GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
PRELIMINARY GEOTECHNICAL EVALUATION
FOR
EASTERN PORTION OF 225 N. LAS POSAS ROAD
SAN MARCOS , CALIFORNIA
P
REPARED FOR
Las Posas, LLC
c/o Avenue Secured Capital Group
2555 Locus Street
San Diego, California 92069
P
REPARED BY
GEO TEK , INC .
1384 POINSETTIA AVENUE , SUITE A
VISTA , CALIFORNIA 92106
PROJECT NO. 3865 -SD AUGUST 10, 2023
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
May 30, 2023
Revised August 10, 2023
Project No. 3865-SD
Las Posas, LLC
c/o Avenue Secured Capital Group
2555 Locust Street
San Diego, CA 92106
Attention: Dan Tate
Subject: Preliminary Geotechnical Evaluation
Eastern Portion of 225 N. Las Posas Rd.
San Marcos, CA 92069
References: See Page 5
Dear Mr. Tate
We are pleased to provide herein the results of our preliminary geotechnical evaluation for the subject project located in the City of San Marcos, California. This report presents the results of our evaluation and provides preliminary geotechnical recommendations for earthwork, foundation design, and construction. In our opinion, site development appears feasible from a geotechnical viewpoint provided that the recommendations included herein are incorporated into the design and construction phases of site development. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to call our office.
Respectfully submitted,
GeoTek, Inc.
Christopher D. Livesey
CEG 2733, Exp. 05/31/25
Vice President
Edwin R. Cunningham
RCE 81687, Exp. 03/31/2024
Project Engineer
Distribution: (1) Addressee via email
Las Posas, LLC Project No. 3865-SD
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TABLE OF CONTENTS
1. PURPOSE AND SCOPE OF SERVICES ..................... ................................................... ................................. 1
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT ............................................................ ............. 1
2.1 Site Description ..................................................................................................... ................................ 1
2.2 Proposed Development ..................................................................................................... ..................... 2
3. FIELD EXPLORATION AND LABORATORY TESTING ............................................................. .............. 2
3.1 Previous Evaluation by Alta California Geotechnical .................................................. ............................... 2
3.2 Field Exploration ..................................................................................................... ............................... 3
3.3 Laboratory Testing ..................................................................................................... ............................ 3
4. GEOLOGIC AND SOILS CONDITIONS ........................................................................ ................................ 3
4.1 Regional Setting ..................................................................................................... ................................ 3
4.2 EARTH MATERIALS .................................................. ................................................... ......................... 4
4.2.1 Colluvium and Alluvium, undifferentiated (map symbol Qal) ..................................................................... 4
4.2.2 Tonalite (map symbol Kt) ..................................................................................................... .................. 4
4.3 SURFACE WATER AND GROUNDWATER ............................................................................................. 4
4.3.1 Surface Water ..................................................................................................... .................................. 4
4.3.2 Groundwater ..................................................................................................... .................................... 5
4.4 EARTHQUAKE HAZARDS ..................................................................................................... ................ 5
4.4.1 Surface Fault Rupture ..................................................................................................... ....................... 5
4.4.2 Liquefaction/Seismic Settlement ................................................... ................................................... ........ 5
4.4.3 Other Seismic Hazards ..................................................................................................... ..................... 5
5. CONCLUSIONS AND RECOMMENDATIONS ...................................................................... ....................... 6
5.1 General ..................................................................................................... ............................................ 6
5.2 EARTHWORK CONSIDERATIONS .................................................. ................................................... ... 6
5.2.1 General ..................................................................................................... ............................................ 6
5.2.2 Site Clearing and Preparation ..................................................................................................... ............ 6
5.2.3 Remedial Grading ..................................................................................................... ............................. 6
5.2.4 Cut Building Pads ..................................................................................................... .............................. 7
5.2.5 Over-Excavation .................................................. ................................................... ............................... 7
5.2.6 Engineered Fill ..................................................................................................... .................................. 7
5.2.7 Structural Rock Fills ..................................................................................................... .......................... 7
5.2.8 Compaction Procedures of Rock Fills ..................................................................................................... .. 8
5.2.9 Slope Construction ..................................................................................................... ............................ 9
5.2.10 Excavation Characteristics ..................................................................................................... .......... 10
5.2.11 Shrinkage and Bulking ..................................................................................................... ............... 10
5.2.12 Trench Excavations and Backfill ..................................................................................................... . 11
5.3 DESIGN RECOMMENDATIONS ..................................................................................................... ..... 11
5.3.1 Foundation Design Criteria ..................................................................................................... .............. 11
5.3.2 Underslab Moisture Membrane ................................................... ................................................... ...... 13
5.3.3 Miscellaneous Foundation Recommendations ........................................................................................ 14
5.3.4 Foundation Set Backs ................................................... ................................................... ..................... 14
5.3.5 Seismic Design Parameters .................................................. ................................................... ............. 15
5.3.6 Soil Corrosivity ..................................................................................................... ................................ 15
5.3.7 Soil Sulfate Content ..................................................................................................... ........................ 15
5.4 RETAINING WALL DESIGN AND CONSTRUCTION ............................................................................. 16
5.4.1 General Design Criteria ..................................................................................................... ................... 16 Las Posas, LLC Project No. 3865-SD
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TABLE OF CONTENTS
5.4.2 Seismic Induced Incremental Addition ................................................................................................... 1 6
5.4.3 Wall Backfill and Drainage .................................................. ................................................... ............. 17
5.4.4 Restrained Retaining Walls .................................................. ................................................... ............. 17
5.4.5 Preliminary Pavement Design ..................................................................................................... .......... 18
5.4.6 Portland Cement Concrete (PCC) ..................................................................................................... ..... 18
5.4.7 Exterior Concrete Slabs and Sidewalks ................................................... ............................................... 19
5.5 POST CONSTRUCTION CONSIDERATIONS .................................................. ...................................... 19
5.5.1 Landscape Maintenance and Planting ................................................................................................... 1 9
5.5.2 Drainage ..................................................................................................... ........................................ 20
5.6 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS .................................................. .................... 20
6. LIMITATIONS .......................................................................................... ................................................... ..... 21
7. SELECTED REFERENCES .................................................................................. .......................................... 22
ENCLOSURES
Figure 1 – Site Location Map
Figure 2A & 2B – Geotechnical Map
Appendix A – Exploratory Trench Logs and Seismic Refraction Survey Appendix B – Results of Laboratory Testing
Appendix C – General Earthwork Grading Guidelines
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1. PURPOSE AND SCOPE OF SERVICES
The purpose of this study was to evaluate the geote chnical conditions on the site. Services provided for this study included the following:
Research and review of available geologic and geote chnical data, and general information pertinent to the site.
