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CARB. 2005. Air Quality and Land Use Handbook: A Community Health Perspective. April 2005.
Accessed August 2016. http://www.arb.ca.gov/ch/landuse.htm.
CARB. 2009. “ARB Fact Sheet: Air Pollution Sources, Effects and Control.” Page last reviewed December 2, 2009. Accessed October 2018. https://www.arb.ca.gov/research /health/fs/fs2/fs2.htm.
CARB. 2011. Regulation for In-Use Off-Road Diesel-Fueled Fleets. December 2011. Accessed December 2016. https://www.arb.ca.gov/msprog/ordiesel/documents /finalregorder-dec2011.pdf.
CARB. 2014. Regulation to Reduce Emissions of Diesel Particulate Matter, Oxides of Nitrogen and Other Criteria Pollutants from In-Use Heavy-Duty Diesel-Fueled Vehicles. January 2014.
Accessed December 2016. https://www.arb.ca.gov/regact/2014/truckbus14/tbfrooal.pdf.
CARB. 2016a. “Glossary of Air Pollution Terms.” Accessed October 26, 2016. http://www.arb.ca.gov /html/gloss.htm.
CARB. 2016b. “Overview: Diesel Exhaust and Health.” April 12, 2016. Accessed December 2016. https://www.arb.ca.gov/research/diesel/diesel-health.htm.
CARB. 2016c. “Ambient Air Quality Standards.” May 4, 2016. Accessed December 2016. http://www.arb.ca.gov/research/aaqs/aaqs2.pdf.
CARB. 2017. Inhalable Particulate Matter and Health (PM2.5 and PM10). https://www.arb.ca.gov /research/aaqs/common-pollutants/pm/pm.htm.
CARB. 2018. “Area Designation Maps/State and National.” Last reviewed December 28, 2018. http://www.arb.ca.gov/desig/adm/adm.htm.
CARB. 2019a. “Glossary.” Accessed January 2019. https://ww2.arb.ca.gov/about/glossary.
CARB. 2019b. “Ozone & Health.” https://ww2.arb.ca.gov/resources/ozone-and-health.
CARB. 2019c. “Nitrogen Dioxide & Health.” https://ww2.arb.ca.gov/resources /nitrogen-dioxide-and-health.
CARB. 2019d. “Carbon Monoxide & Health.” https://ww2.arb.ca.gov/resources /carbon-monoxide-and-health.
CARB. 2019e. “Sulfur Dioxide & Health.” https://ww2.arb.ca.gov/resources/sulfur-dioxide-and-health.
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CARB. 2019f. “iADAM: Air Quality Data Statistics.” Accessed September 2020. https://www.arb.ca.gov/adam/topfour/topfourdisplay.php.
City of St. Helena. 1993. City of St. Helena 1993 General Plan. September 28, 1993.
City of St. Helena. 2018. St. Helena General Plan Update 2040, Draft Environmental Impact Report. SCH# 2010042001. October 23, 2018.
City of St. Helena. 2019. City of St. Helena General Plan Update 2040. June 2019.
EPA (U.S. Environmental Protection Agency). 2013. “Integrated Science Assessment of Ozone and Related Photochemical Oxidants.” https://cfpub.epa.gov/ncea/isa /recordisplay.cfm?deid=247492.
EPA. 2016. “Criteria Air Pollutants.” July 21, 2016. Accessed June 2018. https://www.epa.gov /criteria-air-pollutants.
EPA. 2018a. “Criteria Air Pollutants.” March 8, 2018. Accessed October 2018. https://www.epa.gov /criteria-air-pollutants.
EPA. 2018b. “Region 9: Air Quality Analysis, Air Quality Maps.” Last updated September 28, 2018. http://www.epa.gov/region9/air/maps/.
EPA. 2019. “AirData: Access to Air Pollution Data.” Last updated June 13, 2018. Accessed November 2018. http://www.epa.gov/airdata/ad_rep_mon.html.
NRC (National Research Council). 2005. Interim Report of the Committee on Changes in New Source Review Programs for Stationary Sources of Air Pollutants. Washington, DC: The National Academies Press. https://doi.org/10.17226/11208.
WRCC (Western Regional Climate Center). 2016. Saint Helena, California (047643), Monthly Climate Summary. https://wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca7643.
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3.4 BIOLOGICAL RESOURCES
3.4.1 Introduction
This section describes the existing biological resources present within the proposed Hunter Subdivision Project (Proposed Project) site and vicinity, identifies associated regulatory requirements, evaluates potential impacts, and identifies feasible mitigation measures.
Comments received in response to the Notice of Preparation included general concerns regarding potential Proposed Project impacts to wildlife species and the Napa River, and specific concerns regarding potential Proposed Project effects on fish species in the Napa River. All of the concerns raised are addressed in this section. A copy of the Notice of Preparation and comments received is included in Appendix A.
Biological resources discussed herein were identified through the review and compilation of existing information and field reconnaissance surveys conducted by Dudek staff. Existing documentation of potential biological resources at the Project site include an Updated Biological Assessment report prepared by Wetland Research Associates (WRA), a Wetland Delineation prepared by Dudek, and the results of a rare plant survey all provided in Appendix D. Other sources reviewed are listed in Section 3.4.6, References.
3.4.2 Environmental Setting
This section provides information on the condition of natural resources in the region and on the Project site, the extent of sensitive natural communities and critical habitat, presence or absence of jurisdictional wetlands on the site, and the distribution and habitat requirements of special-status species that have been recorded from or are likely to occur in the Proposed Project vicinity and identifies the biological resources that could be affected by implementation of the Proposed Project.
Summary of Previous Studies
Wetland Delineation (North Fork Associates 2006): North Fork Associates conducted a formal wetland delineation of the Project site in July 2006. Two ditches were mapped as present in the Project site. No wetlands were identified during the fieldwork. The results of the delineation were summarized in a formal report (dated September 12, 2006). The U.S. Army Corps of Engineers (USACE) verified the delineation in 2008, which is valid for 5 years from the date of the letter.
Biological Assessment (WRA 2011): WRA conducted a field reconnaissance survey of the Project site in November 2011, to verify site conditions, assess habitat suitability for specialAgenda Item #5.4.
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status species, and evaluate the potential presence of any wetlands or other waters of the U.S.
The survey was conducted after any wetlands that may have formed as a result of the placement of fill assocated with the Napa River Flood Control project in 2010. No special-status species were detected in or near the Project site during the 2011 survey.
Updated Biological Assessment (WRA 2015): WRA conducted a biological assessment of the Project site in March 2015. The purpose of the survey was to compare existing site conditions to those documented in 2011. The report concluded that existing site conditions have not changed substantially since 2011. No special-status species were detected during the 2015 site assessment.
Summary of Studies Conducted as Part of This Project
The following technical studies and site assessments were conducted in 2018 and/or 2019 by Dudek and are included in Appendix D:
• In February 2018, Dudek conducted a biological reconnaissance survey to to verify WRA’s 2015 Biological Assessment. The survey included a general assessessment of on-site habitats and their potential to support various special-status plant and wildlife species and to characterize and map on-site vegetation communities. The survey consisted of pedestrian transects throughout the Project site to collect data related to biological resources present or potentially present within the site. An aerial photograph and digital georeferenced map with an overlay of the property boundary was used to map the vegetation communities and record any anecdotally observed special-status or sensitive biological resources while in the field. Incidental observations of wildlife (common and/or special-status) or wildlife sign (e.g., tracks, scat) were also recorded.
The field survey included the Project site only; however, general characteristics of adjacent properties were also noted during the survey by scanning with and without binoculars. A separate report summarizing Dudek’s February 2018 survey was not prepared because the results of the survey have been incorporated into this section. • In February and April 2019, Dudek biologists conducted a jurisdictional delineation to characterize and map wetland/aquatic areas potentially under the jurisdiction of USACE pursuant to Section 404 of the federal Clean Water Act and under California Department of Fish and Wildlife (CDFW) jurisdiction pursuant to Section 1600 of the California Fish and Game Code. Potentially jurisdictional features were delineated based on methodology described in the 1987 Corps of Engineers Wetlands Delineation Manual (USACE 1987) and the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region (USACE 2008). Nonwetland waters of the United States are delineated based on the presence of an ordinary high water mark, as determined using the methodology in A Field Guide to Agenda Item #5.4.
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the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States (USACE 2010).
• In June 2020, a Dudek botanist conducted a plant survey for the bent-flowered fiddleneck (Amsinckia lunaris), a California Rare Plant Rank (CRPR) 1B.2 species, which is defined by the California Native Plant Society (CNPS) as “fairly endangered in California.” The survey was conducted according to the 2018 CDFW plant survey protocol during the blooming period (March through June) when the plant would be evident and identifiable. No bent-flowered fiddleneck plants were detected.
Regional Setting
The City of St. Helena (City) is situated within the Napa Valley floor, bounded by the Mayacamas Mountain Range on the western and northern sides and the Howell Mountains on the eastern side. The City is generally characterized by a mix of urban development and agricultural uses with some undeveloped wooded hillsides to the east and west of downtown and wooded hillsides interspersed with residential development to the west of downtown (City of St. Helena 2018). The Project site is located approximately three blocks east of downtown and State Route 29, and west of the Napa River in an area of medium- to low-density housing.
The Proposed Project site is located in the North Coast Ranges geographic subregion, on the border of the Inner North Coast Ranges district and the Outer North Coast Ranges District (Jepson Flora Project 2019). The Inner North Coast Ranges district is characterized by low rainfall and hot, dry summers while the Outer North Coast Ranges district has more marine influences and is characterized by higher rainfall (Baldwin et al. 2012). The Napa Valley, in which the city is located, separates these two districts. The western hills of the Napa Valley contain more redwoods and mixed evergreen forest while the eastern hills are dominated by chaparral and oak woodlands. Rainfall is intermediate between the two districts and averages
34.61 inches a year and temperatures range from an average low of 36°F in January to an average high of 89°F in July (WRCC 2019).
Local Setting
The Project site has been extensively altered by past activities associated with agriculture, and the construction of the City’s Flood Protection Project, which included the placement of excess fill material from the Flood Protection Project on the site. The Project site is bordered on the south and east by medium-density residential development, to the northeast by the Napa River and associated riparian vegetation, and to the northwest by a gravel levee maintenance road/public trail and agricultural and rural residential land.
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Topography
The Project site is generally flat, with micro topography created by past agriculture and grading practices, including the placement of fill on the site. The current elevation of the site varies from approximately 230 feet above mean sea level on its southern edge to approximately 212 feet above mean sea level on its northern edge. The portion of the site planned for the extension of Adams Street ranges from 243 feet above mean sea level to 230 feet above mean sea level.
See Section 3.6, Geology and Soils, for an in-depth discussion of soils, geology, and topography of the Project site.
Soils
The United States Department of Agriculture’s Natural Resources Conservation Service conducts soil surveys and creates maps representing the location and type of soil in order to aid in agricultural, conservation, and land use decisions. The Natural Resources Conservation Service identifies the following soils as occurring on the Project site (USDA 2019):
• Bale clay loam, 0 to 2% slopes
• Bale clay loam, 2 to 5% slopes
• Cole silt loam, 0 to 2% slopes
• Cortina very gravelly loam, 0 to 5% slopes, moist
Hydrology
The Project site is within the greater Napa River Watershed, which drains water from hillsides through the Napa Valley and into the San Pablo Bay, approximately 50 miles to the south (NCWICC 2019a). The Napa River flows from northwest to southeast approximately 500 feet north/northeast of the Project site. The Project site has been partially graded in the past for construction of a City storm water detention basin which is currently located directly north/northeast of the site. A drainage ditch along the southwestern edge of the Project site drains rainwater runoff from the site north and east and into this detention basin. See Section 3.9, Hydrology and Water Quality, for an in-depth discussion of drainage and hydrology on the Project site.
Vegetation Communities and Land Cover Types
One vegetation community, three anthropogenic land cover types, and two aquatic land cover types are present in the Project site. The vegetation community is California annual grassland.
Anthropogenic land cover types include agriculture (vineyard), ruderal, and upland swale.
Aquatic land cover types include seasonal wetlands and a drainage ditch. Table 3.4-1 provides a breakdown of the various vegetation communities or land cover types and Figures 3.4-1 and
3.4-2 graphically depicts this information. A more detailed discussion is included below.
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Hunter Subdivision Project
SOURCE: Bing Maps 2019
0 150 300Feet
Project Boundary
Upland Swale
Vegetation Communities and Landcover
AGS, Annual grassland
RUD, Ruderal
VIN, Vineyard
FIGURE 3.4-1
Upland Swale
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CAMPO CT
PASEO GRAND DR
SAN JUAN CT
DEL RIO CT
SW-3
SW-1
SW-4
D-1
D-2
SW-2
On-Site Seasonal Wetlands and Drainage Features
Hunter Subdivision Project
SOURCE: USDA 2016
0 80 160Feet
Project Boundary
Seasonal Wetland
Ditch
FIGURE 3.4-2
Detention
Basin
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Table 3.4-1
Vegetation Communities and Land Cover Types
Vegetation Community or Land Cover Type Acres
Vegetation Communities
California Annual Grassland 9.67
Subtotal 9.67
Anthropogenic Land Cover Types
Agriculture (Vineyard) 6.02
Ruderal 0.45
Upland Swale 0.02
Subtotal 6.49
Aquatic Land Cover
Seasonal Wetland 0.07
Ditch 0.06
Subtotal 0.13
Total 16.29
Source: Dudek 2019.
California Annual Grassland. California annual grassland comprises 9.67 acres of the Project site. Non-native and ruderal grass and forb species such as wild oat (Avena fatua), Mediterranean barley (Hordeum murinum), seaside barley (Hordeum marinum), redstem stork’s bill (Erodium cicutarium), wild radish (Raphanus sativus), and Italian thistle (Carduus pycnocephalus) are common in this vegetation community. This vegetation community does not correspond to any identified community in the Manual of California Vegetation, Online Edition, and it is not a sensitive natural community (CDFW 2018; CNPS 2018).
The California annual grassland on the Project site is mowed or disked on a semi-annual basis.
Although dominated by non-native grasses, the California annual grassland onsite provides foraging opportunities for raptor species. Additional wildlife that may use this vegetation community for foraging or breeding include ground-nesting birds such as mourning dove (Zenaida macroura), black-tailed jackrabbit (Lepus californicus), and fossorial mammals such as California vole (Microtus californicus) and Botta’s pocket gopher (Thomomys bottae).
Agriculture (Vineyard). An approximately 6.02-acre vineyard occupies the southwestern portion of the Project site along with an approximately 1-acre area of vineyard located in the southwestern “panhandle” portion of the site. These vineyards are maintained on an annual basis through pruning, mowing, and disking. Cultivated grapes (Vitis spp.) is the primary species in this land cover type, with a sparse herbaceous layer between vine rows consisting of nonnative grasses and forbs similar to those found in the adjacent California annual grasslands.
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Ruderal. Ruderal non-natural land cover type includes areas disturbed by anthropogenic or human activities that retain a pervious surface without vegetation or that support an assortment of weedy, non-native vegetation. Vegetation common in the 0.45 acres of ruderal land cover onsite include wild oat, prickly lettuce (Lactuca serriola), black mustard (Brassica nigra), and yellow star thistle (Centaurea solsitialis). On the Project site, ruderal areas include areas regularly maintained through disking and mowing. Vegetation in these areas is dominated by non-native annual species such as cheeseweed (Malva parviflora), winter marigold (Calendula arvensis), and grasses similar to those discussed in the annual grasslands.
Upland Swale. There is one upland swale in the northwest corner of the Project site. The swale directs surrounding surface runoff to the detention basin north of the Project site.
Apart from the detention basin, the upland swale is isolated from aquatic features.
Vegetation in the swale is consistent with the surrounding California annual grassland. No defined bed and bank are associated with the swale, which was likely excavated specifically for stormwater drainage purposes.
Seasonal Wetlands. Four seasonal wetlands occur in the California annual grassland onsite.
These areas are approximately 0.07 acres, combined, and are discernable from the surrounding grassland by a change in the dominant vegetation and/or lack of vegetation in the deepest portions due to seasonal ponding of water. Vegetation common in seasonal wetlands onsite include seaside barley, curly dock (Rumex crispus) and fiddle dock (Rumex pulcher), all of which are common in areas of seasonal inundation.
Drainage Ditch. An approximately 0.06-acre ditch runs the length of the northwestern edge of the Project site (see Figure 3.4-2, On-Site Seasonal Wetlands and Drainage Features).
Himalayan blackberry (Rubus armeniacus) brambles dominate the vegetation in the ditch. The farther northeast the ditch travels, the more incised it becomes. At the northeastern end of the Project site, the ditch is approximately five feet deep with a defined bed and bank, as well as a canopy of valley oak (Quercus lobata) trees. Himalayan blackberry, toyon (Heteromeles arbutifolia), poison oak (Toxicodendron diversilobum), and oak seedlings dominate the understory of the valley oak canopy.
Sensitive Natural Communities
Sensitive natural communities are communities that are of limited distribution statewide or within a county or region and are often vulnerable to environmental effects of projects. The CDFW maintains a list of natural vegetation communities. Those communities with a State or Global Rarity ranking of S or G 1 through 3 are considered sensitive (CDFW 2018). In addition to sensitive natural communities, wetlands and riparian vegetation communities otherwise protected under state and federal law are also considered sensitive.
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Based on review of available resources and observation of the previously disturbed nature of vegetation communities and land cover types within the Project site, no sensitive natural communities, as defined by the CDFW (2018), occur within the Project site (Figure 3.4-1).
Seasonal wetlands onsite, as well as the drainage ditch may be considered sensitive (Figure
3.4-2); these features are discussed in more detail under potentially jurisdictional wetlands and waters below.
Wildlife Movement and Nursery Sites
Wildlife corridors are linear features that connect large patches of natural open space and provide avenues for the migration of animals. Wildlife corridors contribute to population viability by assuring continual exchange of genes between populations, providing access to adjacent habitat areas for foraging and mating, and providing routes for recolonization of habitat after local extirpation (extinction) or ecological catastrophes (e.g., fires). Habitat linkages are small patches that join larger blocks of habitat and help reduce the adverse effects of habitat fragmentation. Habitat linkages provide a potential route for gene flow and long-term dispersal of plants and animals and may serve as primary habitat for smaller animals, such as reptiles and amphibians. Habitat linkages may be continuous habitat or discrete habitat islands that function as “steppingstones” for dispersal.
The Project site is bordered by development to the east, south, and agriculture to the north/northwest. The Napa River riparian corridor is located approximately 500 feet northeast of the Project site and is identified as a major, regional north-south wildlife movement route in Napa County (Napa County Watershed Information & Conservation Council 2018). Additional landscape blocks and habitat linkages are located to the north, east, and west of the Project site, but are at least 1.4 miles from the site (refer to Figure 3.4-3, Wildlife Corridors and Habitat Linkages).
While the mature trees and shrubs along the Napa River provide cover and essential habitat linkage for resident and migratory wildlife, the Project site itself does not function as a wildlife movement corridor due to the surrounding development, lack of connectivity with other undeveloped areas, and existing and historic agricultural uses of the site. The grassland on the Project site does not provide adequate cover or nursery sites for mammal species with the exception of small, fossorial mammals such as pocket gophers and field mice.
The Napa River, generally north of the site, supports native resident and migratory fish, including Chinook salmon and steelhead. The two linear features onsite are ephemeral and separated from the Napa River to the north by culverts that are not regularly open for drainage to the river (see details in Section 3.9, Hydrology and Water Quality). As such, these fish species are not expected to occur on or adjacent to the Project site.
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Special-Status Resources
For the purposes of this report, special-status plant species are those plants listed, proposed for listing, or candidates for listing as threatened or endangered by the U.S. Fish and Wildlife Service (USFWS) under the federal Endangered Species Act (FESA) (16 USC Section 1531 et seq.); those listed or proposed for listing as rare, threatened, or endangered by the CDFW under the California Endangered Species Act (CESA) (Fish & Game Code, Section 2050 et seq.); and plants that are CRPR 1 and 2 in the CNPS’s online Inventory of Rare and Endangered Plants (CNPS 2019). Special-status wildlife species are those that are designated as either rare, threatened, or endangered (or candidate) by CDFW or the USFWS; are protected under either the CESA or FESA; meet the California Environmental Quality Act (CEQA) definition for endangered, rare, or threatened (CCR Tit. 14, Section 15380(b),(d)); are considered fully protected under the California Fish & Game Code, Section 3511, 4700, 5050, and 5515; or that are on the CDFW Special Animals List (CDFW 2018) and determined by CDFW to be a Species of Special Concern.
As noted in the Methods of Analysis section below, WRA initially evaluated the potential occurrence of special-status plant and wildlife species on the Project site in 2015. Dudek biologists conducted additional resource database searches in 2018, 2019, and the species list was updated (Tables 3.4-2 and 3.4-3 and Figure 3.4-4, CNDDB Occurrences). This list was primarily derived from a review of the California Natural Diversity Database (CNDDB) (CDFW 2019), the CNPS Inventory of Rare and Endangered Plants (CNPS 2019), and the USFWS lists of federal endangered and threatened species (USFWS 2019).
The potential for those species identified in the literature search to occur on the Project site were evaluated based on the habitat requirements of each species relative to the observed existing conditions, results of previous general and focused habitat assessments and surveys for plants and animals conducted in November 3, 2011, and March 20, 2015 (WRA 2015), and surveys conducted by Dudek biologists on February 20, 2018, April 10, 2019, and June 1, 2020.
Special-Status Plants
Based on the review of the databases and other information sources, 57 special-status plant species are documented as occurring or potentially occurring in the vicinity of the Project site (Table 3.4-2). Review of Project site conditions and results of surveys conducted by WRA and Dudek staff biologists demonstrate that no special-status plants are expected to occur on the Project site for varying reasons such as the absence of habitat requirements for the species, the distance to known occurrences, the species distribution or elevation ranges, or species absence during focused protocol surveys.
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Hunter Subdivision Project
SOURCE: CDFW 2015/2016, Bing Maps 2019
08 4,050 ,100
Feet
Project Boundary
5-Mile Radius from Project Boundary
Napa River Potential Riparian Connections
Essential Connectivity Areas
Lake Marie - The Cedars/ Adams Ridge
Linkage Design
Blue Ridge-Marin Coast
Coast Range-Blue Ridge
Natural Landscape Blocks
California Bay Area Linkage Network
California Essential Habitat Connectivity
FIGURE 3.4-3
Project Site
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Hunter Subdivision Project
SOURCE: CDFW 2019, USFWS 2005/2012, Bing Maps 2019
0 3,000 6,000Feet
FIGURE 3.4-4
Project Boundary
CNDDB Species Occurence
Plant
1, Bent-flowered fiddleneck (Amsinckia lunaris)
2, Calistoga ceanothus (Ceanothus divergens)
3, Calistoga popcornflower (Plagiobothrys strictus)
4, Clara Hunt’s milk-vetch (Astragalus claranus)
5, Cobb Mountain lupine (Lupinus sericatus)
6, Colusa layia (Layia septentrionalis)
7, Green jewelflower (Streptanthus hesperidis)
8, Greene’s narrow-leaved daisy (Erigeron greenei)
9, Holly-leaved ceanothus (Ceanothus purpureus)
10, Jepson’s leptosiphon (Leptosiphon jepsonii)
11, Marsh checkerbloom (Sidalcea oregana ssp. hydrophila) 12, Napa bluecurls (Trichostema ruygtii)
13, Napa checkerbloom (Sidalcea hickmanii ssp. napensis) 14, Napa false indigo (Amorpha californica var. napensis) 15, Narrow-anthered brodiaea (Brodiaea leptandra)
16, Rincon Ridge ceanothus (Ceanothus confusus)
17, Sharsmith’s western flax (Hesperolinon sharsmithiae) 18, Sonoma ceanothus (Ceanothus sonomensis)
Wildlife
1, American peregrine falcon (Falco peregrinus anatum)
2, Bald eagle (Haliaeetus leucocephalus)
3, California giant salamander (Dicamptodon ensatus)
4, Foothill yellow-legged frog (Rana boylii)
5, Fringed myotis (Myotis thysanodes)
6, North American porcupine (Erethizon dorsatum)
7, Obscure bumble bee (Bombus caliginosus)
8, Pallid bat (Antrozous pallidus)
9, Purple martin (Progne subis)
10, Steelhead - central California coast DPS (Oncorhynchus mykiss irideus pop. 8)
11, Townsend’s big-eared bat (Corynorhinus townsendii)
12, Western pond turtle (Emys marmorata)
Critical Habitat
Northern Spotted Owl (Strix occidentalis caurina)
Steelhead (Oncorhynchus mykiss)
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Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Allium
peninsulare
var.
franciscanum
Franciscan
onion
None/None/1B.2 Cismontane woodland, Valley
and foothill grassland; clay,
volcanic, often
serpentinite/perennial
bulbiferous herb/(Apr)May–
June/170–1,000
Not expected to occur. No
clay, volcanic, or serpentinite
soils present.
Alopecurus
aequalis var.
sonomensis
Sonoma
alopecurus
FE/None/1B.1 Marshes and swamps
(freshwater), Riparian
scrub/perennial herb/May–
July/15–1,200
Not expected to occur. No
marsh or riparian scrub
habitat present.
Amorpha
californica var.
napensis
Napa false
indigo
None/None/1B.2 Broadleafed upland forest
(openings), Chaparral,
Cismontane woodland/
perennial deciduous
shrub/Apr–July/390–6,560
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Amsinckia
lunaris
bent-flowered
fiddleneck
None/None/1B.2 Coastal bluff scrub,
Cismontane woodland, Valley
and foothill grassland, often
serpentine/annual herb/Mar–
June/5–1,640
Not expected to occur. The
annual grassland onsite
provides marginal habitat for
this species due to a lack of
serpentine soils and past
and present anthropogenic
disturbances at the site.
Present mowing/vegetation
management and past
grading and agricultural uses
of the site likely preclude the
potential for this species to in
the Project site. The plant
survey did not identify the
presence of the plant (see
Appendix D).
Arctostaphylos
manzanita
ssp. elegans
Konocti
manzanita
None/None/1B.3 Chaparral, Cismontane
woodland, Lower montane
coniferous forest;
volcanic/perennial evergreen
shrub/(Jan)Mar–
May(July)/1,295–5,300
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no chaparral or
woodland habitat present.
Arctostaphylos
stanfordiana
ssp.
decumbens
Rincon Ridge
manzanita
None/None/1B.1 Chaparral (rhyolitic),
Cismontane woodland/
perennial evergreen
shrub/Feb–Apr(May)/ 245–
1,215
Not expected to occur. No
chaparral or woodland
habitat present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-18
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Astragalus
claranus
Clara Hunt's
milk-vetch
FE/ST/1B.1 Chaparral (openings),
Cismontane woodland, Valley
and foothill grassland;
serpentinite or volcanic, rocky,
clay/annual herb/Mar–
May/245–900
Not expected to occur. No
serpentinite or volcanic,
rocky, clay soils present.
Astragalus
rattanii var.
jepsonianus
Jepson's milkvetchNone/None/1B.2 Chaparral, Cismontane woodland, Valley and foothill
grassland; often serpentinite/
annual herb/Mar–June/ 965–
2,295
Not expected to occur. The
site is outside of the species’
known elevation range.
Brodiaea
leptandra
narrowanthered
brodiaea
None/None/1B.2 Broadleafed upland forest,
Chaparral, Cismontane
woodland, Lower montane
coniferous forest, Valley and
foothill grassland;
volcanic/perennial bulbiferous
herb/May–July/360–3,000
Not expected to occur. The
site is outside of the species’
known elevation range.
Calycadenia
micrantha
small-flowered
calycadenia
None/None/1B.2 Chaparral, Meadows and
seeps (volcanic), Valley and
foothill grassland; Roadsides,
rocky, talus, scree, sometimes
serpentinite, sparsely
vegetated areas/annual
herb/June–Sep/15–4,920
Not expected to occur. No
chaparral, meadows and
seeps, or volcanic or
serpentine soils with sparse
vegetation present.
Castilleja
ambigua var.
meadii
Mead's owl'scloverNone/None/1B.1 Meadows and seeps, Vernal pools; Gravelly, volcanic,
clay/annual herb
(hemiparasitic)/Apr–
May/1,475–1,560
Not expected to occur. The
site is outside of the species’
known elevation range.
