was married twice. His first marriage, circa 1900, was to Jessie L. Sabin (formerly Mrs.

Stephen Fiddler), who passed away circa 1914.55 In 1915, Theodore Halsey married Emma Wright in 53 “Glass Must Stand Trial,” Oroville Daily Register, July 24, 1912.; “Theo. V. Halsey Will Wed Miss Emma Wright,” The San Francisco Examiner, June 16, 1915. 54 This office/library appears to have been located where the original grouping of three eight-lite casement windows were located. After the construction of the 1928 addition, a hallway led from Myra Wright’s rooms through this office area to reach the living room. General location of Theodore’s office/library is shown on Helen Buss Halsey’s “Map of the Garden and House,” provided to staff at ARG via email from Katherine Buss, May 2019.; recollections of the hallway between the study and Myra’s rooms are related in an email from Katherine Buss to staff at ARG, May 30, 2019. 55 “Theodore V. Halsey Weds [Emma] Minerva Wright,” Oakland Tribune, June 16, 1915.; United States Federal Census, San Francisco County, 1910.

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Los Altos at the subject property. They had two children (refer to Ownership and Occupancy History, above).

Halsey appears to have suffered from poor health for many years. He was hospitalized and believed to be “on his death bed” during his 1907 trial and suffered a stroke in 1936.56 Halsey passed away in 1943.

Emma Minerva Wright Halsey (1880–1975)
Emma Wright was born in 1880 to William H. and Myra E. (née Quinby) Wright. William Wright’s parents were considered California pioneers, who settled in California in 1869 and established a ranch along Summit Road in the Santa Cruz mountains.57 William Wright was president of the San Jose Fruit Packing Company, and later worked as a contractor in the dredging business. Myra Wright was born to the Quinby family, for whom Quinby Road in San Jose is named, and worked as a schoolteacher prior to her marriage to William Wright.58 The Wrights moved to San Francisco in 1900. In 1912, when Emma was in her early 30s, she found the future Halsey House property when her father asked her to locate a property along the Peninsula to serve as the Wrights’ summer home.

In 1915, Emma married Theodore Vail Halsey. No announcement was made of their engagement. 59 Emma was an avid gardener, and the choice to relocate to Los Altos in 1923, with their two young children, gave her the opportunity to garden extensively. As related by Halsey family descendants, the Halseys’ bedroom at Halsey House opened to the courtyard, and Emma was known to rise early and garden in the courtyard before other family members had risen.60 Following Theodore Halsey’s death in 1943, and the forced internment of the Hongo family at Heart Mountain Relocation Center, Emma sold the Halsey House and property. She and her mother moved to Palo Alto. Emma is reported to have found the house and grounds too lonely and isolated for only herself and Myra.
61 Emma Wright Halsey passed away in 1975 in Palo Alto. 56 “Halsey’s Story is ‘Cooked Up,’” The Fresno Morning Republican, October 12, 1907. 57 H.S. Foote, ed., Pen Pictures From The Garden of the World or Santa Clara County, California. Illustrated., (Chicago: The Lewis Publishing Company, 1888), 302. 58 “Mira [sic] Wright was a Pioneer Resident,” Los Gatos Times-Saratoga Observer, October 13, 1944. 59 “Theodore V. Halsey Weds [Emma] Minerva Wright,” Oakland Tribune, June 16, 1915. 60 Email correspondence between Katherine Buss and staff of ARG, May 2019. 61 “Eugenia Halsey Buss Interview, August 23, 2001,” Los Altos History Museum, Oral History Program.

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The Design of the Halsey House
The Halsey House was designed in a modest Spanish Colonial Revival style in 1923 and was expanded with two early additions in 1928 and the 1930s.

Historically rooted in the building traditions of early Spanish and Mexican settlers of California and other Spanish colonies, the Spanish Colonial Revival style was popular in California and the rest of the Southwest from the early 1900s to the 1930s, with variations on the style remaining popular today. Earlier Hispanic Revival styles were rooted in regional interpretations of traditional Spanish, Native American, and Mexican design and construction techniques, which were indigenous to California. Not as ornate as its earlier Mexican prototypes, the Mission Revival style in the 1910s was characterized by low-pitched or flat roofs (often composed of thatch, terracotta tile or tar), thick masonry walls of adobe brick or stucco, multiple doorways, deeply recessed openings with multi-lite windows, arcades/colonnades, sculpted parapets resembling the typical espadaña (belfry), and red clay tile roofs. The Mission Revival style was popular in California and much of the Southwest because it was derived from indigenous prototypes.

By the 1920s, the Mission Revival style in California was joined by the more elaborate Mediterranean and Spanish Colonial Revival styles. Making use of terracotta tile gable roofs, thick masonry walls, plaster finishes, wrought iron grilles, balconies, and smaller fenestration openings, the Spanish Colonial Revival style was popular for commercial buildings, institutions, apartments, and singlefamily residences. In California, the Spanish Colonial Revival style came into prominence after the Panama-California Exposition in San Diego in 1915 and remained popular into the 1930s, when the Great Depression, and then World War II, had a chilling effect on construction.62 The Halsey House illustrates some of the common features of the Spanish Colonial Revival style through its material palette of clay tile roofing, lightly colored stucco cladding, and multi-lite windows and doors with wood sash, but lacks the decorative detailing that is common to the highstyle examples of the Spanish Colonial Revival style. Decorative detailing that is typical of the style generally includes the integration of stucco grilles, the presence of metal features including lamps, window grilles, and balcony railings, an emphasis around primary entrances through the presence of carved wood doors, spiraled columns, carved stonework, or decorative tiles, and the use of unpainted wood elements.
63 As originally designed, the Halsey House incorporated one balconette along the inner courtyard (since removed) and several simple metal lamps that are partially extant. 62 San Francisco Planning Department, San Francisco Preservation Bulletin No. 18 – Residential and Commercial Architectural Periods and Styles in San Francisco (January 2003). 63 Virginia Savage McAlester, A Field Guide to American Houses, Second Edition (New York: Knopf, 2018), 520-534.

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Other decorative elements were limited to the inclusion of the fountain along the south wall of the rear courtyard.

The integration of interior and exterior spaces, as seen at Halsey House through the use of French doors and courtyards, is an element of the Spanish Colonial Revival style but also demonstrates a regional preference for taking advantage of California’s temperate climate. The open design of the Halsey House’s living spaces, emphasizing the relationship of the landscape and the outdoors with the interior, is a vernacular interpretation of the style that was likely a particular request of the Halseys during the design of the building.

Figure 38: Example of the Spanish Colonial Revival
style in Los Altos at 10 Pasa Robles Avenue. Source:

Redfin.com.

Figure 39: St. Nicholas Church in Los Altos, an
example of the Spanish Colonial Revival style.

Source: St. Nicholas Church.

Overall, the Halsey House has a cohesive design that is unified through its limited material palette and its use of numerous multi-lite windows and doors that intimately relate the building to its site.

However, the building is not a high-style example of the Spanish Colonial Revival style. An extensive comparative survey of other local examples of the Spanish Colonial Revival style was not undertaken for this report, but a brief review of the other properties included in the Los Altos HRI identified several other Spanish Colonial Revival style buildings in Los Altos, including six residential properties, two religious properties, and one commercial property (Figure 38 and Figure 39). 64 Of these nine additional properties that are local examples of the Spanish Colonial Revival style, two 64 The other properties listed in the HRI were all constructed in the early decades of the twentieth century, and include: 10 Pasa Robles Avenue, 52 Almond Avenue, 211 Yerba Buena Avenue, 90 Cody Lane (early Los Altos apartment building), 388- 398 Main Street, 571 Cherry Avenue, 566 S. El Monte Road, the Jesuit Retreat House at 662 University Avenue, 350 Main Street, and St. Nicholas Roman Catholic Church at 473 Lincoln Avenue.

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properties were also designated city Historic Landmarks.65 The presence of other local examples of the style illustrates that the Halsey House is not a rare example of the style in Los Altos.

Figure 40: Pettigrew House at 1336 Cowper Street,
Palo Alto. Listed in the National Register in 1980 for
its architecture. Source: Google StreetView.

Figure 41: Dunker House at 420 Maple Street, Palo
Alto. Listed in the National Register in 1982 for its
architecture. Source: National Park Service.

Additionally, within the larger region, the Spanish Colonial Revival style is well represented with high style examples in nearby cities like Palo Alto, Mountain View, Hillsborough, and San Jose (Figure 40 and Figure 41). As such, the Halsey House is a good example of a vernacular interpretation of the Spanish Colonial Revival style but is not a high style or rare example of the style. As the architect or builder of the residence remains unidentified at this time, the Halsey House would not be considered significant for its association with an architect or builder. 65 The two local Historic Landmarks are 388-398 Main Street (commercial, built circa 1909) and 571 Cherry Avenue (residential, built circa 1925).

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VI. EVALUATION
California Register of Historical Resources
The California Register of Historical Resources (California Register) is an inventory of significant architectural, archaeological, and historical resources in the State of California. Resources can be listed in the California Register through a number of methods. State Historical Landmarks and National Register-listed properties are automatically listed in the California Register. Properties can also be nominated to the California Register by local governments, private organizations, or citizens.

The evaluative criteria used by the California Register for determining eligibility are closely based on those developed by the National Park Service for the National Register of Historic Places.

In order for a property to be eligible for listing in the California Register, it must be found significant under one or more of the following criteria.
• Criterion 1 (Events): Resources that are associated with events that have made a significant contribution to the broad patterns of local or regional history, or the cultural heritage of California or the United States.
• Criterion 2 (Persons): Resources that are associated with the lives of persons important to local, California, or national history.
• Criterion 3 (Architecture): Resources that embody the distinctive characteristics of a type, period, region, or method of construction, or represent the work of a master, or possess high artistic values.
• Criterion 4 (Information Potential): Resources or sites that have yielded or have the potential to yield information important to the prehistory or history of the local area, California, or the nation.

The following section examines the eligibility of the Halsey House for individual listing in the California Register.

CRITERION 1 (EVENTS)
The site of the Halsey House and the Redwood Grove was first developed in 1912 with a summer cottage to provide a sunny summer retreat for the Wright family when they sought to escape the fog of San Francisco. This was a typical use of early residential properties in the Los Altos area and along the Peninsula.

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In the 1920s, as schools, businesses, and institutions were adequately developed to support the year-round living of middle- and upper-class residents who were looking to move out of San Francisco, the property at Redwood Grove became an appealing location for the Halsey family to settle permanently. In 1923, the previous summer cottage was demolished and the Halsey House was constructed. The young Halsey children attended nearby schools, and the well-established commuter train allowed Theodore Halsey to easily travel to and from his office in San Francisco.

Emma Halsey was most involved with the development of the property itself, and established the gardens, orchards, and redwood grove. Emma’s gardening and landscaping at the Halsey House, with the assistance of her Japanese gardeners, Mori and Yoshio (Frank) Hongo, reflected the increasing residential use of the area but retained the rural feeling of the many orchards that still characterized Los Altos in the early twentieth century.

Many of the residences that were established in Los Altos during this period were located in the University/Orange area and developed as freestanding single-family homes that faced the street on small parcels of land. The Halsey House and property was developed in 1923 in the style of a more rural property and was sited to complement the existing topography, creek, and trees, including several mature oaks. Today, the property remains a rare example of an early Los Altos summer retreat that was developed into a permanent residential property at a time when Los Altos saw considerable growth in year-round residential properties. Although the Halsey House was developed as a permanent residence, it retained its rural character through the interests of its owners and the planting of many redwood trees that today define Redwood Grove Park. While most of the landscape planted by Emma, Mori, and Yoshio – including the many fruit trees and flowering plants surrounding the residence and within the rear courtyard – is no longer extant, the surviving oak trees, numerous redwoods, and the presence of Adobe Creek remain and convey the historic setting of the residence.

The Halsey House and the Redwood Grove is an excellent example of early residential patterns of Los Altos, and the establishment of Redwood Grove is a unique property developed by Emma Halsey and her Japanese gardeners in the 1920s. Therefore, the Halsey House and the Redwood Grove appear to be individually eligible for the California Register under Criterion 1 (Events), with a period of significance from the construction of the Halsey House in 1923 through the end of Emma Halsey’s ownership of the property in 1945.

CRITERION 2 (PERSONS)
The Halsey House was constructed for Theodore and Emma Halsey in 1923 to serve as their permanent family home in Los Altos. Theodore lived at the house until his death in 1943, and Emma sold the house and property two years later in 1945. She passed away in the 1970s while residing in

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Palo Alto. Following the Halseys’ ownership, the property was owned by Edward and Rachel Bessey, who rented the property to a number of currently unidentified residents. The house was briefly owner-occupied for a period of a few months in 1970 by Meredith Pearson. Since the property was purchased by the city in 1974, it has been used as a museum and educational center, but was closed to the public in 2008 and has been vacant since that date.

Theodore Vail Halsey, Sr. had a successful career in the telephone industry and held executive positions at the Pacific Telephone & Telegraph Company, the Telephone Investment Company, and the Philippine Long Distance Telephone Company (PLDT). These professional accomplishments, however, are more closely associated with the locations of Halsey’s work, particularly with regard to the PLDT’s work in the Philippines, and not his family home. While he had a personal office/library within the residence (located in the original northwest corner of the building), research has not indicated that Halsey entertained professional colleagues, or held important business meetings at the Halsey House that would identify it as significant in relation to Theodore Halsey’s professional accomplishments. Therefore, the Halsey House is not significant for its associate with Theodore Halsey under Criterion 2.

Emma Wright Halsey is the individual most closely associated with the subject building and the property, as she first located the property for her parents to purchase in 1912, was married on the property in 1915, lived at the Halsey House from 1923 to 1945, and transformed the site through her gardening work with the assistance of gardeners Mori and Yoshio Hongo. Little is known about the personal accomplishments of Emma Halsey beyond her gardening at the Halsey House. Research has not identified Emma Halsey as a gardener or landscape designer of any additional properties beyond her own, and the Halsey House and Redwood Grove would therefore not be considered as part of a larger body of work. Thus, Emma Halsey’s contributions to the Halsey House are tied to the development of the property itself and the accomplishment of creating the Redwood Grove, which is more clearly represented through Criterion 1 (Events). She did not otherwise contribute to local, state, or national history such that she should be considered a historically significant person. The Halsey House and landscape are not individually eligible for their association with Emma Halsey under Criterion 2.

The Halsey House and Redwood Grove are also related to the professional careers of both Mori and Yoshio Hongo, who were employed as gardeners by Emma and Theodore Halsey and resided on the property during their periods of employment. Both Mori and Yoshio were born in Japan and immigrated to the United States where they found work as orchard farmers and gardeners. Mori was hired by the Halseys in the early 1920s and was involved in the initial planting of the redwoods on the property and the early landscaping of the property. Mori retired in the 1930s and recommended Yoshio “Frank” Hongo as his replacement. Yoshio, who was already employed as a

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gardener in Los Altos, had also previously worked in the fruit orchards of the Los Altos area. Yoshio and his family resided in the caretaker’s cottage until 1942, when they were forcibly relocated by the United States Government to Heart Mountain Relocation Center in Wyoming. Both men played important roles in the creation and maintenance of Redwood Grove, but their individual contributions to the creation of the property do not rise to a level of importance such that they would be considered significant at the local, state, or national level for the property to be eligible under Criterion 2 for its association with either man as an individual. Much like Emma Halsey, their contributions to the property are better represented through Criterion 1 (Events).

Aside from the Halsey family, later owners of the Halsey House lived at the residence either only briefly or not at all, and are therefore not significantly associated with the house such that it would be significant for their personal or professional accomplishments. The other occupants of the Halsey House, from 1945 until 1974, rented the property for unknown periods of time, and their identities are largely unknown. Archival research did not uncover any significant personal achievements connected with the subject building.

Therefore, the Halsey House does not appear to be eligible for the California Register under Criterion 2 (Persons).

CRITERION 3 (DESIGN/ARCHITECTURE)
The Halsey House was constructed in 1923 and was designed by an unknown architect. The building was expanded through two early additions, including a 1928 addition to the northwest corner of the building and the extension of the east wing at an unknown date, possibly in the early 1930s. Both additions were designed to blend with the existing style and design of the building and matched the exterior finish, clay tile roofing, and existing wood sash multi-lite windows and doors of the 1923 residence. The building was designed in a modest Spanish Colonial Revival style and demonstrates characteristics of the style through its stucco cladding, hipped clay tile roof, low one-story massing arranged around a private courtyard with bench seating and a fountain, and extensive use of multilite windows and doors. Detailing is largely limited to the scored and tinted cement patios, stone paving of the courtyard, and some metal features, including original door and lamp fixtures. Overall, the building lacks the decorative features that are typical of both modest and high-style examples of the style, such as decorative plasterwork, tile, or exposed wood elements. The Halsey House is not the only example of the Spanish Colonial Revival style in Los Altos, and nine other properties designed in the Spanish Colonial Revival style are listed in the Los Altos HRI. Therefore, the Halsey House would not be considered a rare example. Additionally, within the larger region of the San Francisco Peninsula and South Bay, the Spanish Colonial Revival style is well represented, with fine examples in nearby cities like Palo Alto, Mountain View, Hillsborough, and San Jose.

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As such, the Halsey House is an example of a simple interpretation of the Spanish Colonial Revival style but is not a high style or rare example of the style such that it would be individually significant for its architecture. It does not represent distinctive methods of construction or craftsmanship. As the architect or builder of the residence remains unidentified, the Halsey House is not considered significant for its association with a master architect or builder. Therefore, the Halsey House does not appear to be eligible for the California Register under Criterion 3 (Design/Architecture).

The residence was initially set within a planned landscape of flowering plants, hedges, ferns, and fruit trees, with built landscape elements including stone-lined planting beds, wood benches, and wood bridges over Adobe Creek, which was developed by Emma Halsey with her gardeners. While the oak trees, redwoods, and Adobe Creek survive today and characterize the setting of the Halsey House, the majority of the designed plantings of the landscape have been removed since Emma Halsey sold the property in 1945. Therefore, the landscape of the Halsey House would not be considered significant as a formally designed landscape designed by Emma Halsey. The Redwood Grove as a natural landscape is therefore more clearly significant under Criterion 1 (Events) and would not be considered individually significant under Criterion 3 for its landscape design.

CRITERION 4 (INFORMATION POTENTIAL)
The “potential to yield information important to the prehistory or history of California” typically relates to archeological resources, rather than built resources.66 When California Register Criterion 4 (Information Potential) does relate to built resources, it is relevant for cases when the building itself is the principal source of important construction-related information. The analysis of the Halsey House for eligibility under Criterion 4 is beyond the scope of this report.