Site reconnaissance by a field professional from our firm. Compilation of this geotechnical report which prese nts our findings of pertinent site geotechnical conditions and geotechnical recommendations for site development.
2. SITE DESCRIPTION AND PROPOSED DEVELOPMENT
2.1 Site Description
The subject site is the eastern portion of Assessor ’s Parcel Number (APN) 219-162-62-00, which is located on Armorlite Drive, in the City of San Marcos, California, see figure 1 (Site Location Map). The Site Location Map differentiate s the site vs the legal address of 225 North Las Posas Road. This geotechnical due diligence is focused only on the site and not the entirety of 225 North Las Posas Road.
The site is currently vacant land and bounded by a railroad easement to the north (NCTD), by Armorlite Drive to the south, by a multifamily resi dential property to the east (Palomar Station Apartments at 1257 Armorlite Drive), and George’s B urgers Restaurant (217 North Las Posas Road) and AT&T Facility Building (225 North Las Posas Road) to the west.
Based on a review of Google Earth and our site reco nnaissance, topography is characterized by a topographic knoll in the north-center of the subj ect site sloping outward. A natural slope grades to the south at an approximate 13:1 slope. Cut slopes approximately eight feet tall at an approximate gradient of 2:1 descending to the west and north (225 N Las Posas and NCTD, respectively). The descending grade to the east is supported by an offsite concrete masonry retaining wall approximately 2-3 feet. Elevations range from 575 near the center of the knoll to 562 feet along Armorlite Drive. Vegetation consists mostly of waist-high brush and shrubs.
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Several granitic boulders outcrop the surface in th e north and scattered animal burrows are found throughout the site.
2.2 Proposed Development
Based on the Site Plan prepared by Latitude 33, Geo Tek anticipates that the proposed development will consist of four levels of wood-fra med apartment homes above a concrete podium facilitating vehicular parking and commercial space for a total of five stories.
Based on preliminary discussions regarding potentia l hard rock, site grades for the commercial building along the project frontage are designed wi th a finished floor of 563.50 feet to approximately match Armorlite Drive grades. The pa rking lot podium structure is designed with a finish floor of 576 feet. Designed grades r esult in minor cuts and fills (2 feet) in the north and cuts of approximately 4 feet in the south.
As site development planning progresses and plans b ecome available, the plans should be provided to GeoTek for review and comment.
3. FIELD EXPLORATION AND LABORATORY TESTING
3.1 Previous Evaluation by Alta California Geotechnical Alta California Geotechnical Inc. (Alta) prepared a preliminary geotechnical investigation on March 31, 2021, for the subject site. Relevant aspects of the report include:
A John Deere 310 backhoe was utilized to excavate n ine test pits in an effort to explore the subsurface conditions.
Two seismic refraction survey lines were performed, SL-1 and SL-2, 250 and 150 feet in length, respectively.
A summary of the seismic refraction results was pre sented, with rippability recommendations and graphical data included. Variab ility in the rippability of the subsurface material was expected across the subject site, with non-rippable rock for SL-1 and SL-2 interpreted to be at depths of 5 to 20 feet and 3 to 20 feet, respectively. Two infiltration tests were conducted on site using shallow percolation test methods in general accordance with County of San Diego standar ds. The tests were conducted at the the bottom of the test pits (4 and 4.5 feet bel ow the existing surface) in approximately 1-foot deep hand dug borings. During the test, the handdug borings were filled with water and the level was measured e very 30 minutes until the readings Las Posas, LLC Project No. 3865-SD
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stabilized. The data was then adjusted to provide an infiltration rate utilizing the Porchet Method.
3.2 Field Exploration
A site visit was performed on December 14, 2022, by a GeoTek representative. The site was traversed to observe and document surface condition s. Weathered granitics was observed at the surface. Weathering profile of the granitics co nsisted of a “decomposed granite” type soil and is profiled in cut slopes descending from the s ite to the AT&T parking lot and NCTD railroad tracks. Exposed granite outcrops as bould ers or “floaters” are at the surface in the northern portion of the site. Site conditions were consistent with those described by Alta.
3.3 Laboratory Testing
Laboratory testing was performed by Alta and is presented in Appendix B.