Ceanothus
confusus
Rincon Ridge
ceanothus
None/None/1B.1 Closed-cone coniferous
forest, Chaparral, Cismontane
woodland; volcanic or
serpentinite/ perennial
evergreen shrub/ Feb–
June/245–3,495
Not expected to occur. No
forest, chaparral, or
woodland habitat present.
Ceanothus
divergens
Calistoga
ceanothus
None/None/1B.2 Chaparral (serpentinite or
volcanic, rocky)/ perennial
evergreen shrub/Feb–
Apr/555–3,115
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-19
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Ceanothus
purpureus
holly-leaved
ceanothus
None/None/1B.2 Chaparral, Cismontane
woodland; volcanic,
rocky/perennial evergreen
shrub/Feb–June/390–2,100
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Ceanothus
sonomensis
Sonoma
ceanothus
None/None/1B.2 Chaparral (sandy, serpentinite
or volcanic)/perennial
evergreen shrub/ Feb–
Apr/705–2,625
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Centromadia
parryi ssp.
parryi
pappose
tarplant
None/None/1B.2 Chaparral, Coastal prairie,
Meadows and seeps,
Marshes and swamps
(coastal salt), Valley and
foothill grassland (vernally
mesic); often alkaline/annual
herb/May–Nov/0–1,380
Not expected to occur. No
alkaline soils present within
the vernally mesic areas of
the annual grassland onsite.
Cryptantha
dissita
serpentine
cryptantha
None/None/1B.2 Chaparral (serpentinite)/
annual herb/Apr–June/1,295–
1,905
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Downingia
pusilla
dwarf
downingia
None/None/2B.2 Valley and foothill grassland
(mesic), Vernal pools/annual
herb/Mar–May/0–1,460
Not expected to occur. No
vernal pool habitat present.
Erigeron
greenei
Greene's
narrow-leaved
daisy
None/None/1B.2 Chaparral (serpentinite or
volcanic)/perennial herb/May–
Sep/260–3,295
Not expected to occur. No
chaparral habitat present.
Eryngium
constancei
Loch Lomond
button-celery
FE/SE/1B.1 Vernal pools/annual/perennial
herb/Apr–une/1,505–2,805
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Eryngium
jepsonii
Jepson's
coyote thistle
None/None/1B.2 Valley and foothill grassland,
Vernal pools; clay/perennial
herb/Apr–Aug/5–985
Not expected to occur. No
potential vernal pool habitat
or clay soils present.
Fritillaria
liliacea
fragrant
fritillary
None/None/1B.2 Cismontane woodland,
Coastal prairie, Coastal scrub,
Valley and foothill grassland;
Often serpentinite/perennial
bulbiferous herb/Feb–Apr/5–
1,345
Not expected to occur. No
serpentine soils present in
the annual grassland onsite.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-20
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Fritillaria
pluriflora
adobe-lily None/None/1B.2 Chaparral, Cismontane
woodland, Valley and foothill
grassland; often
adobe/perennial bulbiferous
herb/Feb–Apr/195–2,315
Not expected to occur. No
adobe soils present within
the annual grassland onsite.
Harmonia
hallii
Hall's
harmonia
None/None/1B.2 Chaparral (serpentinite)/
annual herb/Apr–June/1,000–
3,200
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Hesperolinon
bicarpellatum
two-carpellate
western flax
None/None/1B.2 Chaparral (serpentinite)/
annual herb/ May–July/ 195–
3,295
Not expected to occur. No
chaparral habitat present.
Hesperolinon
sharsmithiae
Sharsmith’s
western flax
None/None/1B.2 Chaparral; serpentinite/annual
herb/May–July/885–985
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Juncus
luciensis
Santa Lucia
dwarf rush
None/None/1B.2 Chaparral, Great Basin scrub,
Lower montane coniferous
forest, Meadows and seeps,
Vernal pools/annual
herb/Apr–July/980–6,695
Not expected to occur. The
site is outside of the species’
known elevation range.
Lasthenia
burkei
Burke's
goldfields
FE/SE/1B.1 Meadows and seeps (mesic),
Vernal pools/annual
herb/Apr–June/45–1,970
Not expected to occur. No
vernal pool habitat present.
Lasthenia
conjugens
Contra Costa
goldfields
FE/None/1B.1 Cismontane woodland, Playas
(alkaline), Valley and foothill
grassland, Vernal pools;
mesic/annual herb/Mar–
June/0–1,540
Not expected to occur. No
vernal pool habitat or
alkaline mesic areas
present.
Layia
septentrionalis
Colusa layia None/None/1B.2 Chaparral, Cismontane
woodland, Valley and foothill
grassland; sandy,
serpentinite/annual herb/Apr–
May/325–3,595
Not expected to occur. The
site is outside of the species’
known elevation range.
Leptosiphon
jepsonii
Jepson's
leptosiphon
None/None/1B.2 Chaparral, Cismontane
woodland, Valley and foothill
grassland; usually volcanic
/annual herb/Mar–May/ 325–
1,640
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-21
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Limnanthes
vinculans
Sebastopol
meadowfoam
FE/SE/1B.1 Meadows and seeps, Valley
and foothill grassland, Vernal
pools; vernally mesic/annual
herb/Apr–May/45–1,000
Not expected to occur. No
vernal pool or vernally mesic
habitat present.
Lupinus
sericatus
Cobb
Mountain
lupine
None/None/1B.2 Broadleafed upland forest,
Chaparral, Cismontane
woodland, Lower montane
coniferous forest/perennial
herb/Mar–June/900–5,005
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Navarretia
leucocephala
ssp. bakeri
Baker's
navarretia
None/None/1B.1 Cismontane woodland, Lower
montane coniferous forest,
Meadows and seeps, Valley
and foothill grassland, Vernal
pools; Mesic/annual
herb/Apr–July/15–5,710
Not expected to occur. No
vernal pool or vernally mesic
habitat present.
Navarretia
leucocephala
ssp. pauciflora
few-flowered
navarretia
FE/ST/1B.1 Vernal pools (volcanic ash
flow)/annual herb/ May–
June/1,310–2,805
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Navarretia
leucocephala
ssp. plieantha
many-flowered
navarretia
FE/SE/1B.2 Vernal pools (volcanic ash
flow)/annual herb/ May–
June/95–3,115
Not expected to occur. No
potential vernal pool habitat
present.
Navarretia
myersii ssp.
deminuta
small
pincushion
navarretia
None/None/1B.1 Vernal pools (clay loam)/
annual herb/Apr–May/ 1,160–
1,165
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Navarretia
paradoxinota
Porter’s
navarretia
None/None/1B.3 Meadows and seeps;
Serpentinite, openings,
vernally mesic, often
drainages/ annual herb/May–
June(July)/ 540–2,755
Not expected to occur. The
site is outside of the species’
known elevation range.
Navarretia
rosulata
Marin County
navarretia
None/None/1B.2 Closed-cone coniferous
forest, Chaparral; serpentinite,
rocky/annual herb/ May–July/
655–2,085
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Penstemon
newberryi var.
sonomensis
Sonoma
beardtongue
None/None/1B.3 Chaparral (rocky)/ perennial
herb/Apr–Aug/2,295–4,495
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-22
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Plagiobothrys
strictus
Calistoga
popcornflower
FE/ST/1B.1 Meadows and seeps, Valley
and foothill grassland, Vernal
pools; alkaline areas near
thermal springs/annual
herb/Mar–June/295–525
Not expected to occur. No
alkaline areas near thermal
springs or vernal pool habitat
present.
Poa napensis Napa blue
grass
FE/SE/1B.1 Meadows and seeps, Valley
and foothill grassland;
alkaline, near thermal
springs/perennial herb/May–
Aug/325–655
Not expected to occur. The
site is outside of the species’
known elevation range.
Puccinellia
simplex
California
alkali grass
None/None/1B.2 Chenopod scrub, Meadows
and seeps, Valley and foothill
grassland, Vernal pools;
Alkaline, vernally mesic;
sinks, flats, and lake margins/
annual herb/Mar–May/5–
3,050
Not expected to occur. No
alkaline, vernally mesic, or
lake margin habitat present.
Sagittaria
sanfordii
Sanford's
arrowhead
None/None/1B.2 Marshes and swamps
(assorted shallow freshwater)/
perennial rhizomatous herb
(emergent)/May–Oct(Nov)/0–
2,135
Not expected to occur. No
potential habitat present.
Sidalcea
hickmanii ssp.
napensis
Napa
checkerbloom
None/None/1B.1 Chaparral; rhyolitic/perennial
herb/ Apr–June/1,360–2,000
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Sidalcea
oregana ssp.
hydrophila
marsh
checkerbloom
None/None/1B.2 Meadows and seeps, Riparian
forest; mesic/perennial
herb/(June)July–Aug/3,605–
7,545
Not expected to occur. The
site is outside of the species’
known elevation range.
Sidalcea
oregana ssp.
valida
Kenwood
Marsh
checkerbloom
FE/SE/1B.1 Marshes and swamps
(freshwater)/perennial
rhizomatous herb/June–
Sep/375–490
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Spergularia
macrotheca
var. longistyla
long-styled
sand-spurrey
None/None/1B.2 Meadows and seeps,
Marshes and swamps;
Alkaline/perennial herb/Feb–
May/0–835
Not expected to occur. No
meadows, seeps, marsh or
swamp habitat present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-23
Table 3.4-2
Special-Status Plant Species Occurrence Potential on the Project Site Scientific
Name
Common
Name
Status
(Federal/State/CRPR)1
Primary Habitat
Associations/ Life Form/
Blooming Period/ Elevation
Range (Feet)2 Potential to Occur
Streptanthus
batrachopus
Tamalpais
jewelflower
None/None/1B.3 Closed-cone coniferous
forest, Chaparral; serpentinite/
annual herb/Apr–July/1,000–
2,135
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Streptanthus
brachiatus
ssp.
brachiatus
Socrates Mine
jewelflower
None/None/1B.2 Closed-cone coniferous
forest, Chaparral; usually
serpentinite/perennial
herb/May–June/1,785–3,280
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Streptanthus
hesperidis
green
jewelflower
None/None/1B.2 Chaparral (openings),
Cismontane woodland;
serpentinite, rocky/annual
herb/May–July/425–2,495
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Streptanthus
morrisonii ssp.
elatus
Three Peaks
jewelflower
None/None/1B.2 Chaparral (serpentinite)/
perennial herb/June–
Sep/295–2,675
Not expected to occur. No
chaparral habitat present.
Streptanthus
vernalis
early
jewelflower
None/None/1B.2 Closed-cone coniferous
forest, Chaparral; serpentinite/
annual herb/Mar–May/2,000–
2,000
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Trichostema
ruygtii
Napa bluecurls None/None/1B.2 Chaparral, Cismontane
woodland, Lower montane
coniferous forest, Valley and
foothill grassland, Vernal
pools/annual herb/June–
Oct/95–2,230
Not expected to occur. No
vernal pool habitat present.
Trifolium
amoenum
two-fork clover FE/None/1B.1 Coastal bluff scrub, Valley and foothill grassland
(sometimes serpentinite)/
annual herb/Apr–June/15–
1,360
Not expected to occur. No
serpentine soils present in
the annual grassland onsite.
Trifolium
hydrophilum
saline clover None/None/1B.2 Marshes and swamps, Valley and foothill grassland (mesic,
alkaline), Vernal pools/annual
herb/Apr–June/0–985
Not expected to occur. No
mesic, alkaline habitat
present.
Viburnum
ellipticum
oval-leaved
viburnum
None/None/2B.3 Chaparral, Cismontane
woodland, Lower montane
coniferous forest/perennial
deciduous shrub/May–June/
705–4,595
Not expected to occur. The
site is outside of the species’
known elevation range and
there is no potential habitat
present.
Sources: Jepson Flora Project (2019) and CNPS (2019).
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-24
Status Legend:
FE: Federally listed as endangered
FT: Federally listed as threatened
SE: State listed as endangered
ST: State listed as threatened
CRPR 1A: Plants Presumed Extirpated in California and either Rare or Extinct Elsewhere CRPR 1B: Plants Rare, Threatened, or Endangered in California and Elsewhere CRPR 2A: Plants Presumed Extirpated in California, But More Common Elsewhere CRPR 2B: Plants Rare, Threatened, or Endangered in California, But More Common Elsewhere .1 Seriously threatened in California (over 80% of occurrences threatened / high degree and immediacy of threat) .2 Moderately threatened in California (20-80% occurrences threatened / moderate degree and immediacy of threat) .3 Not very threatened in California (<20% of occurrences threatened / low degree and immediacy of threat or no current threats known) Bent-flowered fiddleneck (Amsinckia lunaris). Bent-flowered fiddleneck is a CRPR 1B.21 species found in coastal bluff scrub, cismontane woodland, and valley and foothill grasslands between 5 and 1,640 feet above mean sea level (CNPS 2019). This species often occurs on serpentine soils (Jepson Flora Project 2019). Bent-flowered fiddleneck blooms March through June (CNPS 2019). The nearest documented CNDDB occurrence for this species is located approximately 2 miles southeast of the Project site (Figure 3.4-1) (CDFW 2019b). This occurrence is based on a March 2010 collection of the species in ruderal grassland at the edge of a vineyard located approximately 2 miles to the southeast (CDFW 2019b). Due to a lack of serpentine soils, as well as the disturbed nature of the Project site, and past grading activities associated with development of the vineyard and the nearby detention basin, there is only marginally suitable habitat for this species on the site. Surveys conducted by Dudek biologists and botanists in April 2019 and again in June 2020, were conducted within the period when this plant would be evident and identifiable. Dudek botanists did not find evidence of this species on the Project site, nor were any species within the genus Amsinckia observed during the surveys, which involved one focused survey for the plant conducted according to CDFW plant survey protocol (CDFW 2018; refer to Appendix D). This species is not anticipated to occur within the Proposed Project development footprint.
A polygon representing previously documented occurrences for Geene’s narrow-leaved daisy (Erigeron greenei) and Clara Hunt’s milk-vetch (Astragalus claranus) encompass the Project site; however, this polygon is large and non-specific and represents historic occurrences. These occurrences are old and likely extirpated as a result of development within the city limits (CDFW 2019b). Additionally, past disturbance and the ubiquity of non-native grass cover at the site likely precludes the presence of these sensitive species. 1 CRPR 1B: Plants Rare, Threatened, or Endangered in California and Elsewhere; 2 Fairly endangered in California (20%–80% occurrences threatened/moderate degree and immediacy of threat).
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-25
Special-Status Wildlife
Based on results of the surveys conducted by WRA and Dudek staff biologists, review of the databases and other relevant sources, 24 special-status wildlife species have been documented as occurring or potentially occurring in the vicinity of the Project site. Of these species, two are considered to have potential for occurrence (Palid Bat and White-Tailed Kite); they are identified in Table 3.4-3 and discussed below. The remaining special-status animals are not expected to occur on the Project site for varying reasons such as the absence of essential habitat requirements for the species, the distance to known occurrences, and/or the species distribution and elevation ranges.
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Fish
Oncorhynchus mykiss
irideus pop. 8
steelhead – central
California coast DPS
FT/None Coastal basins from
Redwood Creek south
to the Gualala River,
inclusive; does not
include summer-run
steelhead
Not expected to
occur. Although the
Project site is located
in the Napa River
watershed, the site is
not accessible to fish
residing in the Napa
River.
Oncorhynchus
tshawytscha
Chinook – Napa River
fall-run
None/None Genetically similar to
the Central Valley
fall/late fall-run
Evolutionary
Significant Unit (ESU).
Known to occur in the
Napa River watershed
(NCWICC 2019b).
Not expected to
occur. Although the
Project site is located
in the Napa River
watershed, the site is
not accessible to fish
residing in the Napa
River.
Amphibians
Dicamptodon ensatus California giant
salamander
None/SSC Known from wet
coastal forests and
chaparral near
streams and seeps
from Mendocino Co.
south to Monterey Co.
and east to Napa Co.
Aquatic larvae found
in cold, clear streams,
occasionally in lakes
and ponds. Adults
known from wet
forests under rocks
and logs near streams
and lakes.
Not expected to
occur. No stream or
seep habitat in the
present site. The
nearest documented
occurrence was
observed in 2016
along Sulphur Creek,
approximately 1.9
miles southwest of the
Project site (CDFW
2019b).
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-26
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Rana boylii foothill yellow-legged
frog
None/PST, SSC Rocky streams and
rivers with open banks
in forest, chaparral,
and woodland
Not expected to
occur. No rocky
stream or river habitat
in the Project site. The
nearest documented
occurrence was
observed in 2015
approximately 0.3
miles southwest of the
intersection of Pope
Street and Silverado
Trail, along Sulphur
Creek (CDFW 2019b).
Rana draytonii California red-legged
frog
FT/SSC Lowland streams,
wetlands, riparian
woodlands, livestock
ponds; dense,
shrubby or emergent
habitat associated
with deep, still or slowmoving water; uses
adjacent uplands
Not expected to
occur. There is no
breeding habitat for
this frog at the Project
site. The Riparian
woodland along Napa
River may provide
dispersal and/or
migration habitat;
however, the nearest
documented
occurrence of this
species is located
greater than 9 miles
west of the Project site
(CDFW 2019b).
Taricha rivularis red-bellied newt None/SSC Redwood forests (and sometimes other
forest types) along
coastal drainages
from Humboldt County
south to Sonoma
County, inland to Lake
County. Lives in
terrestrial habitats,
juveniles generally
underground, adults
active at surface in
moist environments.
Will migrate over 1 km
to breed, typically in
streams with
moderate flow and
clean rocky substrate.
Not expected to
occur. No redwood
forest or breeding
habitat present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-27
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Reptiles
Actinemys marmorata western pond turtle
(WPT)
None/SSC Slow-moving
permanent or
intermittent streams,
ponds, small lakes,
and reservoirs with
emergent basking
sites; adjacent
uplands used for
nesting and during
winter
Not expected to
occur. No aquatic
habitat present. The
detention basin just
north of the site does
not contain sufficient
water during the active
season to support
WPT. The nearest
potential aquatic
habitat for WPT is in
Napa Creek, which is
nearly 600 feet from
the site. Given the
lack of aquatic habitat
on and adjacent to the
site, it is unlikely WPT
would disperse
through the Project
site or remain present
for nesting or
overwintering
purposes. The nearest
documented
occurrence is in Conn
Creek adjacent to
Lake Hennessy,
approximately 3.5
miles southeast of the
site (CDFW 2019b).
No WPT, nor their
sign, were observed
on the Project site
during the 2011, 2015,
2018, and 2019
biological fieldwork.
Birds
Accipiter striatus
(nesting)
sharp-shinned hawk None/WL Nests in coniferous
forests, ponderosa
pine, black oak,
riparian deciduous,
mixed conifer, Jeffrey
pine; winters in
lowland woodlands
and other habitats
Not expected to
occur. No coniferous
forest, black oak, or
woodland nesting
habitat present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-28
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Agelaius tricolor
(nesting colony)
tricolored blackbird BCC/SE, SSC Nests near freshwater, emergent wetland with
cattails or tules, but
also in Himalayan
blackberry; forages in
grasslands, woodland,
and agriculture
Not expected to
occur. Although the
annual grassland
onsite may provide
foraging habitat, no
breeding habitat for
this species is present
within or adjacent to
the Project site. The
nearest documented
occurrence of this
species was observed
in 2014 approximately
7.8 miles northeast of
the Project site
(CDFW 2019b).
Aquila chrysaetos
(nesting & wintering)
golden eagle BCC/FP, WL Nests and winters in
hilly, open/semi-open
areas, including
shrublands,
grasslands, pastures,
riparian areas,
mountainous canyon
land, open desert
rimrock terrain; nests
in large trees and on
cliffs in open areas
and forages in open
habitats
Not expected to
occur. No breeding
habitat present. The
nearest documented
occurrence is located
greater than 10 miles
southwest of the
Project site (CDFW
2019b).
Athene cunicularia
(burrow sites & some
wintering sites)
burrowing owl BCC/SSC Nests and forages in
grassland, open
scrub, and agriculture,
particularly with
ground squirrel
burrows
Not expected to
occur. Although the
grassland at the
Project site may
provide breeding and
foraging habitat, no
suitable burrows for
this species were
observed during the
biological site surveys.
The nearest
documented
occurrence for this
species is located
greater than 12 miles
southwest of the
Project site (CDFW
2019b).
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-29
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Buteo swainsoni
(nesting)
Swainson's hawk BCC/ST Nests in open
woodland and
savanna, riparian, and
in isolated large trees;
forages in nearby
grasslands and
agricultural areas such
as wheat and alfalfa
fields and pasture
Not expected to
occur. Although the
Project site provides
potential foraging
habitat, the site is
outside the
geographic range of
this species and there
are no suitable nesting
trees present. The
nearest documented
occurrence is located
along the Napa River
just south of
Rutherford,
approximately 5.2
miles southeast of the
Project site (CDFW
2019b).
Cypseloides niger
(nesting)
black swift BCC/SSC Nests in moist
crevices, caves, and
cliffs behind or
adjacent to waterfalls
in deep canyons;
forages over a wide
range of habitats
Not expected to
occur. The Project
site is outside the
geographic range of
this species, and there
is no cave or cliff
nesting habitat
present.
Elanus leucurus
(nesting)
white-tailed kite None/FP Nests in woodland,
riparian, and individual
trees near open lands;
forages
opportunistically in
grassland, meadows,
scrubs, agriculture,
emergent wetland,
savanna, and
disturbed lands
Low potential to
occur. Trees on the
perimeter of the
Project site and
directly offsite to the
north may provide
nesting habitat for this
species. Grassland at
the Project site may
provide foraging
habitat for this
species. The nearest
documented
occurrence for this
species is located
approximately 8 miles
southeast of the
Project site (CDFW
2019b).
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-30
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Falco mexicanus
(nesting)
prairie falcon BCC/WL Forages in grassland,
savanna, rangeland,
agriculture, desert
scrub, alpine
meadows; nest on
cliffs or bluffs
Not expected to
occur. Although
grassland at the
Project site provides
potential foraging
habitat, there is no
nesting habitat
present onsite or in
the vicinity. The
nearest documented
occurrence is
approximately 8.4
miles northwest of the
Project site (CDFW
201b9).
Falco peregrinus
anatum (nesting)
American peregrine
falcon
FDL, BCC/SDL, FP Usually nests on high
cliffs, dunes, buildings,
bridges; forages in
wetlands, riparian,
meadows, croplands,
especially where
waterfowl are present
Not expected to
occur. No nesting or
foraging habitat
present. The nearest
documented
occurrence is located
in habitat consisting of
small, volcanic cliffs,
approximately 2 miles
west of the Project site
(CDFW 2019b).
Haliaeetus
leucocephalus
(nesting & wintering)
bald eagle FDL, BCC/SE, FP Nests in forested
areas adjacent to
large bodies of water,
including seacoasts,
rivers, swamps, large
lakes; winters near
large bodies of water
in lowlands and
mountains
Not expected to
occur. No suitable
large trees for nesting
or aquatic hunting
habitat present.
Pandion haliaetus
(nesting)
osprey None/WL Large waters (lakes,
reservoirs, rivers)
supporting fish;
usually near forest
habitats, but widely
observed along the
coast
Not expected to
occur. No suitable
large trees for nesting
or aquatic hunting
habitat present.
Phalacrocorax auritus
(nesting colony)
double-crested
cormorant
None/WL Nests in riparian trees
near ponds, lakes,
artificial
impoundments, slowmoving rivers,
lagoons, estuaries,
Not expected to
occur. No suitable
large trees for nesting
or aquatic hunting
habitat present.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-31
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
and open coastlines;
winter habitat includes
lakes, rivers, and
coastal areas
Progne subis (nesting) purple martin None/SSC Nests and forages in woodland habitats
including riparian,
coniferous, and valley
foothill and montane
woodlands; in the
Sacramento region
often nests in weep
holes under elevated
freeways
Not expected to
occur. Although there
are documented
occurrences in the
vicinity of the Project
site (CDFW 2019b),
there is no nesting or
foraging habitat
present onsite.
Strix occidentalis
caurina
northern spotted owl FT/ST Nests and forages in
dense, old growth
forests with a
complex, multi-layer
canopy; prefers
narrow, steep-sided
canyons with northfacing slopes in
northern California
Not expected to
occur. No nesting or
foraging habitat
present.
Fish
Hypomesus
transpacificus
Delta smelt FT/SE Sacramento–San
Joaquin Delta;
seasonally in Suisun
Bay, Carquinez Strait,
and San Pablo Bay
Not expected to occur.
The site is outside of the
species’ known
geographic range and
there is no potential
habitat present.
Oncorhynchus mykiss
irideus pop. 8
steelhead - central
California coast DPS
FT/None Coastal basins from
Redwood Creek south
to the Gualala River,
inclusive; does not
include summer-run
steelhead
Not expected to occur.
There is no aquatic
habitat present.
Although the Project site
is located in the Napa
River watershed, the site
is not accessible to fish
residing in the Napa
River.
Oncorhynchus
tshawytscha
Chinook – Napa River
fall-run
None/None Genetically similar to
the Central Valley
fall/late fall-run
Evolutionary
Significant Unit (ESU).
Known to occur in the
Napa River watershed
(NCWICC 2019b)
Not expected to occur.
There is no aquatic
habitat present.
Although the Project site
is located in the Napa
River watershed, the site
is not accessible to fish
residing in the Napa
River.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-32
Table 3.4-3
Special-Status Wildlife Occurrence Potential on the Project Site Scientific Name Common Name
Status
(Federal/State)1 Habitat2 Potential to Occur
Mammals
Antrozous pallidus pallid bat None/SSC Grasslands,
shrublands,
woodlands, forests;
most common in
open, dry habitats with
rocky outcrops for
roosting, but also
roosts in built
structures and trees;
extremely sensitive to
disturbance of
roosting sites
Low potential to
occur. The Project
site lacks roosting
habitat due to ongoing
anthropogenic activity
in the vicinity.
Grassland at the
Project site could
provide potential
foraging habitat,
although use of the
site for foraging is
unlikely given the lack
of roosting habitat in
the surrounding area.
Corynorhinus
townsendii
Townsend's big-eared
bat
None/SSC Mesic habitats
characterized by
coniferous and
deciduous forests and
riparian habitat, but also
xeric areas; roosts in
limestone caves and
lava tubes, built
structures, and tunnels;
extremely sensitive to
disturbance of roosting
sites
Not expected to
occur. No suitable
caves, lava tubes, or
tunnels for roosting.
Ongoing
anthropogenic activity
at adjacent residences
likely preclude
roosting on residential
properties.
Invertebrates
Syncaris pacifica California freshwater
shrimp
FE/SE Endemic to Marin,
Napa, and Sonoma
Counties; found in
low-elevation, lowgradient streams
where riparian cover is
moderate to heavy
Not expected to
occur. No lowgradient, freshwater
stream habitat
present.
Sources: CDFW 2019c.
Status Abbreviations
FE: Federally Endangered
FT: Federally Threatened
PFE: Proposed Federally Endangered
PFT: Proposed Federally Threatened
FC: Federal Candidate
FDL: Federally Delisted
BCC: U.S. Fish and Wildlife Service Bird of Conservation Concern BLM: Bureau of Land Management Sensitive Species
USFS: U.S. Forest Service Sensitive Species
SSC: California Species of Special Concern
FP: California Fully Protected Species
WL: California Watch List Species
SE: State Endangered
ST: State Threatened
PSE: Proposed State Endangered
PST: Proposed State Threatened
SDL: State Delisted
SS: List Special Animals List, but no other status
CDF: California Department of Forestry Sensitive Species Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
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September 2021 3.4-33
Native bats [including Pallid Bat (Antrozous pallidus)]. Pallid bats, a California Species of Special Concern, are widespread throughout the western United States; southern British Columbia, Canada; and mainland and Baja California, Mexico (Hermanson and O’Shea 1983; Hall 1981). Within the United States, it ranges east into southern Nebraska, western Oklahoma, and western Texas. The pallid bat is locally common in arid deserts and grasslands throughout the western United States, and occurs in shrublands, woodlands, and forests at elevations up to 8,000 feet (Hermanson and O’Shea 1983; Hall 1981). Although this species prefers rocky outcrops, cliffs, and crevices with access to open habitats for foraging, it has been observed far from such areas (Hermanson and O’Shea 1983). Pallid bat day roosts of single- or mixed-sex colonies, often including greater than 20 individuals and sometimes more than 200 individuals, usually are established in crevices or built structures (Hermanson and O’Shea 1983). This species has also been observed using live trees and snags for day and night roosts; however, preference appears to be for tall, large-diameter trees located in mature stands with low overstory cover (Baker et al. 2008).