Integrity
In order to qualify for listing in any local, state, or national historic register, a property or landscape must possess significance under at least one evaluative criterion as described above and retain integrity. Integrity is defined by the California Office of Historic Preservation as “the authenticity of an historical resource’s physical identity evidenced by the survival of characteristics that existed during the resource’s period of significance,” or more simply defined by the National Park Service as “the ability of a property to convey its significance.”67 66 California State Office of Historic Preservation. Technical Assistance Bulletin No. 7: How to Nominate a Resource to the California Register of Historical Resources. Sacramento: California Office of State Publishing, (September 4, 2001), 11. 67 Ibid.

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In order to evaluate whether the subject property retains sufficient integrity to convey its historic significance, Page & Turnbull used established integrity standards outlined by the National Register Bulletin 15: How to Apply the National Register Criteria for Evaluation. Seven variables, or aspects, that define integrity are used to evaluate a resource’s integrity—location, setting, design, materials, workmanship, feeling, and association.68 A property must possess most, or all, of these aspects in order to retain overall integrity. If a property does not retain integrity, it can no longer convey its significance and is therefore not eligible for listing in local, state, or national registers.

The seven aspects that define integrity are defined as follows:

Location is the place where the historic property was constructed or the place where the historic event occurred;
Setting addresses the physical environment of the historic property inclusive of the landscape and spatial relationships of the building(s); Design is the combination of elements that create the form, plan, space, structure, and style of the property;
Materials refer to the physical elements that were combined or deposited during a particular period of time and in a particular pattern or configuration to form the historic property; Workmanship is the physical evidence of the crafts of a particular culture or people during any given period in history or prehistory;
Feeling is the property’s expression of the aesthetic or historic sense of a particular period of time; and
Association is the direct link between an important historic event or person and the historic property.

LOCATION
The Halsey House and property retains integrity of location. The building has remained situated at its location of original construction since 1923 and the overall property has retained its location and its approximate size.
68 U.S. Department of the Interior, National Park Service, National Register Bulletin 15: How to Apply the National Register Criteria for Evaluation (Washington, D.C.: National Park Service, 1995), 44.

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SETTING
The Halsey House retains integrity of setting. The building was erected within a large, six-acre piece of land and was sited to take advantage of the landscape and the curve of Adobe Creek. Early in the property’s history, Emma Halsey and Mori, her gardener, planted many redwood saplings to complement the existing oak trees on the property. The landscaping work by Emma was continued into the early 1940s with the assistance of Yoshio Hongo, following Mori’s retirement. These redwoods remain today and have grown to maturity. The Halsey House therefore retains its wooded and natural setting.

DESIGN
The Halsey House retains integrity of design. The building has undergone several alterations to both its exterior and interior; however, it retains its overall form, massing, and materials and is recognizable as a modest example of a 1920s Spanish Colonial Revival style residence. The building retains its one-story form organized around a private rear courtyard, and its use of stucco cladding and clay-tile hipped roofs demonstrate the typical materials of the style. While lacking the more ornate features of the style including decorative plasterwork, tile, and exposed wood elements, the building features a large number of multi-lite windows and French doors that illustrate the porous relationship between the interior and exterior spaces of the building. Alterations to the massing and footprint of the building were undertaken during the ownership of the Halsey family and are considered historic. The original design of the building remains intact, and the materials, decoration, craftsmanship, and massing of the building have remained largely unchanged with the exception of some replacement windows and doors since 1945, when Emma Halsey sold the property. Therefore, the building retains integrity of design.

MATERIALS
The Halsey House retains integrity of materials. While the condition of the building is currently poor, the Halsey House does retain a high degree of original materials including its stucco cladding, clay tile roof, multi-lite windows and doors, and some metal features including original hardware and portions of lighting fixtures. Other features that remain include the rear courtyard wall with its fountain, benches, and round-arched door, the stone patio within the courtyard, stone semi-circular steps outside the rear courtyard door, and the tinted concrete patios along the entrance porch, north façade, and rear courtyard.

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WORKMANSHIP
The Halsey House retains integrity of workmanship. The Halsey House is a wood-frame building with stucco cladding and a clay tile hipped roof. The building is modest, with few decorative details, and the workmanship of the building is most clearly demonstrated through the simplicity of its detailing that provides a unified feeling to the design of the building. The consistent stucco cladding and clay tile roofing, the presence of multi-lite wood sash windows and doors, and the detailing of the scored and tinted concrete patios and metal features, including original door and lamp fixtures, demonstrate the workmanship of this 1920s residence.

FEELING
The Halsey House retains integrity of feeling. The building retains the feeling of an early 1920s residence that was intended to serve as a year-round home for the Halsey family and was set within a wooded, lush landscape along Adobe Creek. The property retains its semi-rural feeling through its wooded setting that is removed from the main public right-of-way on University Avenue.

ASSOCIATION
The Halsey House retains integrity of association. The building is significant for its residential development history and the development of Redwood Grove in the early 1920s by Emma Halsey and Mori. These associations continue to be represented through the retention of the residence’s architectural characteristics that date to the time of Emma Halsey’s period of residence and the retention of the property’s landscape and the redwood trees that were transplanted to the site by Emma and Mori in the early 1920s.

Therefore, the Halsey House retains all seven aspects of integrity such that it conveys its significance under Criterion 1 (Events) of the California Register, with a period of significance from 1929-1945.

Character-Defining Features
For a property to be eligible for national or state designation under criteria related to type, period, or method of construction, the essential physical features (or character-defining features) that enable the property to convey its historic identity must be evident. These distinctive characterdefining features are the physical traits that commonly recur in property types and/or architectural styles. To be eligible, a property must clearly contain enough of those characteristics to be considered a true representative of a particular type, period, or method of construction, and these features must also retain a sufficient degree of integrity. Characteristics can be expressed in terms such as form, proportion, structure, plan, style, or materials.

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The character-defining features of the Halsey House consist of those features which date to the building’s period of significance from 1923 to 1945 under Criterion 1, for the Halsey House as an excellent example of the changing residential development of Los Altos and for its direct connection to the establishment of the wooded property that is now Redwood Grove Park. The characterdefining features of the Halsey House include the original features, materials, and design elements of the building and landscape as completed in 1923 and any alterations undertaken during Emma Halsey’s period of residence, which ended when she sold the property in 1945. These features include, but are not limited to:

EXTERIOR FEATURES OF THE HALSEY HOUSE
• Overall form and massing of the building (low, horizontal emphasis) • Clay tile clad hipped roof
• Stucco cladding along exterior with a textured finish • Original multi-lite wood sash windows, including three-over-one double-hung windows with ogee lugs, four-lite wood casement windows, six-lite wood casement windows, and six-lite wood sash slider windows
• Multi-light glazed French doors
• Multi-light sidelights flanking doors at the entrance porch and along south-facing wall of rear courtyard
• Tinted and stamped concrete at front entry porch and terrace • Enclosed rear courtyard with tinted and stamped concrete patio at north end, built-in bench seating, fountain, and stone patio with steps at south end, and concrete stairs and metal railing at south end of west wing
• Original chimney with stucco cladding along south-facing wall of courtyard • South courtyard wall with round arched wood plank door • Semi-circular stone stairs along exterior of courtyard door in south courtyard wall • Extant original metal fixtures including portions of original lamps and original door hardware at primary entrance

INTERIOR FEATURES OF THE HALSEY HOUSE
• Original brick and tile fireplaces
• Original wood floors
• Plaster walls and ceilings
• Original wood panel doors
• Original hardware and wood trim of doors and windows
• Original wood baseboards and picture molding

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SITE
• Residence located deep within the approximately six-acre parcel and not visible from University Avenue
• Natural setting including:
o Mature redwood trees
o Mature oak trees
o Adobe Creek
• Additional fruit trees, flowering trees, and plantings that appear to date from the period of significance
Los Altos Historic Landmark and Historic Resource Criteria The City of Los Altos has adopted a similar evaluation framework for the evaluation of historic resources as the California Register and the National Register. For a property to be a historic resource, it must be over fifty years of age, retain its physical integrity, and have historical significance related to historic events, persons, architecture and design, or archaeological significance.69 These four areas of significance are nearly identical to the California Register’s Criteria 1 through 4.

In order to be a City of Los Altos Historic Landmark, the resource must additionally have either a heightened level of significance or be a rare example of its type.

Halsey House as a Designated Historic Landmark
As discussed previously (refer to Existing Historic Status), the Halsey House and the Redwood Grove property is a designated Historic Landmark. The property was first listed in 1981, and subsequent architectural surveys have established that the residence was identified as significant for its association with the Halsey family and as a good example of the Spanish Colonial Revival style, and that the Redwood Grove is considered a unique natural landscape of Los Altos. Due to the existing condition of the building and the length of time since the Halsey House was previously evaluated, Page & Turnbull was asked to reevaluate the Halsey House to determine if it remains a Los Altos Historic Landmark.

As mentioned earlier, in 2012, the HRI was revised and the criteria for evaluation were aligned with the existing evaluation criteria for both the National Register and California Register. Today, a historic resource for the City of Los Altos is determined through establishing that it meets the age 69 CIRCA: Historic Property Development, City of Los Altos Historic Resource Inventory, (October 2012), I-13.

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threshold of fifty years, retains its physical integrity, and meets one or more of the criteria for historic significance.70
The Halsey House is nearly a century old at the time of this report and meets the age threshold as a historic resource. In addition, while the condition of the building is poor overall due to environmental damage and vandalism, the building retains over 50 percent of its original materials, form, and character-defining features, which is the threshold for physical integrity as established in the Los Altos HRI.71 Overall, as discussed in the previous section (refer to Integrity), the Halsey House retains a high level of integrity such that it continues to meet the requirements for listing as a Historic Landmark. Lastly, as discussed above in the California Register evaluation section, the Halsey House is significant in association with important local events.

As stated by the Los Altos Preservation Ordinance, in order to be a Historic Landmark, a resource must also possess “special historical, cultural, archeological, scientific, architectural or aesthetic interest or value as part of the heritage or history of the city, the county, the state or the nation.” 72 While the specific criterion for significance that is discussed within this report (association with important patterns of local development) differs from the previously identified criteria for significance (an association with persons and rare architectural design), the property clearly continues to represent a rare or unique property. The writing of a property-specific Historic Resource Evaluation, in contrast to the previous findings that were documented as part of a larger architectural survey, allowed for in-depth study of the resource that uncovered additional information. This targeted study supports a more nuanced narrative of the building and property’s development and incorporates the individual actions of Emma Halsey as an aspect of that significance. The Halsey House and Redwood Grove continue to express a special historical and aesthetic value to the City of Los Altos through its unique development and setting, and therefore the building and the larger property of the Redwood Grove continues to meet the requirements for listing as a City of Los Altos Historic Landmark.

Halsey House as a Contributor to a Possible Historic District The Halsey House was identified as a possible contributor to the University/Orange Historic District during the 1990 architectural survey. This district has never been formally adopted and Page & Turnbull recommends an updated survey of the proposed historic district to determine whether renovations, rehabilitations, and new construction since the 2012 revised HRI was issued have impacted the overall physical integrity of the possible district. 70 Ibid., I-11 to I-14. 71 Ibid., I-12. 72 Los Altos Municipal Code, Chapter 12.44 – Historic Preservation. Article 2. 12.44.070 - Historic landmark designation.

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From an initial review of the possible University/Orange Historic District, Page & Turnbull believes that the Halsey House does not fit the overall character of the potential historic district. The characteristics of the possible historic district include: a unified street layout with alleyways, continuity of the overall streetscape despite a large variety of lot size and scale, a period of construction from 1908 to 1930, and a significant number of architect-designed residences that are representative of the typical styles of the period.73 While constructed within the period of development of the possible district, the other characteristics that identify the Halsey House and Redwood Grove as a unique property that meets the criteria as a local landmark and California Register-eligible property, are some of the same characteristics that identify it as distinct from the typical patterns of the University/Orange Historic District. The Halsey House and Redwood Grove has a unique wooded and semi-rural setting that is far removed from the street, and while constructed for an upper-class family, the residence lacks the architectural pedigree of many of the other architect-designed residences of the potential historic district. Therefore, it does not appear to be a potential contributor to the possible historic district. 73 Ibid., II-6 to II-7.

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VII. CONCLUSION
The Halsey House was erected in 1923 as a single-family residence for Theodore and Emma Halsey by an unknown architect or builder. Located on a large, approximately six-acre, parcel of land, the Halsey House is set within a wooded landscape along Adobe Creek. The building was constructed in a modest Spanish Colonial Revival style that consists of a one-story building arranged around a rear courtyard. The building features stucco cladding, a clay tile hipped roof, and a large number of multilite windows and doors that create a porous relationship between the interior of the residence and the exterior landscape of the Redwood Grove and the rear courtyard.

Page & Turnbull found the Halsey House and Redwood Grove eligible for the California Register under Criterion 1 (Events) at the state level of significance as an excellent example of the residential development patterns of Los Altos and for the establishment of the Redwood Grove, which is a unique property developed initially by Emma Halsey and her Japanese gardener, Mori, in the early 1920s. Under Criterion 1, the building and property have a period of significance from 1923 to 1945, beginning with the construction of the residence and ending with the sale of the property by Emma Halsey. Page & Turnbull did not find the property significant under Criterion 2 (Persons), Criterion 3 (Design/Architecture), or Criterion 4 (Information Potential). The building retains a high level of integrity as many of the original materials and design features are extant, and the form and massing of the building have remained largely unchanged despite interior alterations and the replacement of some doors and windows. While a large portion of the planned landscape and courtyard garden have been lost, the property retains its unique wooded setting that was developed in the early 1920s.

The subject building and the larger property of Redwood Grove Park have been a listed Los Altos Historic Landmark since 1981 and continue to retain adequate physical integrity to remain a listed Historic Landmark Resources despite the recent deterioration caused by vandalism and environmental conditions.

Therefore, the Halsey House and Redwood Grove is a historic resource, both as a listed local Historic Landmark, and as an individual resource that is eligible for listing on the California Register under Criterion 1.

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VIII. REFERENCES
Published Works & Reports
Archibald, Robert. “Indian Labor at the California Missions.” The Journal of San Diego History. Spring 1978, v. 24, no. 2. Accessed July 2020, https://sandiegohistory.org/journal/1978/april/labor/ Architectural Resources Group. Halsey House Historic Structures Report. Prepared for the City of Los Altos, November 2019.

California State Office of Historic Preservation. Built Environment Resource Directory (BERD). Santa Clara County, updated March 2020.

California State Office of Historic Preservation. “California Historical Resource Status Codes.” updated March 2020
California State Office of Historic Preservation. Technical Assistance Bulletin No. 7: How to Nominate a Resource to the California Register of Historical Resources. Sacramento: California Office of State Publishing, September 4, 2001.

California State Office of Historic Preservation. Technical Assistance Bulletin No. 8: User’s Guide to the California Historical Resource Status Codes & Historic Resources Inventory Directory. Sacramento:

California Office of State Publishing. November 2004. Accessed October 22, 2018, http://ohp.parks.ca.gov/pages/1069/files/tab8.pdf.

Circa: Historic Property Development, City of Los Altos Historic Resource Inventory, (October 2012) Eastman, Shirley. “History of the Los Altos Area.” in Memories of Los Altos. Joe Salameda (ed.). Los Altos: Los Altos Historical Association, 1982.

Foote, H.S. (ed.). Pen Pictures From The Garden of the World or Santa Clara County, California.

Illustrated. Chicago: The Lewis Publishing Company, 1888.

National Park Service, National Register Bulletin 15: How to Apply the National Register Criteria for Evaluation. Washington, D.C.: National Park Service, 1995.

San Francisco Planning Department. Preservation Bulletin 18: Residential and Commercial Architectural Periods and Styles in San Francisco. Accessed May 12, 2021, https://sfplanning.org/sites/default/files/documents/preserv/bulletins/HistPres_Bulletin_18.P DF
Savage McAlester, Virginia. A Field Guide to American Houses. Second Edition. New York: Knopf, 2018.

Wollenberg, Charles. Golden Gate Metropolis: Perspectives on Bay Area History. Berkeley, California:

Institute of Governmental Studies, University of California, Berkeley, 1985.

Newspapers & Periodicals
“Air Lines Sued for $200,000 by Pilot in Crash,” Oakland Tribune, April 12, 1950. “Atlantic Airliner Toll Drops to 8,” The Fresno Bee, August 17, 1949.

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Chapman, Robin. “Santa Clara Valley Lives: Revisit the Story of the Halsey House and its Pioneering Owners.” Los Altos Town Crier. March 14, 2018.
“Glass Must Stand Trial,” Oroville Daily Register, July 24, 1912. “Halsey’s Story is ‘Cooked Up,’” The Fresno Morning Republican, October 12, 1907. “Mira [sic] Wright was a Pioneer Resident,” Los Gatos Times-Saratoga Observer, October 13, 1944. “Rachel Miller Shaw Bessey,” Los Altos Town Crier, February 8, 2012, Accessed July 27, 2021, https://www.losaltosonline.com/people/obituaries/rachel-miller-shawbessey/article_0f19701f-f092-59ac-b987-a91c08119d8c.html “Theo. V. Halsey Will Wed Miss Emma Wright,” The San Francisco Examiner, June 16, 1915. “Theodore V. Halsey Weds [Emma] Minerva Wright,” Oakland Tribune, June 16, 1915.

Public Records
Circa: Historic Property Development. “Halsey House (Redwood Grove Park). State of California DPR 523A and 523B forms. Completed March 2009.

Los Altos Municipal Code. Chapter 12.44 – Historic Preservation.

United States Federal Census. 1900, 1920, 1930, 1940. Available via Ancestry.com.

Archival Records
Ancestry.com
Backs, Marie. Photographs, plans, and material in personal collection.

City and County Directories. Various cities and counties. Available via Ancestry.com.

City of Los Altos. “Halsey House.” Plans, photographs, and files. “Eugenia Halsey Buss Interview, August 23, 2001.” Transcribed interview of Eugenia Halsey Buss (and Robert Buss) by Don McDonald, Los Altos History Museum, Oral History Program.

Los Altos History Museum. “Halsey House.” Historic photographs and files.

Newspapers.com
Phillips, Meredith. Written history of memories of Halsey House, supplied to author by Phillips.

Sanborn Map Company. Various maps. Available via the San Francisco Public Library.

Voter Registration Records, Purissima. 1940. Available via Ancestry.com.

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Internet Sources
Friends of Historic Redwood Grove. “History of Halsey House and Redwood Grove.” http://www.friendsofhistoricredwoodgrove.org/
“History of Los Altos,” City of Los Altos, Accessed July 2021, https://www.losaltosca.gov/community/page/history-los-altos Personal Communications
Backs, Marie. Telephone conversations with author on July 15 and 21, 2021.

Phillips, Meredith. Telephone conversation with author on July 22, 2021.