4. GEOLOGIC AND SOILS CONDITIONS
4.1 Regional Setting
The subject property is located in the Peninsular R anges geomorphic province. The Peninsular Ranges province is one of the largest geomorphic un its in western North America. Basically, it extends roughly 975 miles from the north and northe asterly adjacent the Transverse Ranges geomorphic province to the tip of Baja California. This province varies in width from about 30 to 100 miles. It is bounded on the west by the Pac ific Ocean, on the south by the Gulf of California and on the east by the Colorado Desert Province.
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The Peninsular Ranges are essentially a series of n orthwest-southeast oriented fault blocks.
Several major fault zones are found in this provinc e. The Elsinore Fault zone and the San Jacinto Fault zones trend northwest-southeast and a re found in the near the middle of the province. The San Andreas Fault zone borders the n ortheasterly margin of the province. No faults are shown in the immediate site vicinity on the map reviewed for the area.
4.2 EARTH MATERIALS
A brief description of the earth materials encounte red during subsurface exploration is presented in the following sections. Based on our field observations and review of published geologic maps and previous studies the subject site area is locally underlain by a layer of colluvium over Cretaceous age Tonalite (granitic) b edrock. Alta described the surficial material as alluvium, however considering the topography of the site GeoTek interprets the material as colluvium. Alluvial soils may be present in the to pographic lows of the site. The colluvial and alluvial soils are not considered to be competent t o support structural foundations in their current state, thus differentiation of alluvial and colluvial soils is not considered to be necessary.
4.2.1 Colluvium and Alluvium, undifferentiated (map symbol Qal) Colluvium/alluvium was locally observed on the surf ace of the site and dispersed throughout and generally consisted of brown to tannish brown t o orange brown silty sand.
Colluvium/alluvium material is not considered suita ble for support of structural site improvements, but may be re-used as engineered fill, if properly placed.
4.2.2 Tonalite (map symbol Kt)
Based off the most recent regional geologic map sho wing the overall site geology (Kennedy, 2007) and our site reconnaissance, we observed Cret aceous-age tonalite (granitic) bedrock at the surface across the site, with outcrops and part ially exposed core stones of bedrock materials or boulders. Anticipated bedrock excavat ion characteristics are discussed in a later section of this report. The results of the subsurf ace seismic refraction surveys are included in Appendix A.
4.3 SURFACE WATER AND GROUNDWATER
4.3.1 Surface Water
Surface water was not observed during our site visi t. If encountered during earthwork construction, surface water on this site is the res ult of precipitation. Provisions for surface drainage will need to be accounted for by the project civil engineer.
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4.3.2 Groundwater
Groundwater is not anticipated to be within 50 feet of the ground surface at the subject site and is not anticipated to be a factor in site devel opment. Localized perched groundwater could be present but is also not anticipated to be a factor in site development.
4.4 EARTHQUAKE HAZARDS
4.4.1 Surface Fault Rupture
The geologic structure of the entire southern Calif ornia area is dominated mainly by northwest-trending faults associated with the San A ndreas system. The site is in a seismically active region. No active or potentially active fau lt is known to exist at this site nor is the site situated within an “Alquist-Priolo” Earthquake Fault Zone or a Special Studies Zone (Br yant and Hart, 2007). No faults are identified on the readi ly available geologic maps that were reviewed by this firm for the immediate study area.
4.4.2 Liquefaction/Seismic Settlement
Liquefaction describes a phenomenon in which cyclic stresses, produced by earthquake- induced ground motion, create excess pore pressures in relatively cohesionless soils. These soils may thereby acquire a high degree of mobility , which can lead to lateral movement, sliding, consolidation and settlement of loose sedi ments, sand boils and other damaging deformations. This phenomenon occurs only below th e water table, but, after liquefaction has developed, the effects can propagate upward into ov erlying non-saturated soil as excess pore water dissipates.
The factors known to influence liquefaction potenti al include soil type and grain size, relative density, groundwater level, confining pressures, an d both intensity and duration of ground shaking. In general, materials that are susceptibl e to liquefaction are loose, saturated granular soils having low fines content under low confining pressures.
The liquefaction potential and seismic settlement p otential on this site is considered to be negligible, due to anticipated medium dense consist ency and thickness of less than 10 feet of anticipated fills, shallow bedrock and absence of a shallow groundwater table.
4.4.3 Other Seismic Hazards
Evidence of ancient landslides or slope instabiliti es at this site was not observed during our investigation. Thus, the potential for landslides is considered negligible.
The potential for secondary seismic hazards such as seiche and tsunami is considered to be remote due to site elevation and distance from an open body of water.
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5. CONCLUSIONS AND RECOMMENDATIONS
5.1 General
Development of the site appears feasible from a geo technical viewpoint provided that the following recommendations are incorporated in the d esign and construction phases of the development. The following sections present genera l recommendations for currently anticipated site development plans.
5.2 EARTHWORK CONSIDERATIONS
5.2.1 General
Earthwork and grading should be performed in accord ance with the applicable grading ordinances of the City of San Marcos, the 2022 Cali fornia Building Code (CBC), and recommendations contained in this report. The Grad ing Guidelines included in Appendix C outline general procedures and do not anticipate al l site specific situations. In the event of conflict, the recommendations presented in the text of this report should supersede those contained in Appendix C.
5.2.2 Site Clearing and Preparation
Site preparation should start with removal of delet erious materials and vegetation. These materials should be disposed of properly off site. Any existing underground improvements, utilities and trench backfill should also be remove d or be further evaluated as part of site development operations.