Pallid bats forage for a variety of species, including flightless arthropods picked up from the ground (e.g., scorpions and ground crickets), insects gleaned from vegetation (e.g., cicadas), insects taken in flight, and small vertebrates that are taken on the ground. Although the species is capable of flying more than 18 miles, most foraging occurs within about 2 miles of the day roost (Hermanson and O’Shea 1983).
While mature trees north and east of the site along the Napa River, as well as barns and other agricultural buildings to the north of the site may provide roosting habitat for this species, the absence of caves, mines, rocky outcrops, and cliffs, as well as past development and current human uses of the site limits habitat suitability. The grassland onsite provides potential foraging habitat for these species. The CNDDB lists a sighting of pallid bat approximately 0.34 miles northeast of the Project site; however, this occurrence is very old (1953) and no bats or signs of bats were observed on the Project site during field surveys (CDFW 2019b). It is unlikely any bat species would occur on the site given the ruderal nature of potential roosting habitat, the history of disturbance, and the lack of proper hydrology and topography for preferred foraging.
Other native bats, such as silver-haired bat (Lasionycteris noctivagans) and fringed myotis (Myotis thysanodes) have a potential to forage and/or roost in the vicinity of the Project site.
These species are protected by California Fish & Game Code Section 4150.
White-tailed Kite (Elanus leucurus). The white-tailed kite is a California Fully Protected species.
It is commonly associated with certain types of agriculture areas (Grinnell and Miller 1944). It also generally occurs in low-elevation grassland, wetland, oak woodland, low shrub, open woodlands, or savannah habitats. It is tolerant of moderate disturbance, such as occurs near residential subdivision developments. This species also uses fencerows and irrigation ditches Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
Hunter Subdivision Project EIR 10839
September 2021 3.4-34
(with residual vegetation). Riparian areas adjacent to open space areas are typically used for nesting, where kites prefer dense, broadleafed deciduous trees for nesting and night roosting (Brown and Amadon 1968). They also nest in young redwoods and mid-sized Douglas firs in Northern California.
White-tailed kite was not observed by WRA or Dudek biologists during the site surveys. The nearest documented occurrence for this species is approximately 7.8 miles southeast of the Project site. However, mature trees along the eastern boundary and trees located north of the Project site provide potential nesting habitat for this species. The riparian tree canopy associated with the Napa River, approximately 500 feet northeast of the Project site, also provides potential nesting habitat for white-tailed kite, and grasslands within the Project site provide potential foraging habitat for this species.
3.4.3 Regulatory Setting
Federal Regulations
Federal Endangered Species Act
Section 9 of the FESA protects federally-listed endangered and threatened wildlife species from unlawful take (16 USC Section 1538(a)(1)). “Take” is defined to mean “harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in any such conduct” (16 USC Section 1532(19)). In addition, federal agencies are required to determine whether a project is likely to jeopardize the continued existence of any species proposed to be listed under FESA or result in the destruction or adverse modification of critical habitat designated for such species (16 USC 1536[3], [4]). Projects that would result in “take” of any federally listed threatened or endangered species are required to obtain authorization from the National Marine Fisheries Service and/or USFWS through either Section 7 (interagency consultation) or section 10(a) (incidental take permit) of the FESA, depending on whether the federal government is involved in permitting or funding that project.
No federally listed threatened or endangered species are anticipated to occur within the Project site. As a result, the provisions of the FESA would not apply to the Proposed Project.
Federal Migratory Bird Treaty Act
The Migratory Bird Treaty Act (MBTA) prohibits the take of any migratory bird or any part, nest, or eggs of any such bird. Under the MBTA, “take” is defined as pursuing, hunting, shooting, capturing, collecting, or killing, or attempting to do so (16 USC 703 et seq.). In December 2017, Department of Interior Principal Deputy Solicitor Jorjani issued a memorandum (M-37050) that interprets the MBTA to only prohibit intentional take. Similarly, the Ninth Circuit Court of Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
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Appeals, like the Fifth Circuit and the Eighth Circuit, has held that the MBTA applies only to intended takes. See Seattle Audubon Soc’y v. Evans, 952 F.2d 297, 303 (9th Cir. 1991).
Unintentional or accidental take is not prohibited. In January 2021, USFWS published in the Federal Register the final regulation codifying the interpretation of the 2017 memorandum. This rule has an effective date of March 8, 2021, unless the USFWS opts to amend, rescind, or delay the rule. Regardless, USFWS reviews actions that might affect these species.
Birds may use vegetation communities or land cover types within the Project site for nesting.
Intentional take of any of these birds or their nests and young, if present, is prohibited under the MBTA.
Clean Water Act
The objective of the Clean Water Act is to restore and maintain the chemical, physical, and biological integrity of waters of the United States (as defined in the Code of Federal Regulations [CFR]: 33 CFR 328.3[a]). Section 401 of the Act (33 USC 1341) prohibits the discharge of any pollutant into waters of the United States. Project applicants for a federal license or permit to conduct activities including, but not limited to, the creation or operation of facilities, which may result in discharge into waters of the United States, must obtain certification that a project would not violate applicable effluent limitations and water quality standards. Section 404 of the Act (33 USC 1344) requires a federal license or permit from USACE prior to the discharge of dredge or fill material into waters of the United States, unless the activity is exempt from Section 404 permit requirements. Permit applicants must demonstrate that they have attempted to avoid or minimize impacts on the resource; however, if no further minimization of impacts is possible, the applicant is required to mitigate remaining impacts on all federally regulated waters of the United States. In California, the State Water Resources Control Board (SWRCB) and its nine Regional Water Quality Control Boards are responsible for the protection of water quality.
Based on a delineation of wetlands and other waters of the United States (Dudek 2019), seasonal wetlands and ditches within the Project site are not anticipated to be jurisdictional under Section 404 of the Clean Water Act as they are isolated and lack connectivity to any downstream waters of the United States. These features may be considered waters of the state and would be regulated by the Regional Water Quality Control Board under Section 401 of the Clean Water Act.
State Regulations
California Endangered Species Act
The CESA and Section 2081 of the California Department of Fish and Game Code identifies measures to ensure state-listed species and their habitats are conserved, protected, restored, Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
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and enhanced. The Act requires permits from the CDFW for activities that could result in the take of a state-listed threatened or endangered species. “Take” is defined as to hunt, pursue, catch, capture, or kill, or attempt to hunt, pursue, catch, capture or kill (Fish and Game Code Section 86). Section 2080 of the Fish and Game Code prohibits the take of state-listed plants and animals unless otherwise permitted under Sections 2080.1, 2081, and 2835. Section 20814(b) affords CDFW the authority to issue permits for incidental take for otherwise lawful activities. To authorize an incidental take, the impacts of the take must be minimized and fully mitigated. Issuance of incidental take permits may not jeopardize the continued existence of a state-listed species. For species listed as threatened or endangered under FESA, CDFW may rely on a federal incidental take statement or permit to authorize an incidental take under CESA.
The California Fish and Game Commission maintains a list of threatened and endangered species (Fish and Game Code Section 2070). The California Fish and Game Commission maintains two additional lists: a Candidate species list, which identifies species under review for addition to either the endangered or threatened species list, and a Species of Special Concern list which serves as a watch list based on limited distribution, declining populations, diminishing habitat, or unusual scientific, recreational, or educational value.
No state-listed threatened or endangered species are anticipated to occur within the Project site. As a result, the provisions of the CESA would not apply to the Project Proposed.
California Fully Protected Species and Species of Special Concern The classification of “fully protected” was the CDFW’s initial effort to identify and provide additional protection to those animals that were rare or faced possible extinction. California Fish and Game Code sections (fish at Section 5515, amphibians and reptiles at Section 5050, birds at Section 3511, and mammals at Section 4700) dealing with “fully protected” species state that these species may not be taken or possessed at any time, and no provisions in this code or any other law shall be construed to authorize permits for the take of fully protected species.
In October 2011, the State passed legislation allowing take of a fully protected species covered under an approved Natural Community Conservation Plan. Species of Special Concern are broadly defined as animals not listed under the FESA or CESA, but which are nonetheless of concern to the CDFW because they are declining at a rate that could result in listing, or they historically occurred in low numbers and known threats to their persistence currently exist. This classification is intended to elicit special consideration for these animals by the CDFW, land managers, consulting biologists, and others. Additionally, this classification is intended to stimulate collection of additional information on the biology, distribution, and status of poorly known at-risk species, and focus research and management attention on them.
Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
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One California Fully Protected species, white-tailed kite, has the potential to use the Project site for foraging. Potential nesting habitat is present in trees adjacent to the southeast boundary of the Project site and offsite, but within sound and visual range of the Project site. Take of this species, including harm or harassment of any kind, is not permitted.
California Department of Fish and Game Code Sections 3503 and 4150 Birds of prey are protected in California under the Fish and Game Code Section 3503.5 (1992).
Under Section 3503.5, it is “unlawful to take, possess, or destroy any birds in the order Falconiformes (diurnal birds of prey) or Strigiformes (owls) or to take, possess, or destroy any nest or egg of any bird except as otherwise provided by this code or any regulation adopted pursuant thereto.” Disturbance during breeding season that results in the incidental loss of fertile eggs or nestlings or otherwise leads to nest abandonment is considered “taking” by the CDFW.
There is potential for common raptor species such as red-tailed hawk (Buteo jamaicensis) and great horned owl (Bubo virginianus) to use mature trees for nesting to the north and east of the Project site, primarily along the Napa River corridor. If present offsite but within visual and auditory range of the Project site, nests of these species are protected during the breeding season.
Fish and Game Code Section 4150 states a mammal occurring naturally in California that is not a game mammal, fully protected mammal, or fur-bearing mammal is a nongame mammal. A nongame mammal may not be taken or possessed under this code. All bat species occurring naturally in California are considered nongame mammals and are therefore prohibited from take as stated in Fish and Game Code Section 4150.
There is a potential for native bats to forage in the Project site and/or roost in the vicinity. If these species are present during construction, measures must be implemented to avoid take of these species.
California Native Plant Protection Act
The California Native Plant Protection Act (California Fish and Game Code Sections 1900– 1913) and the Natural Communities Conservation Planning Act provide guidance on the preservation of plant resources. Vascular plants which have no designated status or protection under state or federal endangered species legislation, but are ranked as rare or endangered by the CNPS, are defined as follows:
1. Rank 1A: Plants presumed extinct
2. Rank 1B: Plants rare, threatened, or endangered in California and elsewhere
3. Rank 2: Plants rare, threatened, or endangered in California, but more numerous elsewhere Agenda Item #5.4.
3.4 – BIOLOGICAL RESOURCES
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4. Rank 3: Plants about which more information is needed – a review list
5. Rank 4: Plants of limited distribution – a watch list Generally, plants with a CRPR of 1A, 1B, or 2 are considered to meet the criteria for endangered, threatened, or rare species as outlined by Section 15380 of the CEQA Guidelines.
Additionally, plants listed on CNPS List 1A, 1B, or 2 also meet the definition of Section 1901, Chapter 10 (Native Plant Protection Act) and Sections 2062 and 2067 (CESA) of the California Fish and Game Code.
One plant, bent-flowered fiddleneck, has a CRPR of 1B and has low potential to occur within the grassland habitat on the Project site; however, it was not observed within the site during site surveys conducted when it would be evident and identifiable. Plants protected under the Native Plant Protection Act are not anticipated to be present at the Project site. As a result, the provisions of the Native Plant Protection Act would not apply to the Proposed Project.
California Department of Fish and Game Code Sections 1600–1616 Under Sections 1600–1616 of the California Fish and Game Code, CDFW regulates activities that would substantially alter the flow, bed, channel, or bank of streams and lakes. Such activities require a 1602 Lake and Streambed Alteration Agreement from CDFW. The California Code of Regulations (CCR) defines a stream as “a body of water that flows at least periodically or intermittently through a bed or channel having banks and supports fish or other aquatic life.
This includes watercourses having a surface or subsurface flow that supports or has supported riparian vegetation” (14 CCR 1.72). The term “stream” includes rivers, creeks, ephemeral streams, dry washes, canals, aqueducts, irrigation ditches, and other means of water conveyance if they support aquatic life, riparian vegetation, or stream-dependent terrestrial wildlife. Removal of riparian vegetation also requires a Section 1602 Lake and Stream Alteration Agreement from CDFW.
Because ditches on the Project site contain a defined bed and bank and flow periodically, they are potentially regulated under Sections 1600–1616 of the California Fish and Game Code.
Alteration of ditches onsite would require a Section 1602 Stream Alteration Agreement from CDFW. It is anticipated the Proposed Project would not fill or remove any of the existing ditches located adjacent to the Proposed Project boundaries.
State Water Resources Control Board
The SWRCB administers Section 401 of the Clean Water Act which requires that an applicant for a Clean Water Act Section 404 permit first obtain a certification, or waiver thereof, that a project will not violate applicable state water quality standards. The authority to either grant certification or Agenda Item #5.4.
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waive the requirement for certification has been delegated by the SWRCB to nine regional boards, including, in St Helena, the San Francisco Bay Regional Water Quality Control Board. The SWRCB protects all waters of the state, but has special responsibility for isolated wetlands and headwaters.
These water bodies have high resources value but are vulnerable to filling and may lack regulation by other programs. Projects that require a USACE permit, or fall under other federal jurisdiction, and have the potential to impact waters of the state are required to comply with the terms of the Water Quality Certification Program. If a project does not require a federal license or permit, but does involve activities that may result in a discharge of harmful substances to waters of the state, the water boards have the option to regulate such activities under its state authority in the form of Waste Discharge Requirements or Certification of Waste Discharge Requirements.
Seasonal wetlands and ditches within the Project site may be considered waters of the state and fall within the jurisdiction of the SWRCB. Discharge in these features would require regulation in the form of Waste Discharge Requirements or Certification of Waste Discharge Requirements.
Local Regulations
City of St. Helena 1993 General Plan
The Open Space and Conservation Element of the St. Helena 1993 General Plan provides guiding and implementing policies regarding biological resources, including the following:
Policy 6.2.3: Protect the riparian vegetation and habitat value of the City’s stream corridors by requiring development setbacks and open space easements along the Napa River, Sulphur Creek, York Creek, and Spring Creek.
Policy 6.2.10: Protect natural habitats which have the potential to support rare, endangered, or special status wildlife and plant species.
Implementing Policy 6.2.13: Require new development to be sited to maximize the protective tree species, riparian vegetation, important concentrations of natural plants, and important wildlife habitat.
Implementing Policy 6.2.14: Require all proposed projects adjacent to a riparian corridor or located in the City’s hillside areas, to submit management plans for protecting natural habitat values, including provisions to:
• Employ supplemental planting and maintenance of grasses, shrubs and trees of similar quality and quantity to provide adequate vegetation cover to keep the watersheds, on steep slopes and along streams, in good condition and to provide shelter and food for wildlife.
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• Provide protection for wildlife habitat.
• Provide replacement habitat of like quantity and quality.
Implementing Policy 6.2.15: Require a biological assessment of any proposed project site where species or the habitat of species defined as sensitive or special status by the California Department of Fish and Game or the U.S. Fish and Wildlife Service might be present.
Policy 6.4.11: Integrate existing significant trees into future development.
Policy 6.4.12: Require replacement trees where existing significant trees cannot be saved.
Policy 6.4.13: Require street trees as a condition of new development.
City of St. Helena 2019 General Plan (“General Pan Update 2040”) The Open Space and Conservation Element of the St. Helena 2019 General Plan provides policies regarding biological resources, including the following:
Policy OS1.1: Preserve and enhance St. Helena’s riparian corridors for their value in providing wildlife habitat, biodiversity, natural drainage, and visual amenity.
Policy OS1.2: Prohibit development, alteration, and/or removal of native vegetation from riparian areas. Disallow invasive species that degrade habitat quality.
Policy OS1.3: Protect and enhance contiguous corridors of riparian vegetation along the Napa River and its tributaries in order to support regional wildlife movement and enhance aquatic habitat.
Policy OS1.4: Protect natural habitats that have the potential to support rare, endangered, or special-status wildlife and plant species. Control invasive species that degrade habitat quality.
Policy OS1.5: Restrict development of hillside areas in order to protect wildlife, vegetation, viewsheds, and open space characteristics.
Policy OS1.6: Manage invasive species that degrade habitat quality, especially along the Napa River and its tributaries.
Policy OS1.7: Promote, encourage, and require sustainable agricultural practices that are sensitive to natural habitat and do not harm wildlife.
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Policy 6.4.12: Require replacement trees where existing significant trees cannot be saved.
Policy 6.4.13: Require street trees as a condition of new development.
St. Helena Municipal Code
Title 12, Chapter 12.24 of the St. Helena Municipal Code protects trees and other vegetation within the City by executing provisions to protect protected trees. Protected trees include heritage trees, protected replacement trees, street trees, and city trees (Section 12.24.020).
Heritage trees are defined as “any tree or grove of trees within the city boundaries designated by a resolution of the city council and having met the requirements set for in [Chapter 12.24, Section 12.22.020 ].”
Section 12.24.130 provides guidance for pruning, maintenance and removal of any protected trees, while Sections 12.24.140 and 12.24.150 address damage to protected trees and protection of trees during and after construction.
No tree removal is anticipated as a result of the Proposed Project. There are multiple oak trees on the banks of the ditch that runs along the southeast boundary of the Project site, near Del Rio Court. These trees would be retained and would not be removed to accommodate the Proposed Project.
3.4.4 Impacts
Methods of Analysis
The following resource databases and documents were reviewed in the course of preparing the biological resources review for the Proposed Project to establish the existing conditions as they relate to biological resources including plant and wildlife species, vegetation, and wetland and water resources. This review was supplemented with field observations as part of the previous biological resources studies conducted by WRA in 2011 and 2015, and reconnaissance surveys conducted by Dudek in 2018, 2019, and 2020.
• North Fork Associates. 2006. Wetland Delineation for the ±16-acre Hunter-St. Helena Property, St. Helena, Napa County, California. Technical Report. September 12, 2006. • WRA 2015. Hunter Subdivision Project, St. Helena, CA. Technical Letter Report.
September 15, 2015.
• Updated queries of the CNDDB (CDFW 2019), CNPS’s Inventory of Rare and Endangered Vascular Plants (CNPS 2019), and the USFWS Information for Planning and Consultation (IPaC) occurrence data (USFWS 2019).
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• Dudek. 2019. Preliminary Jurisdictional Delineation of Wetlands and Waters of the United States: Hunter Subdivision Project, Napa County, California. Technical Report. • Dudek. 2020. Rare Plant Survey Results for the Hunter Subdivision Project. Memorandum.
CEQA requires that projects analyze the potential impacts on special-status plant and wildlife species, as well as on sensitive habitats, wildlife corridors, and waters of the United States.
Impacts on wildlife species that are not considered special-status under CEQA are generally not considered significant unless impacts are associated with the species’ migration routes or movements, or the species are considered locally important. In the area surrounding the Project site, other common species (e.g., skunk, raccoon, possum, deer) would not be considered special-status species; however, impacts on their movements and migration routes would be considered significant under CEQA. Regardless of status, all nesting native bird species are protected from harm under the state Fish and Game Code and the federal MBTA.
Thresholds of Significance
Consistent with Appendix G of the CEQA Guidelines, a significant impact would occur if development of the Proposed Project would do any of the following:
• Have a substantial adverse effect, either directly or through habitat modifications, on any species identified as a candidate, sensitive, or special-status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Wildlife or U.S. Fish and Wildlife Service.
• Have a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, regulations or by the California Department of Fish and Wildlife or U.S. Fish and Wildlife Service. • Have a substantial adverse effect on state or federally protected wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) through direct removal, filling, hydrological interruption, or other means.
• Interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites.
• Conflict with any local policies or ordinances protecting biological resources, such as a tree preservation policy or ordinance.
• Conflict with the provisions of an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan.
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Threshold Criteria not Applicable to the Proposed Project Due to the location and characteristics of the Proposed Project, certain significance criteria are not applicable and therefore, are not considered potential impacts. These criteria are addressed briefly below and are not discussed further in this document.
Sensitive Natural Communities
As discussed in Section 3.4.2 Environmental Setting, there are no natural communities identified as sensitive by CDFW and the USFWS within the Project site. The natural communities present onsite are not regulated by CDFW, USFWS, regional plans, or policies.
Because the Project site lacks sensitive natural communities, there would be no impact and this issue (second significance threshold listed above) is not further addressed.
Conflict with any Local Policies or Ordinances Protecting Biological Resources The Proposed Project would not conflict with applicable 1993 General Plan policies and city ordinances designed to protect biological resources including habitat (see Section 3.4.3, Regulatory Setting). For example, no tree removal is required; therefore, the Proposed Project would not need to obtain a tree permit. As such, there would be no impacts and this issue (fifth significance threshold listed above) is not further addressed.
Habitat Conservation Plan/Natural Communities Conservation Plan The Proposed Project would not conflict with the provisions of an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan. Because the Project site is not located in an area subject to an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other similar plan, there would be no impacts and this issue (last significance threshold listed above) is not further addressed.
Impacts and Mitigation Measures
3.4-1: Would the Proposed Project have a substantial adverse effect, either directly or through habitat modifications, on species identified as a candidate, sensitive, or special-status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Wildlife or U.S. Fish and Wildlife Service? This impact would be potentially significant.
As discussed above and in Section 3.4.2, Environmental Setting, habitat for special-status species is generally limited in the Project site. The site is seasonally mowed/disked, and in 2010, approximately 2 feet of clean fill was spread across the site in support of the Napa River Flood Control Project. Given the disturbed nature of the site, and its proximity to frequent human Agenda Item #5.4.
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disturbance (e.g., residences and dog walkers), the site has a low potential to support sensitive plant and wildlife species. The few resources that have potential to occur are discussed below, including any potential impacts to these resources as a result of future development.
Special-Status Plants
No federal or state-listed plant species have the potential to occur onsite. One CRPR 1B.2 species, bent-flowered fiddleneck (Amsinckia lunaris), has the potential to occur onsite, but the likelihood of occurrence is low (see Section 3.4.2 for details). No evidence of the plant was identified on the Project site during the focused plant survey conducted in June 2020. The survey followed recommended methodology described in the CDFW Protocols for Surveying and Evaluating Impacts to Special-Status Native Plant Populations and Sensitive Natural Communities (CDFW 2018). The timing of the survey was such that bent-flowered fiddleneck would be evident and identifiable. In addition, bent-flowered fiddleneck was not identified on the Project site during multiple surveys conducted by biologists and botanists since 2006, including site visits during the bloom period in March and April (refer to Appendix D). Because the plant is not present on the site, the potential direct impact is considered less than significant.
Special-Status Wildlife
Comments received in response to the Notice of Preparation included concerns over potential impacts to salmonids (a grouping of fish that includes steelhead trout and salmon) residing in the Napa River. A summary of why the Proposed Project development would not adversely impact salmonids is provided below.
Salmonids: The Project site is located within the Napa River watershed; however, the Project site is not located adjacent to the river and there is no aquatic habitat for salmonids within the Project site (including central California coast steelhead DPS [distinct population segment] and fall-run Chinook salmon). The Central California coast steelhead DPS (hereafter ‘steelhead’) and fall-run Chinook salmon (hereafter ‘Chinook’) are known to occur in the Napa River, located approximately 500 feet north/northeast of the Project site. Although aquatic habitat for steelhead and Chinook is present in the Napa River, there are no fish passage opportunities between the Napa River and the Project site. As such, no direct impacts to steelhead would occur as a result of the Proposed Project.
Indirect impacts to steelhead and Chinook during construction, such as those related to water quality, are not expected to occur. Indirect impacts to salmonids as a result of poor water quality are limited to instances when salmonids are exposed to relatively high quantities of pollutants for prolonged periods of time (Bisson and Bilby 1982; Sigler et al. 1984). It is extremely unlikely that water quality stressors associated with Proposed Project construction activities such as increased turbidity or pollutants would enter the Napa River at a quantity that would harm Agenda Item #5.4.
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salmonids. The Project site does not drain directly into the Napa River, instead draining to an existing City-owned detention basin located adjacent to the site with a low-flow outlet to the Napa River. This lack of direct drainage would provide additional buffering of any discharge from Proposed Project construction, allowing additional time for mixing, settling, or other amelioration of pollutant concentrations before entering the river. Considering these factors, together with mixing provided by Napa River flows, any waterquality stressors generated by Proposed Project construction would not be expected to remain present for a prolonged time (i.e., several hours to days), further limiting potential for indirect harm to salmonids.
Implemention of Proposed Project permitting requirements and conditions of approval, such as those discussed in Section 3.9 Hydrology and Water Quality would be sufficient to avoid water quality degradation, meet water quality standards and Basin Plan objectives, and prevent adverse effects on salmonids during Proposed Project construction.
Indirect impacts to steelhead and Chinook as a result of Proposed Project operation are also not anticipated. As discussed Section 3.9, Hydrology and Water Quality, the Proposed Project would result in impervious surface area as compared to existing conditions, which has the potential to increase storm water runoff rates and transport of accumulated pollutants to surface waters.
However, the Proposed Project is not expected to adversely impact surface waters via storm water runoff, as all development would be subject to the most recent standards and performance criteria contained in the City’s Small Municipal Separate Storm Sewer System (MS4) Permit (described in Section 3.9.3, Regulatory Setting). Further, the Proposed Project’s grading plan includes all the elements necessary to demonstrate it can successfully comply with post construction MS4 Permit requirements. The Small MS4 Permit requires the Proposed Project to prepare and submit for City approval a Stormwater Control Plan that complies with the Bay Area Stormwater Management Agencies Post Construction Manual. Best management practices listed in the grading plans would be implemented including water quality features such as downspouts to landscaped swales; vegetated swales; hydrodynamic oil, water and solid separators; private street sweeping; labeled storm drains (“drains to river”) and homeowner educational materials on stormwater pollution prevention are best management practices to be implemented to prevent storm runoff of poor quality from entering the Napa River or seeping into the underlying groundwater table. For more details regarding the specific best management practices proposed, refer to Section 3.9.4 (Hydrology and Water Quality; Impacts). Compliance with these requirements would prevent indirect impacts to salmonids during Proposed Project operation.
Additionally, as discussed in Section 3.9, according to the groundwater basin assessment report, groundwater pumping is a relatively small outflow component compared to surface water stormflows and groundwater baseflow discharged to the Napa River. Therefore, the basin groundwater is dominated more by precipitation than it is by groundwater pumping and the proposed groundwater pumping by the Project would be expected to have a negligible effect on flows in the Napa River (LSCE 2016). This includes any indirect impacts to salmonids within the Napa River.
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No federal or state-listed wildlife species have the potential to occur onsite. Only two specialstatus wildlife species have the potential to occur onsite; these species are addressed below.
White-tailed kite: There is potential for white-tailed kite to use trees along the southeastern margins of the Project site or directly north of the Project site for nesting. No white-tailed kites have been observed on or near the Project site during the 2011, 2015, 2018, and 2019 biological surveys of the site. However, should white-tailed kite be breeding near the site prior to Proposed Project initiation, construction-related activities could potentially cause an adult kite to abandon an active nest that is in close proximity to the construction area and therefore leave eggs or chicks vulnerable to predation or without provisions. In addition, increased noise, glare, and lighting associated with Proposed Project operation could result in indirect impacts to nesting habitat for this species. However, noise levels associated with Proposed Project operation would be well within the City’s noise thresholds and would be typical of noise from existing residential land uses directly south and west of the Project site; refer to Section 3.11, Noise and Vibration, for a full discussion.
No tree removal is proposed as part of the Proposed Project, so no direct impacts, such as mortality and/or injury to nesting kites, is anticipated. However, the potential indirect impacts associated with construction and operation of the Proposed Project are considered substantial effects on a special-status species and, therefore, would be considered a potentially significant impact.
Native bats (including pallid bat): There is a low potential for native bats, including pallid bat, to roost onsite. Roosting habitat, such as rock outcrops, trees, caves, and human-made structures, are absent from the Project site. Moreover, pallid bat is unlikely to roost on or near the site due to frequent human disturbance (see Section 3.4.2 for details). However, there are trees and buildings near the Project site that provide potential roosting habitat for bats, and onsite grassland could be used for foraging by these species, or others roosting within dispersal distance of the Project site.