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IX. APPENDIX
Significance and Chronology Diagrams of the Halsey House

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Significance Diagrams

CATEGORIES OF SIGNIFICANCE

SIGNIFICANT/HISTORIC
Features or spaces that date to the period of
significance (1923-1945) and are the most historically
significant components of the building.

CONTRIBUTING
Features or spaces that date to the period of
significance (1923-1945) and are characterized by a
lesser degree of significance (such as service spaces,
closets, etc.) or are slightly altered or replaced
elements. They cumulatively contribute to the overall
historic character of the building.

NON-CONTRIBUTING
Features or spaces that were constructed after
the period of significance (post-1945), have been
significantly altered, or do not contribute to the
overall historic character of the building. These
features are not considered historic.

Base drawings: Floor plan dated April 1978 provided by the City of Los Altos. Minor revisions were made by Page & Turnbull to reflect the existing building in 2021. Drawings are not to scale and may contain some inaccuracies.

Plan North
Notes:

Lighter hues of significance categories
show built features of the courtyard and
landscape.

White space within diagrams denotes
planting and dirt areas without built
features.

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Significance Diagrams

CATEGORIES OF SIGNIFICANCE

SIGNIFICANT/HISTORIC

CONTRIBUTING

NON-CONTRIBUTING
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

PRIMARY (NORTH) FACADE

SOUTH FACADE

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Significance Diagrams

CATEGORIES OF SIGNIFICANCE

SIGNIFICANT/HISTORIC

CONTRIBUTING

NON-CONTRIBUTING
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

WEST FACADE

EAST FACADE

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Significance Diagrams

CATEGORIES OF SIGNIFICANCE

SIGNIFICANT/HISTORIC

CONTRIBUTING

NON-CONTRIBUTING
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

EAST-FACING WALL OF REAR COURTYARD

WEST-FACING WALL OF REAR COURTYARD

SOUTH-FACING WALL OF REAR COURTYARD

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Construction Chronology Diagrams

CONSTRUCTION CHRONOLOGY
ORIGINAL 1923 CONSTRUCTION
Features that date to the original construction of the
residence in 1923.

ALTERATIONS BY THE HALSEY FAMILY
Early alterations and additions to the Halsey House
were completed by the Halsey family in 1928 and at
an unknown date circa the 1930s.
1928 Addition
Circa 1930s Addition/Alterations
ALTERATIONS POST-1945
Alterations that have taken place since the end of
the Halsey family’s ownership of the house and the
period of significance.

Base drawings: Floor plan dated April 1978 provided by the City of Los Altos. Minor revisions were made by Page & Turnbull to reflect the existing building in 2021. Drawings are not to scale and may contain some inaccuracies.

Plan North
Notes:

Lighter hues of chronology categories
show built features of the courtyard and
landscape.

White space within diagrams denotes
planting areas and dirt areas without built
features.

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Construction Chronology Diagrams

BUILDING CHRONOLOGY
ORIGINAL 1923 CONSTRUCTION

ALTERATIONS BY THE HALSEY FAMILY
1928 Addition
Early Additions/Alterations (circa 1930s)
ALTERATIONS POST-1945
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

PRIMARY (NORTH) FACADE

SOUTH FACADE

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Construction Chronology Diagrams

BUILDING CHRONOLOGY
ORIGINAL 1923 CONSTRUCTION

ALTERATIONS BY THE HALSEY FAMILY
1928 Addition
Early Additions/Alterations (circa 1930s)
ALTERATIONS POST-1945
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

WEST FACADE

EAST FACADE

HALSEY HOUSE - LOS ALTOS, CALIFORNIA
Construction Chronology Diagrams

BUILDING CHRONOLOGY
ORIGINAL 1923 CONSTRUCTION

ALTERATIONS BY THE HALSEY FAMILY
1928 Addition
Early Additions/Alterations (circa 1930s)
ALTERATIONS POST-1945
Base drawings based on the 2015 proposed project drawings by M. Sandoval Architects, altered to reflect the existing building by Page & Turnbull, 2021. Drawings are not to scale and may contain some inaccuracies.

EAST-FACING WALL OF REAR COURTYARD

WEST-FACING WALL OF REAR COURTYARD

SOUTH-FACING WALL OF REAR COURTYARD

This page intentionally left blank.

Imagining change in historic environments through
design, research, and technology
417 S. HILL STREET, SUITE 211 LOS ANGELES, CALIFORNIA 90013 TEL 213.221.1200 2600 CAPITOL AVENUE, SUITE 120 SACRAMENTO, CALIFORNIA 95816 TEL 916-930-9903 170 MAIDEN LANE, 5TH FLOOR SAN FRANCISCO, CALIFORNIA 94108 TEL 415.362.5154

TYPE OF SERVICES

PROJECT NAME

LOCATION
CLIENT

PROJECT NUMBER
DATE
Geotechnical Investigation
Halsey House
University Avenue and University Terrace
Los Altos, California
David J. Powers & Associates
118-161
February 16, 2024
Attachment 6 - Appendix E

Type of Services Geotechnical Investigation
Project Name Halsey House
Location University Avenue and University Terrace
Los Altos, California
Client David J. Powers & Associates
Client Address 1871 The Alameda, Suite 200
San Jose, California
Project Number 118-161-1
Date February 16, 2024
Prepared by Jesse D. Serpa, E.I.T.

Senior Staff Engineer
Stephen C. Ohlsen, P.E., G.E.

Senior Project Engineer
Geotechnical Project Manager

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Page i

TABLE OF CONTENTS
SECTION 1: INTRODUCTION ..................................................................................................... 1

1.1 Project Description ------------------------------------------------------------------------------------------- 1

1.2 Scope of Services--------------------------------------------------------------------------------------------1

1.3 Exploration Program ----------------------------------------------------------------------------------------2

1.4 Laboratory Testing Program ------------------------------------------------------------------------------- 2

1.5 Environmental Services ------------------------------------------------------------------------------------ 2 SECTION 2: REGIONAL SETTING .............................................................................................. 2

2.1 Geological Setting ------------------------------------------------------------------------------------------- 2

2.2 Regional Seismicity ------------------------------------------------------------------------------------------ 2 Table 1: Approximate Fault Distances ...................................................................................... 3 SECTION 3: SITE CONDITIONS ................................................................................................. 3

3.1 Site Background ---------------------------------------------------------------------------------------------- 3

3.2 Surface Description ------------------------------------------------------------------------------------------ 3

3.3 Subsurface Conditions -------------------------------------------------------------------------------------- 4

3.3.1 In-Situ Moisture Contents .......................................................................................... 4

3.4 Groundwater -------------------------------------------------------------------------------------------------- 4 SECTION 4: GEOLOGIC HAZARDS............................................................................................ 4

4.1 Fault Surface Rupture -------------------------------------------------------------------------------------- 4

4.2 Estimated Ground Shaking -------------------------------------------------------------------------------- 5

4.3 Liquefaction Potential --------------------------------------------------------------------------------------- 5

4.3.1 Background ............................................................................................................... 5

4.3.2 Analysis .................................................................................................................... 5

4.3.3 Summary .................................................................................................................. 6

4.3.4 Ground Deformation and Surficial Cracking Potential ................................................ 6

4.4 Lateral Spreading -------------------------------------------------------------------------------------------- 7

4.5 Seismic Settlement/Unsaturated Sand Shaking ------------------------------------------------------7

4.6 Tsunami/seiche ----------------------------------------------------------------------------------------------- 7

4.7 Flooding --------------------------------------------------------------------------------------------------------8 SECTION 5: CONCLUSIONS ...................................................................................................... 8

5.1 Summary ------------------------------------------------------------------------------------------------------- 8

5.1.1 Potential for Liquefaction-Induced Settlements ......................................................... 8

5.1.2 Presence of Undocumented Fill and Redevelopment Considerations ....................... 9

5.1.3 Shallow Groundwater ................................................................................................ 9

5.2 Plans and Specifications Review ------------------------------------------------------------------------- 9

5.3 Construction Observation and Testing ------------------------------------------------------------------ 9 SECTION 6: EARTHWORK ........................................................................................................10

6.1 Site Demolition---------------------------------------------------------------------------------------------- 10

6.1.1 Demolition of Existing Slabs, Foundations and Pavements ......................................10

6.1.2 Abandonment of Existing Utilities .............................................................................11

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Page ii

6.2 Site Clearing and Preparation--------------------------------------------------------------------------- 11

6.2.1 Site Stripping ............................................................................................................11

6.2.2 Tree and Shrub Removal .........................................................................................11

6.3 Mitigation of Undocumented Fills----------------------------------------------------------------------- 12

6.4 Temporary Cut and Fill Slopes ------------------------------------------------------------------------- 12

6.5 Subgrade Preparation ------------------------------------------------------------------------------------ 12

6.6 Wet Soil Stabilization Guidelines----------------------------------------------------------------------- 12

6.6.1 Scarification and Drying ...........................................................................................13

6.6.2 Removal and Replacement......................................................................................13

6.6.3 Chemical Treatment .................................................................................................13

6.7 Material for Fill ---------------------------------------------------------------------------------------------- 13

6.7.1 Re-Use of On-site Soils ............................................................................................13

6.7.2 Potential Import Sources..........................................................................................13

6.8 Compaction Requirements ------------------------------------------------------------------------------ 14 Table 2: Compaction Requirements ........................................................................................15

6.9 Trench Backfill ---------------------------------------------------------------------------------------------- 15

6.10 Site Drainage------------------------------------------------------------------------------------------------ 16 SECTION 7: 2022 CBC SEISMIC DESIGN CRITERIA................................................................16

7.1 Seismic Design Criteria ----------------------------------------------------------------------------------- 16 Table 3: CBC Site Categorization and Site Coefficients ...........................................................17 SECTION 8: FOUNDATIONS......................................................................................................17

8.1 Summary of Recommendations ------------------------------------------------------------------------ 17

8.2 Shallow Foundations -------------------------------------------------------------------------------------- 17

8.2.1 Conventional Shallow Footings ................................................................................17

8.2.2 Footing Settlement ...................................................................................................18 Table 4: Assumed Structural Loading ......................................................................................18

8.2.3 Lateral Loading ........................................................................................................18

8.2.4 Conventional Shallow Footing Construction Considerations .....................................18

8.3 Ground Anchors -------------------------------------------------------------------------------------------- 19 SECTION 9: CONCRETE SLABS AND PEDESTRIAN PAVEMENTS ........................................19

9.1 Interior Slabs-on-Grade----------------------------------------------------------------------------------- 19

9.2 Interior Slabs Moisture Protection Considerations ------------------------------------------------- 20

9.3 Exterior Flatwork ------------------------------------------------------------------------------------------- 21 SECTION 10: LIMITATIONS .......................................................................................................21 SECTION 11: REFERENCES .....................................................................................................22 FIGURE 1: VICINITY MAP
FIGURE 2: SITE PLAN
FIGURE 3: REGIONAL FAULT MAP
FIGURE 4A TO 4C: LIQUEFACTION ANALYSIS SUMMARY – CPT-01 TO CPT-03 APPENDIX A: FIELD INVESTIGATION
APPENDIX B: LABORATORY TEST PROGRAM

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Type of Services Geotechnical Investigation
Project Name Halsey House
Location University Avenue and University Terrace
Los Altos, California
SECTION 1: INTRODUCTION
This geotechnical report was prepared for the sole use of David J. Powers & Associates for the Halsey House project in Los Altos, California. The location of the site is shown on the Vicinity Map, Figure 1.

1.1 PROJECT DESCRIPTION
The project will consist of evaluating the existing Halsey House structure for rehabilitation or reconstruction. The original structure was built in 1923 and was primarily used as an education and recreational nature center until 2008, when it was then closed due to its deteriorating conditions. As a result of these conditions, the Halsey House structure has remained closed since 2008. The City of Los Altos has planned for the structure to be renovated for re-use, or to be demolished and reconstructed to replace the Halsey House with a purpose-designed facility.

The structure is located within the approximately 6-acre Redwood Grove Nature Preserve. The Halsey House structure is reportedly built on a concrete foundation, is of wood-framed construction, has a clay tile roof, and has an approximate footprint of 3,400 square feet.

Structural loads are not currently known for the proposed structure; however, structural loads for rehabilitation or a new structure are expected to be relatively light and typical of similar type structures. Grading plans are not available at this time; however, as the current project scope focuses on the existing structure, grading is anticipated to consist of minor cuts and fills on the order of 1 to 3 feet to potentially facilitate the rehabilitation of the existing structure, which could include underpinning and the installation of new improvements such as flatwork and utilities.

Therefore, the overall topography of the Preserve is expected to remain the same following this project.

1.2 SCOPE OF SERVICES
Our scope of services was presented in our proposal dated July 10, 2023, and consisted of field and laboratory programs to evaluate physical and engineering properties of the subsurface soils, engineering analysis to prepare recommendations for site work and grading, building

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foundations, flatwork, and pavements, and preparation of this report. Brief descriptions of our exploration and laboratory programs are presented below.

1.3 EXPLORATION PROGRAM
Field exploration consisted of two borings drilled on January 23, 2024 with track-mounted, limited-access, hollow-stem auger drilling equipment, as well as three Cone Penetration Tests (CPTs) advanced on January 16, 2024. The borings were drilled to depths of 25 and 30 feet; the CPTs were each advanced to depths of 44½ feet. Seismic shear wave velocity measurements were collected from CPT-1. Borings EB-1 and EB-2 were advanced adjacent to CPT-1 and CPT-2, respectively, for direct evaluation of physical samples to correlated soil behavior. The borings and CPTs were backfilled with cement grout in accordance with local requirements.

The approximate locations of our exploratory borings are shown on the Site Plan, Figure 2.

Details regarding our field program are included in Appendix A.

1.4 LABORATORY TESTING PROGRAM
In addition to visual classification of samples, the laboratory program focused on obtaining data for foundation design and seismic ground deformation estimates. Testing included moisture contents, dry densities, and washed sieve analyses. Details regarding our laboratory program are included in Appendix B.

1.5 ENVIRONMENTAL SERVICES
Environmental services were not requested for this project. If environmental concerns are determined to be present during future evaluations, the project environmental consultant should review our geotechnical recommendations for compatibility with the environmental concerns.

SECTION 2: REGIONAL SETTING

2.1 GEOLOGICAL SETTING
The site is located within the Santa Clara Valley, which is a broad alluvial plane between the Santa Cruz Mountains to the southwest and west, and the Diablo Range to the northeast. The San Andreas Fault system, including the Monte Vista-Shannon Fault, exists within the Santa Cruz Mountains and the Hayward and Calaveras Fault systems exist within the Diablo Range.

Alluvial soil thicknesses in the project area have been mapped at less than 100 feet (Rogers & Williams, 1974).

2.2 REGIONAL SEISMICITY
While seismologists cannot predict earthquake events, geologists from the U.S. Geological Survey have recently updated (in 2015) earlier estimates from their 2014 Uniform California Earthquake Rupture Forecast (Version 3; UCERF3) publication. The estimated probability of

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one or more magnitude 6.7 earthquakes (the size of the destructive 1994 Northridge earthquake) expected to occur somewhere in the San Francisco Bay Area has been revised (increased) to 72 percent for the period 2014 to 2043 (Aagaard et al., 2016). The faults in the region with the highest estimated probability of generating damaging earthquakes between 2014 and 2043 are the Hayward (33%), Calaveras (26%), and San Andreas Faults (22%). In this 30-year period, the probability of an earthquake of magnitude 6.7 or larger occurring is 22 percent along the San Andreas Fault and 33 percent for the Hayward Fault.

The faults considered capable of generating significant earthquakes are generally associated with the well-defined areas of crustal movement, which trend northwesterly. The table below presents the State-considered active faults within 25 kilometers of the site.

Table 1: Approximate Fault Distances
Fault Name
Distance
(miles) (kilometers)
Monte Vista-Shannon 2.7 4.3
San Andreas (1906) 4.3 7.0
Hayward (Southeast Extension) 13.7 22.0
Hayward (Total Length) 15.4 24.8
A regional fault map is presented as Figure 3, illustrating the relative distances of the site to significant fault zones.

SECTION 3: SITE CONDITIONS

3.1 SITE BACKGROUND
As mentioned above, the Halsey House was originally constructed in 1923. We reviewed historic aerial imagery provided online by Historic Aerials (historicaerials.com). A summary of pertinent surface changes at and near the site is as follows:
1948: The existing Halsey House structure is observed and the residential development to the north and east of the project site appears to have been constructed by this time.

The Halsey House structure is bounded by agricultural fields to the west and south. 1980: Additional residential development is constructed to the west of the project site. 1997: Residential development to the south of the project site appears completed. No pertinent changes were observed since this image.

3.2 SURFACE DESCRIPTION
As noted above, the existing historic Halsey House is located within the Redwood Grove Nature Preserve. The Preserve is generally characterized by gentle slopes and plentiful mature trees and vegetation, with dirt and gravel walking trails present throughout. The Preserve appears to

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generally slope downwards to the north, and the Halsey House structure is situated within the southern section of the Preserve. The current Adobe Creek runs approximately 50 feet north of the Halsey House. Grades around the property range from Elevation 212 feet to the south to Elevation 206 feet to the north. Numerous mature trees are present within the Preserve and the immediate vicinity of the Halsey House.

3.3 SUBSURFACE CONDITIONS
Below the surficial topsoil, our explorations generally encountered undocumented fill consisting of sandy lean clay to a depth of up to 1 foot. Beneath the undocumented fill, Boring EB-1 generally encountered native stiff to hard sandy lean clay down to a depth of 14½ feet, underlain by medium dense to dense clayey sand with variable amounts of clay and gravel to 21½ feet and very stiff lean clay to 23½ feet before terminating in dense clayey sand at a depth of 25 feet. Beneath the undocumented fill Boring EB-2 generally encountered native stiff sandy lean clay to a depth of 3 feet, underlain by medium dense to dense clayey sands with variable amounts of clay and gravel down to 30 feet, the maximum boring depth.

Beneath the terminal boring depths, our CPTs generally encountered interbedded dense sands and hard clays to the maximum depth explored of 44½ feet.

3.3.1 In-Situ Moisture Contents
Laboratory testing indicated that the in-situ moisture contents within the upper 10 feet range from 3 percent under to 5 percent over the estimated laboratory optimum moisture.

3.4 GROUNDWATER
Groundwater was encountered in our explorations EB-1 and EB-2 at depths ranging from 10 to 15 feet below current grades. All measurements were taken at the time of drilling and may not represent the stabilized levels that can vary from the initial levels encountered.

Based on the above, we recommend a design groundwater depth of 8 feet. Fluctuations in groundwater levels occur due to many factors including seasonal fluctuation, underground drainage patterns, regional fluctuations, and other factors.