5.2.3 Remedial Grading
Prior to placement of engineered fill materials, th e upper loose and compressible materials should be removed in preparation for areas to recei ve structural improvements and engineered fills. Removal depths in areas of existing colluvi um and highly weathered bedrock are estimated to be an average of approximately 2 to 3 feet in mo st areas. In areas not explored, deeper colluvium may exist and should anticipate deeper re movals of 5 feet. The lateral extent beyond the outside edge of all settlement sensitive struct ures/foundations should be equivalent to that vertically removed.
Removal bottom gradients should be sloped towards t he street to reduce potential long term perched groundwater conditions. The bottom of all removals should be brought to at or above optimum moisture content, and then compacted to min imum project standards prior to fill placement. The remedial excavation bottoms should be observed by a GeoTek representative.
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The resultant voids from remedial grading/overexcav ation should be filled with materials placed in general accordance with Section 5.2.6 Engineered Fill of this report.
Depending on final proposed grades relative to the less weathered bedrock materials, additional excavation may be required to enable utility trench excavation with typically employed equipment. If this is desired, such excavation wou ld extend to the bottom of the deepest proposed utility trench bedding zone.
5.2.4 Cut Building Pads
Foundations bearing completely on competent graniti c bedrock may remain as a cut condition, however, foundation and underground utility excavat ions may be difficult with conventional light duty excavation equipment.
5.2.5 Over-Excavation
At a minimum, the cut portion(s) of any cut/fill tr ansition building pad areas in bedrock should be overexcavated a minimum of three feet below fini sh pad grade or a minimum of two (2) feet below the bottom of the deepest proposed footing or underground utility servicing the building. whichever is deeper.
5.2.6 Engineered Fill
Onsite materials are generally considered suitable for reuse as engineered fill provided, they are free from vegetation, roots, debris and oversized m aterial (rock or hard lumps) greater than 6 inches. Oversized materials generated from grading operations should be anticipated and can be utilized onsite provided they are incorporated i nto fills as structural rock fills (see section
5.2.7) or other methods presented in appendix C. T he earthwork contractor should have the proposed excavated materials to be used as engineer ed fill at this project approved by the soils engineer prior to placement.
Engineered fill materials should be moisture condit ioned to at or above optimum moisture content and compacted in horizontal lifts not excee ding 8 inches in loose thickness to a minimum relative compaction of 90% as determined in accordance with laboratory test procedure ASTM D 1557.
If fill is being placed on slopes steeper than 5:1 (h:v), the fill should be properly benched into the existing slopes and a sufficient size keyway sh all be constructed in accordance with grading guidelines presented in Appendix C.
5.2.7 Structural Rock Fills
It should be anticipated that hard rock will be enc ountered during rough grading. Remedial removals are anticipated to be relatively shallow. As a result, the site is not anticipated to be a Las Posas, LLC Project No. 3865-SD
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good candidate for incorporating oversized rock int o engineered fills. However, if the materials generated for placement in structural fills contain s a significant percentage of material more than six (6) inches in one dimension, then placemen t using conventional soil fill methods with isolated burial or windrows would not be feasible. In such cases the following could be considered:
1. Mixes of large rock or boulders may be placed as ro ck fill. They should be below the depth of all utilities both on pads and in roadways and below any proposed swimming pools or other excavations. If these fills are pla ced within five feet of finished grade, they may affect foundation design.
2. Rock fills are required to be placed in horizontal layers that should not exceed two feet in thickness, or the maximum rock size present, whi ch ever is less. All rocks exceeding two feet should be broken down to a smaller size, o r disposed of in isolated burial pits.
Localized larger rock up to 4 feet in largest dimen sion may be placed in rock fill as individual rocks are placed in a given lift so as t o be roughly 50% exposed above the typical surface of the fill. Loaded rock trucks or alternate compactors are worked around the rock on all sides to the satisfaction of the soil engineer. The portion of the rock above grade is covered with a second lift.
3. Material placed in each lift should be well graded. No unfilled spaces (voids) should be permitted in the rock fill.
5.2.8 Compaction Procedures of Rock Fills
Compaction of rock fills is largely procedural. Th e following procedures have been found to generally produce satisfactory compaction.
1. Provisions for routing of construction traffic over the fill should be implemented. a) Placement should be by rock trucks crossing the lif t being placed and dumping at its edge.
b) The trucks should be routed so that each pass acros s the fill is via a different path and that all areas are uniformly traversed.
c) The dumped piles should be knocked down and spread by a large dozer (D-8 or larger suggested). (Water should be applied before and during spreading.)
2. Rock fill should be generously watered (sluiced)
a) Water should be applied by water trucks to the:
i) dump piles,
ii) front face of the lift being placed and,
iii) surface of the fill prior to compaction.
b) No material should be placed without adequate water. c) The number of water trucks and water supply should be sufficient to provide constant water.
d) Rock fill placement should be suspended when water trucks are unavailable:
i) for more than 5 minutes straight, or,
ii) for more than 10 minutes/hour.
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3. In addition to the truck pattern and at the discret ion of the soil engineer, large, rubber tired compactors may be required.
a) The need for this equipment will depend largely on the ability of the operators to provide complete and uniform coverage by wheel rolling with the trucks. b) Other large compactors will also be considered by t he soil engineer provided that required compaction is achieved.
4. Placement and compaction of the rock fill is largel y procedural. Observation by trenching should be made to check:
a) the general segregation of rock size,
b) for any unfilled spaces between the large blocks, and c) the matrix compaction and moisture content.