Should native bats roost near the site or use the on-site grassland for foraging, they could be impacted by the Proposed Project. If bats were to roost in the area during construction, they could be indirectly impacted by construction-related noise. Potential direct impacts from noise include acute acoustic trauma, degradation of physiological condition and social order, avoidance of foraging areas, and disturbance from and/or abandonment of roost sites. In particular, loud ultrasonic noise (i.e., having frequencies above the range of human hearing >20 kilohertz) can deter bats from accessing and using known roosts [Caltrans 2016]). Depending on noise attenuation rates and other factors, construction equipment such as graders, dozers, and diesel engines can produce sound sufficient to disturb roosting bats.
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Indirect impacts to roosting bats could also result from increased noise, light, glare, and activity associated with Proposed Project operation; however, noise levels would be within City thresholds and lighting associated with the Proposed Project would adhere to guidelines and standards set forth in Mitigation Measure AES-1 (see Section 3.1, Aesthetics) that would reduce glare and spillover light. Such standards include, but are not limited to, shielded and downward focused lighting, limited up-cast decorative lighting, and no use of mirrored glass .
No direct impacts to roosting bats are anticipated as potential roost sites, such as the trees along the southeastern margin of the site, would be avoided by the Proposed Project. However, the potential indirect impacts associated with construction and operation of the Proposed Project are considered substantial effects on a special-status species and, therefore, would be considered a potentially significant impact pursuant to the CEQA significance thresholds identified above.
Nesting and Migratory Birds
Trees, shrubs, grassland, and vineyards on or adjacent to the Project site provide potential nesting habitat for bird species protected under the MBTA and the California Fish and Game Code Section 3500. The quality of nesting habitat on the Project site is marginal due to regular mowing of the grassland and cultivation of the vineyard and lack of trees. No active nests were documented on or near the Project site during the 2011, 2015, 2018, and 2019 biological surveys. However, no focused surveys for nesting birds or birds of prey have been conducted at the site to date.
Direct impacts to nesting birds could result from vegetation clearing and site grading during Proposed Project construction. A majority of the Proposed Project footprint is limited to the annual grassland and vineyard, which generally do not provide nesting habitat for birds of prey, but would support some nesting bird species. Should active nests become established in the Proposed Project footprint during the time of construction, potential direct impacts could include direct harm or mortality due to construction equipment and destruction of an active nest due to vegetation removal or grading activities.
Potential indirect impacts to birds nesting near the Project site during construction would essentially be identical to those described above for white-tailed kite. The impact of noise on avian species varies among species and depends on source, duration and schedule (e.g., Hirvonen 2001; Reijnen et al. 1996; Slabbekoorn and Peet 2003; Wood and Yezerinac 2006). However, noise levels associated with Proposed Project operation would be well within the City’s noise thresholds and would be typical of noise from residential land uses directly south and west of the Project site; refer to Section 3.11, Noise and Vibration. The potential direct and indirect impacts associated with construction and operation of the Proposed Project are considered substantial effects on a specialstatus species and, therefore, would be a potentially significant impact.
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Mitigation Measures
Measures to mitigate potentially significant impacts on special-status wildlife species, known to occur or could potentially occur on the Project site, are described below. Implementation of the actions and measures described in Mitigation Measures BIO-1 and BIO-2, and Mitigation Measure AES-1 (see Section 3.1, Aesthetics), which also addresses this impact by reducing spillover light that can affect some species. Compliance with these mitigation measures addresses impacts to nesting birds, birds of prey, and special-status bat species and would avoid/minimize potential impacts to these species ensuring impacts would be reduced to less than significant.
BIO-1: A qualified biologist shall conduct a habitat assessment for bats in trees adjacent to the Project site within 2 weeks prior to any Project construction (site clearing, grading). The habitat assessment shall include a visual inspection of potential roosting features (bats need not be present) and presence of guano within the Project site and 50 feet around these areas. Potential roosting features found during the survey shall be mapped and described in a survey letter report. If roosting bats (individuals or colonies) are detected within the Project site, California Department of Fish and Wildlife shall be notified as soon as possible prior to any construction activity to confirm the bats can be avoided during construction. If a bat roosting or maternity colony cannot be completely avoided, a qualified biologist shall prepare a bat mitigation and monitoring plan for California Department of Fish and Wildlife review and approval, and that plan shall be implemented prior to commencement of construction that could impact the roosting bats or maternity colony.
BIO-2: If construction activities are scheduled to occur during the breeding season for birds (February 1 through August 31), the Project applicant or their contractor shall implement the following measures to avoid potential adverse effects to nesting raptors and other nesting birds:
• Preconstruction surveys by a biologist of all potential nesting habitats within 500- feet of construction activities, where accessible, shall be conducted by a qualified biologist. Surveys shall occur no more than 14 days prior to the initiation of site disturbance. If construction is stopped for 14 days or more during the breeding season, a new preconstruction nesting bird survey must be conducted before work can be restarted to ensure no new nesting has occurred in the interim. • If preconstruction surveys indicate that nests are inactive or potential habitat is unoccupied during the construction period, no further mitigation is required, following submittal of a survey report letter to the City of St.
Helena Planning Department.
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• If active nests are found during preconstruction surveys, a no-disturbance buffer shall be created around active nests during the breeding season or until it is determined by the biologist that all the young have fledged. The buffers shall be established by the biologist in conjunction with the California Department of Fish and Wildlife. Typical buffers may include 500 feet for raptors and 50 to 250 feet for other bird species based on the location of the nest, the nesting species present, and types of construction activities that may cause potential nest abandonment. The perimeter of the buffer zone shall be fenced or marked with staked flagging.
3.4-2: Would the Proposed Project have a substantial adverse effect on federally protected wetlands as defined by Section 404 of the Clean Water Act through direct removal, filling, hydrological interruption, or other means? This impact would be potentially significant.
The Project site supports 0.07 acres of wetlands and 870 linear feet of other waters, in the form of four seasonal wetlands and two agricultural ditches, as shown on Figure 3.4-2. These features are anticipated to meet the criteria for jurisdictional waters of the United States based on the jurisdictional delineation conducted on the Project site in February and April 2019, on an analysis of the three parameters for wetlands (soils, hydrology, and vegetation), and connectivity/proximity to known waters of the United States in the site vicinity (i.e., Napa River).
Four seasonal wetlands are present within the Proposed Project footprint. Construction activities would result in the fill of the four wetlands. As part of the current Proposed Project design, construction of a retaining wall on or near the property line may potentially impact the agricultural ditches by filling or otherwise altering the structure or flow of these features. This is considered a potentially significant impact.
Mitigation Measures
Implementation of Mitigation Measure BIO-3 would ensure no net loss of wetlands or other protected waters of the U.S. or state2 and would reduce impacts to less than significant.
BIO-3: Wetland permits (e.g., 404 Nationwide Permit, 401 Water Quality Certification, and 1602 Streambed Alteration Agreement, respectively) shall be obtained prior to any grading work. Prior to issuance of a grading permit, the Project applicant shall demonstrate authorization from the Army Corp of Engineers and any other regulatory agency to alter the wetland.
2 Note: Permit processing can take six to nine months for minor impacts less than one half-acre in size; and up to 2 years for impacts greater than one half-acre and with special-status species impacts (Individual Permit).
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3.4-3: Would the Proposed Project interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites? This impact would be potentially significant.
As discussed in Section 3.4.2 Environmental Setting, the Project site does not provide an essential habitat linkage or migratory corridor functions for resident or migratory wildlife. As shown on Figure 3.4-3, the Project site itself does not function as a wildlife movement corridor due to the surrounding development, lack of connectivity with other undeveloped areas, and existing and historic uses of the site. Moreover, the Project site does not provide suitable aquatic habitat for native resident or migratory fish species (see Section 3.4.2 for details).
Indirect impacts, such as construction run-off to the onsite agricultural ditches, has the potential to impact fish in the Napa River. Existing permitting requirements and conditions of approval (i.e., MS4 Permit and the City’s Stormwater and Runoff Pollution Control Ordinance) are sufficient to avoid water quality degradation, meet water quality standards and Basin Plan objectives; therefore, potential indirect impacts to any native resident or migratory fish via construction runoff in the Napa River are less than significant. See Section 3.9, Hydrology and Water Quality, for further details.
Although the annual grassland onsite does not provide adequate cover or nursery sites for many mammal species, trees along the edge of the site provide suitable habitat for nesting birds and roosting bats. In addition, some birds may use the grassland for nesting when sufficient (i.e., tall) vegetation is present. In addition, the riparian corridor along the Napa River is located approximately 500 feet north of the Project site. Lighting and increased usage of the site by humans may result in indirect effects to local wildlife using the riparian corridor for nursery sites or as a migratory corridor. Any site disturbance to these resources could result in a potentially significant impact.
Mitigation Measures
Implementation of Mitigation Measure AES-1 (see Section 3.1, Aesthetics) would ensure that lighting associated with the Proposed Project would adhere to guidelines and standards that reduce glare and spillover light and impacts would be less than significant. Such standards include, but are not limited to, shielded and downward focused lighting, limited up-cast decorative lighting, and no use of mirrored glass in the Proposed Project design. Compliance with Mitigation Measure BIO-5 that reimposes Mitigation Measures BIO-1, BIO-2, and BIO-3 would ensure direct and indirect impacts to the movement of any wildlife species or migratory wildlife corridors, or to wildlife nursery sites (e.g., bird nests, bat maternity roosts) would be reduced to less than significant.
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Compliance with Mitigation Measures AES-1, BIO-1, and BIO-2 mitigate this impact. No additional mitigation is necessary.
3.4.5 Cumulative Impacts
The geographic context for the analysis of cumulative biological impacts includes the areas contained within the Napa Valley and adjacent foothills (identified as the region), but primarily focused on the area within the city limits. Present and probable future projects within the region (which include, but not limited to, development in the city of St. Helena, Napa County, cities of Calistoga and Napa) are anticipated to permanently remove plant and wildlife resources, which could affect both common and special-status species and their habitat.
3.4-4: Would the Proposed Project contribute to cumulative impacts with respect to biological resources? The Project’s contribution would not be considerable.
The City recently updated its General Plan and adopted the 2019 General Plan and certified the Environmental Impact Report in May 2019. The 2019 General Plan Draft Environmental Impact Report (City of St. Helena 2018) notes that development in the City and elsewhere in the cumulative analysis area could cause significant cumulative impacts to nesting raptors and other special-status species; however, these cumulative impacts would be mitigated by compliance with General Plan policies. The Project site is located within an area that has been developed for residential and agricultural purposes and development of this site would not result in the reduction of available habitat, migration corridors, or other essential elements required by special-status species in the region. No special-status species have been documented at the Project site. While the Proposed Project would convert approximately 9 acres of potential foraging habitat for raptor species, the area has been disturbed in the past and provides only marginal habitat for burrowing mammal species that are the preferred prey for many resident raptor species. The existing disturbance at the site also greatly limits availability of insect prey for special-status bat species. Additionally, agriculture and natural lands in the vicinity of the city provide greater function and value as foraging habitat for these species. Due to the lack of biological value provided by the Project site, the Proposed Project’s contribution to any effects on biological resources would be considered negligible. Implementation of Mitigation Measures BIO-1 through BIO-7, would further reduce the Proposed Project’s cumulative contribution to regional biological resources impacts. However, absent mitigation the Proposed Project’s contribution would not represent a considerable contribution to potentially significant impacts on biological resources. The Proposed Project’s contribution to any existing cumulative impacts is not considerable resulting in a less-than-significant cumulative contribution.
Mitgation Measures
None required.
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3.4.6 References
Baker, M.D., M.J. Lacki, G.A. Falxa, P.L. Droppleman, R.A. Slack, and S.A. Slankard. 2008. “Habitat Use of Pallid Bats in Coniferous Forests of Northern California.” Northwest Science 82(4):269–275.
Bisson, P. A. and R. E. Bilby. 1982. Avoidance of Suspended Sediment by Juvenile Coho Salmon. North American Journal of Fisheries Management 4:317–374.
Brown, L., and D. Amadon. 1968. Eagles, Hawks and Falcons of the World. 2 Vols. London, United Kingdom: Country Life Books.
California Wilderness Coalition. 2001. Missing Linkages: Restoring Connectivity to the California Landscape.
Caltrans (California Department of Transportation). 2016. Technical Guidance for the Assessment and Mitigation of the Effects of Traffic Noise and Road Construction Noise on Bats. July. (Contract 43A0306.) Sacramento, CA. Prepared by ICF International, Sacramento, California, and West Ecosystems Analysis, Inc., Davis, California.
CDFW (California Department of Fish and Wildlife). 2016. California Essential Habitat Connectivity Project. Biogeographic Information and Observation System (BIOS).
Sacramento, California: CDFW. Accessed April, 2016 from http://bios.dfg.ca.gov.
CDFW. 2018. List of Vegetation Alliances and Associations: Natural Communities List Arranged Alphabetically by Life Form. October 2018. https://www.wildlife.ca.gov/Data/VegCAMP /Natural-Communities/List.
CDFW. 2019a. RareFind 5. California Natural Diversity Database. CDFW, Biogeographic Data Branch. Accessed April 2019. https://www.dfg.ca.gov/biogeodata/cnddb/mapsanddata.asp.
CDFW. 2019b. Natural Diversity Database. Special Animals List. Periodic publication. Updated November 2018. Accessed April 2019. https://www.wildlife.ca.gov/Data/CNDDB /Plants-and-Animals.
CDFW. 2019c. California Wildlife Habitat Relationships. Accessed April 2019. https://www.wildlife.ca.gov/Data/CNDDB/Plants-and-Animals.
City of St. Helena. 1993. City of St. Helena 1993 General Plan. September 28, 1993.
City of St. Helena. 2018. City of St. Helena General Plan Update 2040 Draft EIR, SCH# 2010042001. October 23, 2018.
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City of St. Helena. 2019. City of St. Helena General Plan Update 2040. June 2019.
CNPS (California Native Plant Society). 2018. A Manual of California Vegetation, Online Edition.
Accessed April 2019. http://www.cnps.org/cnps/vegetation/. California Native Plant Society, Sacramento, California.
CNPS. 2019. Inventory of Rare and Endangered Plants (online edition, v8-02). California Native Plant Society. Sacramento, California. Accessed April 2019. http://www.rareplants.cnps.org.
Dudek. 2019. Preliminary Jurisdictional Delineation of Wetlands and Other Waters of the U.S.
Prepared for the Hunter Subdivision Project. May 2019.
Grinnell, J., and A.H. Miller. 1944. "The Distribution of the Birds of California." Pacific Coast Avifauna Number 27. Berkeley, California: Copper Ornithological Club. Reprinted in Lee Vining, California: Artemisia Press. April 1986.
Hall, E.R. 1981. The Mammals of North America. 2nd ed. New York, New York: John Wiley and Sons Inc.
Hermanson, J.W., and T.J. O’Shea. 1983. “Antrozous Pallidus.” Mammalian Species 213:1–8.
Hirvonen, H. 2001. “Impacts of Highway Construction and Traffic on a Wetland Bird Community.” In Proceedings of the 2001 International Conference on Ecology and Transportation, edited by C.L. Irwin, P. Garrett, and K.P McDermott, 369–372. Raleigh, North Carolina: North Carolina State University, Center for Transportation and the Environment. Accessed March 5, 2012. http://escholarship.org/uc/item/3ts9d194.
Jennings, M.R., and M.P. Hayes. 1994. Amphibian and Reptile Species of Special Concern in California. Final report submitted to the California Department of Fish and Game, Rancho Cordova, California. Contract 8023.
Jepson Flora Project. 2019. Jepson eFlora. Berkeley, California: University of California. http://ucjeps.berkeley.edu/IJM.html.
LSCE (Luhdorff and Scalmanini Consulting Engineers). 2016. Napa Valley Groundwater Sustainability – A Basin Analysis Report for the Napa Valley Subbasin. Alternative Groundwater Sustainability Plan (GSP) Submitted to DWR. Prepared for Napa County. December 16, 2016.
NCWICC (Napa County Watershed Information and Conservation Council). 2019a. Napa River Basin Description. Accessed May 2, 2019.
https://www.napawatersheds.org/app_pages/view/44.
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NCWICC. 2019b. Wildlife. Accessed May 2, 2019. https://www.napawatersheds.org/wildlife.
North Fork Associates. 2006. Wetland Delineation for the ±16-acre Hunter-St. Helena Property, St. Helena, Napa County, California. Technical Report. September 12, 2006.
Reijnen, R., R. Foppen, and H. Meeuwsen. 1996. "The Effects of Traffic on the Density of Breeding Birds in Dutch Agricultural Grasslands." Biological Conservation 75:255–260.
Sigler, J. W., T. C. Bjornn, and F. H. Everest. 1984. Effects of Chronic Turbidity on Densities and Growth of Steelheads and Coho Salmon. Transactions of the American Fisheries Society 113: 142–150.
Slabbekoorn, H., and M. Peet. 2003. “Birds Sing at a Higher Pitch in Urban Noise.” Nature 424:267.
USACE (U.S. Army Corps of Engineers). 1987. Corps of Engineers Wetlands Delineation Manual. Online ed. Environmental Laboratory, Wetlands Research Program Technical Report Y-87-1. Vicksburg, Mississippi: U.S. Army Engineer Waterways Experiment Station. January 1987. Accessed February 2019. http://www.fedcenter.gov/Bookmarks /index.cfm?id=6403&pge_id=1606.
USACE. 2008. Regional Supplement to the Corps of Engineers Wetland Delineation Manual:
Arid West Region (Version 2.0). Environmental Laboratory, ERDC/EL TR-08-28.
Vicksburg, Mississippi: U.S. Army Engineer Research and Development Center.
September 2008. Accessed February 2019. http://el.erdc.usace.army.mil /elpubs/pdf/trel08-28.pdf.
USACE. 2010. A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States. Accessed February 2019. http://www.dtic.mil/dtic/tr/fulltext/u2/a486603.pdf.
USDA (U.S. Department of Agriculture). 2018. Web Soil Survey: Sonoma County, California.
USDA Natural Resources Conservation Service, Soil Survey Staff. Accessed September 28, 2018. http://websoilsurvey.nrcs.usda.gov/.
Western Regional Climate Center. 2016. Saint Helena, California (047643) Coop Station Monthly Climate Summary. Accessed May 2, 2019. https://wrcc.dri.edu/cgi-bin /cliMAIN.pl?ca7643.
Wood, W.E., and S.M. Yezerinac. 2006. “Song Sparrow (Melospiza melodia) Song Varies with Urban Noise.” Auk 123(3):650–659.
WRA (Wetland Research Associates Inc.). 2015. Hunter Subdivision Project, St. Helena, CA.
Technical Letter Report. September 15, 2015. WRA Inc.
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3.5 CULTURAL AND TRIBAL CULTURAL RESOURCES
3.5.1 Introduction
This section describes the cultural and tribal cultural resources present in the proposed Hunter Subdivision Project (Proposed Project) area and discusses applicable federal, state, and regional regulations pertaining to protection of cultural resources. This section evaluates the potential effects on cultural resources associated with development of the Proposed Project.
No comments were received that raised concerns regarding cultural or tribal cultural resources in response to the Notice of Preparation. The City of St. Helena (City) sent letters to all tribes requesting notification pursuant to Assembly Bill (AB) 52 and received responses from the Federated Indians of Graton Rancheria and the Yocha Dehe Wintun Nation. A copy of the Notice of Preparation and comments received is included in Appendix A. The Yocha Dehe Wintun Nation notes that the Project site is within their aboriginal territories and requests the cultural resources study prepared for the Proposed Project be provided for their review. The City provided the cultural report to the Yocha Dehe Nation in May 2020. Neither the Federated Indians of Graton Rancheria nor the Yocha Dehe Wintun Nation tribe requested formal consultation with the City.
The primary source referenced to prepare this section is based on the Cultural Resources Inventory and Extended Phase I and Phase II Report prepared by Dudek in March 2020. The reports are included in a confidential appendix (Appendix E) that is not available for public review given the sensitivity of the information.
3.5.2 Environmental Setting
Existing Site
The Project site is located on undeveloped land within the Napa Valley, immediately south of the Napa River, and within the City of St. Helena. The Pacific Ocean is located approximately 30 miles west, San Pablo Bay is 25 miles to the south, and Lake Berryessa is 12 miles northeast. A canal constructed for the St. Helena Flood Protection Project in 2010 bounds the site to the west and north and a residential community is present to the south. Local vegetation consists primarily of low-laying plants and grasses, with some scattered oak woodland and riparian community trees and shrubs along the drainages at the margins of the Project site. The western portion of the Project site includes an existing vineyard. The gradual slope throughout most of this area (less than 5 degrees) and proximity of Napa River and smaller drainages, would have historically resulted in the regular seasonal inundation of much of this area. The high level of surrounding topographic variability lends to the biodiversity of the area, this has traditionally provided for a broad range of flora and fauna that historically could have been used by local Wappo populations.
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Geologic maps of the Project area indicate it is underlain primarily by Quaternary Alluvium consisting of Holocene-era alluvial soils deposited through stream action and erosion of the surrounding hillslopes and Franciscan Complex metamorphic deposits (Jennings et al. 1977, updated 2010). Napa Glass Mountain, the primary source of obsidian in Napa Valley, is upriver from the Project site. Soils within the Project site are mapped as Bale Clay Loam with 0 to 5% slopes. These soils are formed through alluvial action on a Holocene alluvial fan, with soils comprised of sit and clay with moderate gravel and sand components (see also Section 3.6, Geology and Soils).
Cultural Context – Ethnography
Based on ethnographic information, it is believed that at least 88 different languages were spoken from Baja California Sur to the southern Oregon state border at the time of Spanish contact (Johnson and Lorenz 2006). The distribution of recorded Native American languages has been dispersed as a geographic mosaic across California through six primary language families (Golla 2007).
The Project area was traditionally occupied by the Wappo, whose language origins are associated with the Yukian language group. The name “Wappo” is said to be taken from the Spanish word “guapo” meaning handsome or brave, which was given to the group during Mission times by the Franciscans (Kroeber 1925). The Wappo language is the only Southern Yukian language and differs greatly from Northern Yukian with less than 20% of the basic vocabulary shared (Golla 2011). Isolated from other Yukian-speaking peoples, this group was bound on all sides by other native groups: the Lake Miwok to the north, the Patwin (Wintun) to the south and east, the Pomo to the north and west, and the Coast Miwok to the southwest (Heizer and Whipple 1971). The split between Northern Yukian and Wappo is somewhat unclear, likely ranging between 1,000 and 3,000 years ago (Kroeber 1925; Golla 2007). This split was likely related to the intrusion of Pomo-speaking communities during this period, which is evidenced through structural linguistic changes found within Wappo. These Wappo-speaking communities are indicated to have moved into the Napa region relatively, 500-1,500 years ago, based on the relatively limited presence of Miwok within the Wappo lexicon.
The territory occupied by the Wappo included Alexander Valley, most of Napa Valley, and the northern portion of Sonoma Valley. There are numerous regional subgroups including the Mishewal people of the Alexander and Knights Valley whose territory also included a small segment of the Russian River; the Mayacama people of the upper Napa Valley whose major village of mayakma was located near present-day Calistoga; and the Caymus people whose territory was centered around a village located at Yountville. The Guilicos Wappo community were situated over the mountains to the west at the head of Sonoma Creek. Yet another Wappo group was located on the south shore of Clear Lake known as Lile’ek (Golla 2011).
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Wappo settlements were organized in permanent villages throughout the valleys, typically found along major watercourses, such as rivers and creeks (Sawyer 1978). Districts of smaller settlements or tribelets were generally arranged around a larger community site (Kroeber 1925).
The chiefs of these smaller tribelets resided in the larger villages but were responsible for maintaining close relationships with their tribelet as well as neighboring tribes. Subsistence for the Wappo was largely dependent upon the acorn (a staple food item), as well as other native plants, and hunting of a variety of animals, including deer, bear, elk, and rabbits.
Material cultural for the Wappo included tools made of stone, sticks, and shells. Basket making, likely influenced by the Pomo, was also an important aspect of the group’s material culture and was of particularly high quality and aesthetic. The last description of a traditional village (Driver 1936) describes oval-shaped houses made of grass thatch placed over bent poles (Sawyer 1978). A lack of geographical restrictions in combination with their central location between the Pomo to the west and the Patwin to the east gave the Wappo the opportunity to act as middlemen in trading of items, such as shells for use as beads or ornaments (Heizer and Elsasser 1980). The Wappo would both bury and cremate the remains of the dead. Death rituals were complex and could involve burning personal possessions and relatives cutting their hair, rubbing clay on their heads, scoring of their flesh, and participating in intense ritual dances (Sawyer 1978).
Historic Period
Spanish Period (1769–1822)
The first Spanish expedition to enter the San Francisco Bay Area occurred under Gaspar de Portola in 1769. Portola’s chronicler, Fray Juan Crespi, detailed the journey of the group as it ventured up the coast. The first Spanish overland expedition into the San Francisco Bay region was led by Juan Bautista de Anza. The expedition reached San Francisco in 1776, where its members founded Mission Dolores and the Presidio. Spanish missionization of Alta California was initiated in San Diego (1769). A total of 21 missions were constructed by the Dominican and Franciscan orders between 1769 and 1823. Missions in the region included San Francisco de Asís (1776), Santa Clara de Asís (1776), San José de Guadalupe (1797 in Alameda County), San Rafael Arcángel (1817 in Marin County), and San Francisco Solano (1823 in Sonoma County; Grunsky 1989).
Mexican Period (1822–1848)
Spanish-Mexican settlers arrived in the Napa Valley in 1823. In 1836, the first land grant within the Napa Valley area was awarded to George Yount at Caymus (Bartoy et al. 2005). Local Native Americans assisted Yount in constructing his two-story Kentucky-style log house. Within the next ten years, the Napa Valley was divided and parceled into numerous ranchos. In 1836, Agenda Item #5.4.
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Nicolás Higuera, a soldier who served at the San Francisco Presidio, received several land grants from the Mexican government within Napa Valley, including an area called the Rancho Entre Napa, which included property that is now part of the present-day City of Napa.
Mexico’s separation from the Spanish empire in 1821 and the secularization of the California missions in the 1830s caused further disruptions to Native American populations. Following the establishment of the Mexican republic, the government seized many of the lands belonging to Native Americans, providing them as parts of larger Land Grants to affluent Mexican citizens and rancheros. The 1833 Secularization Act passed by the Mexican Congress ordered half of all mission lands to be transferred to Native Americans, and the other half to remain in trust and managed by an appointed administrator. These orders were never implemented due to several factors that conspired to prevent Native Americans from regaining their patrimony.
Under the command of General Vallejo, Mexican soldiers had a series of conflicts with Wappo Native American tribes and allied Pomo tribes. Known as the Satiyomi Campaigns, the Wappo fought successfully against Vallejo and his Patwin allies in 1834, 1836, and 1842 (Bartoy et al. 2005). Largely as a result of these conflicts, Vallejo signed two treaties with the Wappo in 1836.
American Period (Post 1848)
California was officially ceded to the United States in 1848, which led to the continued appropriation of Native American Lands by ranchers, prospectors, and an increasing number of settlers. The United States Government did little to dissuade these trespasses. From 1850, with the passage of California’s Indian Act, until legislative reforms in the late 1880s, state laws promoted conditions that amounted to indentured servitude for much of the Native American population throughout California. On February 8, 1850, Napa became one of California’s original 27 counties, with the City of Napa as the seat of the county. In 1852, the first mineral springs resort in California was established at White Sulphur Springs, approximately 4 miles to the west of St. Helena (Bartoy et al. 2005). These bolstered the local economy, supporting the presence of multiple hotels and other businesses. A tremendous influx of individuals occurred in this area as a result of the California Gold Rush, which initiated in 1848. Since 1850, the economic growth of Napa County has been largely based on agriculture, ranching, timber, and mineral resources.
By 1868, the railroad had been extended to St. Helena, and with easier transportation came more residents and a thriving community. St. Helena, officially founded in 1876, was originally part of Dr. Edward Turner Bale’s Rancho Carne Humana (Napa County Historical Society 2019).