SECTION 4: GEOLOGIC HAZARDS

4.1 FAULT SURFACE RUPTURE
As discussed above several significant faults are located within 25 kilometers of the site. The site is not located within a State-designated Alquist Priolo Earthquake Fault Zone, or a Santa Clara County Fault Hazard Zone. As shown in Figure 3, no known surface expression of fault traces is thought to cross the site; therefore, fault surface rupture hazard is not a significant geologic hazard at the site.

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4.2 ESTIMATED GROUND SHAKING
Moderate to severe (design-level) earthquakes can cause strong ground shaking, which is the case for most sites within the Bay Area. A peak ground acceleration (PGA) was estimated for analysis using a value equal to FPGA x PGA, as allowed in the 2022 edition of the California Building Code when an exception has been taken per ASCE 7-16, Section 11.4.8. For our liquefaction analysis we used a PGAM of 1.112g.

4.3 LIQUEFACTION POTENTIAL
The site is within a State-designated Liquefaction Hazard Zone (CGS, Cupertino 7.5-Minute Quadrangle, 2002) as well as a Santa Clara County Liquefaction Hazard Zone (Santa Clara County, 2003). Our field and laboratory programs addressed this issue by testing and sampling potentially liquefiable layers to maximum depths explored, performing visual classification on sampled materials, evaluating CPT data, and performing various tests to further classify soil properties.

4.3.1 Background
During strong seismic shaking, cyclically induced stresses can cause increased pore pressures within the soil matrix that can result in liquefaction triggering, soil softening due to shear stress loss, potentially significant ground deformation due to settlement within sandy liquefiable layers as pore pressures dissipate, and/or flow failures in sloping ground or where open faces are present (lateral spreading) (NCEER 1998). Limited field and laboratory data is available regarding ground deformation due to settlement; however, in clean sand layers settlement on the order of 2 to 4 percent of the liquefied layer thickness can occur. Soils most susceptible to liquefaction are loose, non-cohesive soils that are saturated and are bedded with poor drainage, such as sand and silt layers bedded with a cohesive cap.

4.3.2 Analysis
As discussed in the “Subsurface” section above, several sand layers were encountered below the design groundwater depth of 8 feet. Following the liquefaction analysis framework in the 2008 monograph, Soil Liquefaction During Earthquakes (Idriss and Boulanger, 2008), incorporating updates in CPT and SPT Based Liquefaction Triggering Procedures (Boulanger and Idriss, 2014), and in accordance with CDMG Special Publication 117A guidelines (CDMG, 2008) for quantitative analysis, these layers were analyzed for liquefaction triggering and potential post-liquefaction settlement. These methods compare the ratio of the estimated cyclic shaking (Cyclic Stress Ratio - CSR) to the soil’s estimated resistance to cyclic shaking (Cyclic Resistance Ratio - CRR), providing a factor of safety against liquefaction triggering. Factors of safety less than or equal to 1.3 are considered to be potentially liquefiable and capable of postliquefaction re-consolidation (i.e. settlement).

The CSR for each layer quantifies the stresses anticipated to be generated due to a designlevel seismic event, is based on the peak horizontal acceleration generated at the ground surface discussed in the “Estimated Ground Shaking” section above, and is corrected for

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overburden and stress reduction factors as discussed in the procedure developed by Seed and Idriss (1971) and updated in the 2008 Idriss and Boulanger monograph.

In estimating post-liquefaction settlement at the site, we have implemented a depth weighting factor proposed by Cetin (2009). Following evaluation of 49 high-quality, cyclically induced, ground settlement case histories from seven different earthquakes, Cetin proposed the use of a weighting factor based on the depth of layers. The weighting procedure was used to tune the surface observations at liquefaction sites to produce a better model fit with measured data. Aside from the better model fit it produced, the rationale behind the use of a depth weighting factor is based on the following: 1) upward seepage, triggering void ratio redistribution, and resulting in unfavorably higher void ratios for the shallower sublayers of soil layers; 2) reduced induced shear stresses and number of shear stress cycles transmitted to deeper soil layers due to initial liquefaction of surficial layers; and 3) possible arching effects due to nonliquefied soil layers. All these may significantly reduce the contribution of volumetric settlement of deeper soil layers to the overall ground surface settlement (Cetin, 2009).

The soil’s CRR is estimated from the in-situ measurements from CPTs and laboratory testing on samples retrieved from our borings. SPT “N” values obtained from hollow-stem auger borings were not used in our analyses, as the “N” values obtained are less reliable in sands below groundwater. The tip pressures are corrected for effective overburden stresses, taking into consideration both the groundwater level at the time of exploration and the design groundwater level, and stress reduction versus depth factors. The CPT method utilizes the soil behavior type index (IC) to estimate the plasticity of the layers.

The results of our CPT analyses (CPT-1 through CPT-3) are presented in Figures 4A through 4C of this report.

4.3.3 Summary
Our analyses indicate that several layers could potentially experience liquefaction triggering that could result in post-liquefaction total settlement at the ground surface ranging -inch based on the Yoshimine (2006) method. As discussed in SP 117A, differential movement for level ground sites over deep soil sites will be up to about two-thirds of the total settlement between independent foundation elements. In our opinion, differential settlements are anticipated to be on the order of up to ½-inch over a horizontal distance of 30 feet.

4.3.4 Ground Deformation and Surficial Cracking Potential The methods used to estimate liquefaction settlements assume that there is a sufficient cap of non-liquefiable material to prevent ground deformation or sand boils. For ground deformation to occur, the pore water pressure within the liquefiable soil layer will need to be great enough to break through the overlying non-liquefiable layer, which could cause significant ground deformation and settlement. The work of Youd and Garris (1995) indicates that the 25-feet thick layer of non-liquefiable cap is sufficient to prevent ground deformation and significant surficial cracking; therefore, the above total settlement estimates are reasonable.

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4.4 LATERAL SPREADING
Lateral spreading is horizontal/lateral ground movement of relatively flat-lying soil deposits towards a free face such as an excavation, channel, or open body of water; typically, lateral spreading is associated with liquefaction of one or more subsurface layers near the bottom of the exposed slope. As failure tends to propagate as block failures, it is difficult to analyze and estimate where the first tension crack will form.

The current Adobe Creek runs approximately 50 feet north of the Halsey House. The channel bottom was observed to be roughly 6 to 7 feet deep relative to the existing adjacent site grades.

As part of our liquefaction analyses, we calculated the Lateral Displacement Index (LDI) for potentially liquefiable layers based on methods presented in the 2008 monograph, Soil Liquefaction During Earthquakes (Idriss and Boulanger, 2008). LDI is a summation of the maximum shear strains versus depth, which is a measurement of the potential maximum displacement at that exploration location. Summations of the LDI values to a depth equal to twice the open face height were included. Estimated displacements in the vicinity of CPT-1 through CPT-3 based on the LDI calculations are considered negligible.

We also reviewed the historical ground failure map presented in the Seismic Hazard Zone Report for the vicinity (CGS, Cupertino 7.5-Minute Quadrangle, 2002), which indicated no occurrences of lateral spread within the project site vicinity. Therefore, in our opinion, the potential for lateral spreading to impact the project is relatively low.

4.5 SEISMIC SETTLEMENT/UNSATURATED SAND SHAKING
Loose unsaturated sandy soils can settle during strong seismic shaking. We evaluated the potential for seismic compaction of the loose to medium dense sands based on the work by Robertson and Shao (2010). Based on our analyses, the potential for significant seismic settlement affecting the proposed improvements is low.

4.6 TSUNAMI/SEICHE
The terms tsunami or seiche are described as ocean waves or similar waves usually created by undersea fault movement or by a coastal or submerged landslide. Tsunamis may be generated at great distance from shore (far field events) or nearby (near field events). Waves are formed, as the displaced water moves to regain equilibrium, and radiates across the open water, similar to ripples from a rock being thrown into a pond. When the waveform reaches the coastline, it quickly raises the water level, with water velocities as high as 15 to 20 knots. The water mass, as well as vessels, vehicles, or other objects in its path create tremendous forces as they impact coastal structures.

Tsunamis have affected the coastline along the Pacific Northwest during historic times. The Fort Point tide gauge in San Francisco recorded approximately 21 tsunamis between 1854 and 1964. The 1964 Alaska earthquake generated a recorded wave height of 7.4 feet and drowned eleven people in Crescent City, California. For the case of a far-field event, the Bay area would

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have hours of warning; for a near field event, there may be only a few minutes of warning, if any.

A tsunami or seiche originating in the Pacific Ocean would lose much of its energy passing through San Francisco Bay. Based on the mapping of tsunami inundation potential for the San Francisco Bay Area by CGS (conservation.ca.gov/cgs/tsunami/maps), areas most likely to be inundated are marshlands, tidal flats, and former bay margin lands that are now artificially filled, but are still at or below sea level, and are generally within 1½ miles of the shoreline. The site is approximately 5¾ miles inland from the San Francisco Bay shoreline and is approximately 206 to 212 feet above mean sea level (WGS84). Therefore, the potential for inundation due to tsunami or seiche is considered low.

4.7 FLOODING
Based on our internet search of the Federal Emergency Management Agency (FEMA) flood map public database, the site is located within Zone AE, defined as a “Regulatory Floodway” and Zone A, with base flood elevations between 204 and 208. We recommend the project civil engineer be retained to confirm this information and verify the base flood elevation, if appropriate.

The Department of Water Resources (DWR), Division of Safety of Dams (DSOD) compiled a database of Dam Failure Inundation Hazard Maps (DSOD, 2015). The generalized hazard maps were prepared by dam owners as required by the State Office of Emergency Services; they are intended for planning purposes only. Based on our review of these maps, the site is not located within a dam failure inundation area.

SECTION 5: CONCLUSIONS

5.1 SUMMARY
From a geotechnical viewpoint, retrofitting the existing structure or building new facilities should both be feasible provided the concerns listed below are addressed in the project design.

Descriptions of each concern with brief outlines of our recommendations follow the listed concerns.

Potential for liquefaction-induced settlements
Presence of undocumented fill and redevelopment considerations Presence of undocumented fill
Shallow groundwater

5.1.1 Potential for Liquefaction-Induced Settlements
As discussed, our liquefaction analysis indicates that there is a potential for liquefaction of localized sand layers during a significant seismic event. Although the potential for liquefied sands to vent to the ground surface through cracks in the surficial soils is low, our analysis

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indicates that liquefaction-induced settlement on the order of up to -inch could occur, resulting in differential settlement up to ½-inch. New foundations should be designed to tolerate the anticipated total and differential settlements. Liquefaction does not appear to pose a severe risk to the structure; therefore, existing foundations should not be impacted to a degree that would necessitate replacement. Detailed foundation recommendations are presented in the “Foundations” section.

5.1.2 Presence of Undocumented Fill and Redevelopment Considerations As discussed, the site is currently occupied by the existing Halsey House and appurtenant flatwork, site fixtures, and landscaping. We understand that the City is considering renovating the existing structure, which may include new foundation elements, or demolishing the existing structure and reconstructing a purpose-designed facility as a replacement. Potential issues that are often associated with new foundations or redeveloping sites include demolition of existing improvements, abandonment of existing utilities, and undocumented fills. As discussed, our borings generally encountered up to one foot of undocumented fill. Any undocumented fill encountered during site grading should be completely removed from within improvement areas and to a lateral distance equal to fill depth below the perimeter footing. Provided the fills meet the “Material for Fill” requirements below, the fills may be reused when backfilling the excavations. The existing fill should not affect the performance of the existing structure, and should not impact new improvements provided the recommendations in this report to remove and replace the undocumented fill as engineered fill are followed. Please refer to the “Earthwork” section below for further recommendations.

5.1.3 Shallow Groundwater
Shallow groundwater was measured at depths ranging from approximately 10 to 15 feet below the existing ground surface. As discussed above, we recommend a design groundwater depth of 8 feet. Our experience with similar sites in the vicinity indicates that shallow groundwater could significantly impact grading and underground construction, depending on the depth of excavations. These impacts typically consist of potentially wet and unstable subgrade, difficulty achieving compaction, and difficult underground utility installation. Dewatering and shoring of utility trenches may be required in some isolated areas of the site. Shallow groundwater should not impact the performance of the existing structure. Detailed recommendations addressing this concern are presented in the “Earthwork” section of this report.

5.2 PLANS AND SPECIFICATIONS REVIEW
We recommend that we be retained to review the geotechnical aspects of the project structural, civil, and landscape plans and specifications, allowing sufficient time to provide the design team with any comments prior to issuing the plans for construction.

5.3 CONSTRUCTION OBSERVATION AND TESTING
As site conditions may vary significantly between the small-diameter borings performed during this investigation, we also recommend that a Cornerstone representative be present to provide

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geotechnical observation and testing during earthwork and foundation construction. This will allow us to form an opinion and prepare a letter at the end of construction regarding contractor compliance with project plans and specifications, and with the recommendations in our report.

We will also be allowed to evaluate any conditions differing from those encountered during our investigation and provide supplemental recommendations as necessary. For these reasons, the recommendations in this report are contingent of Cornerstone providing observation and testing during construction. Contractors should provide at least a 48-hour notice when scheduling our field personnel.

SECTION 6: EARTHWORK

6.1 SITE DEMOLITION
If renovation and seismic retrofit of the existing structure is planned, the areas designated for improvements should be cleared of all surface and subsurface deleterious materials including any pre-existing foundations, flatwork, pavements, utilities, and other improvements, if encountered. If the existing structure will be removed and reconstructed as a purpose-designed facility, all existing improvements not to be reused for the development should be demolished and removed from the site. Excavations extending below the planned finished improvement grades should be cleaned and backfilled with suitable material compacted to the recommendations in the “Compaction” section of this report.

Cornerstone should be notified prior to the start of demolition and should be present on at least a part-time basis during all backfill and mass grading as a result of demolition. Occasionally, other types of buried structures (wells, cisterns, debris pits, etc.) can be found on sites with prior development. If encountered, Cornerstone should be contacted to address these types of structures on a case-by-case basis.

6.1.1 Demolition of Existing Slabs, Foundations and Pavements All slabs and foundations not designated for reuse should be completely removed from within planned building areas.

Special care should be taken during the demolition and removal of existing floor slabs, foundations, utilities, and pavements to minimize disturbance of the subgrade. Excessive disturbance of the subgrade, which includes either native or previously placed engineered fill, resulting from demolition activities can have serious detrimental effects on planned foundation and paving elements.

Existing foundations are typically mat-slabs, shallow footings, or piers/piles. If slab or shallow footings are encountered, they should be completely removed. If drilled piers are encountered, they should be cut off at an elevation at least 60-inches below proposed footings or the final subgrade elevation, whichever is deeper. The remainder of the drilled pier could remain in place. Foundation elements to remain in place should be surveyed and superimposed on the proposed development plans to determine the potential for conflicts or detrimental impacts to

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the planned construction. Following review, additional mitigation or planned foundation elements may need to be modified.

6.1.2 Abandonment of Existing Utilities
All utilities not designated for reuse should be completely removed from within planned building areas. For any utility line to be considered acceptable to remain within building areas, the utility line must be completely backfilled with grout or sand-cement slurry (sand slurry is not acceptable), the ends outside the building area capped with concrete, and the trench fills either removed and replaced as engineered fill with the trench side slopes flattened to at least 1:1, or the trench fills are determined not to be a risk to the structure. The assessment of the level of risk posed by the particular utility line will determine whether the utility may be abandoned in place or needs to be completely removed. The contractor should assume that all utilities will be removed from within building areas unless provided written confirmation from both the owner and the geotechnical engineer.

Utilities extending beyond the building area may be abandoned in place provided the ends are plugged with concrete, they do not conflict with planned improvements, and that the trench fills do not pose significant risk to the planned surface improvements.

The risk for owners associated with abandoning utilities in place include the potential for future differential settlement of existing trench fills, and/or partial collapse and potential ground loss into utility lines that are not completely filled with grout.

6.2 SITE CLEARING AND PREPARATION

6.2.1 Site Stripping
The site should be stripped of all surface vegetation, and surface and subsurface improvements to be removed within the proposed development area. Demolition of existing improvements is discussed in the prior paragraphs. Surface vegetation and topsoil should be stripped to a sufficient depth to remove all material greater than 3 percent organic content by weight. Based on our site observations, surficial stripping should extend about 3 to 6 inches below existing grade in vegetated areas.

6.2.2 Tree and Shrub Removal
Trees and shrubs designated for removal should have the root balls and any roots greater than ½-inch diameter removed completely. Mature trees are estimated to have root balls extending to depths of 2 to 4 feet, depending on the tree size. Significant root zones are anticipated to extend to the diameter of the tree canopy. Grade depressions resulting from root ball removal should be cleaned of loose material and backfilled in accordance with the recommendations in the “Compaction” section of this report.

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6.3 MITIGATION OF UNDOCUMENTED FILLS
Undocumented fill was encountered in our Boring EB-1 and EB-2 ranging from approximately ½ to 1 foot. All undocumented fills should be completely removed from within proposed improvement areas and to a lateral distance of at least equal to fill depth below the perimeter footing, whichever is greater. Provided the fills meet the “Material for Fill” requirements below, the fills may be reused when backfilling the excavations. Based on review of the samples collected from our borings, it appears that the fill may be reused. If materials are encountered that do not meet the requirements, such as debris, wood, trash, those materials should be screened out of the remaining material and be removed from the site. Backfill of excavations should be placed in lifts and compacted in accordance with the “Compaction” section below.

Fills extending into planned pavement and flatwork areas may be left in place provided they are determined to be a low risk for future differential settlement and that the upper 12 to 18 inches of fill below pavement subgrade is re-worked and compacted as discussed in the “Compaction” section below. In our opinion, the fills encountered at this site are acceptable to be left in place beneath planned new pavement and flatwork.

6.4 TEMPORARY CUT AND FILL SLOPES
The contractor is responsible for maintaining all temporary slopes and providing temporary shoring where required. Temporary shoring, bracing, and cuts/fills should be performed in accordance with the strictest government safety standards. On a preliminary basis, the upper 10 feet at the site may be classified as OSHA Soil Type C materials.

Excavations performed during site demolition and fill removal should be sloped at 2:1 (horizontal:vertical) within the upper 5 feet below building subgrade. Actual excavation inclinations should be reviewed in the field during construction, as needed. Excavations below building subgrade and excavations in pavement and flatwork areas should be sloped in accordance with OSHA soil classification requirements.

6.5 SUBGRADE PREPARATION
After the areas designated for improvements have been properly cleared, stripped and necessary excavations have been made, the exposed surface soils in those areas to receive fills, slabs-on-grade, and/or pavements should be scarified to a depth of 6 inches, moisture conditioned, and compacted in accordance with the “Compaction” section below.