5. Test fills may be required to evaluate relative com paction of finer grained zones or as deemed appropriate by the soil engineer.
a) A lift should be constructed by the methods proposed, as proposed.
6. Frequency of the test trenching is to be at the dis cretion of the soil engineer. Control areas may be used to evaluate the contractor’s procedures.
A minimum horizontal distance of 7 feet should be m aintained from the face of the rock fill and any finish slope face. At least the outer 7 feet s hould be built of general fill materials, not structural rock fill material.
5.2.9 Slope Construction
An engineering geologist should observe all cut slo pes. Cut slopes should expose competent bedrock. If adverse structure or unsuitable materi als are exposed and identified in the cut slopes, stabilization fills may be recommended.
Where fill is to be placed against sloping ground wi th gradients of 5:1 (h:v) or steeper, the sloping ground surface should be benched to provide horizontal surfaces for fill placement. A keyway should be constructed at the toe of the fill slope areas into dense natural material and in accordance with Plate G-3, Appendix C.
The base of the keyways and benches should be slope d back into the hillside at a gradient of at least two percent. The base of the benches should be evaluated by a representative of GeoTek prior to processing. Upon approval, the exposed ma terials should be moistened to at least the optimum moisture content and densified to a relativ e compaction of at least 90 percent (ASTM D1557). Details showing slope construction are presented in Appendix C.
Fill slopes should be overfilled during construction and then cut back to expose compacted soil.
A suitable alternative would be to compact the slop es during construction and then roll the final slope to provide a dense, erosion resistant surface.
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Back drains should be installed in the keyways in a ccordance with the recommendations outlined in Appendix C.
5.2.10 Excavation Characteristics
Excavations in the onsite colluvium/alluvium materi als can generally be accomplished with heavy-duty earthmoving or excavating equipment in g ood operating condition. Less weathered bedrock materials are also likely to be encountered at depth or at the surface and could locally require special techniques to excavate.
In certain conditions it may be more cost effective to rip a small quantity of hard rock (given equipment wear and tear), than fracturing hard rock by blasting techniques in a mass grade condition. In general, rock displaying high seismic velocities can be more readily excavated in an open cut than in a trench condition. Contractors wh o perform work in a hard rock environment can better assess their ability to excavate potential hard rock materials.
Seismic refraction data for the areas evaluated see ms to generally indicate that excavations on the order of roughly 5 to 20 feet should be excavat able with conventional earthmoving equipment. Shallow hard rock should be anticipated in the central and northern portions of the site. Hard rock material is anticipated to descend to greater depths (i.e. 20 feet) towards Armorlite and the AT&T property. Core stones and b oulders were also noted in the seismic refraction data, and also observed on the site, whi ch could necessitate special excavation techniques if encountered during site earthwork. A dditional review and interpretation with respect to rock hardness is recommended by the proj ect grading and utility construction contractors.
5.2.11 Shrinkage and Bulking
Several factors will impact earthwork balancing on the site, including bedrock bulking, undocumented fill and colluvium shrinkage, trench s poil from utilities and footing excavations, as well as the accuracy of topography.
Shrinkage and bulking are largely dependent upon th e degree of compactive effort achieved during construction. For planning purposes, a shri nkage factor ranging from 5 percent may be considered for the colluvial/alluvial materials req uiring removal and re-compaction. Bedrock bulking could range from 10 to 20 percent. Subside nce should not be a factor on the subject site if removals are completed down to the recommen ded depths to expose bedrock materials. Site balance areas should be available in order to adjust project grades, depending on actual field conditions at the conclusion of site earthwork construction.
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5.2.12 Trench Excavations and Backfill
Temporary excavations within the onsite materials should be stable at 1:1 inclinations for short durations during construction, and where cuts do no t exceed 10 feet in height. Temporary cuts to a maximum height of 4 feet can be excavated vertically.
Trench excavations should conform to Cal-OSHA regul ations. The contractor should have a competent person, per OSHA requirements, on site during construction to observe conditions and to make the appropriate recommendations.
Utility trench backfill should be compacted to at l east 90% relative compaction of the maximum dry density as determined per ASTM D 1557. Under-slab trenches should also be compacted to project specifications.
Onsite materials may not be suitable for use as bed ding material but should be suitable as backfill provided particles larger than 6± inches are removed.
Compaction should be achieved with a mechanical com paction device. Ponding or jetting of trench backfill is not recommended. If backfill so ils have dried out, they should be thoroughly moisture conditioned prior to placement in trenches.
5.3 DESIGN RECOMMENDATIONS
5.3.1 Foundation Design Criteria
Preliminary foundation design criteria, in general conformance with the 2022 CBC, are presented herein. These are typical design criteri a and are not intended to supersede the design by the structural engineer.
Based on our visual classification of materials enc ountered onsite and laboratory testing, soils near subgrade may be classified as “very low” expan sive (EI<20) per ASTM D 4829. Additional laboratory testing should be performed at the compl etion of site grading to verify the expansion potential and plasticity index, if necessary, of the subgrade soils.
The following criteria for design of foundations are preliminary. Additional laboratory testing of the samples obtained during grading should be perfo rmed and final recommendations should be based on as-graded soil conditions.