Bale died in 1849, leaving his wife, Maria Ygnacia Soberanes, a member of the prominent Vallejo family. Maria built Bale’s grist and lumber mill into a profitable enterprise, and later sold 126 acres in the City to Henry Still and Charles Walters. She also provided land to numerous individuals as an incentive to open local businesses.
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A portion of downtown St. Helena was designated a National Register Historic District in 1998. Based on records maintained by the Napa County Historical Society, it contains 35 historic buildings mostly along Main Street but also extending onto Railroad Avenue and Money Way (2019).
Records Search
The Cultural Resources Inventory and Extended Phase I and Phase II Report (confidential Appendix E) prepared for the Proposed Project included a California Historical Resources Information System (CHRIS) records search, which was conducted at the Northwest Information Center (NWIC) on October 22, 2018, for the Project site and surrounding 0.5-mile radius. This search included their collection of mapped prehistoric, historical and built-environment resources, Department of Parks and Recreation (DPR) Site Records, technical reports, archival resources, and ethnographic references. Additional consulted sources included the National Register of Historic Places (NRHP), California Inventory of Historical Resources/California Register of Historical Resources (CRHR) and listed Office of Historic Preservation Archaeological Determinations of Eligibility, California Points of Historical Interest, California Historical Landmarks, and Caltrans Bridge Survey information.
The records search conducted at the NWIC concluded that 59 previous cultural resources technical investigations have been conducted within a one half-mile of the Project site. Of these, seven have included a portion of the Project site (Appendix E, Table 1). Approximately 90% of the Project site has been included in previous investigations. Cultural resource technical investigations S-043810 through S-043810d, which include the Project site, are summarized below.
Archaeological investigations conducted by Pacific Legacy in support of the St. Helena Flood Protection Project (Flood Protection Project) occurred between 2004 and 2013. The Flood Protection Project overlapped the western and northern portions of the present Project site. As a result of the survey and Extended Phase I exploratory work, eight archaeological resources were identified (all in the general vicinity of the present Project site): CA-NAP-399, CA-NAP-406, CANAP-413, CA-NAP-843, CA-NAP-863, CA-NAP-1007 (formerly HMS Vineyards Site), CA-NAP1008 (formerly Miller Vineyard Site), and CA-NAP-1009/H (formerly HMS Historic Stone Wall).
Based on the results of the Phase I Inventory and Phase II Evaluation efforts conducted for the Flood Protection Project, the U.S. Army Corps of Engineers (USACE) and State Water Resources Control Board (SWRCB) determined that five of the identified archaeological sites (CA-NAP-413, CA-NAP-843, CA-NAP-1007, CA-NAP-1008, and Cal-NAP-1009H) lacked sufficient data potential and integrity to meet the criteria for NRHP eligibility. It was determined that three sites (CA-NAP-399, CA-NAP-406, and CA-NAP-863) were eligible for listing in the NRHP listing under Criterion D. Avoidance of the sites was considered, and it was determined that the objectives of the proposed Flood Protection Project were important and could not be met without destroying or damaging the identified Historic Properties. The State Historic Preservation Agenda Item #5.4.
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Office (SHPO) concurred with these findings in 2006. A Historic Properties Treatment Plan was prepared outlining a program for Phase III Data Recovery and analysis that addressed the research potential of cultural deposits situated within the Flood Protection Project area of potential effects (APE). As part of this process, a Memorandum of Agreement was prepared between SHPO, USACE, and SWRCB in 2007. With the expectation that human remains would be encountered during investigations and later monitoring activities, the Mishewal Wappo Tribe of Alexander Valley and the City developed a burial agreement for the treatment of human remains in 2007 (Bartoy and Holson 2007: 87). Phase III Data Recovery was completed of the entirety of CA-NAP-399 and CA-NAP-863, as well as an approximate 500 x 100-foot section of CA-NAP-406. Site CA-NAP-406 was indicated in report maps to continue eastward into what represents the present Project site (Bartoy et al. 2005: 90). The eastern limits of this site were not determined as part of this work, nor was subsurface evaluation or data recovery completed of this area within the present Project site.
The NWIC records search indicated that 30 individual cultural resources have been recorded within the records search area. Three of the above-mentioned resources intersect the Project site: CA-NAP-406, CA-NAP-843, and CA-NAP-1008 (Appendix E). Of these three resources, CA-NAP-406 is the only resource that meets the criteria for NRHP eligibility. As described above, work for the Flood Protection Project resulted in a substantial level of previous archaeological investigation work along the western and northern portions of the Project site. This work has demonstrated the area to contain significant and highly sensitive archaeological resources. A total of 163 human burials were recovered from one site (CA-NAP-399) as part of the Flood Protection Project, the largest number of burials recovered from a single site in Napa Valley to date (Schneider et al. 2013: 44). Human remains were not documented within archaeological resources intersecting the Project site. Documented cultural resources that intersect or are located within the Project site (CA-NAP-406, CA-NAP-843 and CA-NAP-1008) are described further, below.
P-28-000307 (CA-NAP-406)
P-28-000307 was recorded initially during survey and subsurface testing completed by Yolande Beard in 1976 as a small site with worked obsidian, a pestle fragment and a small piece of magnesite. The resource was relocated by Stuart Guedon on June 13, 1995, at this recorded location. Guedon observed light scatter of obsidian debitage. The site was recorded as part of investigations and data recovery efforts for the Flood Protection Project between 2004 and 2009 (Bartoy et al. 2005; Schneider et al. 2013). The eastern and western extent of this site remain unconfirmed, however the resource as currently recorded measures 130 x 95 meters (m). An undetermined portion of this site intersects the Project site.
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Durring Pacific Legacy’s 2005 evaluation, archaeological investigation of CA-NAP-406 consisted of the placement of 17 auger bores, 22 shovel test probes (50 centimeters [cm] x 50 cm), two excavation units (1 m x 1 m), and one mechanically excavated trench (3 m x 0.5 m; Bartoy et al. 2005). Four of the auger bores were placed within excavation units and shovel test probes to ensure that the maximum depth of the cultural deposit had been reached. Testing was limited to the APE, which was defined as approximately 100 feet to the east of the then proposed Adams Street extension. The total amount of soil excavated in the 22 shovel test probes and two excavation units amounted to 4.24 cubic meters. A total of 4,244 artifacts were recovered from this site during this investigation.
Phase III data recovery at CA-NAP-406 was completed between 2007 and 2009, and involved excavation of two Control Units measuring 1 x 1 m; four Rapid Recovery Units measuring 2 x 1 m; and four trenches, measuring 3 x 1 m. In total, including Phase II investigations, the recovered assemblage included 5,711 pieces of lithic debitage, 17 bifaces, one core, seven edge-modified flakes, one hammerstone, 101 charcoal fragments, seven pieces of baked clay, and 40 historical-era artifacts.
This resource was determined eligible for inclusion in the NRHP/CRHR by the USACE and SWRCB in 2005. SHPO provided concurrence with these determinations in 2006. As such, an undetermined portion of this site, continuing from the west into the Project site, is assumed eligible for NRHP/CRHR listing.
P-28-000701 (CA-NAP-843)
CA-NAP-843 was recorded initially during the survey and subsurface testing completed by J.
Abell of Archaeo-Tec on April 1, 1993, for the proposed Safeway Relocation project. The site was recorded as a sparse obsidian lithic scatter with 3 projectile point fragments, one biface and several modified flakes, and debitage distributed across an area measuring 85 x 35 m. The recorded location of this site was located immediately southwest of the Project site; however, Abell noted that the resource may continue into the parcel representing the Project site. All items were identified on the surface; auguring yielded no subsurface material or identified midden-like soils. The resource was relocated by Stuart Guedon on June 13, 1995 at this recorded location.
Guedon observed an extremely light and diffuse scatter of obsidian debitage that did not extend into adjoining areas.
The site was re-identified during subsurface testing by Pacific Legacy for the Flood Protection Project in 2004. While NWIC resource files map this site to the southwest, Pacific Legacy’s technical report indicates that this testing occurred within the boundaries of the Project site (Bartoy et al. 2005: 126). Archaeological investigation consisted of the placement of 29 auger bores and 15 shovel test probes (50 cm x 50 cm). The total amount of soil excavated in the Agenda Item #5.4.
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shovel test probes amounted to 1.5 cubic meters. A total of four artifacts were recovered from this site during this investigation. Testing confirmed the characterization of this site as a lowdensity lithic scatter with no associated midden (Bartoy et al. 2005). The site was considered a sparse surface scatter with no depth to the deposit. The artifact assemblage from the site included three edge-damaged obsidian flakes and one fragment of historic glass.
Given the low density of cultural materials and the lack of spatial patterning, this resource was determined not eligible for inclusion in the NRHP or the CRHR by the USACE and SWRCB.
SHPO provided concurrence with these determinations in 2006.
P-28-001267 (CA-NAP-1008)
CA-NAP-1008 (also referred to as “Miller Vineyard Site”) was identified by Pacific Legacy for the Flood Protection Project initiating in 2004 at a location that falls within the northeastern portion of the Project site. The site was recorded as a surface scatter and shallow deposit of flaked lithic artifacts, predominantly Napa Valley obsidian, measuring 150 x 100 m. Extended Phase I Inventory and Phase II Evaluation work completed by Pacific Legacy occurred in 2004 and 2005 (Bartoy et al. 2005). Subsurface archaeological investigation included 32 augers, 13 shovel test pits (measuring 50 x 50 cm), two excavation units (measuring 1 x 1 m), and two mechanically excavated trenches (measuring 3 m x 0.5 m). A total of 396 artifacts were recovered from within
3.88 cubic meters of removed soil. Soil mixing to a depth of 60 centimeters below the surface (cmbs) was observed, presumably as a result of past discing activities associated with the surrounding vineyard. Obsidian hydration placed the sited chronologically between 2,500 years BP and 500 years BP.
The site was determined not eligible for CRHR/NRHP listing by the USACE and SWRCB based on the results of extended Phase I Inventory and Phase II Evaluation work for the Flood Protection Project (Bartoy et al. 2005). SHPO provided concurrence with these determinations in 2006.
Pedestrian Survey and Extended Phase I Testing
A Phase I Survey of the entire Project site was completed November 15, 2018 (Appendix E). The southern half of the Project site is occupied by a small vineyard, allowing for approximately onehalf of the ground surface to be directly visible. Low-lying grasses were present throughout the northern half of the Project site, restricting visibility of the ground surface to less than 10% in most areas on this initial site visit. Evidence for buried cultural deposits was opportunistically sought through inspection of natural or artificial erosion/excavation exposures and the spoils from rodent burrows. The Project site has been subject to a number of past disturbances. The most notable of these have included present and past agricultural activities, as well as likely earth moving work in the northernmost portion of the Project site. During construction of the Agenda Item #5.4.
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Flood Protection Project placement of excess fill material was placed on the Project site. No artifacts were observed on the surface during the survey; however, visibility was highly restricted in most areas by low-lying vegetation and organic debris.
Subsurface probing (XPI probing or investigation) was conducted by a Dudek archeologist from November 15, 2018 to November 17, 2018. The intent of this work was to assess if subsurface conditions are present for significant archaeological deposits to be present. Excavation included three 6-inch hollow-stem augers and 5 shovel test probes. Excavations did result in the identification of soils within the Project site that had potential to contain archaeological deposits.
The XPI investigations resulted in the identification of areas within the Project site that contain, and have the potential to contain, archaeological resources.
While the intent of the XPI investigation was to assess the potential for subsurface soils to be present, artifacts were identified in the locations nearest previously recorded archaeological resources. Archaeological testing was not intended to evaluate the frequencies or distribution of archaeological materials and deposits within the Project site. However, general results indicate artifact frequencies were highest in the central (near CA-NAP-406) and northern (CA-NAP-1008) portions of the Project site. One artifact was also identified in the southern portion of the Project site (near CA-NAP-843). The majority of cultural material was recovered from the lower, darker stratum (20-60 cmbs). Artifacts consisted predominantly of small obsidian tertiary flakes. These findings are generally consistent with results documented for Phase II excavations completed for the Flood Control Project along the western side of the central portion of the Project site (Bartoy et al. 2005). This study suggested that previous agricultural activities may have extended as deep as 60 cmbs in some areas, below which artifact frequencies decreased until encountering a gray clay sterile soil sub-stratum at approximately 1.5 meters below the surface (Schneider et al. 2013: 27). It is quite likely that this pattern extends into the Project site.
Phase II Testing and Ground Penetrating Radar
Based on the finding of the Phase I testing and the potential for unknown subsurface resources to be present within the site, further excavations were necessary to fully understand the extent of disturbances resulting from the previous Flood Protection Project and the changes in the soils.
Dudek archeologists conducted the Phase II testing starting on January 20, 2020 through January 24, 2020. The intent of the Phase II survey was to build upon the Phase I survey and XPI investigation work. Results of these excavations are provided in Table 3.5-1.
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Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
AT-01 0-20 Negative None 2.5Y 5/3 Light olive brown clay silt with gravel, compact 20-40 Positive 1 obsidian shatter 2.5Y 5/3 Light olive brown clay silt with gravel, compact: 1 obsidian shatter fragment
40-60 Negative None 2.5Y 6/2 Light brown gray clay silt with gravel, compact.
Rock impasses at 60 cmbs
AT-02 0-20 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
20-40 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
40-60 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
AT-03 0-20 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
20-40 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
40-60 Negative None 10YR 3/2 Very dark grayish brown loamy clay with gravel, compact
AT-04 0-20 Positive 1 green bottle glass
fragment
10YR 4/1 Dark gray silty clay, no gravels: 1 fragment
green bottle glass
20-40 Negative None 10YR 4/1 Dark gray clay, < 2% angular gravels 40-60 Negative None 10 YR 4/1 Dark gray clay < 5% angular gravels 60-80 Negative 4 obsidian debitage 10 YR 4/1 Dark gray clay < 5% angular gravels. Rock impasse at 75 cmbs
AT-05 0-20 Negative None 2.5 YR 3/2 Very dark grayish brown clay loam 20-40 Positive 2 obsidian debitage 10YR 3/2 Very dark grayish brown silty loam with increased sand content
40-60 Positive 2 obsidian debitage 10YR 3/2 Very dark grayish brown silty loam with increased sand content
60-80 Positive 1 obsidian debitage 10YR 2/2 Very dark brown silty loam with increased grit, moderately compact. Rock impasse at 80 cmbs
AT-06 0-20 Negative None 10YR 3/2 Very dark grayish brown silty loam 20-40 Negative None 10YR 3/2 Very dark grayish brown silty loam 40-60 Negative None 10YR 3/2 Very dark grayish brown silty loam 60-80 Negative None 10YR 3/2 Very dark grayish brown silty loam 80-100 Negative None 10YR 3/2 Very dark grayish brown silty loam 100-120 Negative None 10YR 3/2 Very dark grayish brown silty loam 120-140 Negative None 2.5Y 4/3 Olive brown sandy silt, with 20% gravel. 140-160 Negative None 2.5Y 4/3 Olive brown sandy silt, with 20% gravel. 160-180 Negative None 2.5Y 4/3 Olive brown sandy silt, with 20% gravel. 180-200 Negative None 2.5Y 4/3 Olive brown sandy silt, with 20% gravel. Auger terminated at 187 cmbs
Agenda Item #5.4.
3.5 – CULTURAL AND TRIBAL CULTURAL RESOURCES
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September 2021 3.5-11
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
AT-07 0-20 Negative None 10YR 3/2 Very dark grayish brown silty loam, gradual increase in sand content with depth
20-40 Negative None 10YR 3/2 Very dark grayish brown silty loam, gradual increase in sand content with depth
40-60 Negative None 10YR 4/2 Dark grayish brown sandy loam 60-80 Negative None 10YR 4/2 Dark grayish brown sandy loam 80-100 Negative None 10YR 5/3 Brown sandy clay, coarse sand with 15% angular gravels. Rock impasse at 90 cmbs
AT-08 0-20 Negative None 10YR 3/2 Very dark grayish brown clay loam 20-40 Negative None 2.5Y 3/2 Very dark gray brown clay loam, increased sand, <5% small cobbles and gravel
40-60 Negative None 2.5Y 3/2 Very dark gray brown clay loam, increased sand, <5% small cobbles and gravel
60-80 Negative None 2.5Y 4/3 Olive brown sandy silt, some oxidation present 80-100 Negative None 2.5Y 4/4 Olive brown sandy silt, some oxidation present AT-09 0-20 Negative None 10YR 3/3 Dark brown silt loam
20-40 Negative None 10YR 3/3 Dark brown silty loam
40-60 Negative None 10 YR 3/2 Very dark gray brown silty clay loam. Rock impasse at 55 cmbs
AT-10 0-20 Negative None 10YR 3/2 Very dark grayish brown silty loam with coarse sand
20-40 Negative None 10YR 3/3 Dark brown silty clay loam 40-60 Negative None 10YR 3/3 Dark brown silty clay loam. Rock impasse at 53 cmbs
AT-11 0-20 Negative None 10YR 3/1 Very dark gray clay silt 20-40 Negative None 2.5Y 3/3 dark olive brown silty clay 40-60 Negative None 2.5Y 3/3 dark olive brown silty clay 60-80 Negative None 2.5Y 3/3 dark olive brown silty clay 80-100 Negative None 2.5Y 2.5/1 Black silty clay
100-120 Negative None 2.5Y 2.5/1 Black silty clay
120-140 Negative None 2.5Y 2.5/1 Black silty clay
140-160 Negative None 2.5Y 2.5/1 Black silty clay
AT-12 0-20 Positive 1 obsidian debitage 2.5Y 3/2 Very dark gray brown clay loam 20-40 Positive 2 obsidian debitage 2.5Y 3/2 Very dark gray brown clay loam 40-60 Negative None 2.5Y 3/2 Very dark gray brown clay loam 60-80 Negative None 2.5Y 3/2 Very dark gray brown sandy clay loam, with 20% small-medihm gravels and cobbles. Rock impasse at 70
cmbs
AT-13 0-20 Positive 1 obsidian flake 2.5Y 3/2 Very dark gray brown silty loam 20-40 Negative None 2.5Y 3/2 Very dark gray brown silty loam 40-60 Negative None 2.5Y 4/1 dark geay silty clay loam with oxidation throughout
Agenda Item #5.4.
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September 2021 3.5-12
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
60-80 Negative None 2.5Y 2.5/1 black silty clay loam, compact 80-100 Negative None 2.5Y 2.5/1 black silty clay loam, compact 100-120 Negative None 2.5Y 2.5/1 black silty clay loam, compact 120-140 Negative None 10YR 4/1 dark gray mottled with 10YR 4/3 brown clay loam, compact
140-160 Negative None 2.5Y 5/2 grayish brown sandy clay loam 160-180 Negative None 2.5Y 5/2 grayish brown sandy clay loam 180-200 Negative None 2.5Y 5/2 grayish brown sandy clay loam 200-220 Negative None 2.5Y 4/2 Dark grayish brown sandy clay loam 220-240 Negative None 2.5Y 4/2 Dark grayish brown sandy clay loam 240-260 Negative None 2.5Y 4/2 Dark grayish brown sandy clay loam 260-280 Negative None 2.5Y 4/2 Dark grayish brown sandy loam, water table at 280 cmbs
STP-01 0-20 Positive 21 obsidian flakes, 1
retouched obsidian
flake
10YR 3/2 very dark gray brown loamy clay with gravel,
compact
20-40 Positive 45 obsidian flakes 10YR 3/2 Very dark gray brown clay silt, compact STP-02 0-20 Positive 9 obsidian flakes 2.5Y 5/3 Light olive brown clay silt with gravel, compact 20-40 Positive 44 obsidian flakes 10YR 3/2 Very dark gray brown clay silt, compact STP-03 0-20 Positive 3 obsidian flakes, 1
chert flake
2.5Y 5/3 Light olive brown clay silt with gravel, compact 20-40 Positive 3 obsidian flakes 10YR 3/2 Very dark gray brown clay silt, compact STP-04 0-20 Positive 14 obsidian flakes 10YR 3/3 Dark Brown sandy clay silt with gravel, compact 20-40 Positive 8 obsidian flakes 10YR 3/2 Very dark gray brown clay silt, compact STP-05 0-20 Positive 34 obsidian flakes 10YR 4/2 Dark grayish brown loamy clay with gravel, compact
20-40 Positive 63 obsidian flakes, 1
obsidian
chopper/scraper
10YR 3/2 Very dark gray brown clay silt, compact
STP-08 0-20 Positive 50 obsidian debitage 10YR 3/2 very dark gray brown loamy clay, lightly compacted, with <5% small rounded gravels
20-40 Positive 44 obsidian debitage 10YR 3/2 very dark gray brown loamy clay, lightly compacted, with <5% small rounded gravels
40-60 Positive 4 obsidian debitage 10YR 3/2 very dark gray brown loamy clay, lightly compacted, with <2% small rounded gravels
60-80 Negative None 10YR 4/3 Brown clay with <2% small angular and rounded gravels
80-100 Negative None 10YR 4/4 Dark yellowish-brown sandy clay, <5% gravel and cobbles
100-120 Negative None 10YR 4/4 Dark yellowish-brown sandy clay, <5% gravel and cobbles. Terminated at 105 cmbs due to water table
Agenda Item #5.4.
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September 2021 3.5-13
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
STP-09 0-20 Positive 21 obsidian debitage 2.5Y 3/1 Very dark gray silty clay with <10% angular gravel
20-40 Positive 14 obsidan debitage,
modern plastic
2.5Y 3/1 Very dark gray silty clay with <10% angular
gravel
40-60 Positive 21 obsidian debitage,
brick fragment,
wooden lathe
fragment, and modern
plastic
2.5Y 3/1 Very dark gray silty clay with <10% angular
gravel
60-80 Positive 21 obsidian debitage,
1 obsidian retouched
edge tool, brick
fragment
2.5Y 3/2 very dark gray brown sandy silt with <15%
angular gravel, very compact
80-100 Positive 22 obsidian debitage,
brick fragment
2.5Y 3/2 very dark gray brown sandy silt with <15%
angular gravel, very compact
100-120 Positive 1 obsidian debitage Auger - 2.5Y 3/2 very dark gray brown clay loam with <15% angular gravel, slightly compact. Rock impase at
120 cmbs
STP-10 0-20 Positive 1 obsidian biface, 17
obsidian debitage
2.5Y 3/2 Very dark gray brown silty clay loam
20-40 Positive 3 obsidian debitage, 2
glass fragments,
plastic, and aluminum
2.5Y 3/2 Very dark gray brown silty clay loam, increasing clay content and compaction with depth
40-60 Positive 1 obsidian debitage 2.5Y 3/2 Very dark gray brown sandy silty clay loam 60-80 Negative None Auger - 2.5Y 3/2 Very dark gray brown sandy silt 80-100 Negative None Auger - 2.5Y 3/2 Very dark gray brown sandy silt 100-120 Negative None Auger - 2.5Y 3/2 Very dark gray brown sandy silt 120-140 Negative None Auger - 2.5Y 3/1 Very dark gray sandy clay 140-160 Negative None Auger - 2.5Y 3/2 Very dark gray coarse sand. Terminated at 160 cmbs
STP-11 0-20 Positive 6 obsidian debitage 7.5YR 3/2 dark brown loamy clay with <5% rounded gravel
20-40 Positive 3 obsidian debitage 7.5YR 3/2 dark brown loamy clay with <5% rounded gravel
40-60 Positive 3+ pieces of plastic 10YR 3/2 dark grayish brown loam with <5% rounded gravel
60-80 Negative None 7.5YR 3/4 dark brown loam
80-100 Negative None 80-90 cmbs: 7.5YR 3/4 dark brown loam 90-100 cmbs: coarse gray sand
STP-12 0-20 Positive 3 obsidian debitage 10YR 3/3 Dark brown sandy silt 20-40 Positive 6 obsidian debitage 10YR 3/3 Dark brown sandy silt 40-60 Positive 13 obsidian debitage 40-50 cmbs: 10YR 3/3 Dark brown sandy silt 50-60: 10YR 3/2 Very dark grayish brown sandy silt with ~50% cobbles
Agenda Item #5.4.
3.5 – CULTURAL AND TRIBAL CULTURAL RESOURCES
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September 2021 3.5-14
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
60-80 Negative None 10YR 3/2 Very dark grayish brown sandy silt with ~50% cobbles. Terminated at 75 cmbs due to rock impasse
STP-14 0-20 Negative None 10YR 4/3 Brown sandy loam with <5% gravel 20-40 Negative None 10YR 3/3 Dark brown sandy loam with <5% gravel 40-60 Negative None 10YR 3/3 Dark brown sandy loam with <5% gravel, cobbles at 55 cmbs
STP-16 0-20 Negative None 10YR 3/2 Very dark grayish brown loamy clay 20-40 Negative None 10YR 3/2 Very dark grayish brown loamy clay 40-60 Negative None 10YR 3/2 Very dark grayish brown loamy clay, 55cmbs increased cobbles (5-10 cm diam.)
STP-17 0-20 Positive 1 obsidian debitage 10YR 3/2 Very dark grayish brown sandy loam with angular cobbles (5-15 cm diam.)
20-40 Negative None 10YR 3/2 Very dark grayish brown sandy loam with angular cobbles (5-15 cm diam.)
40-60 Negative None 10YR 3/2 Very dark grayish brown sandy loam with angular cobbles (5-15 cm diam.)
STP-18 0-20 Negative None 10YR 3/2 Very dark grayish brown sandy loam with <5% angular gravels. Angular cobbles (4-8 cm diam.) at 15
cmbs
20-40 Negative None 10YR 4/1 Dark gray loamy clay, < 2% angular gravels, clobbles (~10 cm diam.)
40-60 Negative None 10YR 4/1 Dark gray loamy clay, < 2% angular gravels, clobbles (~10 cm diam.)
STP-19 0-20 Negative None 10YR 3/2 Very dark grayish brown loamy clay 20-40 Negative None 10YR 3/3 Dark brown loamy clay with cobbles (4-8 cm diam.)
40-60 Negative None 10YR 3/3 Dark brown loamy clay with cobbles (4-8 cm diam.)
STP-21 0-20 Positive 1 obsidian debitage 10YR 3/2 Very dark grayish brown loamy clay with <5% angular gravels
20-40 Negative None 10YR 3/2 Very dark grayish brown loamy clay with <5% angular gravels
40-60 Negative None 10YR 3/2 Very dark grayish brown loamy clay with <5% angular gravels
STP-22 0-20 Negative None 10YR 3/3 Dark brown sandy loam with <5% gravel 20-40 Negative None 10YR 3/3 Dark brown sandy loam with <5% gravel 40-60 Negative None 10YR 3/3 Dark brown sandy loam with >50% cobbles (4- 10 cm diam.)
STP-23 0-20 Positive 1 obsidian debitage 2.5Y 3/2 Dark Brown clay silt 20-40 Negative None 2.5Y 3/2 Dark Brown clay silt
40-60 Negative None 2.5Y 3/2 Dark Brown clay silt
60-80 Negative None Auger - 60-70 cmbs: 2.5Y 3/2 Dark brown clay silt 70-80 cmbs: 2.5Y 2.5/1 Black silty clay
Agenda Item #5.4.
3.5 – CULTURAL AND TRIBAL CULTURAL RESOURCES
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September 2021 3.5-15
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
80-100 Negative None Auger - 2.5Y 2.5/1 black silty clay 100-120 Negative None Auger - 2.5Y 2.5/1 black silty clay 120-140 Negative None Auger - 2.5Y 2.5/1 black silty clay 140-160 Negative None Auger - 2.5Y 2.5/1 black silty clay STP-24 0-20 Negative None 10YR 3/3 Dark brown sandy silt 20-40 Negative None 10YR 3/3 Dark brown sandy silt
40-60 Negative None 10YR 3/3 Dark brown sandy silt
STP-25 0-20 Positive 1 obsidian debitage 7.5YR 3/2 Dark brown sandy loam with 5% large cobbles (5-15 cm diam.)
20-40 Positive 1 historic ceramic 7.5YR 3/2 Dark brown sandy loam with 70% large cobbles (5-15 cm diam.)
STP-26 0-20 Negative None 7.5YR 3/2 Dark brown silty sandy loam 20-40 Negative None 7.5YR 3/2 Dark brown silty sandy loam 40-60 Negative None 7.5YR 3/2 Dark brown silty sandy loam with 50% cobbles (5-15 cm diam.)