6.6 WET SOIL STABILIZATION GUIDELINES
Native soil and fill materials, especially soils with high fines contents such as clays and silty soils, can become unstable due to high moisture content, whether from high in-situ moisture contents or from winter rains. As the moisture content increases over the laboratory optimum, it becomes more likely the materials will be subject to softening and yielding (pumping) from construction loading or become unworkable during placement and compaction.

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As discussed in the “Subsurface” section in this report, the in-situ moisture contents can range up to 15 percent over the estimated laboratory optimum in the upper 10 of the soil profile. The contractor should anticipate drying any overly wet soils prior to reusing them as fill. In addition, repetitive rubber-tire loading will likely de-stabilize the overly wet soils.

There are several methods to address potential unstable soil conditions and facilitate fill placement and trench backfill. Some of the methods are briefly discussed below.

Implementation of the appropriate stabilization measures should be evaluated on a case-bycase basis according to the project construction goals and the site conditions.

6.6.1 Scarification and Drying
The subgrade may be scarified to a depth of 6 to 12 inches and allowed to dry to near optimum conditions, if sufficient dry weather is anticipated to allow sufficient drying. More than one round of scarification may be needed to break up the soil clods.

6.6.2 Removal and Replacement
As an alternative to scarification, the contractor may choose to over-excavate the unstable soils and replace them with dry on-site or import materials. A Cornerstone representative should be present to provide recommendations regarding the appropriate depth of over-excavation, whether a geosynthetic (stabilization fabric or geogrid) is recommended, and what materials are recommended for backfill.

6.6.3 Chemical Treatment
Where the unstable area exceeds about 5,000 to 10,000 square feet and/or site winterization is desired, chemical treatment with quicklime (CaO), kiln-dust, or cement may be more costeffective than removal and replacement. Recommended chemical treatment depths will typically range from 12 to 18 inches depending on the magnitude of the instability.

6.7 MATERIAL FOR FILL

6.7.1 Re-Use of On-site Soils
On-site soils with an organic content less than 3 percent by weight may be reused as general fill. General fill should not have lumps, clods, or cobble pieces larger than 6 inches in diameter; 85 percent of the fill should be smaller than 2½ inches in diameter. Minor amounts of oversized material (smaller than 12 inches in diameter) may be allowed provided the oversized pieces are not allowed to nest together and the compaction method will allow for loosely placed lifts not exceeding 12 inches.

6.7.2 Potential Import Sources
Imported and non-expansive material should be inorganic with a Plasticity Index (PI) of 15 or less, and not contain recycled asphalt concrete where it will be used within the habitable

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building areas. To prevent significant caving during trenching or foundation construction, imported material should have sufficient fines. Samples of potential import sources should be delivered to our office at least 10 days prior to the desired import start date. Information regarding the import source should be provided, such as any site geotechnical reports. If the material will be derived from an excavation rather than a stockpile, potholes will likely be required to collect samples from throughout the depth of the planned cut that will be imported.

At a minimum, laboratory testing will include PI tests. Material data sheets for select fill materials (Class 2 aggregate base, ¾-inch crushed rock, quarry fines, etc.) listing current laboratory testing data (not older than 6 months from the import date) may be provided for our review without providing a sample. If current data is not available, specification testing will need to be completed prior to approval.

Environmental and soil corrosion characterization should also be considered by the project team prior to acceptance. Suitable environmental laboratory data to the planned import quantity should be provided to the project environmental consultant; additional laboratory testing may be required based on the project environmental consultant’s review. The potential import source should also not be more corrosive than the on-site soils, based on pH, saturated resistivity, and soluble sulfate and chloride testing.

6.8 COMPACTION REQUIREMENTS
All fills, and subgrade areas where fill, slabs-on-grade, and pavements are planned, should be placed in loose lifts 8 inches thick or less and compacted in accordance with ASTM D1557 (latest version) requirements as shown in the table below. In general, clayey soils should be compacted with sheepsfoot equipment and sandy/gravelly soils with vibratory equipment; opengraded materials such as crushed rock should be placed in lifts no thicker than 18 inches and consolidated in place with vibratory equipment. Each lift of fill and all subgrade should be firm and unyielding under construction equipment loading in addition to meeting the compaction requirements to be approved. The contractor (with input from a Cornerstone representative) should evaluate the in-situ moisture conditions, as the use of vibratory equipment on soils with high moistures can cause unstable conditions. General recommendations for soil stabilization are provided in the “Wet Soil Stabilization Guidelines” section of this report.

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Table 2: Compaction Requirements
Description Material Description
Minimum Relative1
Compaction
(percent)
Moisture2
Content
(percent)
General Fill (within upper 5 feet) On-Site Soils 90 >1
General Fill (below a depth of 5
feet)
On-Site Soils 95 >1
Trench Backfill On-Site Soils 90 >1
Trench Backfill (upper 6 inches
of subgrade)
On-Site Soils 95 >1
Crushed Rock Fill ¾-inch Clean Crushed Rock Consolidate In-Place NA Non-Expansive Fill Imported Non-Expansive Fill 90 Optimum Flatwork Subgrade On-Site Soils 90 >1
Flatwork Aggregate Base Class 2 Aggregate Base3 90 Optimum Pavement Subgrade On-Site Soils 95 >1
Pavement Aggregate Base Class 2 Aggregate Base3 95 Optimum Asphalt Concrete Asphalt Concrete 95 (Marshall) NA
1 – Relative compaction based on maximum density determined by ASTM D1557 (latest version) 2 – Moisture content based on optimum moisture content determined by ASTM D1557 (latest version) 3 – Class 2 aggregate base shall conform to Caltrans Standard Specifications, latest edition, except that the relative compaction should be determined by ASTM D1557 (latest version)

6.9 TRENCH BACKFILL
Utility lines constructed within public right-of-way should be trenched, bedded and shaded, and backfilled in accordance with the local or governing jurisdictional requirements. Utility lines in private improvement areas should be constructed in accordance with the following requirements unless superseded by other governing requirements.

All utility lines should be bedded and shaded to at least 6 inches over the top of the lines with crushed rock ( -inch-diameter or greater) or well-graded sand and gravel materials conforming to the pipe manufacturer’s requirements. Open-graded shading materials should be consolidated in place with vibratory equipment and well-graded materials should be compacted to at least 90 percent relative compaction with vibratory equipment prior to placing subsequent backfill materials.

General backfill over shading materials may consist of on-site native materials provided they meet the requirements in the “Material for Fill” section, and are moisture conditioned and compacted in accordance with the requirements in the “Compaction” section.

Where utility lines will cross perpendicular to strip footings, the footing should be deepened to encase the utility line, providing sleeves or flexible cushions to protect the pipes from anticipated foundation settlement, or the utility lines should be backfilled to the bottom of footing with sandPage 351 of 419

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cement slurry or lean concrete. Where utility lines will parallel footings and will extend below the “foundation plane of influence,” an imaginary 1:1 plane projected down from the bottom edge of the footing, either the footing will need to be deepened so that the pipe is above the foundation plane of influence, or the utility trench will need to be backfilled with sand-cement slurry or lean concrete within the influence zone. Sand-cement slurry used within foundation influence zones should have a minimum compressive strength of 75 psi.

6.10 SITE DRAINAGE
Ponding should not be allowed adjacent to building foundations, slabs-on-grade, or pavements.

Hardscape surfaces should slope at least 2 percent towards suitable discharge facilities; landscape areas should slope at least 3 percent to at least 10 feet from the structure. Roof runoff should be directed away from building areas in closed conduits, to approved infiltration facilities, or on to hardscaped surfaces that drain to suitable facilities. Retention, detention, or infiltration facilities should be spaced at least 10 feet from buildings, and preferably at least 5 feet from slabs-on-grade or pavements. However, if retention, detention, or infiltration facilities are located within these zones, we recommend that these treatment facilities meet the requirements in the Storm Water Treatment Design Considerations section of this report.

Where minimal side yards are planned (10 feet or less), we recommend that area drains collect surface runoff and transmit the runoff to other suitable landscape drainage facilities to prevent ponding adjacent to building foundations. Landscape drainage such as drain inlets and storm water filtration and/or infiltration trenches should be provided to collect and transmit storm water runoff to project storm drains, and/or detention or retention facilities.

SECTION 7: 2022 CBC SEISMIC DESIGN CRITERIA

7.1 SEISMIC DESIGN CRITERIA
We understand that the project structural design for a seismic retrofit or structure reconstruction will be based on the 2022 California Building Code (CBC), which provides criteria for the seismic design of buildings in Chapter 16. The “Seismic Coefficients” used to design buildings are established based on a series of tables and figures addressing different site factors, including the time-weighted average shear wave velocity of the top 100 feet (30 meters) of the soil profile (VS30), and soil profile in the upper 100 feet below grade and mapped spectral acceleration parameters based on distance to the controlling seismic source/fault system.

Our explorations generally encountered stiff clay and medium dense to dense sand deposits to a depth of 44½ feet, the maximum depth explored. Shear wave velocity (VS) measurements were performed while advancing CPT-1, resulting in a time-averaged shear wave velocity for the top 30 meters (VS30) of 367 meters per second. Therefore, we have classified the site as Soil Classification C. The mapped spectral acceleration parameters Ss and S1 were calculated using the web-based program ATC Hazards by Locations, located at https://hazards.atcouncil.org/, based on the site coordinates presented below and the site classification. Recommended values for design are presented in Table 3. The table below lists the various factors used to determine the seismic coefficients and other parameters.

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Table 3: CBC Site Categorization and Site Coefficients
Classification/Coefficient Design Value
Site Class C
Site Latitude 37.372911
Site Longitude -122.119684

0.2-second Period Mapped Spectral Acceleration1, SS 2.242g 1-second Period Mapped Spectral Acceleration1, S1 0.806g Short-Period Site Coefficient – Fa 1.2
Long-Period Site Coefficient – Fv 1.4

0.2-second Period, Maximum Considered Earthquake Spectral Response Acceleration Adjusted for Site Effects - SMS 2.69g
1-second Period, Maximum Considered Earthquake Spectral Response Acceleration Adjusted for Site Effects – SM1 1.128g

0.2-second Period, Design Earthquake Spectral Response Acceleration – SDS 1.794g 1-second Period, Design Earthquake Spectral Response Acceleration – SD1 0.752g Site Amplification Factor at PGA – FPGA 1.2
Site Modified Peak Ground Acceleration – PGAM 1.112g
SECTION 8: FOUNDATIONS

8.1 SUMMARY OF RECOMMENDATIONS
In our opinion, both a proposed remodel and seismic retrofit or a reconstructed structure may be supported on shallow foundations provided the recommendations in the “Earthwork” section and the sections below are followed. If ground anchors or other foundation types are desired, we should be retained to provide further recommendations as needed.

8.2 SHALLOW FOUNDATIONS

8.2.1 Conventional Shallow Footings
New conventional shallow footings should bear on natural, undisturbed soil or engineered fill, be at least 15 inches wide, and extend at least 12 inches below the lowest adjacent grade. Lowest adjacent grade is defined as the deeper of the following: 1) bottom of the adjacent interior slabon-grade, or 2) finished exterior grade, excluding landscaping topsoil.

Footings constructed to the above dimensions and in accordance with the “Earthwork” recommendations of this report are capable of supporting maximum allowable bearing pressures of 2,500 psf for dead loads, 3,750 psf for combined dead plus live loads, and 5,000 psf for all loads including wind and seismic. These pressures are based on factors of safety of

3.0, 2.0, and 1.5 applied to the ultimate bearing pressure for dead, dead plus live, and all loads,

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respectively. These pressures are net values; the weight of the footing may be neglected for the portion of the footing extending below grade (typically, the full footing depth). Top and bottom mats of reinforcing steel should be included in continuous footings to help span irregularities and differential settlement.

8.2.2 Footing Settlement
Structural loads were not provided to us at the time this report was prepared; therefore, we assumed the typical loading in the following table.

Table 4: Assumed Structural Loading
Foundation Area Range of Assumed Loads
Isolated Column Footing 20 to 25 kips
Perimeter Strip Footing 1 to 3 kips per lineal foot
Based on the above loading and the allowable bearing pressures presented above, we estimate that the total static footing settlement will be on the order of -inch, with ¼-inch or less of postconstruction differential settlement between adjacent foundation elements. In addition, we estimate that differential seismic movement will be on the order of ½-inch over a horizontal distance of 30 feet, resulting in a total estimated differential footing movement of ¾-inch between foundation elements, assumed to be on the order of 30 feet. As our footing loads were assumed, we recommend we be retained to review the final footing layout and loading, and verify the settlement estimates above.

8.2.3 Lateral Loading
Lateral loads may be resisted by friction between the bottom of footing and the supporting subgrade, and also by passive pressures generated against footing sidewalls. An ultimate frictional resistance of 0.40 applied to the footing dead load, and an ultimate passive pressure based on an equivalent fluid pressure of 450 pcf may be used in design. The structural engineer should apply an appropriate factor of safety (such as 1.5) to the ultimate values above.

Where footings are adjacent to landscape areas without hardscape, the upper 12 inches of soil should be neglected when determining passive pressure capacity.

8.2.4 Conventional Shallow Footing Construction Considerations Where utility lines will cross perpendicular to strip footings, the footing should be deepened to encase the utility line, providing sleeves or flexible cushions to protect the pipes from anticipated foundation settlement, or the utility lines should be backfilled to the bottom of footing with sandcement slurry or lean concrete. Where utility lines will parallel footings and will extend below the “foundation plane of influence,” an imaginary 1:1 plane projected down from the bottom edge of the footing, either the footing will need to be deepened so that the pipe is above the foundation plane of influence, or the utility trench will need to be backfilled with sand-cement slurry or lean

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concrete within the influence zone. Sand-cement slurry used within foundation influence zones should have a minimum compressive strength of 75 psi.

Footing excavations should be filled as soon as possible or be kept moist until concrete placement by regular sprinkling to prevent desiccation. A Cornerstone representative should observe all footing excavations prior to placing reinforcing steel and concrete. If there is a significant schedule delay between our initial observation and concrete placement, we may need to re-observe the excavations.

8.3 GROUND ANCHORS
As discussed, we understand the City is considering a renovation and seismic retrofit for the existing Halsey House, which may include new foundation elements, or potentially new ground anchors to support new shear elements within the structure. Cuts adjacent to the existing slab or foundations should be properly supported to prevent soil from sloughing out from underneath the existing slab or footings. Excavations extending into the influence zone of existing foundations may need to be performed in sequence and may need to be underpinned depending on the specific situation. There are several methods that could be used to underpin existing footings, if needed. In our opinion, helical anchors or drilled piers could be used as ground anchors to support the existing foundations or new foundation elements. Helical anchors should be designed and installed by a helical anchor design build contractor.

Drilled piers may be used to provide additional uplift and vertical capacity. The piers should have a minimum diameter of 18 inches and extend to a depth of at least 10 feet below the surface. The vertical capacity may be designed based on an allowable skin friction of 200 pounds per square foot (psf) for the upper 5 feet and 500 psf for depths deeper than 5 feet.

These allowable values are for combined dead plus live loads based on a factor of safety of 2.0; dead loads should not exceed two-thirds of the allowable capacities. The allowable skin friction may be increased by one-third for wind and seismic loads. Frictional resistance to uplift loads may be developed along the pier shafts based on 80 percent of the ultimate frictional resistance; the structural engineer should apply an appropriate factor of safety (such as 1.5) to the ultimate uplift capacity.

Cornerstone should review any proposed underpinning design prior to the start of construction and should be onsite while operations for underpinning or excavation in sequence beneath foundations are being performed.

SECTION 9: CONCRETE SLABS AND PEDESTRIAN PAVEMENTS

9.1 INTERIOR SLABS-ON-GRADE
As the Plasticity Index (PI) of the surficial soils is 15 or less, the proposed new areas of slabson-grade may be supported directly on subgrade prepared in accordance with the recommendations in the “Earthwork” section of this report. If moisture-sensitive floor coverings are planned, the recommendations in the “Interior Slabs Moisture Protection Considerations” section below may be incorporated in the project design if desired. If significant time elapses

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between initial subgrade preparation and slab-on-grade construction, the subgrade should be proof-rolled to confirm subgrade stability, and if the soil has been allowed to dry out, the subgrade should be re-moisture conditioned to near optimum moisture content.

The structural engineer should determine the appropriate slab reinforcement for the loading requirements and consider the expansion potential of the underlying soils. For unreinforced concrete slabs, ACI 302.1R recommends limiting control joint spacing to 24 to 36 times the slab thickness in each direction, or a maximum of 18 feet.

9.2 INTERIOR SLABS MOISTURE PROTECTION CONSIDERATIONS
The following general guidelines for concrete slab-on-grade construction where floor coverings are planned are presented for consideration by the developer, design team, and contractor.

These guidelines are based on information obtained from a variety of sources, including the American Concrete Institute (ACI) and are intended to reduce the potential for moisture-related problems causing floor covering failures, and may be supplemented as necessary based on project-specific requirements. The application of these guidelines or not will not affect the geotechnical aspects of the slab-on-grade performance.

Place a minimum 15-mil vapor retarder conforming to ASTM E 1745, Class C requirements or better directly below the concrete slab; the vapor retarder should extend to the slab edges and be sealed at all seams and penetrations in accordance with manufacturer’s recommendations and ASTM E 1643 requirements. A 4-inch-thick capillary break, consisting of crushed rock should be placed below the vapor retarder and consolidated in place with vibratory equipment. The mineral aggregate shall be of such size that the percentage composition by dry weight as determined by laboratory sieves will conform to the following gradation:

Sieve Size Percentage Passing Sieve
1” 100
¾” 90 – 100
No. 4 0 – 10
No. 200 0 – 5
The concrete water:cement ratio should be 0.45 or less. Mid-range plasticizers may be used to increase concrete workability and facilitate pumping and placement.

Water should not be added after initial batching unless the slump is less than specified and/or the resulting water:cement ratio will not exceed 0.45.

Polishing the concrete surface with metal trowels is not recommended.

Where floor coverings are planned, all concrete surfaces should be properly cured.

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Water vapor emission levels and concrete pH should be determined in accordance with ASTM F1869-98 and F710-98 requirements and evaluated against the floor covering manufacturer’s requirements prior to installation.

9.3 EXTERIOR FLATWORK
New exterior concrete flatwork subject to pedestrian and/or occasional light pick up loading should be at least 4 inches thick and supported on at least 4 inches of Class 2 aggregate base overlying subgrade prepared in accordance with the “Earthwork” recommendations of this report. Flatwork that will be subject to heavier or frequent vehicular loading should be designed in accordance with the recommendations in the “Vehicular Pavements” section below. To help reduce the potential for uncontrolled shrinkage cracking, adequate expansion and control joints should be included. Consideration should be given to limiting the control joint spacing to a maximum of about 2 feet in each direction for each inch of concrete thickness. Flatwork should be isolated from adjacent foundations or retaining walls except where limited sections of structural slabs are included to help span irregularities in retaining wall backfill at the transitions between at-grade and on-structure flatwork.