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MINIMUM DESIGN REQ UIREMENTS FOR CONVENTIONALLY RE INFORCED
FOUNDATIONS
DESIGN PARAMETER “Very Low”
Expansion Potential (0 ≤EI≤20)
Foundation Embedment Depth or Minimum Perimeter
Beam Depth (inches below lowest adjacent finished grade) Five Story – 24 Minimum Foundation Width (Inches) Five Story - 18
Minimum Slab Thickness (actual) 5 inches
Minimum Slab Reinforcing (parking floor) No. 3 rebar 24” on -center, each way, placed in the middle o ne -third of the slab thickness
Minimum Footing Reinforcement Four No. 4 Reinforcin g Bars, two (1) top and two (1) bottom
Pre satu ration of Subgrade Soil (percent of optimum
moistur e content) Minimum 100% to a depth of 12 inches
It should be noted that the above recommendations a re based on soil support characteristics only. The structural engineer should design the sl ab and beam reinforcement based on actual loading conditions.
The following recommendations should be implemented into the design:
An allowable bearing capacity of 2500 pounds-per-sq uare-foot (psf) may be used for design of continuous and perimeter footings that me et the depth and width requirements in the table above. This value may be increased by 400 pounds per square foot for each additional 12 inches in depth and 200 pounds per square foot for each additional 12 inches in width to a maximum value of 3000 psf. Additionally, an increase of one-third may be applied when consid ering short-term live loads (e.g. seismic and wind loads).
Based on our experience in the area, structural fou ndations may be designed in accordance with 2022 CBC, and to withstand a total settlement of 1 inch and maximum differential settlement of one-half of the total settlement over a horizontal distance of 40 feet. These values assum e that seismic settlement potential is not a significant constraint.
The passive earth pressure may be computed as an eq uivalent fluid having a density of 300 psf per foot of depth, to a maximum earth pr essure of 3000 psf for footings founded on engineered fill. A coefficient of frict ion between soil and concrete of
0.35 may be used with dead load forces. When combin ing passive pressure and frictional resistance, the passive pressure compone nt should be reduced by one- third.
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A grade beam, a minimum of 12 inches wide and the d epth of the grade beam should be at the same elevation as the bottom of the adjoining footings.
5.3.2 Underslab Moisture Membrane
A moisture and vapor retarding system should be pla ced below slabs-on-grade where moisture migration through the slab is undesirable. Guideli nes for these are provided in the 2022 California Green Building Standards Code (CALGreen) Section 4.505.2 and the 2022 CBC Section 1907.1.1.
It should be realized that the effectiveness of the vapor retarding membrane can be adversely impacted as a result of construction related punctu res (e.g. stake penetrations, tears, punctures from walking on the vapor retarder placed atop the underlying aggregate layer, etc.). These occurrences should be limited as much as possible d uring construction. Thicker membranes are generally more resistant to accidental puncture that thinner ones. Products specifically designed for use as moisture/vapor retarders may al so be more puncture resistant. Although the CBC specifies a 6-mil vapor retarder membrane, it is GeoTek’s opinion that a minimum 10- mil membrane with joints properly overlapped and se aled should be considered, unless otherwise specified by the slab design professional.
Moisture and vapor retarding systems are intended t o provide a certain level of resistance to vapor and moisture transmission through the concret e, but do not eliminate it. The acceptable level of moisture transmission through the slab is to a large extent based on the type of flooring used and environmental conditions. Ultimately, the vapor retarding system should be comprised of suitable elements to limit migration o f water and reduce transmission of water vapor through the slab to acceptable levels. The s elected elements should have suitable properties (i.e. thickness, composition, strength a nd permeability) to achieve the desired performance level.
Moisture retarders can reduce, but not eliminate, m oisture vapor rise from the underlying soils up through the slab. Moisture retarder systems sho uld be designed and constructed in accordance with applicable American Concrete Instit ute, Portland Cement Association, Post- Tensioning Concrete Institute, ASTM and California Building Code requirements and guidelines.
GeoTek does not practice in the field of moisture v apor transmission evaluation/migration, since that practice is not a geotechnical disciplin e. Therefore, we recommend that a qualified person, such as the flooring contractor, structural engineer, architect, and/or other experts specializing in moisture control within the buildin g be consulted to evaluate the general and specific moisture and vapor transmission paths and associated potential impact on the proposed construction. That person (or persons) should prov ide recommendations relative to the slab moisture and vapor retarder systems and for migrati on of potential adverse impact of moisture Las Posas, LLC Project No. 3865-SD
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vapor transmission on various components of the str uctures, as deemed appropriate. In addition, the recommendations in this report and ou r services in general are not intended to address mold prevention; since we, along with geote chnical consultants in general, do not practice in the area of mold prevention. If specif ic recommendations addressing potential mold issues are desired, then a professional mold prevention consultant should be contacted.
5.3.3 Miscellaneous Foundation Recommendations
To reduce moisture penetration beneath the slab on grade areas, utility trenches should be backfilled with engineered fill, lean con crete or concrete slurry where they intercept the perimeter footing or thickened slab edge.
Spoils from the footing excavations should not be p laced in the slab-on-grade areas unless properly compacted and tested. The excavati ons should be free of loose/sloughed materials and be neatly trimmed at the time of concrete placement.
We recommend that control joints be placed in two di rections spaced the numeric equivalent roughly 24 times the thickness of the sl ab in inches (e.g. a 4 inch slab would have control joints at 96 inch [8 feet] cente rs). These joints are a widely accepted means to control cracks and should be revi ewed by the project structural engineer.
5.3.4 Foundation Set Backs
Where applicable, the following setbacks should appl y to all foundations. Any improvements not conforming to these setbacks may be subject to lateral movements and/or differential settlements:
The outside bottom edge of all footings should be s et back a minimum of H/3 (where H is the slope height) from the face of any descending slope. The setback should be at least 7 feet and need not exceed 40 feet.