STP-27 0-20 Negative None 10YR 4/2 Dark grayish brown loamy clay with ~50% gravel
20-40 Negative None 10YR 3/2 Very dark gray sandy clay with ~50% gravel 40-60 Positive 12 obsidian debitage 10YR 3/2 Very dark grayish brown clay with 10% gravels:
12 obsidian debitage
60-80 Negative None 10YR 3/2 Very dark grayish brown sandy loam with 10% gravels
80-100 Negative None 10YR 2/2 Very dark brown sandy loam 100-120 Negative None 10YR 2/2 Very dark brown sandy loam 120-140 Negative None 10YR 2/2 Very dark brown sandy loam. Terminated at 130 cmbs
STP-28 0-20 Positive 6 obsidian debitage 10YR 4/2 Dark grayish brown silty clay 20-40 Negative None 10YR 3/2 Very dark grayish brown clay 40-60 Negative None 2.5YR 3/1 Very dark grayish brown
60-80 Negative None Auger - 2.5YR 4/1 Very dark gray sandy clay 80-100 Negative None Auger - 2.5YR 4/1 Very dark gray sandy clay 100-120 Negative None Auger - 2.5YR 4/1 Very dark gray sandy clay 120-140 Negative None Auger - 2.5YR 4/1 Very dark gray sandy clay 140-160 Negative None Auger - 2.5YR 4/1 Very dark gray sandy clay STP-29 0-20 Positive 6 obsidian debitage 10YR 2/2 Very dark brown clay 20-40 Positive 3 obsidian debitage 10YR 2/2 Very dark brown clay 40-60 Positive 4 obsidian debitage 10YR 3/2 Very dark grayish brown silty clay 60-80 Positive 1 obsidian debitage, 3
glass fragments
10YR 3/2 Very dark grayish brown silty clay
80-100 Negative None 10YR 3/2 Very dark grayish brown silty clay 100-120 Negative None 10YR 3/2 Very dark grayish brown silty clay Agenda Item #5.4.
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September 2021 3.5-16
Table 3.5-1
Extended Phase I and Phase II Testing Results
Unit ID
Depth
(cmbs) Results Artifacts Recovered Soil Description
120-140 Negative None 10YR 3/2 Very dark grayish brown silty clay 140-160 Negative None 5Y 3/1 Very dark gray silty clay. Terminated at 150 cmbs.
STP-30 0-20 Positive 2 obsidian debitage 2.5Y 3/2 Dark brown sandy loam 20-40 Positive 1 obsidian debitage 2.5Y 3/2 Dark brown sandy loam 40-60 Negative None 2.5Y 3/1 Very dark grayish brown sandy loam 60-80 Negative None 2.5Y 4/2 Dark grayish brown sandy silt with 40% large cobbles
80-100 Negative None 2.5Y 4/2 Dark grayish brown sandy silt 100-120 Negative None 2.5Y 4/2 Dark grayish brown sandy silt Source: Appendix E.
Notes: cmbs = centimeters below the surface; STP = shovel test pit Ground-penetrating radar (GPR) was used in transects and blocks to locate any subsurface anomalies. The GPR was set up to record data to a maximum depth of 8 meters (approximately 26 feet). The GPR was useful in assessing the level of previous subsurface disturbance and presence and depth of fill within the Project site, and the potential for soils to support the presence of cultural material and deposits associated with the three previously recorded sites in the vicinity: CA-NAP-406, CA-NAP-843, and CA-NAP-1008.
Phase II testing for the Proposed Project included an additional 10 augers and 25 shovel test probes. Archaeological testing did not result in the identification of intact cultural deposits.
Results indicate artifact frequencies were highest in the central (near CA-NAP-406) and northern (CA-NAP-1008) portions of the Proposed Project APE. Most cultural material was recovered from shallower contexts, above 60 cmbs. Modern debris was encountered to 100 cmbs, confirming clear disturbances to this depth. Artifacts consisted predominantly of small obsidian tertiary flakes. These findings are generally consistent with the assemblage documented by aerial imagery and Phase II excavations completed for the Flood Control Project along the western side of the central portion of the Proposed Project APE (Bartoy et al. 2005). This study suggested that a gray sandy clay sterile soil sub-stratum was present approximately 1.5 m below the surface (Schneider et al. 2013).
The portion of the Project site occupied by the vineyard, while previously disturbed through agricultural activities, was not capped by redistributed soils during the Flood Protection Project.
As such, these areas would have the highest potential for intact cultural deposits to persist. The total assemblage of artifacts recovered from all XPI investigations and Phase II excavation units within this area included four fragments of obsidian debitage and one possibly historical-era Agenda Item #5.4.
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ceramic fragment. It is most likely that soils within the vineyard area are likely representative of the native soils underlying fill to the north of the Project site.
Tribal Cultural Resources and Tribal Consultation
A tribal cultural resource (TCR) is a site, feature, place, cultural landscape, sacred place, or object with cultural value to a tribe that is included or determined to be eligible for inclusion in the California Register of Historic Resources, included in a local register of historical resources, or otherwise determined to be significant by the lead agency of an environmental review process.
On September 28, 2018, a sacred lands file search request and a request for the Native American contact list for the area was sent to the Native American Heritage Commission (NAHC). On October 10, 2018, the NAHC responded with results from the sacred lands file search request. The sacred lands search failed to indicate the presence of recorded Native American cultural resources on the Project site or in the vicinity. The NAHC additionally provided a list of Native American tribes and individuals/organizations that might have knowledge of cultural resources in this area.
The Proposed Project is subject to compliance with AB 52 (PRC Section 21074), which requires consideration of impacts to “tribal cultural resources” as part of the California Environmental Quality Act (CEQA) process, and requires the CEQA lead agency to notify any groups (who have requested notification) of the Proposed Project who are traditionally or culturally affiliated with the geographic area of the Project site. The City sent six letters (two were sent to the Federated Indians of Graton Rancheria to two different people) dated April 23, 2018, to tribes that have requested to be notified.
The City received responses from the Federated Indians of Graton Rancheria and the Yocha Dehe Wintun Nation, but neither Tribe requested formal consultation with the City. Because AB 52 is a government-to-government process, all records of correspondence related to AB 52 notification and any subsequent consultation are on file with the City.
3.5.3 Regulatory Setting
The treatment of cultural resources is governed by federal, state, and local laws and guidelines.
There are specific criteria for determining whether prehistoric and historic sites or objects are significant and/or protected by law. Federal and state significance criteria generally focus on the resource’s integrity and uniqueness, its relationship to similar resources, and its potential to contribute important information to scholarly research. Some resources that do not meet federal significance criteria may be considered significant by state criteria. The laws and regulations seek to mitigate impacts on significant prehistoric or historic resources. The federal, state, and local laws and guidelines for protecting historic resources are summarized below.
Agenda Item #5.4.
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September 2021 3.5-18
Federal Regulations
National Historic Preservation Act
The National Historic Preservation Act of 1966 established the NRHP as the official federal list of cultural resources that have been nominated by state offices for their historical significance at the local, state, or national level. Properties listed in the NRHP, or determined eligible for listing, must meet certain criteria for historical significance and possess integrity of form, location, and setting. Under Section 106 of the act and its implementing regulations, federal agencies are required to consider the effects of their actions, or those they fund or permit, on properties that may be eligible for listing or that are listed in the NRHP. The regulations in 36 Code of Federal Regulations (CFR) 60.4 describe the criteria to evaluate cultural resources for inclusion in the NRHP. Properties may be listed in the NRHP if they possess integrity of location, design, setting, materials, workmanship, feeling, and association, and they:
A. Are associated with events that have made a significant contribution to the broad patterns of our history;
B. Are associated with the lives of persons significant in our past; C. Embody the distinctive characteristics of a type, period, or method of construction, or represent the work of a master, or possess high artistic values, or represent a significant and distinguishable entity whose components may lack individual distinction; or D. Have yielded, or may be likely to yield, information important in prehistory or history.
These factors are known as “Criteria A, B, C, and D.”
In addition, the resource must be at least 50 years old, except in exceptional circumstances.
Eligible properties must meet at least one of the criteria and exhibit integrity, which is measured by the degree to which the resource retains its historical properties and conveys its historical character, the degree to which the original fabric has been retained, and the reversibility of the changes to the property. Archaeological sites are generally evaluated under Criterion D, which concerns the potential to yield information important in prehistory or history.
The Section 106 review process is typically undertaken between USACE as part of issuing a Section 404 permit and the SHPO, involves a four-step procedure:
• Initiate the Section 106 process by establishing the undertaking, developing a plan for public involvement, and identifying other consulting parties. • Identify historic properties by determining the scope of efforts, identifying cultural resources, and evaluating their eligibility for inclusion in the NRHP.
Agenda Item #5.4.
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• Assess adverse effects by applying the criteria of adverse effect on historic properties (resources that are eligible for inclusion in the NRHP). ▪ Resolve adverse effects by consulting with the State Historic Preservation Officer and other consulting agencies, including the Advisory Council on Historic Preservation, if necessary, to develop an agreement that addresses the treatment of historic properties.
The Department of the Interior has set forth Standards and Guidelines for Archaeology and Historic Preservation. These standards and guidelines are not regulatory and do not set or interpret agency policy. A project that follows the standards and guidelines generally shall be considered mitigated to a less than significant level, according to Section 15064.5(b)(3) of the CEQA Guidelines (14 CCR 15000 et seq.). Because it is not a federal agency, the City of St.
Helena is not subject to the National Historical Preservation Act, including Section 106.
State Regulations
California Environmental Quality Act
Under CEQA, public agencies must consider the effects of their actions on both “historical resources” and “unique archaeological resources.” Pursuant to California Public Resources Code (PRC) Section 21084.1, a “project that may cause a substantial adverse change in the significance of an historical resource is a project that may have a significant effect on the environment.” PRC Section 21083.2 requires agencies to determine whether proposed projects would have effects on “unique archaeological resources.” “Historical resource” is a term of art with a defined statutory meaning (see PRC Section 21084.1 and CEQA Guidelines, Sections 15064.5[a] and 15064.5[b]). The term embraces any resource listed in or determined to be eligible for listing in the CRHR. The CRHR includes resources listed in or formally determined eligible for listing in the NRHP, as well as some California State Landmarks and Points of Historical Interest.
Properties of local significance that have been designated under a local preservation ordinance (local landmarks or landmark districts) or that have been identified in a local historical resources inventory may be eligible for listing in the CRHR and are presumed to be “historical resources” for purposes of CEQA unless a preponderance of evidence indicates otherwise (PRC Section 5024.1 and 14 CCR Section 4850). Unless a resource listed in a survey has been demolished or has lost substantial integrity, or there is a preponderance of evidence indicating that it is otherwise not eligible for listing, a lead agency should consider the resource potentially eligible for the CRHR.
Agenda Item #5.4.
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In addition to assessing whether historical resources potentially impacted by a proposed project are listed or have been identified in a survey process, lead agencies have a responsibility to evaluate them against the CRHR criteria prior to making a finding as to a proposed project’s impacts to historical resources (PRC Section 21084.1 and CEQA Guidelines Section 15064.5(a)(3)). In general, a historical resource, under this approach, is defined as any object, building, structure, site, area, place, record, or manuscript that (CEQA Guidelines Section 15064.5(a)(3)):
Is historically or archaeologically significant, or is significant in the architectural, engineering, scientific, economic, agricultural, educational, social, political, or cultural annals of California; and A. Meets any of the following criteria:
1. Is associated with events that have made a significant contribution to the broad patterns of California’s history and cultural heritage;
2. Is associated with the lives of persons important in our past;
3. Embodies the distinctive characteristics of a type, period, region, or method of construction, or represents the work of an important creative individual, or possesses high artistic values; or
4. Has yielded, or may be likely to yield, information important in prehistory or history.
These factors are known as “Criteria 1, 2, 3, and 4” and parallel Criteria A, B, C, and D under the National Historic Preservation Act. The fact that a resource is not listed or determined to be eligible for listing does not preclude a lead agency from determining that it may be a historical resource (PRC Section 21084.1 and CEQA Guidelines, Section 15064.5(a)(4)).
CEQA also distinguishes between two classes of archaeological resources: archaeological sites that meet the definition of a historical resource, as described above, and “unique archaeological resources.” Under CEQA, an archaeological resource is considered “unique” if it (PRC 21083.2(g)):
• Contains information needed to answer important scientific research questions and there is a demonstrable public interest in that information;
• Has a special and particular quality such as being the oldest of its type or the best available example of its type; or
• Is directly associated with a scientifically recognized important prehistoric or historic event or person.
Agenda Item #5.4.
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CEQA Guidelines states that if a proposed project would result in an impact that might cause a substantial adverse change in the significance of a historical resource, then an Environmental Impact Report (EIR) must be prepared and mitigation measures and alternatives must be considered. A “substantial adverse change” in the significance of a historical resource means physical demolition, destruction, relocation, or alteration of the resource or its immediate surroundings such that the significance of a historical resource would be materially impaired (Section 15064.5(b)(1)).
The CEQA Guidelines (Section 15064.5(c)) also provide specific guidance on the treatment of archaeological resources, depending on whether they meet the definition of a historical resource or a unique archaeological resource. If the site meets the definition of a unique archaeological resource, it must be treated in accordance with the provisions of PRC Section 21083.2.
CEQA Guidelines Section 15126.4(b) sets forth principles relevant to means of mitigating impacts on historical resources. It provides as follows:
(1) Where maintenance, repair, stabilization, rehabilitation, restoration, preservation, conservation or reconstruction of the historical resource will be conducted in a manner consistent with the Secretary of the Interior's Standards for the Treatment of Historic Properties with Guidelines for Preserving, Rehabilitating, Restoring, and Reconstructing Historic Buildings (1995), Weeks and Grimmer, the project’s impact on the historical resource shall generally be considered mitigated below a level of significance and thus is not significant. (2) In some circumstances, documentation of an historical resource, by way of historic narrative, photographs or architectural drawings, as mitigation for the effects of demolition of the resource will not mitigate the effects to a point where clearly no significant effect on the environment would occur. (3) Public agencies should, whenever feasible, seek to avoid damaging effects on any historical resource of an archaeological nature. The following factors shall be considered and discussed in an EIR for a project involving such an archaeological site:
(A) Preservation in place is the preferred manner of mitigating impacts to archaeological sites. Preservation in place maintains the relationship between artifacts and the archaeological context. Preservation may also avoid conflict with religious or cultural values of groups associated with the site.
Agenda Item #5.4.
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(B) Preservation in place may be accomplished by, but is not limited to, the following:
1. Planning construction to avoid archaeological sites;
2. Incorporation of sites within parks, greenspace, or other open space;
3. Covering the archaeological sites with a layer of chemically stable soil before building tennis courts, parking lots, or similar facilities on the site.
4. Deeding the site into a permanent conservation easement. (C) When data recovery through excavation is the only feasible mitigation, a data recovery plan, which makes provision for adequately recovering the scientifically consequential information from and about the historical resource, shall be prepared and adopted prior to any excavation being undertaken. Such studies shall be deposited with the California Historical Resources Regional Information Center. Archaeological sites known to contain human remains shall be treated in accordance with the provisions of Section 7050.5 Health and Safety Code. If an artifact must be removed during project excavation or testing, curation may be an appropriate mitigation.
(D) Data recovery shall not be required for an historical resource if the lead agency determines that testing or studies already completed have adequately recovered the scientifically consequential information from and about the archaeological or historical resource, provided that the determination is documented in the EIR and that the studies are deposited with the California Historical Resources Regional Information Center.
CEQA and the California Public Records Act restrict the amount of information regarding cultural resources that can be disclosed in an EIR in order to avoid the possibility that such resources could be subject to vandalism or other damage (Clover Valley Foundation v. City of Rocklin (2011) 197 Cal.App.4th 200, 219). The State CEQA Guidelines prohibit an EIR from including “information about the location of archaeological sites and sacred lands, or any other information that is subject to the disclosure restrictions of Section 6254 of the Government Code [(part of the California Public Records Act)]” (Section 15120(d)). In turn, California Government Code Section 2654 of the California Public Records Act lists as exempt from public disclosure any records “of Native American graves, cemeteries, and sacred places and records of Native American places, features, and objects described in Sections 5097.9 and 5097.933 of the [California] Public Resources Code maintained by, or in the possession of, the Native American Heritage Commission, another state agency, or a local agency” (Cal. Gov. Code, Section 6254(r)).
Agenda Item #5.4.
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PRC Section 21074 defines tribal cultural resources and Sections 5097.9 and 5097.993 of the Code list the Native American places, features, and objects, the records of which are not to be publicly disclosed under the California Public Records Act: “any Native American sanctified cemetery, places of worship, religious or ceremonial site, or sacred shrine located on public property (Section 5097.9) and any “Native American historic, cultural, or sacred site, that is listed or may be eligible for listing in the California Register of Historic Resources…, including any historic or prehistoric ruins, any burial ground, any archaeological or historic site, any inscriptions made by Native Americans at such a site, any archaeological or historic Native American rock art, or any archaeological or historic feature of a Native American historic, cultural, or sacred site” (Section 5097.993(a)(1)).
The Public Resources Act also generally prohibits disclosure of archaeological records.
Government Code Section 6254.10 provides: “Nothing in [the California Public Records Act] requires disclosure of records that relate to archaeological site information and reports maintained by, or in the possession of … a local agency, including the records that the agency obtains through a consultation process between a California Native American tribe and a state or local agency.”
CEQA Guidelines Section 15064.5(e), require that excavation activities be stopped whenever human remains are uncovered and that the county coroner be called in to assess the remains. If the county coroner determines that the remains are those of Native Americans, the Native American Heritage Commission must be contacted within 24 hours. At that time, the lead agency must consult with the appropriate Native Americans, if any, as identified in a timely manner by the Native American Heritage Commission. Section 15064.5 of the CEQA Guidelines directs the lead agency (or applicant), under certain circumstances, to develop an agreement with the Native Americans for the treatment and disposition of the remains.
Senate Bill 297
This law addresses the disposition of Native American burials in archaeological sites and protects such remains from disturbance, vandalism, or inadvertent destruction; establishes procedures to be implemented if Native American skeletal remains are discovered during construction; and establishes the Native American Heritage Commission to resolve disputes regarding the disposition of such remains (Senate Bill 297). It has been incorporated into Section 15064.5(e) of the CEQA Guidelines.
Assembly Bill 52
AB 52 requires consultation with Native American tribes traditionally and culturally affiliated with the geographic area in which a project requiring CEQA review is proposed if those tribes have requested to be informed of such proposed projects. The intention of such consultation is to Agenda Item #5.4.
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avoid adverse impacts to tribal cultural resources. This law is in addition to existing legislature protecting archaeological resources associated with California Native American tribes. AB 52 applies to all projects initiating environmental review in or after July 2015. The Proposed Project is subject to AB 52 and the City sent letters to all tribes requesting notification.
California Health and Safety Code
Section 7050.5(b) of the California Health and Safety Code specifies protocols to address any human remains that may be discovered. The code states the following:
In the event of discovery or recognition of any human remains in any location other than a dedicated cemetery, there shall be no further excavation or disturbance of the site or any nearby area reasonably suspected to overlie adjacent remains until the coroner of the county in which the human remains are discovered has determined, in accordance with Chapter 10 (commencing with section 27460) of Part 3 of Division 2 of Title 3 of the Government Code, that the remains are not subject to the provisions of section 27492 of the Government Code or any other related provisions of law concerning investigation of the circumstances, manner and cause of death, and the recommendations concerning treatment and disposition of the human remains have been made to the person responsible for the excavation, or to his or her authorized representative, in the manner provided in section 5097.98 of the Public Resources Code.
Local Regulations
The following local/regional regulations pertaining to cultural and historic resources would apply to the Proposed Project.
City of St. Helena 1993 General Plan
The Historic Resources Element of the St. Helena 1993 General Plan provides objectives, policies, and programs regarding cultural resources, including the following:
Policy 7.5.1: Preserve the City’s historic and cultural resources as they contribute to the special character and quality of the City and help support its economic base.
Policy 7.5.4: Include the preservation of the City’s historic resources in all future planning decisions where identified historic resources may be affected.
Policy 7.5.5: Recognize the Historic Resources Inventory as the City’s official list of historic resources.
Policy 7.5.6: Use the Historic Resources Inventory in future planning decisions.
Agenda Item #5.4.
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City of St. Helena 2019 General Plan (“General Plan Update 2040”) The Historic Resources Element of the City’s adopted General Plan provides objectives, policies, and programs regarding cultural resources, including the following that are relevant to the Proposed Project:
Historic Resources Element
Policy HR1.1: Preserve the City’s historic and cultural resources, so that they may contribute to the special character and quality of the City and support its economic base.
Policy HR1.5: For development and redevelopment proposals in archaeologically, tribal cultural, and paleontologically sensitive areas of St. Helena, require an assessment of the potential presence of archaeological, tribal cultural and paleontological resources, including a site survey and a records search of the California Historical Resources Information System at the Northwest Information Center (NWIC). As warranted by the results of the assessment, require additional studies to identify and address project-specific impacts on archaeological, tribal cultural, and paleontological resources. The City shall incorporate the study recommendations as project conditions of approval to ensure that impacts on archaeological, tribal cultural, and/or paleontological resources are mitigated to the extent possible. Studies shall be prepared according to National Register Bulletin 24: Guidelines for Local Surveys: A Basis for Preservation Planning and the Secretary of the Interior’s Standards and Guidelines for Archaeology and Historic Preservation.
3.5.4 Impacts
Methods of Analysis
As described above, a Cultural Resources Inventory and Extended Phase I and Phase II Report was prepared for the Proposed Project in March 2020 (Appendix E). The inventory included a review of the CHRIS records search provided by the NWIC, NAHC sacred lands file search, Native American coordination, historic research, an intensive pedestrian survey, XPI investigations, Phase II excavation, and ground penetrating radar. The study also reviewed historical aerials and topographic maps. The CHRIS records search included a review of their collection of mapped prehistoric, historical and built-environment resources, Department of Parks and Recreation (DPR) Site Records, technical reports, archival resources, and ethnographic references. Additional consulted sources included the NRHP, California Inventory of Historical Resources/CRHR and listed Office of Historic Preservation Archaeological Determinations of Eligibility, California Points of Historical Interest, California Historical Landmarks, and Caltrans Bridge Survey information.
Agenda Item #5.4.
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Thresholds of Significance
Consistent with Appendix G of the CEQA Guidelines, a significant impact would occur if development of the Proposed Project would do any of the following:
• Cause a substantial adverse change in the significance of a historical resource as defined in CEQA Guidelines Section 15064.5.
• Cause a substantial adverse change in the significance of an archaeological resource pursuant to CEQA Guidelines Section 15064.5.
• Disturb any human remains, including those interred outside of formal cemeteries. • Cause a substantial adverse change in the significance of a tribal cultural resource, defined in Public Resources Code section 21074 as either a site, feature, place, cultural landscape that is geographically defined in terms of the size and scope of the landscape, sacred place, or object with cultural value to a California Native American tribe, and that is:
o Listed or eligible for listing in the California Register of Historical Resources, or in a local register of historical resources as defined in Public Resources Code section 5020.1(k), or o A resource determined by the lead agency, in its discretion and supported by substantial evidence, to be significant pursuant to criteria set forth in subdivision (c) of Public Resources Code Section 5024.1. In applying the criteria set forth in subdivision (c) of Public Resource Code Section 5024.1, the lead agency shall consider the significance of the resource to a California Native American tribe.
Impacts and Mitigation Measures
3.5-1: Would the Proposed Project cause a substantial adverse change in the significance of a historical resource as defined in CEQA Guidelines Section 15064.5? This impact would be potentially significant.
The City is the lead agency responsible for compliance with CEQA. The Proposed Project is also assumed to be subject to Section 106 compliance due to future review by USACE to authorize fill of existing wetlands prior to issuance of a grading permit for the Proposed Project (see Section
3.4, Biological Resources). According to CEQA (PRC Section 5024.1, Title 14 CCR, Section 4852), a project with an effect that may cause a substantial adverse change in the significance of an historical resource is a project that may have a significant effect (adverse effect) on the environment and the cultural resource itself. A substantial adverse change in the significance of an historical resource would be constituted by physical demolition, destruction, relocation, or alteration of the resource or its immediate surroundings such that the significance of a historical resource would be materially impaired.
Agenda Item #5.4.
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Effects on historic properties under Section 106 of the NHPA are defined in the assessment of adverse effects in 36 CFR Section 800.5(a)(1). An adverse effect is found when an undertaking may alter, directly or indirectly, any of the characteristics of a historic property that qualify the property for inclusion in the National Register in a manner that would diminish the integrity of the property’s location, design, setting, materials, workmanship, feeling, or association.
Consideration shall be given to all qualifying characteristics of a historic property, including those that may have been identified subsequent to the original evaluation of the property’s eligibility for the National Register. Adverse effects may include reasonably foreseeable effects caused by the undertaking that may occur later in time, be farther removed in distance or be cumulative. To comply with Section 106, the criteria of adverse effect are applied to historic properties, if any exist in the Project site. If no historic properties are identified in the Project site, a finding of “no historic properties affected” would be made for the Proposed Project. If there are historic properties in the Project site, application of the criteria of adverse effect would result in Proposed Project–related findings of either “no adverse effect” or of “adverse effect”. There are no historic buildings present on the Project site that could be affected by construction activities. However, archaeological resource CA-NAP-406 which intersects the Project site has been determined to be eligible for CRHR and NRHP listing.
Consistent with 1993 General Plan Policies 7.5.5 and 7.5.6, and 2019 General Plan Policy HR1.5, a records search was conducted and in-depth testing was done on the Project site to determine the sensitivity of the site to contain subsurface resources. Inventory efforts associated with the Cultural Inventory and Extended Phase I and II Report (Appendix E) conducted for the Proposed Project identified three previously identified archaeological sites within the Project site (CA-NAP-406, CANAP-843, and CA-NAP-1008). An additional five archaeological sites have been identified in the immediate vicinity of the Project site. One recorded site within the Project site has been determined NRHP/CRHR eligible. CA-NAP-406 has been determined with SHPO occurrence to be eligible for listing in the NRHP listing under Criterion D. Resources CA-NAP-843 and CA-NAP-1008 were determined with SHPO concurrence to lack sufficient data potential and integrity to meet the criteria for NRHP/CRHR eligibility.
Resources CA-NAP-843 and CA-NAP-1008 have been subject to previous evaluation efforts as part of the prior Flood Protection Project and are not NRHP/CRHR eligible. Therefore, the Cultural Inventory and Extended Phase I and Phase II Report determined that impacts to CANAP-843 and CA-NAP-1008 would not represent a significant effect, although appropriate mitigation to account for unanticipated impacts would be required.
Resource CA-NAP-406 has been determined to be eligible for CRHR (Criterion 4) and NRHP (Criterion D) listing. However, previous investigations evaluating this resource were restricted to portions of this resource located immediately west of the Project site. Based on the results of the Phase I and Phase II archaeological excavations and a GPR investigation no intact deposits or Agenda Item #5.4.
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features associated with CA-NAP-406 appear to extend to within the Project site. It is likely that this upper layer of fill present on a majority of the site is comprised largely of redeposited and otherwise disturbed cultural deposits associated with CA-NAP-406. Soils identified below the fill were not found to contain cultural deposits or substantial frequencies of cultural material.
However, because there is the potential to unearth unknown resources during Proposed Project construction and due to the presence of recorded resources nearby the impact is considered potentially significant.
Mitigation Measures
Compliance with Mitigation Measure CUL-1 would ensure the proper procedures and protocol are in place in the event a resource is identified. The procedures require work to stop in the event a resource is discovered and an archaeologist and/or Native American representative contacted to determine the appropriate course of action depending on the resource. Compliance with this measure, along with PRC Section 5097.98, Section 7050.5 of the California Health and Safety Code, and Section 15064.5(e) of the CEQA Guidelines. Adherence to this mitigation measure would ensure impacts would be reduced to less than significant.