SECTION 10: LIMITATIONS
This report, an instrument of professional service, has been prepared for the sole use of David J. Powers & Associates specifically to support the design of the Halsey House project in Los Altos, California. The opinions, conclusions, and recommendations presented in this report have been formulated in accordance with accepted geotechnical engineering practices that exist in Northern California at the time this report was prepared. No warranty, expressed or implied, is made or should be inferred.

Recommendations in this report are based upon the soil and groundwater conditions encountered during our subsurface exploration. If variations or unsuitable conditions are encountered during construction, Cornerstone must be contacted to provide supplemental recommendations, as needed.

David J. Powers & Associates may have provided Cornerstone with plans, reports and other documents prepared by others. David J. Powers & Associates understands that Cornerstone reviewed and relied on the information presented in these documents and cannot be responsible for their accuracy.

Cornerstone prepared this report with the understanding that it is the responsibility of the owner or their representatives to see that the recommendations contained in this report are presented to other members of the design team and incorporated into the project plans and specifications, and that appropriate actions are taken to implement the geotechnical recommendations during construction.

Conclusions and recommendations presented in this report are valid as of the present time for the development as currently planned. Changes in the condition of the property or adjacent properties may occur with the passage of time, whether by natural processes or the acts of

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other persons. In addition, changes in applicable or appropriate standards may occur through legislation or the broadening of knowledge. Therefore, the conclusions and recommendations presented in this report may be invalidated, wholly or in part, by changes beyond Cornerstone’s control. This report should be reviewed by Cornerstone after a period of three (3) years has elapsed from the date of this report. In addition, if the current project design is changed, then Cornerstone must review the proposed changes and provide supplemental recommendations, as needed.

An electronic transmission of this report may also have been issued. While Cornerstone has taken precautions to produce a complete and secure electronic transmission, please check the electronic transmission against the hard copy version for conformity.

Recommendations provided in this report are based on the assumption that Cornerstone will be retained to provide observation and testing services during construction to confirm that conditions are similar to that assumed for design, and to form an opinion as to whether the work has been performed in accordance with the project plans and specifications. If we are not retained for these services, Cornerstone cannot assume any responsibility for any potential claims that may arise during or after construction as a result of misuse or misinterpretation of Cornerstone’s report by others. Furthermore, Cornerstone will cease to be the GeotechnicalEngineer-of-Record if we are not retained for these services.

SECTION 11: REFERENCES
Aagaard, B.T., Blair, J.L., Boatwright, J., Garcia, S.H., Harris, R.A., Michael, A.J., Schwartz, D.P., and DiLeo, J.S., 2016, Earthquake outlook for the San Francisco Bay region 2014–2043 (ver. 1.1, August 2016): U.S. Geological Survey Fact Sheet 2016–3020, 6 p., http://dx.doi.org/10.3133/fs20163020. ATC Hazards by Location, Hazards by Location, 2020, https://hazards.atcouncil.org/ ASCE 7-16. American Society of Civil Engineers. (2016). Minimum Design Loads and Associated Criteria for Buildings and Other Structures.

Boulanger, R.W. and Idriss, I.M., 2004, Evaluating the Potential for Liquefaction or Cyclic Failure of Silts and Clays, Department of Civil & Environmental Engineering, College of Engineering, University of California at Davis.

Boulanger, R.W. and Idriss, I.M., 2014, CPT and SPT Based Liquefaction Triggering Procedures, Department of Civil & Environmental Engineering, College of Engineering, University of California at Davis, Report No. UCD/GCM-14/01, April 2014 California Building Code, 2022, Structural Engineering Design Provisions, Vol. 2.

California Department of Conservation Division of Mines and Geology, 1998, Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada, International Conference of Building Officials, February, 1998.

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California Division of Mines and Geology (2008), “Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117A, September.

California Geological Survey, 2002, State of California Seismic Hazard Zones, Cupertino 7.5- Minute Quadrangle, California: Seismic Hazard Zone Report 068.

CGS. (2021). Earthquake Zones of Required Investigation. CGS Homepage. https://maps.conservation.ca.gov/cgs/EQZApp/app/
Cetin, K.O., Bilge, H.T., Wu, J., Kammerer, A.M., and Seed, R.B., Probablilistic Model for the Assessment of Cyclically Induced Reconsolidation (Volumetric) Settlements, ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vo. 135, No. 3, March 1, 2009.

Federal Emergency Management Administration (FEMA), 2009, FIRM City of Los Altos, California, Community Panel #06085C0201H.

Idriss, I.M., and Boulanger, R.W., 2008, Soil Liquefaction During Earthquakes, Earthquake Engineering Research Institute, Oakland, CA, 237 p.

Ishihara, K., 1985, Stability of Natural Deposits During Earthquakes: Proceedings Eleventh International Conference on Soil Mechanics and Foundation Engineering, San Francisco.

Ishihara, K. and Yoshimine, M., 1992, Evaluation of Settlements in Sand Deposits Following Liquefaction During Earthquakes, Soils and Foundations, 32 (1): 173-188.

Kelson, K. I., Simpson, G. D., Lettis, W. R., and Harden, C. C., 1996, Holocene slip rate and recurrence of the northern Calaveras fault at Leyden Creek, eastern San Francisco Bay region, Journal of Geophysical Research, v. 101, No. B3, p. 5961-5975.

Knudsen et al., 2000, Preliminary Maps of Quaternary Deposits and Liquefaction Susceptibility, Nine-County San Francisco Bay Region, California.

Perkins, Moy and Lesser, 1988. Liability of Local Governments for Earthquake Hazards and Losses. Association of Bay Area Governments, Oakland, CA, pp. 114-116 Ritter, J.R., and Dupre, W.R., 1972, Map Showing Areas of Potential Inundation by Tsunamis in the San Francisco Bay Region, California: San Francisco Bay Region Environment and Resources Planning Study, USGS Basic Data Contribution 52, Misc. Field Studies Map MF-480.

Robertson, P.K., Shao, Lisheng, 2010, Estimation of Seismic Compression in Dry Soils Using the CPT, 5th International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, Paper No. 4.05a, May 24-29, 2010.

Rogers, T.H., and J.W. Williams, 1974 Potential Seismic Hazards in Santa Clara County, California, Special Report No. 107: California Division of Mines and Geology.

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Seed, H.B. and I.M. Idriss, 1971, A Simplified Procedure for Evaluation soil Liquefaction Potential: JSMFC, ASCE, Vol. 97, No. SM 9, pp. 1249 – 1274.

Seed, Raymond B., Cetin, K.O., Moss, R.E.S., Kammerer, Ann Marie, Wu, J., Pestana, J.M., Riemer, M.F., Sancio, R.B., Bray, Jonathan D., Kayen, Robert E., and Faris, A., 2003, Recent Advances in Soil Liquefaction Engineering: A Unified and Consistent Framework., University of California, Earthquake Engineering Research Center Report 2003-06.

Tokimatsu, K., and Seed, H. Bolton, 1987, Evaluation of Settlements in Sands due to Earthquake Shaking, ASCE Journal of Geotechnical Engineering, Vol. 113, August 1987, pp. 861-878.

Witter, R.C., Knudsen, K.L., Sowers, J.M., Wentworth, C.M., Koehler, R.D., Randolph, C.E., Brooks, S, K. and Gans, K.D., 2006, Maps of Quaternary deposits and liquefaction susceptibility in the central San Francisco Bay region, California: U.S. Geological Survey, Open-File Report OF-2006-1037, scale 1:200000.

Working Group on California Earthquake Probabilities, 2015, The Third Uniform California Earthquake Rupture Forecast, Version 3 (UCERF), U.S. Geological Survey Open File Report 2013-1165 (CGS Special Report 228). KMZ files available at: www.scec.org/ucerf/images/ucerf3_timedep_30yr_probs.kmz Yoshimine, M., Nishizaki, H., Amano, Kl, and Hosono, Y., 2006, Flow Deformation of Liquefied Sand Under Constant Shear Load and Its Application to Analysis of Flow Slide in Infinite Slope, Soil Dynamics and Earthquake Eng. 26, 253-264.

Youd, T.L. and C.T. Garris, 1995, Liquefaction-Induced Ground-Surface Disruption: Journal of Geotechnical Engineering, Vol. 121, No. 11, pp. 805 - 809.

Youd, T.L. and Idriss, I.M., et al, 1997, Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils: National Center for Earthquake Engineering Research, Technical Report NCEER - 97-0022, January 5, 6, 1996.

Youd et al., 2001, “Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils,” ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vo. 127, No. 10, October, 2001.

Youd, T. Leslie, Hansen, Corbett M., and Bartlett, Steven F., 2002, Revised Multilinear Regression Equations for Prediction of Lateral Spread Displacement: ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol. 128, December 2002, p 1007-1017.

Youd, T.L. and Hoose, S.N., 1978, Historic Ground Failures in Northern California Triggered by Earthquakes, United States Geologic Survey Professional Paper 993.

© 2014 Cornerstone Earth Group, Inc.

Project Title 8 FEET
Project No. 0.00 (Inches)
Project Manager 50 FEET

0.33 (Inches)
Controlling Fault
Earthquake Magnitude (Mw) 7.6
PGA (Amax) 1.02 (g)
LDI2

0.00 L/H 5.0
Ground Water Depth at Time of Drilling (feet) 20 LDI1Corrected for Distance 0.00 (4 < L/H < 40) Design Water Depth (feet) 8
Ave. Unit Weight Above GW (pcf) 120 0.0 to 0.0 feet
Ave. Unit Weight Below GW (pcf) 125 1Not Valid for L/H Values < 4 and > 40. 2 LDI Values Only Summed to 2H Below Grade.

EXPECTED RANGE OF DISPLACEMENT

POTENTIAL LATERAL DISPLACEMENT

DRY SAND SETTLEMENT FROM
TOTAL SEISMIC SETTLEMENT 0.3 INCHES

SEISMIC PARAMETERS
San Andreas

SITE SPECIFIC PARAMETERS

SCO LIQUEFACTION SETTLEMENT FROM
4A

PROJECT/CPT DATA
Halsey House
118-161-1
CPT NO. 1
FIGURE

CPT ANALYSIS RESULTS
0 5
10 15
20 25
30 35
40 45
50 0.0 0.1 0.2 0.3 0.4 Depth (feet)
Cumulative (Liquefaction) Settlement

0 5
10 15
20 25
30 35
40 45
50 0 1 2 Depth (feet)
Factor of Safety 0
5 10
15 20
25 30
35 40
45 50
0 50 100 150 200 250 Depth (feet)
qcN
0 5
10 15
20 25
30 35
40 45
50 0.0 0.5 1.0 1.5 2.0 Depth (feet)
No Liquefaction

CSR CRR

© 2014 Cornerstone Earth Group, Inc.

Project Title 8 FEET
Project No. 0.00 (Inches)
Project Manager 50 FEET

0.62 (Inches)
Controlling Fault
Earthquake Magnitude (Mw) 7.6
PGA (Amax) 1.02 (g)
LDI2

0.00 L/H 18.6
Ground Water Depth at Time of Drilling (feet) 20 LDI1Corrected for Distance 0.00 (4 < L/H < 40) Design Water Depth (feet) 8
Ave. Unit Weight Above GW (pcf) 120 0.0 to 0.0 feet
Ave. Unit Weight Below GW (pcf) 125 1Not Valid for L/H Values < 4 and > 40. 2 LDI Values Only Summed to 2H Below Grade.

EXPECTED RANGE OF DISPLACEMENT

POTENTIAL LATERAL DISPLACEMENT

DRY SAND SETTLEMENT FROM
TOTAL SEISMIC SETTLEMENT 0.6 INCHES

SEISMIC PARAMETERS
San Andreas

SITE SPECIFIC PARAMETERS

SCO LIQUEFACTION SETTLEMENT FROM
4B

PROJECT/CPT DATA
Halsey House
118-161-1
CPT NO. 2
FIGURE

CPT ANALYSIS RESULTS
0 5
10 15
20 25
30 35
40 45
50 0.0 0.2 0.4 0.6 0.8 Depth (feet)
Cumulative (Liquefaction) Settlement

0 5
10 15
20 25
30 35
40 45
50 0 1 2 Depth (feet)
Factor of Safety 0
5 10
15 20
25 30
35 40
45 50
0 50 100 150 200 250 Depth (feet)
qcN
0 5
10 15
20 25
30 35
40 45
50 0.0 0.5 1.0 1.5 2.0 Depth (feet)
No Liquefaction

CSR CRR

© 2014 Cornerstone Earth Group, Inc.

Project Title 8 FEET
Project No. 0.06 (Inches)
Project Manager 50 FEET

0.35 (Inches)
Controlling Fault
Earthquake Magnitude (Mw) 7.6
PGA (Amax) 1.02 (g)
LDI2

0.00 L/H 12.1
Ground Water Depth at Time of Drilling (feet) 20 LDI1Corrected for Distance 0.00 (4 < L/H < 40) Design Water Depth (feet) 8
Ave. Unit Weight Above GW (pcf) 120 0.0 to 0.0 feet
Ave. Unit Weight Below GW (pcf) 125 1Not Valid for L/H Values < 4 and > 40. 2 LDI Values Only Summed to 2H Below Grade.
4C

PROJECT/CPT DATA
Halsey House
118-161-1
CPT NO. 3
FIGURE

CPT ANALYSIS RESULTS

SEISMIC PARAMETERS
San Andreas

SITE SPECIFIC PARAMETERS

SCO LIQUEFACTION SETTLEMENT FROM

EXPECTED RANGE OF DISPLACEMENT

POTENTIAL LATERAL DISPLACEMENT

DRY SAND SETTLEMENT FROM
TOTAL SEISMIC SETTLEMENT 0.4 INCHES
0 5
10 15
20 25
30 35
40 45
50 0.0 0.1 0.2 0.3 0.4 Depth (feet)
Cumulative (Liquefaction) Settlement

0 5
10 15
20 25
30 35
40 45
50 0 1 2 Depth (feet)
Factor of Safety 0
5 10
15 20
25 30
35 40
45 50
0 50 100 150 200 250 Depth (feet)
qcN
0 5
10 15
20 25
30 35
40 45
50 0.0 0.5 1.0 1.5 2.0 Depth (feet)
No Liquefaction

CSR CRR

HALSEY HOUSE
118-161-1
Page A-1
APPENDIX A: FIELD INVESTIGATION
The field investigation consisted of a surface reconnaissance and a subsurface exploration program using track-mounted, limited-access, hollow-stem auger drilling equipment and trackmounted Cone Penetration Test equipment. Two 6½-inch-diameter exploratory borings were drilled on January 23, 2024 to depths of 25 and 30 feet. Three CPT soundings were also performed in accordance with ASTM D 5778-95 (revised, 2002) on January 16, 2024, to depths of approximately 44½ feet each. The approximate locations of exploratory borings and CPTs are shown on the Site Plan, Figure 2. The soils encountered were continuously logged in the field by our representative and described in accordance with the Unified Soil Classification System (ASTM D2488). Boring logs, as well as a key to the classification of the soil and bedrock, are included as part of this appendix.

Boring and CPT locations were approximated using existing site boundaries, a hand-held GPS unit, and other site features as references. Boring and CPT elevations were not determined.

The locations of the borings and CPTs should be considered accurate only to the degree implied by the method used.

Representative soil samples were obtained from the borings at selected depths. All samples were returned to our laboratory for evaluation and appropriate testing. The standard penetration resistance blow counts were obtained by dropping a 140-pound hammer through a 30-inch free fall. The 2-inch O.D. split-spoon sampler was driven 18 inches, and the number of blows was recorded for each 6 inches of penetration (ASTM D1586). 2.5-inch I.D. samples were obtained using a Modified California Sampler driven into the soil with the 140-pound hammer previously described. Unless otherwise indicated, the blows per foot recorded on the boring log represent the accumulated number of blows required to drive the last 12 inches. The various samplers are denoted at the appropriate depth on the boring logs.

The CPT involved advancing an instrumented cone-tipped probe into the ground while simultaneously recording the resistance at the cone tip (qc) and along the friction sleeve (fs) at approximately 5-centimeter intervals. Based on the tip resistance and tip to sleeve ratio (Rf), the CPT classified the soil behavior type and estimated engineering properties of the soil, such as equivalent Standard Penetration Test (SPT) blow count, internal friction angle within sand layers, and undrained shear strength in silts and clays. A pressure transducer behind the tip of the CPT cone measured pore water pressure (u2). Graphical logs of the CPT data are included as part of this appendix.

Field tests included an evaluation of the unconfined compressive strength of the soil samples using a pocket penetrometer device. The results of these tests are presented on the individual boring logs at the appropriate sample depths.

Attached boring and CPT logs and related information depict subsurface conditions at the locations indicated and on the date designated on the logs. Subsurface conditions at other locations may differ from conditions occurring at these boring and CPT locations. The passage of time may result in altered subsurface conditions due to environmental changes. In addition,

HALSEY HOUSE
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Page A-2
any stratification lines on the logs represent the approximate boundary between soil types and the transition may be gradual.