The bottom of all footings for structures near retaining walls should be deepened so as to extend below a 1:1 projection upward from the bottom inside edge of the wall stem. This applies to the existing retaining walls along the perimeter, if they are to remain.
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The bottom of any existing foundations for structur es should be deepened so as to extend below a 1:1 projection upward from the bottom of the nearest excavation.
5.3.5 Seismic Design Parameters
The site is located at approximately 33.14709 latit ude and -117.18820 longitude. Site spectral accelerations (Ss and S1), for 0.2 and 1.0 second p eriods for a risk targeted two (2) percent probability of exceedance in 50 years (MCER) were d etermined using the web interface provided by SEAOC/OSHPD ( https://seismicmaps.org ) to access the USGS Seismic Design Parameters. We have selected a Site Class “C” based on the shallow depth of fill overlying granitic bedrock.
SITE SEISMIC PARAMETERS
Ma pped 0 .2 sec Period Spectral Acceleration, S s 1.03 g Mapped 1.0 sec Period Spectr al Acceleration, S 1 0.33 g Maximum Considered Earthq uake (MCE R) Spe ctral
Respon se Acceler ation for 0.2 Second , S MS 1.12g
Maximum Considered Earthquake ( MCE R) Spectral
Response Acceleration for 1.0 Second, SM1 0.48g
5% Da mped Desi gn Spectral Response
Acceleration Para meter at 0.2 Second, S DS 0.75g
5% Dam ped Design Spec tral Resp onse
Accel eration Parameter at 1 second, S D1 0.32g
5.3.6 Soil Corrosivity
The soil resistivity at this site was tested in the laboratory on samples collected during the field investigation. The results of the testing indicate that the onsite soils are not considered corrosive with current standards used by corrosion engineers. These characteristics are considered typical of soils commonly found in this area of southern California. We recommend that a corrosion engineer be consulted to provide r ecommendations for proper protection of buried metal at this site.
5.3.7 Soil Sulfate Content
Results indicate that the water soluble sulfate ran ge is less than 0.1 percent by weight, which is considered “not applicable” (negligible) as per Tab le 4.2.1 of ACI 318-11. Based upon the test results, no special mix design is required by Code to resist sulfate attack. As a minimum, additional testing should be completed subsequent t o rough grading in order to confirm these initial results.
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5.4 RETAINING WALL DESIGN AND CONSTRUCTION
5.4.1 General Design Criteria
Recommendations presented herein may apply to typic al masonry or concrete vertical retaining walls to a maximum height of 10 feet. Ad ditional review and recommendations should be requested for higher walls.
Retaining wall foundations embedded a minimum of 18 inches into engineered fill or dense formational materials should be designed using an a llowable bearing capacity of 2500 psf. An increase of one-third may be applied when consideri ng short-term live loads (e.g. seismic and wind loads). The passive earth pressure may be com puted as an equivalent fluid having a density of 350 psf per foot of depth, to a maximum earth pressure of 3000 psf. A coefficient of friction between soil and concrete of 0.35 may be u sed with dead load forces. When combining passive pressure and frictional resistance, the passive pressure component should be reduced by one-third.
An equivalent fluid pressure approach may be used t o compute the horizontal active pressure against the wall. The appropriate fluid unit weigh ts are given in the table below for specific slope gradients of retained materials.
Surface Slope of Retained
Materials
(H:V)
Equivalent Fluid Pressure
(PCF)
Select Backfill*
Level 40
2:1 70
*Select backfill should consist of native or import ed sand or other approved materials with an EI<20.
The above equivalent fluid weights do not include o ther superimposed loading conditions such as expansive soil, vehicular traffic, structures, seismic conditions or adverse geologic conditions.
5.4.2 Seismic Induced Incremental Addition
Additional lateral forces can be induced on retaini ng walls during an earthquake. For level backfill and a Site Class “C”, the minimum earthqua ke-induced force (F eq ) should be 13H 2 (lbs/linear foot of wall) for cantilever walls. Th is force can be assumed to act at a distance of
0.6H above the base of the wall, where “H” is the h eight of the retaining wall measured from the base of the footing (in feet). The 2022 CBC on ly requires the additional earthquake induced lateral force be considered on retaining wa lls in excess of six (6) feet in height; Las Posas, LLC Project No. 3865-SD
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however, the additional force may be applied in des ign of lesser walls at the discretion of the wall designer.
5.4.3 Wall Backfill and Drainage
Wall backfill should include a minimum one (1) foot wide section of ¾ to 1-inch clean crushed rock (or approved equivalent). The rock should be placed immediately adjacent to the back of wall and extend up from the backdrain to within app roximately 12 inches of finish grade. The upper 12 inches should consist of compacted onsite materials. If the walls are designed using the “select” backfill design parameters, then the “ select” materials shall be placed within the active zone as defined by a 1:1 (H:V) projection fr om the back of the retaining wall footing up to the retained surface behind the wall. Presence of other materials might necessitate revision to the parameters provided and modification of wall designs.
The backfill materials should be placed in lifts no greater than 8-inches in thickness and compacted to a minimum of 90% of the maximum dry de nsity as determined in accordance with ASTM Test Method D 1557. Proper surface drain age needs to be provided and maintained. Water should not be allowed to pond beh ind retaining walls. Waterproofing of site walls should be performed where moisture migration through the wall is undesirable.