CUL-1: The City shall require that an archaeological monitor is present during all grounddisturbing activities with the potential to impact previously identified cultural resources or to encounter unanticipated cultural deposits including tribal cultural resources. The determination for a Native American monitor to be present shall be made by the City, in consultation with the appropriate Native American tribe prior to the initiation of ground disturbing activities. In addition, prior to the initiation of ground-disturbing work, construction crews shall be made aware of the potential to encounter cultural resources and the requirement for cultural monitors to be present during these activities. Areas observed to have potential to contain yetidentified subsurface cultural material or deposits are located throughout the Project site, but primarily would be in the western portion of the site where the existing vineyard is located. It is anticipated resources would not be present in depths of more than 10 feet below the surface. Archaeological and Native American monitoring may be adjusted at the recommendation of the qualified archaeological principal investigator, meeting the Secretary of the Interior Professional Qualifications for Archaeology, and in consultation with the City, based on inspection of exposed subsurface soils and their observed potential to contain intact cultural deposits or material.
The archaeological and tribal monitors shall be provided a copy of technical reports prepared for the Project and pertinent appendices to inform their monitoring efforts. The archaeological and tribal monitors shall have the authority Agenda Item #5.4.
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to temporarily halt work to inspect areas as needed for potential cultural material or deposits. In the event that archaeological resources (sites, features, or artifacts) are exposed during construction activities, all construction work occurring within 100 feet of the find shall immediately stop until the qualified archaeological principal investigator, that meets the Secretary of the Interior Professional Qualifications for Archaeology, can evaluate the significance of the find and determine whether or not additional study is warranted, in consultation with the Tribe. Should it be determined by the Tribe and the archeologist, temporary flagging may be installed around this resource in order to avoid any disturbances from construction equipment. As approved by the City, in consultation with the Tribe this buffer may be adjusted by the Tribe and the archaeological principal investigator to a distance that maintains a protective perimeter around the unanticipated resource, while still allowing for construction to continue in the surrounding area.
3.5-2: Would the Proposed Project cause a substantial adverse change in the significance of an archaeological resource pursuant to CEQA Guidelines Section 15064.5? This impact would be potentially significant.
As described in Impact 3.4-1, the Cultural Inventory and Extended Phase I and Phase II Report (Appendix E) conducted for the Proposed Project three archeological sites were previously identified within the Project site (CA-NAP-406, CA-NAP-843, and CA-NAP-1008), two of which (CA-NAP-843 and CA-NAP-1008) were determined not to be NRHP/CRHR eligible. The Cultural Inventory Report determined that impacts to CA-NAP-843 and CA-NAP-1008 would not represent a significant effect, although appropriate mitigation to account for unanticipated impacts would be required. Resource CA-NAP-406 has been determined to be eligible for CRHR (Criterion 4) and NRHP (Criterion D) listing.
As discussed above under Impact 3.5-1, the Phase I and Phase II archaeological excavations and GPR investigation did not identify any intact deposits or features associated with CA-NAP406 within the Project site. However, the report notes that such deposits have the highest potential to be present beneath redeposited and disturbed fill areas located north of the planned Starr Avenue expansion, as well as portions of the Project site to the south, presently occupied by vineyards, have a higher potential to contain intact cultural deposits at shallower depths. Due to the sensitivity of the site for unknown archeological resources that may be present subsurface that could be unearthed during construction activities this is considered a potentially significant impact.
Agenda Item #5.4.
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Mitigation Measure
Implementation of Mitigation Measure CUL-1 provides specific procedures to follow in the event a resource is identified. The procedures require work to stop in the event a resource is discovered and an archaeologist and/or Native American representative contacted to determine the appropriate course of action depending on the resource. Compliance with this measure, along with PRC Section 5097.98, Section 7050.5 of the California Health and Safety Code, and Section 15064.5(e) of the CEQA Guidelines, would ensure that potential impacts to previously unidentified subsurface resources are mitigated to less than significant and no additional mitigation is required.
3.5-3: Would the Proposed Project disturb human remains, including those interred outside of formal cemeteries? This impact would be less than significant.
The NWIC records search conducted for the Cultural Inventory and Extended Phase I and Phase II Report indicated that thirty cultural resources have been recorded within the records search area (Appendix E). As described above, work for the Flood Protection Project resulted in a substantial level of previous archaeological investigation work along the western and northern portions of the Project site. This work has demonstrated the area to contain significant and highly sensitive archaeological resources. As part of the Flood Protection Project a total of 163 human burials were recovered from one site (CA-NAP-399), the largest number of burials recovered from a single site in Napa Valley to date (Schneider et al. 2013: 44). Human remains were not documented within archaeological resources intersecting the Project site. The Phase II testing conducted for the Proposed Project by Dudek included GPR which looks for any subsurface anomalies to a depth of approximately 26 feet below the surface. Any potentially sensitive GPR anomaly was ground-truthed and no cultural features were identified as a result of these efforts.
Nevertheless, due to the high archeological sensitivity of the area around the Project site, it is possible to inadvertently uncover human remains during ground-disturbing Proposed Project activities, such as grading and excavation. This is considered a potentially significant impact.
Mitigation Measures
Implementation of Mitigation Measure CUL-2 provides specific procedures to follow in the event human remains are identified. The procedures require work to stop and the County Coroner contacted to determine the origins of the remains. Compliance with this measure, along with PRC Section 7050.5 of the California Health and Safety Code would ensure that potential impacts to any human remains are mitigated to a less-than-significant level.
CUL-2: In the event any human remains are unearthed during site disturbing activities, Section 7050.5(b) of the California Health and Safety Code and Section 15064.5(e) of the CEQA Guidelines specifies protocols to follow in the event Agenda Item #5.4.
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human remains are discovered. The Code mandates stopping work within 100 feet of the find and contacting the County Coroner to determine the origin of the remains. If the remains are determined to be Native American the Coroner shall contact the Native American Heritage Commission within 24 hours to request that the Commission determine the person or persons it believes to be the most likely descendent from the deceased Native American. The most likely descendent shall be provided with the opportunity to make recommendations regarding the means of treating or disposing of the remains with appropriate dignity. Project-related ground disturbance in the vicinity of the find shall not resume until all statutory requirements have been met and evidence of completion has been submitted to the City, in consultation with the Tribe.
3.5-4: Would the Proposed Project cause a substantial adverse change in the significance of a tribal cultural resource that is listed or eligible for listing in the California Register of Historical Resources, or in a local register of historical resources, or a resource determined by the lead agency to be significant? This impact is potentially significant.
Dudek contacted the NAHC to request a review of the sacred lands file. The NAHC responded to Dudek’s request, stating that the sacred lands file search was conducted with “negative results.” The City sent letters to all California Native American tribes traditionally and culturally affiliated with the Proposed Project area requesting notification pursuant to AB 52. None of the tribes contacted requested consultation pursuant to PRC Section 21080.3.1. The Yocha Dehe Wintun Nation requested to review a copy of the Cultural Report which was provided to the Tribe by the City for their review on May 18, 2020.
Based on a review of the Cultural Resources evaluation conducted for the Project site and letters provided by the Tribes in response to letters sent by the City pursuant to AB 52, there are no known TCRs present, as defined in PRC Section 21074, on the Project site or in its immediate vicinity. The general area was previously documented to be of importance to traditionally geographically affiliated tribes through the Flood Protection Project, and active outreach with these parties should continue into the future. The Project site is undeveloped, although has been subject to substantial previous disturbance and has historically been used for agriculture. The CHRIS records search conducted for the Proposed Project area did not identify any previously recorded TCRs on the Project site (Appendix E).
As previously stated, archaeological sites have been identified on the Project site and in the immediate vicinity during the records search and verified during the intensive Phase I and Phase II testing conducted on the Project site. Resource CA-NAP-406 was determined to be eligible for CRHR and NRHP listing, although this resource is not identified as a TCR. Due to the sensitivity Agenda Item #5.4.
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of the site for unknown archeological resources that could be unearthed during construction activities, it was determined there would be a potentially significant impact to archaeological resources. Given the sensitivity of the site for cultural resources, the potential for unknown tribal cultural resources to be encountered during Proposed Project ground-disturbing activities also exists. Therefore, this is considered a potentially significant impact.
Mitigation Measures
While no known TCRs have been identified that may be affected by the Proposed Project, implementation of Mitigation Measure CUL-1 would require construction work to stop and a Native American representative contacted (if not already conducting on-site monitoring) if any TCRs are unearthed and appropriate measures to be implemented to evaluate the significance of the find. Compliance with Mitigation Measure CUL-1 would ensure potential impacts would be less than significant and no additional mitigation is required.
3.5.5 Cumulative Impacts
The geographic scope of the cumulative impact analysis for the evaluation of potential cumulative impacts on cultural resources is the City of St. Helena.
3.5-5: Would the Proposed Project contribute to cumulative impacts to cultural resources, including historical and archeological resources as defined in CEQA Guidelines Section 15064.5 and human remains? The Project’s contribution would be considered potentially significant.
Several historical resources and prehistoric and archeological sites have been recorded within the City, including both on and adjacent to the Project site. Development in the region could result in the damage or destruction of known and unknown archaeological and historical resources, as well as any existing undiscovered subsurface artifacts. The cumulative impact from past, present, and probable future projects, as well as the Proposed Project, is potentially significant.
The 1993 General Plan EIR concluded that the 1993 General Plan could result in substantial adverse changes in the significance of historical resources, and would have a significant and unavoidable impact to prehistoric archaeological sites that may contain human remains with religious significance to local Native American groups (City of St. Helena 2010). The 1993 General Plan states that there are a number of historic resources in the City (dating from the mid-nineteenth to mid-twentieth century) vulnerable to incompatible alterations and demolition.
However, the Proposed Project does not include any known historic resources from this time period. The 2019 General Plan EIR concluded that impacts on cultural resources, including historic, archeological and prehistoric associated with buildout of the city would not result in a significant impact (City of St. Helena 2018). The EIR notes that compliance with 2019 General Agenda Item #5.4.
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Plan Policy HR1.5 would minimize or avoid potential impacts on any resources known or not known at this time and that may be encountered in the future. In addition, there are numerous laws, regulations, and statutes, on both the federal and state levels, that seek to protect cultural resources. These would apply to development within and outside the city. However, because the Project site contains a high likelihood for the discovery of unknown subsurface historical or prehistoric resources, the Proposed Project’s contribution to the cumulative loss of cultural resources is considered potentially significant.
Mitigation Measures
Implementation of Mitigation Measure CUL-1 provides specific procedures to follow in the event a resource is identified. The procedures require work to stop in the event a resource is discovered and an archaeologist and/or Native American representative contacted to determine the appropriate course of action depending on the resource. Compliance with this measure, along with PRC Section 5097.98, Section 7050.5 of the California Health and Safety Code, and Section 15064.5(e) of the CEQA Guidelines, would ensure that potential impacts to previously unidentified subsurface resources are mitigated to a less-than-significant level and the Proposed Project’s incremental contribution would be reduced to less than significant and no additional mitigation is required.
3.5-6: Would the Proposed Project contribute to cumulative impacts to tribal cultural resources, currently listed or eligible for listing in the California Register of Historical Resources, or in a local register of historical resources, or a resource determined by the lead agency to be significant? The Project’s contribution would be potentially significant.
As stated previously, the 1993 General Plan EIR determined that there would be a significant and unavoidable impact to prehistoric archaeological sites that may contain human remains with religious significance to local Native American groups (City of St. Helena 2010). However, the City of St. Helena General Plan Update EIR identified that development under the City’s 2019 General Plan would result in less-than-significant impacts to TCRs. Policy HR1.5 in the 2019 General Plan would minimize or avoid potential impacts on any resources known or not known at this time that may be encountered in the future and would promote coordination with Native American tribes if any tribal resources are discovered at development sites. The impact on Native American tribal cultural resources was therefore determined to be less than significant.
Numerous laws, regulations, and statutes, on both the federal and state levels, seek to protect cultural resources. These would apply to development within and outside the city. In addition, General Plan policies are designed to safeguard cultural resources from unnecessary impacts.
Because all significant tribal cultural resources are unique and non-renewable members of finite Agenda Item #5.4.
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classes, all adverse effects or negative impacts erode a dwindling resource base. Although unlikely, there is the potential the Proposed Project could adversely affect significant tribal cultural resources that are unique and non-renewable members of finite classes if discovered contributing to a potentially considerable contribution. Therefore, the Proposed Project’s incremental contribution to the cumulative loss of cultural resources is considered potentially significant.
Mitigation Measures
Implementation of Mitigation Measure CUL-1 provides specific procedures to follow in the event a TCR is identified. The procedures require work to stop in the event a resource is discovered and an archaeologist and/or Native American representative contacted to determine the appropriate course of action depending on the resource. Compliance with this measure, along with PRC Section 5097.98, Section 7050.5 of the California Health and Safety Code, and Section 15064.5(e) of the CEQA Guidelines, would ensure that potential impacts to TCRs are mitigated to a less-than-significant level and the Proposed Project’s incremental contribution would be reduced to less than significant and no additional mitigation is required.
3.5.6 References
City of St. Helena. 1993. City of St. Helena 1993 General Plan. September 28, 1993.
City of St. Helena. 2010. St. Helena General Plan Update. Prepared by ESA. August 2010.
City of St. Helena. 2018. St. Helena General Plan Update 2040 Draft Environmental Impact Report SCH# 2010042001. October 23, 2018.
City of St. Helena. 2019. St. Helena General Plan Update 2040. June 2019.
Dudek. 2020. Cultural Resources Inventory, Extended Phase I and Phase II Report for the Hunter Subdivision Project, Napa County, California (Confidential Report). May 2020.
Agenda Item #5.4.
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3.6 GEOLOGY AND SOILS
3.6.1 Introduction
This section evaluates the potential effects on geologic and soil resources as well as paleontological resources associated with development of the proposed Hunter Subdivision Project (Proposed Project). This section describes the geologic setting and soil resources located on the Project site and within the Proposed Project’s surrounding area, as well as the applicable federal, state, and regional regulations pertaining to geologic and soil resources.
There were no comments received in response to the Notice of Preparation specifically related to geological impacts. A copy of the Notice of Preparation and comments received is included in Appendix A. Comments related to conversion of prime agricultural farmland and excess runoff and erosion are addressed in Section 3.2, Agriculture and Forestry Resources, and Section 3.9, Hydrology and Water Quality, respectively.
Information contained in this section is based on Project site plans, City of St. Helena (City) planning documents (including the 1993 General Plan, the 2019 General Plan, and the 2019 General Plan Draft Environmental Impact Report), geotechnical engineering reports prepared for the Proposed Project, and publicly available maps, data and reports from the U.S.
Geological Survey (USGS), U.S. Department of Agriculture, and the California Geological Survey. Other sources consulted are listed in Section 3.6.6, References. Copies of the geotechnical reports prepared for the Project site are included in Appendix F.
3.6.2 Environmental Setting
This section describes the existing environmental setting of the region and Project site and identifies the resources that could be affected by the Proposed Project, or which could affect the Proposed Project.
Regional Physiography
The Project site is located within California’s Coast Ranges Geomorphic Province, a geologically young and seismically active region. A conspicuous characteristic of this province, including Napa County, is the general northwest-southeast orientation of physiographic features such as valleys and ridgelines. The City of St. Helena is situated within the Napa Valley floor, bounded by the Mayacamas Mountain Range on the western and northern sides and the Vaca Mountains on the eastern side.
These ranges consist of Sonoma Volcanics (Pliocene rhyolite, dacite, tuff, and pyroclastic rocks) overlying Franciscan Complex mélange (sandstone, shale, chert, conglomerate, and greenstone). The region is located within the Napa Valley American Viticultural Area and is known for the agriculture that characterizes the valley. The Napa River bisects the valley and flows through the eastern portion of the city. The City’s terrain ranges from flat agricultural areas to gently rolling foothills.
Agenda Item #5.4.
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Site Setting
The northern edge of the Project site is located approximately 500 feet southwest of the southeasterly flowing Napa River, on a flat alluvial floodplain formed by the river and its tributaries. Important tributaries to the Napa River in the city include York Creek, which discharges into the Napa River approximately one mile further upstream from the Project site, and Sulphur Creek, which discharges into the Napa River approximately a quarter-mile further downstream. The geology of the site is dominated by unconsolidated Quaternary age1 alluvium, with the northern half of the site consisting of an alluvial terrace deposits formed by the Napa River, and the southern half of the site consisting of the distal end of alluvial fans formed by the northeasterly-flowing streams coming out of the Mayacamas Mountains.
Topography
Based on the Proposed Project’s grading plan, the elevation across the Proposed Project’s development footprint ranges from approximately 230 feet above mean sea level on its southern edge to approximately 212 feet above mean sea level on its northern edge. The average slope gradient across the development footprint is less than 1.5% toward the north and east. There is a slight break in slope near the center of the site, where a gentle (nearly imperceptible) slope transitions to a flat surface. This slight break in slope is coincident with the historical extent of the Napa River floodplain that existed prior to the completion of the City’s Flood Protection Project that constructed a levee along the Napa River in 2010 that now provides a 200-year level of flood protection. Prior to 2010, the topography of the site was slightly different, as mass grading associated with construction of the off-site levee and detention basin resulted in filling in a former pond and placement of a thin layer of engineered fill over portions of the Project site.
The portion of the site planned for the extension of Adams Street ranges from 243 feet to 230 feet above mean sea level, with a gradual slope of 1.5%.
Geology
The Project site is underlain by unconsolidated Holocene2 age alluvial deposits. These deposits consist of alluvial fan and fluvial deposits, which are typically composed of varying mixtures of clay, silt, sand, gravel and cobbles, depending on location. As mapped by the U.S. Geological Survey (USGS 2007), the Project site is underlain by the following two geologic units, shown in Figure 3.6-1, Geologic Map:
1 The Quaternary is a geologic period representing the last 2.5 million years and consists of the Pleistocene epoch and the more recent Holocene epoch.
2 The Holocene is a geologic epoch lasting from 11,700 years ago (+/- 100 years) to the present day.
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• Terrace deposits (Qht): Terrace deposits consist of moderately well sorted sand, silt, gravel, and minor clay deposited in point bar and overbank settings. Mostly undissected3 by later erosion.
• Alluvial fan deposits (Qhf): Alluvial fan deposits consist of moderately to poorly sorted and moderately to poorly bedded sand, gravel, silt and clay deposited where streams emanate from upland regions onto valley floors or plains. The alluvial fans deposits are mostly undissected by later erosion. In places, Holocene deposits may only form a thin layer over Pleistocene and older deposits.
The surface boundary between these two geologic units, shown in Figure 3.6-1, is coincident with the aforementioned topographic break in slope. Based on regional work in reconstructing the subsurface geology exposed in water well driller logs, it is estimated that the Quaternary age alluvium extends to a depth of between 50 and 100 feet below the ground surface (bgs), with Tertiary age4 sedimentary and volcanic rocks (e.g., Sonoma Volcanics) extending below that to over 500 feet bgs (LSCE and MBK 2013).
Geologic units can contain several types of soils that generally have similar properties or are from the same time period and formed in similar ways. Below is a description of the soils present on the Project site.
Soils
The top 5 feet of the geologic units described above is characterized by a mantle of soil that varies in thickness and character. In general, soil characteristics are strongly governed by slope, relief, climate, vegetation, and the geologic unit upon which they form. Soil types are important in describing engineering constraints such as susceptibility to soil erosion (from both water and wind), corrosion risks, and various behaviors that affect structures, such as expansion and settlement. The type, aerial extent, and some key physical and hydrological characteristics of soils within the Project site were identified based on a review of a soil survey of Napa County completed by the U.S. Department of Agriculture’s Natural Resources Conservation Service (USDA 2019). Soil units are described in Table 3.6-1 and shown in Figure 3.6-2, Soils. 3 This term refers to the degree to which streams have incised into the surface. 4 Teriary is a geologic period between 2.5 million and 65 million years ago.
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Table 3.6-1
Soil Map Units Within the Project Site
Soil Unit
Acres /
Percent of
Project
Area
Depth
(inches)
Shrink/Swell
Potential1
Corrosion Risk2 Erosion and Runoff
Uncoated
Steel Concrete
Hydrologic
Soil Group3
Erosion
Factor
(Kf)4
Bale clay loam,
0% - 2% slope
3.6 / 22% 60 Low (0% –
2.9%) to
Moderate (3%
– 5.9%)
High Low B 0.2
Bale clay loam,
2% - 5% slope
8.5 / 53% 60 Low (0% –
2.9%) to
Moderate (3%
– 5.9%)
High Low B 0.2
Cole silt loam,
0% - 2% slope
3.5 / 22% 64 Low (2.3% –
4.1%) to High
(5.7% – 8.3%)
High Low C 0.37
Cortina very
gravelly loam, 0%
- 5% slope
0.6 / 3% 60 Low (0% –
2%)
Low Low A 0.43
Source: USDA 2019.
Notes:
1 “Shink/Swell potential” of soils pertains to the volume change experience by soils, particularly clays, under cycles of wet and dry conditions.
This is measured by the linear extensibility of soils, or the volume change between the water content of the clod at 1/3- or 1/10-bar tension (33kPa or 10kPa tension) and oven dryness. The shrink/swell potential is low if the soil has a linear extensibility of less than 3%; moderate if 3% to 6%; high if 6% to 9%; and very high if more than 9%. The ratings reported in this table refer to the range of soil horizons present within the soil map unit.
2 “Risk of corrosion” pertains to potential soil-induced electrochemical or chemical action that corrodes or weakens uncoated steel or concrete. 3 Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups (A through D) according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. Soils in Group B have a moderate infiltration rate and a moderate rate of water transmission. Soils in Group C have a slow infiltration and transmission rates and consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. Soils in Group D have high runoff potential when thoroughly wet. Water movement through the soil is restricted or very restricted.
4 Erosion factor Kf indicates the susceptibility of a soil to sheet and rill erosion by water. Values of Kf are provided for the surface soil horizon. Values range from 0.02 to 0.69. Other factors being equal, the higher the value, the more susceptible the soil is to sheet and rill erosion by water.
Geotechnical exploration of the Project site was completed by Miller Pacific Engineering Group, which provides site-specific details about shallow subsurface conditions (see Appendix F for the reports). The geotechnical exploration consisted of ten shallow exploratory borings drilled in 2009 using a 4-inch manual bucket auger and associated laboratory testing of selected soil samples (Appendix F). The location of the exploratory borings are shown in Figure 3.6-1. In late 2010, to update site conditions following completion of the City’s Flood Protection Project, Miller Pacific Engineering Group conducted and reviewed field density testing to determine the relative compaction of recently placed fill. More recently, Miller Pacific Engineering Group provided a review of the liquefaction potential on the Project site (Appendix F).
Agenda Item #5.4.
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Hunter Subdivision Project
SOURCE: Bing Maps 2019, USGS 2019 (National Hydrography Dataset), USGS 2007 0 800 1,600Feet
FIGURE 3.6-1
Former Pond
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Geotechnical Borings (2009)
Contours (5 foot)
Index Contours (25 foot)
Streams and Rivers
Perennial Stream/River
Intermittent (Seasonal) Stream/River
Quaternary Faults
Approximately Located
Concealed
Geologic Units
Qhc, Stream channel deposits (late Holocene)
Qhay, Younger alluvium (late Holocene)
Qha, Alluvium (Holocene)
Qht, Terrace deposits (Holocene)
Qhf, Alluvial fan deposits (Holocene)
Qf, Alluvial fan deposits (Holocene and Late Pleistocene) Qpf, Alluvial fan deposits (late Pleistocene)
Pre-Quaternary Geologic Units
Water
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Hunter Subdivision Project
SOURCE: Bing Maps 2019, USDA 2019
0 250 500
Feet
FIGURE 3.6-2
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Soils
104, Bale clay loam, 0 to 2 percent slopes
105, Bale clay loam, 2 to 5 percent slopes
118, Cole silt loam, 0 to 2 percent slopes
124, Cortina very gravelly loam, 0 to 5 percent slopes
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Based on geotechnical exploration, the subsurface consists of clayey silts with varying character (e.g., stiffness, color, moisture, grain size distribution). There is a 1–4-foot thick mantle of recent, compacted fill that was placed over much of the site, with deeper fill extending up to 10 feet bgs where the former pond was filled (the former pond location is shown on Figure 3.6-1).
This occurred in 2010 when the City’s Flood Protection Project was completed. Below the compacted fill is a 0.5–1.5-foot layer of stiff, relatively dry light brown clayey silt with some sand underlain by soft to medium stiff dark brown clayey silt to a depth of 4–7 feet. Based on laboratory testing of soil samples, there is an approximately three-foot thick layer of soft, weak natural soil that remains beneath the recently placed and compacted fill layer that does not meet American Society of Testing and Materials (ASTM) standards for optimum soil moisture and compaction (Appendix F).
Paleontological Resources
The City recently approved a new General Plan in June 2019 and certified the 2019 General Plan Environmental Impact Report. That Environmental Impact Report provides a description of the paleontological resources for each geologic unit mapped within the City’s planning area (City of St. Helena 2018). The City’s 1993 General Plan did not include any discussion pertaining to paleontological resources. Although there have been no recorded fossil finds within the City’s boundaries (including a search of the University of California Museum of Paleontology specimen database), Pleistocene5 age Quaternary deposits are described as potentially fossil bearing, possibly containing significant Rancholabrean fossils (126,000 to 10,000 years B.P.).
Fossils found in alluvium of this age include, but are not limited to, bison, mammoth, ground sloths, sabertoothed cats, dire wolves, horses, cave bears, rodents, birds, reptiles, and amphibians. Older Pleistocene deposits typically occur as terraces incised by Holocene fluvial drainages. Due to their young age, Holocene alluvium is not considered potentially fossil bearing, since insufficient time has passed to result in fossilization of buried flora and fauna.
Although the Proposed Project is mapped at the surface as consisting of Holocene alluvium, which has a low paleontological potential, it may be underlain at unknown depths by Pleistocene alluvial fan deposits. Subsurface logs completed for geotechnical work or well drilling purposes do not typically differentiate between Holocene and Pleistocene age sediments, as they are mainly concerned with soil texture, and because both units are similar in that they consist of various layers of unconsolidated sediment (i.e., sand, gravel, silt and clay). However, Holocene alluvium extends down to at least 4 feet, as evidenced by the discovery of archeological resources down to that depth (see Section 3.5, Cultural Resources for additional information on the excavations conducted for the presence of subsurface archeological resources). 5 The Pleisticene is a geologic epoch lasting from 11,700 years ago (+/- 100 years) to 2.5 million years ago.
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Furthermore, based on the distance to the closest surface expressions of Pleistocene alluvium, which occur over a mile to the southwest (USGS 2007) and the proximity of the Napa River, the Holocene alluvium mapped within the Project site is likely of considerable thickness. However, because the subsurface boundary between Holocene and Pleistocene units has not been confirmed/verified, it is assumed for the purpose of the analysis that deeper excavations (beyond 4 feet in depth) could encounter older Pleistocene age alluvium.
Geologic Hazards and/or Soil Constraints
The following describes the potential geologic hazards and/or soil constraints potentially applicable to the site, based on the mapped soils and subsurface geotechnical investigation.
Slope Failures and/or Mudflows
The Napa Valley floor, including the majority of the City is mapped by the U.S. Geological Survey as being stable in terms of slope stability; for example, areas of less than 5% slope that are not underlain by landslide deposits (City of St. Helena 2018). The Project site is on flat to gentle slopes and therefore is not at risk of experiencing landslides. The eastern flank of the Mayacamas Mountains to the west may be the source of landslide or mudflows; however, as it is more than a mile away, the site is not subject to landslide or mudslide runout. The hills on the east side of the valley are closer (0.3–0.5 miles to the northeast), but the Project site is protected by a levee and thus would not be subject to mudslide runout from the east either.
Expansive and/or Corrosive Soils
Expansion and contraction of soil volume can occur when expansive soils undergo alternating cycles of wetting (swelling) and drying (shrinking). During these cycles, the volume of the soil changes markedly. As a consequence of such volume changes, structural damage to building and infrastructure may occur if the potentially expansive soils were not considered in building design and during construction. Corrosivity is a function of the chemical composition of the soils, and the materials from which it is derived. If not addressed by design measures and proper selection of building materials, corrosive soils could cause substantial damage to building foundations, pavements, utilities, and/or other improvements.
The northern part of the Project site is underlain by the Bale clay loam, which has low to medium shrink/swell potential, as shown in Table 3.6-1. The southern part of the site is underlain by the Cole silt loam which has a low to high shrink/swell potential (generally increasing with depth). The Cortina very gravelly loam underlies the southernmost portion of the site and has a low shrink/swell potential. The Bale and Cole soils generally have a high corrosion potential to steel, and low corrosion potential for concrete. The Cortina very gravelly loam has a low corrosion potential for both steel and concrete (Table 3.6-1).