Cornerstone Earth Group Project Halsey House Operator JM-FA Filename SDF(279).cpt Job Number 118-161-1 Cone Number DDG1596 GPS Hole Number CPT-01 Date and Time 1/16/2024 11:09:52 AM Maximum Depth 44.95 ft EST GW Depth During Test Net Area Ratio .8 Cone Size 15cm² Soil Behavior Referance *Soil behavior type and SPT based on data from UBC-1983 0 5 10 15 20 25 30 35 40 45 0 450 TIP TSF 0 14 FRICTION TSF 0 12 Fs/Qt % 0 300 SPT N 0 12 1 - sensitive fine grained 2 - organic material 3 - clay 4 - silty clay to clay 5 - clayey silt to silty clay 6 - sandy silt to clayey silt 7 - silty sand to sandy silt 8 - sand to silty sand 9 - sand 10 - gravelly sand to sand 11 - very stiff fine grained (*) 12 - sand to clayey sand (*) CPT DATA DEPTH
(ft)
SOIL

BEHAVIOR
TYPE

Depth 5.02ft Ref* Arrival 10.00mS Velocity* Depth 10.04ft Ref 5.02ft Arrival 15.62mS Velocity 853.95ft/S Depth 15.06ft Ref 10.04ft Arrival 21.56mS Velocity 832.66ft/S Depth 20.05ft Ref 15.06ft Arrival 25.78mS Velocity 1173.07ft/S Depth 25.03ft Ref 20.05ft Arrival 29.69mS Velocity 1270.79ft/S Depth 30.09ft Ref 25.03ft Arrival 33.67mS Velocity 1264.22ft/S Depth 35.07ft Ref 30.09ft Arrival 36.17mS Velocity 1990.46ft/S Depth 40.03ft Ref 35.07ft Arrival 39.68mS Velocity 1406.90ft/S 0 10 20 30 40 50 60 70 80 90 100 Depth 44.98ft Ref 40.03ft Arrival 42.89mS Velocity 1544.72ft/S Time (mS) Hammer to Rod String Distance (ft): 2.17 * = Not Determined COMMENT: CPT-01 Halsey House

Cornerstone Earth Group Project Halsey House Operator JM-FA Filename SDF(280).cpt Job Number 118-161-1 Cone Number DDG1596 GPS Hole Number CPT-02 Date and Time 1/16/2024 12:01:25 PM Maximum Depth 44.95 ft EST GW Depth During Test Net Area Ratio .8 Cone Size 15cm² Soil Behavior Referance *Soil behavior type and SPT based on data from UBC-1983 0 5 10 15 20 25 30 35 40 45 0 450 TIP TSF 0 14 FRICTION TSF 0 12 Fs/Qt % 0 300 SPT N 0 12 1 - sensitive fine grained 2 - organic material 3 - clay 4 - silty clay to clay 5 - clayey silt to silty clay 6 - sandy silt to clayey silt 7 - silty sand to sandy silt 8 - sand to silty sand 9 - sand 10 - gravelly sand to sand 11 - very stiff fine grained (*) 12 - sand to clayey sand (*) CPT DATA DEPTH
(ft)
SOIL

BEHAVIOR
TYPE

Cornerstone Earth Group Project Halsey House Operator JM-FA Filename SDF(278).cpt Job Number 118-161-1 Cone Number DDG1596 GPS Hole Number CPT-03 Date and Time 1/16/2024 10:04:52 AM Maximum Depth 44.95 ft EST GW Depth During Test Net Area Ratio .8 Cone Size 15cm² Soil Behavior Referance *Soil behavior type and SPT based on data from UBC-1983 0 5 10 15 20 25 30 35 40 45 0 450 TIP TSF 0 14 FRICTION TSF 0 12 Fs/Qt % 0 300 SPT N 0 12 1 - sensitive fine grained 2 - organic material 3 - clay 4 - silty clay to clay 5 - clayey silt to silty clay 6 - sandy silt to clayey silt 7 - silty sand to sandy silt 8 - sand to silty sand 9 - sand 10 - gravelly sand to sand 11 - very stiff fine grained (*) 12 - sand to clayey sand (*) CPT DATA DEPTH
(ft)
SOIL

BEHAVIOR
TYPE

HALSEY HOUSE
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Page B-1
APPENDIX B: LABORATORY TEST PROGRAM
The laboratory testing program was performed to evaluate the physical and mechanical properties of the soils retrieved from the site to aid in verifying soil classification.

Moisture Content: The natural water content was determined (ASTM D2216) on 16 samples of the materials recovered from the borings. These water contents are recorded on the boring logs at the appropriate sample depths.

Dry Densities: In place dry density determinations (ASTM D2937) were performed on 10 samples to measure the unit weight of the subsurface soils. Results of these tests are shown on the boring logs at the appropriate sample depths.

Washed Sieve Analyses: The percent soil fraction passing the No. 200 sieve (ASTM D1140) was determined on two samples of the subsurface soils to aid in the classification of these soils.

Results of these tests are shown on the boring logs at the appropriate sample depths.

870 Market Street, Suite 1278
San Francisco, 94102
(415) 271-3117

MEMORANDUM
DATE: March 26, 2024
TO: Michael Lisbenee, David J. Powers and Assoc.

FROM: Robin J. Lee, PE
Sarah Weinberg, EIT
SUBJECT: Halsey House CEQA Hydrology
Approach to Analysis
This impact evaluation for the Halsey House (Site) in the City of Los Altos identifies potential hydrologic and water quality impacts of the proposed development. The project would comply with City standard conditions or include measures in the design that would lead to less than significant impacts.

Thresholds of Significance
Appendix G of the CEQA Guidelines and the Regulatory Setting requirements considers the proposed project to have a significant environmental impact with regard to hydrology if it would:
 Impact 1: Violate any water quality standards or waste discharge requirements or otherwise substantially degrade surface or groundwater quality;  Impact 2: Substantially decrease groundwater supplies or interfere substantially with groundwater recharge such that the project may impede sustainable groundwater management of the basin;
 Impact 3: Substantially alter the existing drainage pattern of the Site or area, including through the alteration of the course of a stream or river or through the addition of impervious surfaces, in a manner which would:
 Impact 4: Result in a substantial erosion or siltation on- or off-site;  Impact 5: Substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or offsite;
 Impact 6: Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff;
 Impact 7: Impede or redirect flood flows;
 Impact 8: In flood hazard, tsunami, or seiche zones, risk release of pollutants due to project inundation; or
 Impact 9: Conflict with or obstruct implementation of a water quality control plan or sustainable groundwater management plan.

Attachment 7 - Appendix F

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 2
March 26, 2024
Project Location
The Site’s structure is part of the Redwood Grove in the City of Los Altos. The structure is located partially in the floodway and floodplain of Adobe Creek per the effective FEMA mapping.

The Site is bound by forested park area to the north, south, west, and single-family residences to the east.

University Avenue is located east of the Site. Manresa Way is located south of the Site. Lennox Way is located west of the Site. Regional and aerial maps of the project Site are shown in Figure 1 and Figure 2, respectively.

Figure 1. Regional Map of Project Site

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 3
March 26, 2024
Figure 2. Vicinity Map of Project Site
Project Description
The proposed project would remove the existing structure from Redwood Grove Nature Preserve. This public park is approximately 6.12 acres and contains picnic tables and trails along Adobe Creek. There is also programming that takes place throughout the year, such as a summer camp and daycare.

FEMA Mapping
The Site is on the effective FIRM panel 06085C0201H dated May 18, 2009. The effective FIRM map shows the Site within the Regulatory Floodway and a Special Flood Hazard Area (SFHA) for the 100-year floodplain (Zone AE) of Adobe Creek. A Regulatory Floodway is the area reserved for watercourse and the adjacent land that must be reserved in order to discharge the base flood without cumulatively increasing water surface elevation more than a certain height.

Zone AE has a defined base flood elevation. The current FEMA mapping and the location of the Site can be seen in Figure 3.

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 4
March 26, 2024
Figure 3. Flood Hazard Zones on Project Site
Schaaf & Wheeler did a desktop analysis on the Site and noticed that the alignment of the creek appears differently on the 2020 LIDAR dataset as compared with the FEMA mapping. Schaaf & Wheeler performed a Site visit in January 2024 and determined that the Site should not be in the Regulatory Floodway. GPS points form the Site visit, and the 2020 Santa Clara County LiDAR confirm that the current FEMA map does not accurately show the path of Adobe Creek near the Site. Figure 4 summarizes these findings.

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 5
March 26, 2024
Figure 4. Site Investigation and LiDAR Creek Path

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 6
March 26, 2024
Figure 5 shows what Schaaf & Wheeler believes should be the correct FEMA mapping. The following summary of impacts assumes that the Site should not be in the floodway. While this assumption holds true for the demolition of the building, the City may want to consider a LOMR to revise the FEMA effective map if the building is to be rebuilt in the existing location.

Figure 5. Proposed FEMA Re-Mapping

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 7
March 26, 2024
Project Impacts and Mitigation Measures
Impact 1: Violate any water quality standards or waste discharge requirements or otherwise substantially degrade surface or groundwater quality Finding: Less than significant
The City of Los Altos is located in Regional Water Quality Control Board Region 2 (San Francisco Bay Region). All requirements for the Demolition of an Existing Structure as specified by the Santa Clara County must be followed. Since the project is less than an acre, it is exempt from filing with the State Water Resources Control Board and the Statewide General NPDES Permit for Storm Water Discharges Associated with Construction Activity.

The project has a less than significant impact by complying with the Santa Clara County demolition requirements.

Impact 2: Substantially decrease groundwater supplies or interfere substantially with groundwater recharge such that the project may impede sustainable groundwater management of the basin
Finding: Not studied under this memo
This section is not analyzed further for the reasons given since groundwater impacts are being studied by others.

Impact 3: Substantially alter the existing drainage pattern of the Site or area, including through the alteration of the course of a stream or river or through the addition of impervious surfaces
Finding: Less than significant
In the current condition, runoff generally flows from the west side of the Site to the north and east side of the Site and into Adobe Creek. The proposed project is to demolish the structure, which will decrease the impervious surface. Since Schaaf & Wheeler has determined the Site is not in the floodway, no conveyance will be affected. Since the addition of pervious surface by removing the building will decrease runoff generated, the alter of the existing drainage pattern is less than a significant level.

Impact 4: Result in a substantial erosion or siltation on or off Site of the plan area Finding: Less than Significant
The City is unaware of any flooding or mudslides at the current Site.

During demolition, a Stormwater Pollution Prevention Plan (SWPPP) and a Stormwater Management Plan (SWMP) will be prepared to avoid on-site erosion.

Therefore, since the risk of increased erosion is negligible the project would have a less than significant level as a result of the project.

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 8
March 26, 2024
Impact 5: Substantially increase the rate or amount of surface runoff in a manner which would result in flooding on or off site of the plan area Finding: Less than significant
Since the demolition of the Site will increase the pervious area, the rate of surface runoff will be decreased. Flooding to Adobe Creek is expected to be a less than significant level.

Impact 6: Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff
Finding: Less than significant
Since the Site runoff is expected to decrease due to the removal of impervious surface, the project has a less than significant impact.

Impact 7: Alter existing drainage patterns, including streams and rivers, that impede or redirect flood flows
Finding: Less than significant
The project Site is located within the Regulatory Floodway and a SFHA. Since Schaaf & Wheeler believes that the Site should not be in the Floodway, no conveyance will be altered by the removal of the Site. Therefore, the project would be considered to have a less than significant impact.

Impact 8: In flood hazard, tsunami or seiche zones, risk release of pollutants due to project inundation
Finding: Less than significant
The project removes the structure from the Site, so the risk of pollutant release due to project inundation is not a concern. In addition, the Site is located significantly far enough away from any tsunami or seiche zones.

Therefore, the project would have a less than significant impact with regards to inundation by seiche or tsunami.

Impact 9: Conflict with or obstruct implementation of a water quality control plan or sustainable groundwater management plan
Finding: Less than significant
During demolition of the project, short term impacts to water quality can occur when soils are disturbed, making it susceptible to water erosion and sedimentation. Other pollutants found during demolition are petroleum products (gasoline, diesel, kerosene, oil, and grease), hydrocarbons from asphalt paving, paints, and solvents, detergents, nutrients (fertilizers), pesticides (insecticides, fungicides, herbicides, rodenticides), and trash.

To: Michael Lisbenee, David J. Powers and Assoc.

Schaaf & Wheeler 9
March 26, 2024
Potential demolition pollutant impacts can be mitigated through preparation and implementation of an erosion control plan and a SWPPP consistent with recommended design criteria. The erosion control plan in the SWPPP would include components for erosion control, such as phasing of grading, limiting areas of disturbance, designation of restricted-entry zones, diversion of runoff away from disturbed areas, protective measures for sensitive areas, outlet protection, and provision for re-vegetation or mulching.

The project would have a less than significant impact to control water quality of surface runoff.

PAGE & TURNBULL 1 July 15, 2024

HALSEY HOUSE RELOCATION

FEASIBILITY STUDY

LOS ALTOS, CALIFORNIA
[23219]

PREPARED FOR
David J. Powers & Associates, Inc.

July 15, 2024
FINAL – REVISED
Attachment 8 - Appendix G

PAGE & TURNBULL 2 July 15, 2024

TABLE OF CONTENTS
INTRODUCTION..................................................................................................................................................3 Background and Purpose..............................................................................................................................3 Methodology ...................................................................................................................................................3 BUILDING DESCRIPTION....................................................................................................................................3 RELOCATION .......................................................................................................................................................5 General Considerations.................................................................................................................................5 Structural Considerations .............................................................................................................................5 Logistical Considerations...............................................................................................................................7 Receiver Site Considerations ......................................................................................................................10 EVALUATION OF POTENTIAL IMPACTS..........................................................................................................12 Historic Resource Integrity Considerations ..............................................................................................13 Site Impact Considerations .........................................................................................................................15 CONCLUSION....................................................................................................................................................17 ATTACHMENT A: STRUCTURAL REPORT........................................................................................................18

PAGE & TURNBULL 3 July 15, 2024

INTRODUCTION

BACKGROUND AND PURPOSE
Page & Turnbull has been retained by David J. Powers & Associates to provide Preservation Alternative consultation, including a Feasibility Study Memorandum considering the relocation of the Halsey House related to the Environmental Impact Report (EIR) analyzing the potential demolition of the Halsey House in the Redwood Grove Nature Preserve in Los Altos, California.

This Feasibility Study has been prepared to assess the feasibility of the proposed relocation and evaluate the potential impacts to the historic resource’s integrity as an alternative to its demolition.

This property located at 482 University Avenue, was found eligible under Criterion 1 (Events) for the California Register of Historical Resources (California Register) at the state level by the research and analysis reported in the Halsey House Historic Resource Evaluation (HRE) dated August 30, 2021, prepared by Page & Turnbull.

The focus of the following analysis is (1) on the physical feasibility of relocating the building either on-site or off-site to an acceptable receiver site and (2) on the evaluation of potential adverse impacts to the historic resource and surrounding site. It is not a comprehensive study of the overall feasibility of the option with regard to cost and further repair or rehabilitation scope.

METHODOLOGY
Page & Turnbull staff performed on-site observations of the overall condition of the building, with particular attention to its construction and foundations, to evaluate the structural feasibility of relocating the building. T&S Structural was also consulted regarding the logistical and structural considerations for potentially relocating the building on-site or off-site.

BUILDING DESCRIPTION
The following building description is summarized from the Historic Resource Evaluation dated August 30, 2021, prepared by Page & Turnbull, unless otherwise noted.

The building, currently located in the approximately six-acre Redwood Grove owned by the City of Los Altos (Owner), is a one-story single-family residence constructed in 1923 with a 1928-addition at the west corner of the north façade. The generally U-shaped wood frame building has a clay tile hipped roof, stucco clad exterior walls, and features a brick chimney at the west façade of the addition and a stucco clad chimney centered at the south-facing wall of the courtyard. Fenestration on the building consists of original multi-lite wood windows including asymmetrically divided threeover-one double-hung sash, six-lite casement windows, small four-lite casement windows, some one-over-one double-hung windows, and two pairs of six-lite slider window, and non-original windows including a jalousie window and some fixed single-lite windows. The building also retains several original wood-frame doors that include paired ten-lite French doors. The enclosed courtyard features a stucco clad south wall with an arched entrance preceded by semi-circular stone steps and

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a small fountain attached to the wall and flanked by two curved buttresses with built in benches.

The primary entrance to the residence features a porch reached via low concrete steps and a concrete landing with a wood pergola and plastic roof. Some of the extant original interior features consist of wood floors, painted plaster walls and ceilings, wood window and door trim, wood baseboard trim and picture railing, a brick fireplace at the addition and a tile fireplace at the original north living room. Non-historic finishes such as acoustic panels, drop ceilings and partitions walls were added when the property was acquired by the city in 1974.

Figure 1 - View of courtyard, looking northwest.

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RELOCATION

GENERAL CONSIDERATIONS
Some potential challenges to consider for either on-site or off-site relocation of the building may include the need for soil stabilization or sequencing coordination. In the case of relocation, the current site and building would likely need to undergo a preparation process which could include bracing the building, detaching, or deconstructing portions of the building, and clearing site features, including landscaping, adjacent to the building to make way for building move equipment.

Preparations would also need to be made to the selected receiver site, including clearing an adequate area for equipment access, and constructing new foundations and utility connection points for the building. Due to its overall footprint and general layout, the subject building would need to be selectively deconstructed and relocated in sections for feasible transportation.

STRUCTURAL CONSIDERATIONS
A structural evaluation of the subject building for potential on or off-site relocation was performed by T&S Structural to assess the overall structural condition of the building and inform an appropriate bracing design to ensure the safety of the building during the relocation process. The report considers three primary variables impacting the feasibility of moving the structure: the identification of a suitable receiver site; the availability of a suitable transportation route; and the structural integrity of the structure. Refer to Attachment A for the full structural report.

This feasibility study assumes for the purposes of analysis that an on- or off-site receiver location would be identified, procured, and prepared in any relocation scenario, while recognizing the potential challenges of securing such a site in the City of Los Altos. Assuming a suitable receiver site is secured, however, the most significant challenge to relocating the Halsey House would be the second variable: the availability of a suitable transportation route. T&S Structural evaluated three potential routes for relocating the Halsey House off-site and analyzed the impacts of their respective constraints. Any of the potential routes would significantly impact both the house and the surrounding environment. Of particular concern for the house is that the narrowness of the available routes considered in relation to the geometry of the house results in the necessity of dividing the house into approximately 14 separate sections to be relocated and reassembled.

As to the building’s structural integrity, preliminary visual examination of the building indicates that it appears to be in sound structural condition, thus it is an acceptable candidate for relocation from a structural perspective. The residential building’s wood frame sits on a concrete pier and post system foundation with an accessible crawl space. To relocate the building, the walls and roof would need to be laterally braced and detached from the existing foundation. Considering the size of the building, relocation would require cutting the walls and wood frame at key points while avoiding cutting the building at window or door openings. As noted above, the site constraints dictate that the number of sections would be approximately 14. This approach also requires that all existing floor-mounted interior walls, cabinets, flooring, or fixtures are removed from the building prior to

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relocation. Elements of historic significance can be reinstalled at the receiver site and noncontributing elements discarded. The ancillary components of the building, including the front porch pergola, south courtyard wall and gate, and chimneys, all pose additional considerations for the relocation process. These components would likely need to be detached and either independently shored and transported, or deconstructed at the original site, and reconstructed at the receiver site.

Figure 2 - View of the brick chimney at west addition, view looking northeast.

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LOGISTICAL CONSIDERATIONS
For the purposes of this study, a preliminary review of logistical feasibility for relocation was conducted using Google Maps views of the site and surrounding area, as well as on-site measurement. The Halsey House is approximately 16’-7” in height with an approximate building footprint of 88 feet by 86 feet. The three possible routes for relocation off-site include the Main Entrance to the Preserve; the trail out of the Preserve onto Manresa Way, which is a private road; or through an existing fence onto Manresa Way via Manresa Lane, which is also private. The second and third options both lead to University Ave. from Manresa Way (figure 4).

Key Map: Route Options (background courtesy Google Maps, 2024) The first option is paved and relatively clear but is limited in width by the existing bridge and mature redwoods on either side of the route. The side rails of the bridge could be temporarily removed to

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achieve an approximate maximum section width of 14’-6”. (figures 3 and 6) However, the load capacity of the bridge is reported to be 8 tons, which is an additional limiting factor. If the residence were cut into the 14 or more sections necessary to accommodate the route width, each section would weigh approximately eight (8) tons itself, to which would be added approximately seven (7) tons of shoring beams and power dollies for the move, for a total load of approximately 15 tons. To accommodate this load, a temporary bridge over the existing bridge would be required. Temporary bridge construction for the purpose of building relocation is not an unusual scope of work for building movers, and thus has been factored into the feasibility analysis. The temporary bridge would also need to accommodate the load of service trucks and heavy equipment needed for the project, which range from approximately four (4) to nine (9) tons for typical compact units available, though smaller equipment is also manufactured.

The second option would require trimming and selective removal of the existing native plantings and mature trees along the trail and at key intersections, but overall could accommodate wider sections of up to 19’-0” if the existing median features at the intersection of Manresa Way and University Ave were removed. Finally, the third option is limited by the width of the existing private community gates, which are substantial masonry structures, and would require transported sections to be no more than 16’-0” wide. Both the second and third option would also require coordination with and approval from the gated community in addition to the typical local jurisdictional coordination, particularly for removal and trimming of site features along the route. Therefore, these options are considered infeasible by the Owner.

Beyond the Redwood Grove and the adjacent neighborhoods, the typical street within a half-mile radius of the site is approximately 25 feet to 40 feet in width. Refer to Attachment A for the structural report for photos of the three options and mapping of the different routes.

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Figure 3 - View of the Redwood Grove Nature Preserve entry from University Ave., view looking west.

Figure 4 - View of Manresa Way entry from University Ave., view looking southwest. Source: Google Earth Utility lines run through the south side of the parcel with a relatively low head clearance and further assessment of utility lines on the site should be done prior to a relocation effort. Additional

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obstacles to relocation would be specific to the route taken, distance to and configuration of the receiver site, and may include unforeseen challenges not covered in this study. Relocation of the building within the site would likely require less coordination with external jurisdictional agencies than an offsite relocation.

In advance of relocation, a receiver site would also need to be secured and a transportation route determined. The proposed receiver site must be evaluated for transportation feasibility logistics in addition to the suitability of its setting. The act of relocating the building offsite would require extensive coordination with several key city, transportation, and utility agencies. This process may include mapping locations and heights of utility lines, traffic signals, vegetation, or other objects that exist along the proposed relocation route. As a general rule, the greater the distance between the current site and receiver site, the more complex and potentially expensive the relocation process would become.

The receiver site would need to be prepared in advance of the building relocation. This may include at a minimum clearing debris and other materials from the site to create a path for the buildings to enter the site. A full build-out of a new foundation prior to the building move may be necessary depending on the sequencing of the proposed project. If the buildings are not immediately slated for rehabilitation at the receiver site, they would need to be secured in place following the relocation until a full rehabilitation could be completed. Intermediate protective measures could include mothballing of the building sections and the implementation of routine monitoring until a full rehabilitation could be completed.

RECEIVER SITE CONSIDERATIONS
To help maintain the historic integrity of the building in the case of off-site relocation, potential receiver sites should be reviewed based on specific site selection criteria outlined in this section.

Due to the character-defining relationship of the building’s historic use as a residence and retreat space, a future receiver site for the building would ideally recreate the feeling and setting of the original site. The configuration of the building on the site should be reflective of the historic spatial relationship of the building to the public right-of-way. Refer to Table 1 and Figure 5 - Annotated Existing Site Plan below, which summarize the building’s current relationship to the existing site.

Ideally, a potential receiver site would include as many of these attributes as possible, with priority being given to a site where the building’s setbacks, orientation, and relationship to grade and the public right-of-way could be replicated as closely as possible to the historic condition.

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Table 1 - Receiver Site Selection Criteria -- 482 University Avenue [APN 17530021] Neighborhood
Context & Zoning
Lot Size
Orientation to
Public Right of
Way
Setbacks & Building
Placement on Lot Setting
Early to mid-20th
century 1-2 story
buildings with
residential use and
green spaces with
mature trees.
4+ acres
Northeast-facing
primary entry
200’+ setbacks all sides
Secluded
Park-like
Publicly owned
Forested
Figure 5 - Annotated Existing Site Plan – Image from Google Earth edited by Page & Turnbull.

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EVALUATION OF POTENTIAL IMPACTS
The relocation of the historic resource would have significant implications for the Halsey House and its current historic status and eligibility for the California Register of Historic Places. The following statements are summarized from the HRE unless otherwise noted. The HRE provides a comprehensive analysis and evaluation of the resource according to the seven aspects of integrity set forth by the National Park Service and the California Office of Historic Preservation.

The HRE established that the existing site and its plantings are contributors to the historic resource’s significance. It was determined that the Halsey House is eligible for the California Register under Criterion 1 (Events) at the state level of significance as an excellent example of the residential development patterns of Los Altos and for the establishment of the Redwood Grove, which is a unique property developed by Emma Halsey and her Japanese gardener, Mori, in the 1920s. The character-defining features of the historic resource include the original features, materials, and design elements of the residence and features of the landscape and site. The identified period of significance for the property begins in 1923 and includes any alterations undertaken during Emma Halsey’s period of residence, which ended when she sold the property in 1945.

The identified character-defining features of the property include:

Exterior Features of The Halsey House
• Overall form and massing of the building (low, horizontal emphasis) • Clay tile clad hipped roof
• Stucco cladding along exterior with a textured finish • Original multi-lite wood sash windows, including three-over-one double-hung windows with ogee lugs, four-lite wood casement windows, six-lite wood casement windows, and six-lite wood sash slider windows
• Multi-light glazed French doors
• Multi-light sidelights flanking doors at the entrance porch and along south-facing wall of rear courtyard
• Tinted and stamped concrete at front entry porch and terrace • Enclosed rear courtyard with tinted and stamped concrete patio at north end, builtin bench seating, fountain, and stone patio with steps at south end, and concrete stairs and metal railing at south end of west wing
• Original chimney with stucco cladding along south-facing wall of courtyard • South courtyard wall with round arched wood plank door • Semi-circular stone stairs along exterior of courtyard door in south courtyard wall • Extant original metal fixtures including portions of original lamps and original door hardware at primary entrance
Interior Features of The Halsey House
• Original brick and tile fireplaces

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• Original wood floors
• Plaster walls and ceilings
• Original wood panel doors
• Original hardware and wood trim of doors and windows
• Original wood baseboards and picture molding
Site
• Residence located deep within the approximately six-acre parcel and not visible from University Avenue
• Natural setting including:
o Mature redwood trees
o Mature oak trees
o Adobe Creek
• Additional fruit trees, flowering trees, and plantings that appear to date from the period of significance

HISTORIC RESOURCE INTEGRITY CONSIDERATIONS
The Halsey House is considered individually eligible for the California Register under Criterion 1 for its association with events that have made a significant contribution to the broad patterns of local or regional history, or the cultural heritage of California. In order to qualify for listing in any local, state, or national historic register, a property or landscape must possess significance under at least one evaluative criterion and retain integrity. Seven aspects are used to evaluate a resource’s integrity— location, setting, design, materials, workmanship, feeling, and association.1 A property must possess most, or all, of these aspects in order to retain overall integrity. If a property does not retain integrity, it can no longer convey its significance and is therefore not eligible for listing in local, state, or national registers. The Halsey House currently retains all seven aspects of integrity, however four aspects—location, setting, feeling and association—could be impacted by the off-site relocation of the building. Integrity of design, materials, and workmanship would remain intact. In addition, if the building is removed from the site, the historic integrity of the Redwood Grove would also be impacted due to the interrelated historic significance of the residence and its setting. The following discussion summarizes the existing status of each aspect of integrity in relation to the Halsey House, and how each aspect could be impacted by relocating the building. A short discussion on the resulting impacts on the integrity of the Redwood Grove follows within the Site Impact Considerations section.

Location: The building has remained situated at its location of original construction since 1923 and the overall property has retained its location and its approximate size. 1 U.S. Department of the Interior, National Park Service, National Register Bulletin 15: How to Apply the National Register Criteria for Evaluation (Washington, D.C.: National Park Service, 1995), 44.

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The relocation of the Halsey House would likely adversely impact this aspect of integrity. The National Park Service states in the Moving Historic Buildings publication, dated 1979, that moving a historic structure irreparably diminishes or destroys its integrity of location and that when the decision is made to move a historic structure, careful consideration must be given to determining what aspect of the structure contributes most toward qualifying it as worthy of preservation.2 However, the California Office of Historic Preservation notes that under special circumstances a resource might retain its eligibility for listing in the California Register if it was moved to prevent its demolition at its former location and if the new location is compatible with the original character and use of the historical resource. A historical resource should retain its historic features and be sited such that there is compatibility in orientation, setting, and the general environment of the resource at its new location. 3 Setting: The building was erected within a large, six-acre piece of land and was sited to take advantage of the landscape and the curve of Adobe Creek. Early in the property’s history, Emma Halsey and Mori, her gardener, planted many redwood saplings to complement the existing oak trees on the property. The landscaping work by Emma was continued into the early 1940s with the assistance of Yoshio Hongo, following Mori’s retirement. These redwoods remain today and have grown to maturity. The Halsey House therefore retains its wooded and natural setting.

The relocation of the Halsey House would impact this aspect of integrity as the setting of the Redwood Grove was shaped and created by Emma Halsey and her gardeners from 1923 to 1945, reflecting the preferences of Emma Halsey in nurturing and developing the unique setting of the Halseys’ home. While integrity of setting would be compromised by relocating the building, the selection of a receiver site that features mature redwoods and oaks may help to minimize this potential impact.

Feeling: The Halsey House retains integrity of feeling. The building retains the feeling of an early 1920s residence that was intended to serve as a year-round home for the Halsey family and was set within a wooded, lush landscape along Adobe Creek. The property retains its semi-rural feeling through its wooded setting that is removed from the main public right-of-way on University Avenue.

The relocation of the Halsey House could potentially impact and compromise the integrity of feeling of the historic resource. In order to avoid or minimize this potential impact, the receiver site should allow for the same deep setbacks and relation to the public right-of-way and be of a similar wooded environment.

Association: The Halsey House retains integrity of association. The building is significant for its residential development history and the development of Redwood Grove in the early 1920s by Emma Halsey and Mori. These associations continue to be represented through the retention of the 2 U.S. Department of the Interior, National Park Service, Moving Historic Buildings (Washington, D.C.: National Park Service, 1979), 9.
3 California Office of Historic Preservation Technical Assistance Series #6 California Register and National Register: A Comparison (for purposes of determining eligibility for the California Register) Sacramento: California Office of State Publishing. January 2011. Accessed February 13, 2024,
http://ohp.parks.ca.gov/pages/1069/files/technical/assisstance/bulletin/6/2011/update.pdf

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residence’s architectural characteristics that date to the time of Emma Halsey’s period of residence and the retention of the property’s landscape and the redwood trees that were transplanted to the site by Emma and Mori in the early 1920s.

The relocation of the Halsey House would impact the integrity of association of the resource given the close and interconnected significance between the building and the landscape. Although the architectural characteristics of the property would be retained in full and may continue be able to demonstrate the patterns of early residential development in Los Altos, the property’s significance as it relates to the development of the Redwood Grove would be lost.

As outlined above, the Halsey House, if relocated, would likely lose integrity of setting and association, while integrity of location and feeling would be partially impacted.

SITE IMPACT CONSIDERATIONS
The historic resource is currently located in Redwood Grove Park, which is owned and managed by the City of Los Altos. The Halsey House and the larger property of Redwood Grove was listed as a City of Los Altos Historic Landmark in May 1981. The park is approximately 6.7-acres and is densely vegetated with trees including redwoods, oaks, fruit trees, and flowering trees planted by the original property owners. The park also features a natural stream, native plantings, picnic amenities, a boardwalk, and paved and unpaved pedestrian walkways. The relocation of the historic resource would require potential clearing of vegetation. This may necessitate removal or thinning of some of the mature redwood trees and new growth at the site, as well as clearing the route between the residence and the road. Adobe Creek crosses the site from the north boundary to the center point of the property’s east boundary. The creek acts as the natural western boundary of the City of Los Altos. Use of heavy equipment and large vehicles would potentially impact the surrounding soils and creek banks. A procedure to restore any significant damage incurred or remove debris left at the site and along the route to the closest public street after the building relocation process is completed should be implemented.

As the Redwood Grove is a contributing feature of the identified historic resource, a brief discussion of its potential historic integrity if the Halsey House were to be removed from the site is warranted.

As identified in the HRE, the historic resource consists of both the residence and the site. Removal of the residence from the Redwood Grove would result in the loss of most of the character-defining features that have previously been identified (refer to list of the character-defining features included above). The character-defining features related specifically to the site would be largely retained, with only the loss of the “Residence located deep within the approximately six-acre parcel and not visible from University Avenue.” With the loss of the residence, however, the history of the Redwood Grove as a private and personal landscape created through the personal efforts of Emma Halsey and her gardeners would also be lost. This can be understood as a loss of integrity related to feeling and association. In addition, given the relative changes to the property since the end of the period of significance (1945), there have already been losses to the design and workmanship related to the

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original efforts of Emma Halsey, Mori, and Yoshio. The impacts to these aspects of integrity would ensure that the identified historic resource (consisting of the deeply interconnected history of the residence and its setting) would no longer be eligible for individual listing on the California Register for the criterion discussed within the HRE. The Redwood Grove would likely be able to be listed on the Los Altos Historic Resources Inventory at a local level of significance as a unique landscape in Los Altos, but would require updated documentation and would benefit from a robust interpretive program. Interpretive efforts that retain the footprint of the Halsey House and its rear courtyard, along with an interpretive panel may assist in bringing the story of this unique place to a wider audience.

Figure 6 - View of the existing non-historic wood bridge and mature trees at northeast of the building.

Source: Google Earth.

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CONCLUSION
This feasibility study has been prepared for the Halsey House located at 482 University Avenue, Los Altos, California which is eligible for listing in the California Register of Historic Resources. The report assesses the feasibility of relocating the building offsite, and the potential adverse impact to the historic resource and its current site in the case of a relocation on- or off-site. The report analyzes at a high-level the range of challenges and considerations required for the relocation process and preservation of the building. The relocation of the Halsey House would likely adversely impact several aspects of integrity currently retained by the historic resource including location, setting, feeling, and association. The resource might retain its significance as a good example of changing residential patterns in Los Altos if it is placed on a suitable receiver site, but would lose its significance related to the development of the Redwood Grove. With most of the aspects of integrity impacted, the resource could potentially lose its eligibility for the California Register. In addition to the impacts to the building, relocation could result in significant impacts to the natural resources on the site, including to native plantings, mature trees, and Adobe Creek. Considering the cumulative impacts to site and the integrity of the historic resource determined by this analysis, relocation does not appear to be a feasible alternative for the preservation of the Halsey House.

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ATTACHMENT A: STRUCTURAL REPORT

SAN LUIS OBISPO | PASADENA | SANTA BARBARA | NORTHERN NV | SANTA CLARA 1171 HOMESTEAD ROAD
SANTA CLARA, CA 95050
408-615-9200
WWW.TSSTRUCTURAL.COM 408-615-9200
Halsey House Structural Feasibility
The purpose of this feasibility study is to establish the feasibility of moving the existing Halsey House from its’ current location in the Redwood Grove Preserve at 482 University Avenue in Los Altos California. There are three primary variables that control the feasibility of any move. 1) There will need to be a suitable receiver site within a reasonable distance. Without a receiver site that move cannot take place.

It is our understanding that a receiver site has not yet been identified. We will assume that one will be located.
2) There needs to be a suitable transportation route to move the structure from its current location to the receiver site.

During our site visit T&S Structural was able to Identify three possible transportation routes. In each route there will be low hanging branches that will need to be trimmed back and smaller trees that will need to be removed, there are also major obstructions that will limit the size of the sections that can be transported. The following are highlights of each route. Please see the attached Exhibit A for a diagram of each route and photographs of the major obstructions.  The Main Entrance to the Preserve – The main entrance to the preserve is the first route that was investigated. The route is paved and relatively clear. The major obstruction is in the path over the bridge, where there are redwood trees on each side of the bridge. The clear distance between trees is 16’-2”. These obstructions limit the width of any section to be transported to aa approximate maximum of 14’-6” and to achieve the 14’-6” the bridge rails would need to be temporarily removed. Each section of the building would weigh approximately 8 tons with an additional 7 tons of shoring equipment which includes shoring beams and two power dollies. The bridge capacity is reported to be 8 tons and would not be capable of supporting this 15-ton load. A temporary bridge would be required to be constructed over the top of the existing bridge deck in order to use this route.  The Trail out of the preserve to Manresa Drive – The trail itself is narrow but there is sufficient level area to the east of the trail to allow for transport. This would most likely cause damage to the native planting that is now being restored. There are three major obstructions in the route. At the entrance to the trail from the park there is a large old growth tree. In order to use the trail the section of the structure would need to go off the trail into the native planting to the east and around the tree to the east. At the other end of the trail as it exits to Manresa Drive the access narrows to 20’-9”. At the intersection of Manresa Drive and University Avenue there is a large old growth tree that narrows the exit to University Avenue to 20’-6”. These obstructions limit the width of any section to be transported to an approximate maximum of 19’-0”.
 Through the fence onto Manresa Lane – If the fence is removed Manresa Lane is a paved route out of the area. This is a private road that is part of a planned development. The development is gated. The gates reduce the road width to 17’-4” at the intersection of

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Manresa Lane and Manresa Drive. Once on Manresa Drive the same obstructions exist at the intersection of Manresa Drive and University Avenue. These obstructions limit the width of any section to be transported to an approximate maximum of 16’-0”.

Based on these constraints the structure would need to be cut into a minimum of 14 sections 3) The integrity of the existing structure is very important. The process of disconnecting a structure from its’ foundation, cutting it into manageable sections, lifting them, and transporting them to a new location is stressful. There needs to be adequate integrity for this process to take place without causing irreparable damage to the existing structure.

The Halsey House is a one-story wood frame single family residential that is constructed in a horseshoe shape with a central courtyard. The residence has been vacant for many years and the architectural finishes are showing signs of a lack of maintenance. There are a few locations where the roof has been leaking and the ceiling finishes have deteriorated and fallen. Despite the architectural damage the overall structure is in good condition.

Based on the constraints of each route out of the preserve and the limited size of the sections to be transported, in our opinion the feasibility of successfully moving the structure is very low.

EXHIBIT A

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Figure 1
Figure 2

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Figure 3
Figure 4

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Figure 5
Figure 6

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Figure 7