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Soil Settlement and/or Collapse
Soil settlement or differential settlement could occur if buildings or other improvements were built on low-strength foundation materials (including imported fill) or if improvements straddle the boundary between different types of subsurface materials (e.g., a boundary between native material and fill). Although differential settlement generally occurs slowly enough that its effects are not dangerous to site inhabitants, it can cause significant building damage over time.
Settlement or collapse has the potential to occur if buildings or other improvements were built on materials which are not suited for foundations of structures. As discussed above, the subsurface investigation of the site found that there is an approximately 3-foot-thick layer of clayey silts under recently placed and compacted fill that may be prone to soil settlement or differential settlement. Based on the findings of the geotechnical investigation, the settlement risk at the Project site presents a potentially significant hazard (Appendix F).
Collapsible soils consist of loose, dry, low-density materials that collapse and compact under the addition of water or excessive loading. These soils are distributed throughout the southwestern United States, specifically in areas of young alluvial fans, debris flow sediments, and loess (wind-blown sediment) deposits. Since collapsible soils occur in arid desert environments, it is not a concern for the Project site or more generally in Napa County.
Land Subsidence
Subsidence is the lowering of the land-surface elevation. The mechanism for subsidence is generally related to groundwater pumping and subsequent consolidation of loose aquifer sediments. The primary hazards associated with subsidence are increased flooding hazards and damage to underground utilities. Other effects of subsidence include changes in the gradients of stormwater and sanitary sewer drainage systems in which the flow is gravity-driven.
As further discussed in Section 3.9, Hydrology and Water Quality, regional groundwater levels are reportedly stable. Furthermore, an extensive analysis of the groundwater basin associated with compliance with the 2014 Sustainable Groundwater Management Act found that land subsidence is not an issue in Napa County (LSCE 2016).
Seismic Hazards
Seismic hazards include surface rupture, ground shaking, liquefaction, lateral spreading, and landslides. These potential hazards are further described below.
Regional Seismicity
The Project site is located in the seismically active northern San Francisco Bay area. The main cause of seismic activity in the area results from the tectonic right-lateral strike-slip boundary of the North American plate and the Pacific plate. This boundary and area is named the San Andreas Fault Zone, which includes the San Andreas Fault, and numerous other active faults.
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Numerous moderate and occasional large magnitude earthquakes have historically affected the Northern San Francisco Bay region. Notable earthquakes that have caused major damage to Napa County include the magnitude 7.9 California Earthquake of 1906 on the San Andreas fault and the 1969 Santa Rosa earthquakes on the Rodgers Creek fault. The 1906 and 1969 earthquakes were of moderate magnitude with earthquake epicenters located near downtown Santa Rosa. On August 24, 2014, the South Napa Earthquake, which consisted of a magnitude
6.0 earthquake along the West Napa Fault, caused strong to very strong ground shaking in the southern Napa region with significant damage, though it is estimated to have caused moderate perceived ground shaking in the City, with only light (non-structural) damage (USGS 2014).
Prior to the South Napa Earthquake, the portion of the fault that ruptured in that quake was not widely known to be Holocene-active, nor was it zoned under the Alquist–Priolo Earthquake Fault Zoning Act. In addition to the San Andreas, Rodgers Creek, and West Napa faults, several other faults in the region, including the Green Valley and Rodgers Creek faults, are considered capable of generating moderate to large earthquakes.
Surface Rupture
Surface rupture occurs when the ground surface is broken and separates due to fault movement during an earthquake. Geologists commonly use the age of offset rocks as evidence of fault activity—the younger the displaced rocks, the more recently earthquakes have occurred. To evaluate the likelihood that a fault will produce an earthquake, geologists examine the magnitude and frequency of recorded earthquakes and evidence of past displacement along a fault. Under the Alquist-Priolo Earthquake Fault Zoning Act (AP Act), an active fault is defined by the State of California as a fault that has had surface displacement within Holocene time (last 11,000 years). Earthquake fault zones are designated by the California Geological Survey where concrete evidence (e.g., geologic offsets, geomorphic features, trench studies) demonstrates surface fault rupture has occurred within the past 11,000 years. A potentially active fault is a fault that has shown evidence of surface displacement during the Quaternary (last 1.6 million years). Because the age of many potentially active faults are poorly constrained, and due to the sheer number of such faults in the state, the location and trace of both active and potentially active faults should be identified to examine potential for surface rupture.
The Project site is not crossed by an active earthquake fault zone designated under the AP Act, nor is it crossed by any potentially active fault mapped by the USGS or California Geological Survey (USGS and CGS 2019, DOC 2019). The closest earthquake fault zone designated under the AP Act is the Rodgers Creek Fault, located about 15 miles to the southwest of the Project site. In addition, the southern part of the West Napa Fault, located approximately 17 miles southeast of the Project site, was recently designated as an active fault zone, following the 2014 South Napa Earthquake. The northern segment of the West Napa Fault with evidence of displacement in Quaternary time, shown on Figure 3.6-1, is located approximately 1.2 miles Agenda Item #5.4.
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southwest of the Project site. However, there is no evidence of Holocene or late-Holocene movement on the northern branch of the West Napa Fault (City of St. Helena 2017). A Quaternary segment of the Green Valley Fault is located approximately 4 miles east of the Project site and the closest active portion of this fault is located approximately 17 miles southeast (USGS and CGS 2019).
Because the Project site is not crossed by an active or potentially active fault, it would not be affected by fault-related ground offset (i.e., primary fault rupture).
Ground Shaking
When an earthquake occurs along a fault, a characteristic way to measure its size is to measure the energy released during the event. When an earthquake occurs, a network of seismographs records the amplitude and frequency of the seismic waves it generates. The Richter Magnitude (M) for an earthquake represents the highest amplitude measured by the seismograph at a distance of 100 kilometers from the epicenter. Richter magnitudes vary logarithmically with each whole number step representing a 10-fold increase in the amplitude of the recorded seismic waves. While Richter Magnitude was historically the primary measure of earthquake magnitude, seismologists now use Moment Magnitude as the preferred way to measure earthquakes. The Moment Magnitude scale (Mw) is related to the physical characteristics of a fault, including the rigidity of the rock, the size of fault rupture, and the style of movement or displacement across the fault. Although the formulae of the scales are different, they both contain a similar continuum of magnitude values, except that Mw can reliably measure larger earthquakes and can do so from greater distances.
The third California earthquake rupture forecast by the “Working Group on California Earthquake Probabilities” cites a 72% chance that the greater San Francisco Bay Area will experience one or more earthquakes of M6.7 or larger at some point in the next 30 years (USGS 2015). Based on the number of active and potentially active faults in the North Bay, the Project site will likely be subject to an earthquake on near or distant faults producing moderate to strong perceived seismic ground shaking at least once over the course of a 30 year mortgage.
A primary tool that seismologists use to describe ground-shaking hazard is a probabilistic seismic hazard assessment (PSHA). The PSHA for the State of California takes into consideration the range of possible earthquake sources and estimates their characteristic magnitudes to generate a probability map for ground-shaking. The PSHA maps depict values of peak ground acceleration (PGA)6that have a 10% probability of being exceeded in 50 years (1 6 The peak ground acceleration (PGA) for a given component of motion is the largest value of horizontal acceleration obtained from a seismograph. PGA is expressed as the percentage of the acceleration due to gravity (g), which is approximately 980 centimeters per second squared. In terms of automobile accelerations, one “g” of acceleration is equivalent to the motion of a car traveling 328 feet from rest in 4.5 seconds.
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in 475 chance). This probability level allows engineers to design buildings for ground motions that have a 90% chance of NOT occurring in the next 50 years, making buildings safer than if they were simply designed for the most likely events. Based on the PSHA, the Project site is expected to have a 10% probability of exceeding a PGA of 0.416g (very strong perceived shaking), and a 2% probability of exceeding a PGA of 0.633g (severe perceived shaking) in the next 50 years (DOC 2019; USGS 2014). A 2% probability of exceedance in 50 years is about the same as a 2,500-year average repeat time and is a design standard used for essential services buildings or highly vulnerable occupancies. For comparison purposes, the maximum PGA value recorded during the Loma Prieta earthquake was in the vicinity of the epicenter, near Santa Cruz, at 0.64g. During low-probability events, the PGAs expected at the site range from very strong to severe, resulting in moderate to heavy damage to structures and buildings.
Liquefaction and Lateral Spreading
Liquefaction is a temporary state of loose, saturated granular sediments from a solid state to a “liquefied” state as a result of ground shaking. In the process, the soil and sediment loses stability and cohesion, which causes ground displacement and structural failure of the ground.
Localities most susceptible to liquefaction-induced damage are underlain by loose, watersaturated, granular sediment within 40 feet of the ground surface (DOC 2008). The California Geological Survey determines zones of required investigation for liquefaction based on liquefaction susceptibility (which consist of a combination of the character of sediment and highest recorded groundwater level) and liquefaction opportunity (which is based on the PSHA) (DOC 2008). Although the California Geological Survey has not mapped the Napa Valley for the purpose of designating zones of required investigation under the Seismic Hazards Mapping Act (see Section 3.6.3 for a description), the Project site may be subject to liquefaction based on the combination of soil and groundwater conditions potentially present on-site.
The Project site is mapped as having a moderate liquefaction susceptibility, based on the Quaternary geologic units described above (USGS 2006). Off-site, the active river channel deposits along the Napa River are mapped as having a very high liquefaction susceptibility (USGS 2006). The Project site’s proximity to the Napa River means that groundwater levels onsite are likely to be relatively shallow. As discussed in Section 3.9, Hydrology and Water Quality, groundwater levels measured at the Stonebridge Well operated by the City have fluctuated between 18 and 25 feet between 2015 and 2018. Given the proximity and similar setting, groundwater levels are expected to be similar or possibly shallower beneath the Project site.
According to the well completion report for the on-site well, the static water level was recorded as being 11 feet bgs in 1992 (DWR 1992). Given these factors, there is a potentially significant risk for liquefaction at the Project site.
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Lateral spreading, which is the horizontal displacement of soil toward an open channel or free face, such as an excavation boundary, is not considered to be a significant concern on-site because the site is flat and the only slope immediately adjacent to the Project site is the levee along the Napa River. Based on the Proposed Project’s grading plan, the portion of the levee adjacent to the Project site is roughly 8–10 feet high with slopes 4:1 (horizontal:vertical). Since the levee was constructed in 2010 in accordance with U.S. Army Corps of Engineers and Department of Water Resources standards, it is designed to avoid saturation under normal conditions, and meet earthwork standards necessary to avoid seismic damage. Under very specific conditions, the banks of the Napa River may experience lateral spread in a strong earthquake; however, such an occurrence would not affect the Project site, since earth displacements from lateral spread would be into the river channel, not the Project site.
Seismically Induced Landslides
Because the Proposed Project is on flat to nearly flat land, there is no appreciable risk of seismically induced landslide. In the event an earthquake results in off-site slope instabilities, such as along the levee or on the southern bank of the Napa River (e.g., through lateral spread or shallow soil slumps), the impact would be highly localized to the base of the slope, and would not place the Project site or its residents at risk.
3.6.3 Regulatory Setting
Federal Regulations
The following federal regulations pertaining to geology and soils would apply to the Proposed Project.
Occupational Safety and Health Administration Regulations Excavation and trenching are among the most hazardous construction activities. The Occupational Safety and Health Administration’s Excavation and Trenching standard, Title 29 of the Code of Federal Regulations, Part 1926.650, covers requirements for excavation and trenching operations. The Occupational Safety and Health Administration requires that all excavations in which employees could potentially be exposed to cave-ins be protected by sloping or benching the sides of the excavation, supporting the sides of the excavation, or placing a shield between the side of the excavation and the work area.
State Regulations
The statewide minimum public safety standard for mitigation of earthquake hazards (as established through the California Building Code [CBC], AP Act, and the Seismic Hazards Mapping Act) is that the minimum level of mitigation for a project should reduce the risk of Agenda Item #5.4.
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ground failure during an earthquake to a level that does not cause the collapse of buildings for human occupancy, but in most cases, is not required to prevent or avoid the ground failure itself. It is not feasible to design all structures to completely avoid damage in worst-case earthquake scenarios. Accordingly, regulatory agencies have generally defined an “acceptable level” of risk as that which provides reasonable protection of the public safety, although it does not necessarily ensure continued structural integrity and functionality of a project (14 CCR 3721(a)). Nothing in these acts, however, precludes lead agencies from enacting more stringent requirements, requiring a higher level of performance, or applying these requirements to developments other than those that meet the acts’ definitions of “project.” Alquist–Priolo Earthquake Fault Zoning Act
The AP Act was passed in 1972 to mitigate the hazard of surface faulting to structures for human occupancy. In accordance with this act, the state geologist established regulatory zones, called “earthquake fault zones,” around the surface traces of active faults and has published maps showing these zones. Earthquake fault zones are designated by the California Geological Survey and are delineated along traces of faults where mapping demonstrates surface fault rupture has occurred within the past 11,000 years. Construction within these zones cannot be permitted until a geologic investigation has been conducted to prove that a building planned for human occupancy will not be constructed across an active fault. These types of site evaluations address the precise location and recency of rupture along traces of the faults and are typically based on observations made in trenches excavated across fault traces.
The Proposed Project is not within an Alquist–Priolo Earthquake Fault Zone and therefore is not subject to the requirements of the AP Act.
Seismic Hazards Mapping Act
The Seismic Hazards Mapping Act of 1990 (Public Resources Code, Chapter 7.8, Section 2690–2699.6) directs the California Department of Conservation to protect the public from earthquake-induced liquefaction and landslide hazards (note that these hazards are distinct from fault surface rupture hazard regulated by the AP Act of 1972). This act requires the state geologist to delineate various seismic hazard zones, and requires cities, counties, and other local permitting agencies to regulate certain development projects within these zones (i.e., zones of required investigation). Before a development permit may be granted for a site within a Seismic Hazard Zone, a geotechnical investigation of the site must be conducted and appropriate mitigation measures incorporated into the project design. Evaluation and mitigation of potential risks from seismic hazards within zones of required investigation must be conducted in accordance with the California Geological Survey, Special Publication 117A, adopted March 13, 1997, by the State Mining and Geology Board as updated in 2008 (DOC 2008).
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To date, Seismic Hazard Zone Maps have been prepared for portions of Southern California and the San Francisco Bay Area; however, no seismic hazard zones have yet been delineated for the City including the Proposed Project area (i.e., the Saint Helena USGS 7.5' Quadrangle). As a result, the provisions of the Seismic Hazards Mapping Act would not apply to the Proposed Project.
California Building Code
The CBC has been codified in the California Code of Regulations (CCR) as Title 24, Part 2. Title 24 is administered by the California Building Standards Commission, which, by law, is responsible for coordinating all building standards. Under state law, all building standards must be centralized in Title 24 to be enforceable. The purpose of the CBC is to establish minimum standards to safeguard the public health, safety, and general welfare through structural strength, means of egress facilities, and general stability by regulating and controlling the design, construction, quality of materials, use and occupancy, location, and maintenance of all building and structures within its jurisdiction.
The 2019 edition of the CBC is based on the 2015 International Building Code published by the International Code Conference. The 2019 CBC contains California amendments based on the American Society of Civil Engineers Minimum Design Standards 7-16, which provides requirements for general structural design and includes means for determining earthquake loads as well as other loads (such as wind loads) for inclusion into building codes. The provisions of the CBC apply to the construction, alteration, movement, replacement, and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures throughout California.
The earthquake design requirements take into account the occupancy category of the structure, site class, soil classifications, and various seismic coefficients, which are used to determine a Seismic Design Category (SDC) for a project. The SDC is a classification system that combines the occupancy categories with the level of expected ground motions at the site, and ranges from SDC A (very small seismic vulnerability) to SDC E/F (very high seismic vulnerability and near a major fault). Design specifications are then determined according to the SDC.
Paleontological Resources
Paleontological resources are limited, nonrenewable resources of scientific, cultural, and educational value and are afforded protection under state laws and regulations, namely California Public Resources Code Section 21000 et seq. and Public Resources Code Section 5097.5. Paleontological resources are explicitly afforded protection by the California Environmental Quality Act (CEQA), specifically in Section VII(f) of CEQA Guidelines Appendix G, the Environmental Checklist Form, which addresses the potential for adverse impacts to “unique paleontological resource[s] or site[s] or . . . unique geological feature[s]” (14 CCR 15000 Agenda Item #5.4.
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et seq.). This provision covers fossils of signal importance—remains of species or genera new to science, for example, or fossils exhibiting features not previously recognized for a given animal group—as well as localities that yield fossils significant in their abundance, diversity, preservation, and so forth. Further, CEQA provides that, generally, a resource shall be considered “historically significant” if it has yielded or may be likely to yield information important in prehistory (14 CCR 15064.5 [a][3][D]). Paleontological resources would fall within this category. The California Public Resources Code, Chapter 1.7, Sections 5097.5 and 30244, also regulates removal of paleontological resources from state lands, defines unauthorized removal of fossil resources as a misdemeanor, and requires mitigation of disturbed sites.
Local Regulations
Local regulations relevant to geology, soils, and seismicity are discussed below.
City of St. Helena 1993 General Plan
The following goals, objectives, and policies from the City of St. Helena 1993 General Plan, Public Health and Safety element are relevant to geology, soils, and seismicity issues in the Project site.
Policy 8.4.1: Restrict the intensity of development and the level of land form alteration in the hillside areas in order to minimize the potential for slope failure.
Implementing Policy 8.4.2: Require a soils and geologic report to be submitted for new construction prior to the issuance of grading and building permits and the submission of final maps.
Implementing Policy 8.4.3: Prohibit any development—including any land alteration, grading for roads and structural development—in areas of slope instability or other geologic concerns until mitigating measures are taken to limit potential damage to levels of acceptable risk.
City of St. Helena 2019 General Plan (“General Plan Update 2040”) The following policies from the City of St. Helena 2019 General Plan, Public Health and Safety element are relevant to geology, soils, and seismicity issues in the Project site.
Policy PS3.1: Minimize risk of injury, loss of life and property damage from seismically induced and other known geologic hazards.
Policy PS3.2: Restrict the intensity of development and the level of landform alteration in the hillside areas in order to minimize the potential for slope failure Agenda Item #5.4.
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Policy PS3.3: The required soils and geologic reports for new development shall include geotechnical analysis for construction in areas with potential geological hazards and/or for purposes of environmental analysis. The analysis shall investigate all potential geohazard issues for the site where there is substantial evidence of a potential risk.
Policy PS3.4: Geologic reports for new development shall describe hazards and include mitigation measures to reduce risks to acceptable levels. Where appropriate, an engineer’s or geologist’s certification shall be required stating that risks have been mitigated to an acceptable level.
3.6.4 Impacts
Methods of Analysis
Impacts with respect to geology, soils and seismicity are assessed by comparing conditions expected under implementation of the Proposed Project to the existing environmental setting described in Section 3.6.2. The California Supreme Court has recently confirmed that “CEQA generally does not require an analysis of how existing environmental conditions will impact a project’s future users or residents.” However, an agency must “evaluate existing conditions in order to assess whether a project could exacerbate hazards that are already present.” The analysis evaluates if the Proposed Project would directly or indirectly place people, structures, or the general public at increased exposure to health and/or safety risks associated with soil, geologic or seismic hazards.
Thresholds of Significance
Consistent with Appendix G of the CEQA Guidelines, a significant impact would occur if development of the Proposed Project would do any of the following:
• Directly or indirectly cause potential substantial adverse effects, including the risk of loss, injury, or death involving:
o Rupture of a known earthquake fault, as delineated on the most recent Alquist-Priolo Earthquake Fault Zoning Map issued by the State Geologist for the area or based on other substantial evidence of a known fault. Refer to Division of Mines and Geology Special Publication 42;
o Strong seismic ground shaking;
o Seismic-related ground failure, including liquefaction; o Landslides.
• Result in substantial soil erosion or the loss of topsoil.
Agenda Item #5.4.
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• Be located on a geologic unit or soil that is unstable, or that would become unstable as a result of the project, and potentially result in on- or off-site landslide, lateral spreading, subsidence, liquefaction or collapse.
• Be located on expansive soil, as defined in Table 18-1-B of the Uniform Building Code (1994), creating substantial direct or indirect risks to life or property. • Have soils incapable of adequately supporting the use of septic tanks or alternative wastewater disposal systems where sewers are not available for the disposal of wastewater. • Directly or indirectly destroy a unique paleontological resource or site or unique geologic feature.
Threshold Criteria not Applicable to the Proposed Project Due to the location and characteristics of the Proposed Project, certain significance criteria are not applicable and therefore, are not considered potential impacts. These criteria are addressed briefly below and are not discussed further in this document.
Fault Rupture
As discussed in Section 3.6.2, Environmental Setting, the Proposed Project is not located within a fault rupture hazard zone. This includes both earthquake fault zones designated under the AP Act, as well as potentially active faults of Quaternary age. Because the Project site is not crossed by any known active or potentially active fault, there would be no impact and this issue (first significance threshold listed above) is not further addressed.
Landslides
As discussed in Section 3.6.2, Environmental Setting, the Proposed Project is not at risk of landslides because it is nearly flat, and because there are no substantial slopes or hillside areas in the immediate vicinity. Therefore, there would be no impact and this issue (first significance threshold listed above) is not further addressed.
Soil Erosion and Loss of Topsoil
Potential impacts of erosion on water quality are discussed in Section 3.9, Hydrology and Water Quality and impacts with regard to agricultural resources (e.g., prime soils) are addressed in Section 3.2, Agriculture and Forestry Resources. In the context of this section, a substantial impact would occur if accelerated and significant soil erosion were to be sufficient in magnitude to undermine structures or compromise slope stability. Examples of this style of erosion are rills (small narrow channel) and gullies, whereby storm runoff produces deep incisions into the soils and slopes. Because the Project site is on flat land, and would be developed into a residential Agenda Item #5.4.
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subdivision, there is no reasonable potential for any rills and/or gullies to develop. Runoff would be managed and discharged into an existing detention basin, as described in more detail in Section 3.9. Therefore, this issue (second significance threshold listed above) is not applicable to the Proposed Project and is not further addressed.
Alternative Wastewater Systems
The Proposed Project would connect to the City’s sewer system to provide conveyance of wastewater to the treatment plant. Therefore, this issue (fifth significance threshold listed above) is not applicable to the Proposed Project and is not further addressed.
Unique Geologic Features
The Project site is undeveloped and has been disturbed due to the placement of fill associated with the City’s Flood Control Project. The Project site does not contain any unique geologic features, such as a landform or rock outcrop of scientific, cultural or aesthetic interest.
Therefore, implementation of the Proposed Project would not directly or indirectly destroy a unique geologic feature. Therefore, there would be no impact and this issue (last significance threshold listed above) is not further addressed.
Impacts and Mitigation Measures
3.6-1: Would the Proposed Project directly or indirectly cause potential substantial adverse effects, including the risk of loss, injury, or death involving strong seismic ground shaking and/or liquefaction? This impact would be potentially significant.
Seismic ground shaking is an unavoidable hazard for nearly all man-made facilities (buildings and structures) in the region. The geologic setting means proposed facilities are likely to experience ground shaking from at least one major earthquake (e.g., greater than moment magnitude 6.7) sometime during the operational life of a project. Based on the most recent PSHA for the State of California, the Project site would have an approximately 10% chance of exceeding a PGA of 0.416g, and a 2% probability of exceeding a PGA of 0.633g in the next 50 years (DOC 2019). These levels of ground shaking, while relatively improbable, are very strong to severe, and capable of producing extensive non-structural damage and limited structural damage in buildings at the site. The amount of ground shaking that actually occurs depends on the magnitude of the earthquake, the distance from the epicenter, and the type of earth materials between the receptor and the epicenter. The Project site is also underlain by soils that if not properly engineered during construction site preparation, could be subject to secondary effects such as seismically induced liquefaction, differential settlement or compression.
If future development of the site is not constructed in a manner that protects residents from geologic and seismic hazards, the Proposed Project could have a significant impact. However, Agenda Item #5.4.
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the 1993 General Plan policies implemented by the City require that any geologic or seismic risks be mitigated to an acceptable level as a condition of project approval (Implementing Policy
8.4.3). These General Plan policies (listed in Section 3.6.3) are enforced as part of the tentative subdivision map submittal process, as described under Municipal Code Section 16.32.220 (Soils Investigation and Geotechnical Report Requirements). Furthermore, Municipal Code Chapter 15 (Building and Construction) incorporates the CBC and thus enforces the structural design requirements associated with seismic loads. As part of this process, a design-level geotechnical investigation would be completed (in addition to the existing geotechnical investigation already completed) to assess site conditions at a greater level of detail and make geotechnical recommendations to be incorporated into the site development plan, grading plan and building plan. The City requires that such geotechnical recommendations be verified at time of grading and building construction prior to issuance of a certificate of occupancy.
The initial geotechnical work completed for the Proposed Project by Miller Pacific Engineering Group (Appendix F) identifies a potential issue associated with soft soils occurring under a layer of compacted fills. Specifically, it notes the following (Appendix F):
It is not acceptable to place compacted, engineered fill (designed to support future development) on the Hunter Parcel without first over excavating and recompacting the existing weak surface layer, due to the anticipated settlement of the weak soil layer as a result of the loads imposed by the new fill, as well as future building loads. Settlement of the weak soil layer, if left in place beneath the recently placed compacted fill, could lead to damage to new residential structures, streets, utilities, and concrete flatwork supported over the weak soil layer.
It is this observation that leads to the recommendation to over excavate to an average depth of
4.5 feet (and up to 10 feet in the location of the former pond). Furthermore, the Project site has the potential to be subject to seismically induced liquefaction and/or differential settlement, as discussed in the environmental setting. Because the geotechnical borings completed on-site in 2009 lacks coverage in the southern portion of the site (see Figure 3.6-1), and it occurred prior to fill placement from the Flood Protection Project, the data may no longer adequately represent shallow soil conditions. Because of this, and due to the potential for liquefaction and/or settlement of weak soils, the Proposed Project could potentially expose residences to significant impacts from a major earthquake. This is considered a potentially significant impact.
Mitigation Measures
Implementation of Mitigation Measure GEO-1 would ensure design-level geotechnical reports have the appropriate scope and include recommendations necessary to mitigate potential seismic hazards to a less-than-significant level. Implementation of Mitigation Measure GEO-1 Agenda Item #5.4.
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expands upon the typical steps completed as part of standard building and grading permit approvals in order to ensure the identified impacts (i.e., weak/compressible soils and liquefaction risk) are mitigated. In particular, the requirement to comply with the California Department of Conservation Special Publication 117A (Guidelines for Evaluating and Mitigating Seismic Hazards in California) ensures that the site is treated in the same way as if it were designated as a zone of required investigation for liquefaction under the Seismic Hazards Mapping Act.
GEO-1: Prior to the issuance of any site-specific grading or building permits, the Project applicant shall have a design-level geotechnical report prepared and submitted to the City of St. Helena Building Department for review and approval in accordance with adopted City standards. The structural designs shall adhere to the currently adopted version of the California Building Code. The report shall identify specific site preparation methods, grading practices, foundation designs, and other recommendations appropriate for minimizing damage from weak soils, expansive soils, differential settlement, and seismic hazards, including liquefaction.
Specifically, the following requirements for the geotechnical and soils report shall be met:
• Analysis presented in the geotechnical report shall conduct a detailed evaluation of liquefaction in accordance with California Department of Conservation Special Publication 117A: Guidelines for Evaluating and Mitigating Seismic Hazards in California.
• Additional subsurface soil borings shall be completed as necessary to represent the full range of site conditions, including the southern portion of the parcel mapped as alluvial fan.
• Analysis presented in the geotechnical report shall include recommendations for building foundations and improvements, including sidewalks, parking lots, and subsurface utilities, that take into consideration the potential effects of settlement, collapse, and expansive or corrosive soils. This includes the recommendation to over excavate to an average depth of 4.5 feet (and up to 10 feet in the location of the former pond) due to anticipated settlement. • All design criteria and specifications set forth in the design-level geotechnical report shall be implemented as a condition of project approval. This report shall be completed as a condition of approval of the final tentative map.
Agenda Item #5.4.