Retaining walls should be provided with an adequate pipe and gravel back drain system to reduce the potential for hydrostatic pressures to d evelop. A 4-inch diameter perforated collector pipe (Schedule 40 PVC, or approved equiva lent) in a minimum of one (1) cubic foot per lineal foot of 3/8 to one (1) inch clean crushe d rock or equivalent, wrapped in filter fabric should be placed near the bottom of the backfill an d be directed (via a solid outlet pipe) to an appropriate disposal area.
Walls from two (2) to four (4) feet in height may be drained using localized gravel packs behind weep holes at 10 feet maximum spacing (e.g. approxi mately 1.5 cubic feet of gravel in a woven plastic bag). Weep holes should be provided or the head joints omitted in the first course of block extended above the ground surface. However, nuisance water may collect in front of the wall.
Drain outlets should be maintained over the life of the project and should not be obstructed or plugged by adjacent improvements.
5.4.4 Restrained Retaining Walls
Any retaining wall that will be restrained prior to placing backfill or walls that have male or reentrant corners should be designed for at-rest so il conditions using an equivalent fluid pressure of 60 pcf (select backfill), plus any appl icable surcharge loading. For areas having male Las Posas, LLC Project No. 3865-SD
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or reentrant corners, the restrained wall design sh ould extend a minimum distance equal to twice the height of the wall laterally from the cor ner, or as otherwise determined by the structural engineer.
5.4.5 Preliminary Pavement Design
Traffic indices have not been provided during this stage of site planning. In addition, site conditions have not been graded to a final design t o evaluate specific pavement subgrade conditions. Therefore, the minimum structural sect ions provided below are based on a preliminary laboratory R-Value of 25 and the assumed traffic indices.
PRELIMINARY ASPHALT PAVEMENT STRUCT URAL SECTION
Design Criteria Traffic Index
(TI)
Asphaltic Concrete (AC)
Thickness (inches)
Aggregate Base (AB)
Thickness (inches)
Driveway Aisle or
Parking Lot 5.0 3.0 6.0
Actual structural pavement design is to be determin ed by the geotechnical engineer’s testing (R-Value) of the exposed subgrade. Thus, the actua l R-Value of the subgrade soils can only be determined at the completion of grading for street subgrades and the above values are subject to change based laboratory testing of the as-graded soils near subgrade elevations.
Asphalt concrete and aggregate base should conform to current Caltrans Standard Specifications Section 39 and 26-1.02, respectively . As an alternative, asphalt concrete can conform to Section 203-6 of the current Standard Sp ecifications for Public Work (Green Book). Crushed aggregate base or crushed miscellan eous base can conform to Section 200-2.2 and 200-2.4 of the Green Book, respectively. Pavem ent base should be compacted to at least 95 percent of the ASTM D1557 laboratory maximum dry density as determined by ASTM D1557 test procedures
All pavement installation, including preparation an d compaction of subgrade, compaction of base material, placement and rolling of asphaltic c oncrete, should be done in accordance with the City of San Marcos specifications, and under th e observation and testing of GeoTek and a City Inspector where required. Jurisdictional mini mum compaction requirements in excess of the aforementioned minimums may govern.
5.4.6 Portland Cement Concrete (PCC)
For driveways constructed with Portland Cement Conc rete (PCC), the following recommended minimum PCC pavement section is provided for these areas:
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Driveway into the parking structure or other structural surface pavement
5.5 Inches Portland Cement Concrete (PCC) over
6 Inches Aggregate Base (AB) over
12-inches subgrade compacted to 95% per ASTM D 15 57
For the PCC options, it is recommended concrete hav ing a minimum 28-day flexural strength (or modulus of rupture (MOR)) of 650 psi be used. A “pavement”-type concrete mix (not a “slab”-type) concrete mix should be use. Air-entra inment (5 ± 2 percent) of the concrete should be provided. Sulfate resistant concrete is not required. A maximum joint spacing of 12 feet is also recommended. Reinforcement of the con crete should be provided as recommended by the structural engineer.
5.4.7 Exterior Concrete Slabs and Sidewalks
Exterior concrete slabs, sidewalks and driveways sh ould be designed using a four-inch minimum thickness with 6” x 6” – W1.4/W1.4 welded wire fabri c, placed in the middle of slab. It is recommended that control joints be placed in two di rections spaced the numeric equivalent roughly 24 times the thickness of the slab in inche s (e.g., a 4-inch slab would have control joints at 96 inch [8 feet] centers). These joints are a w idely accepted means to control cracks and should be reviewed by the project structural engine er. Some shrinkage and cracking of the concrete should be anticipated as a result of typic al mix designs and curing practices typically utilized in construction.
Presaturation of flatwork subgrade should be verifi ed to be a minimum of 100% of the soils optimum moisture to a depth of 12 inches for soils having a “very low” expansive index potential.
5.5 POST CONSTRUCTION CONSIDERATIONS
5.5.1 Landscape Maintenance and Planting
Water has been shown to weaken the inherent strength of soil, and slope stability is significantly reduced by overly wet conditions. Po sitive surface drainage away from graded slopes should be maintained and only the amount of irrigation necessary to sustain plant life should be provided for planted slopes. Controlling surface drainage and runoff, and maintaining a suitable vegetation cover can minimize erosion. Plants selected for landscaping should be lightweight, deep-rooted types that require little water and are capable of surviving the prevailing climate.
Overwatering should be avoided. The soils should b e maintained in a solid to semi-solid state as defined by the materials Atterberg Limits. Care should be taken when adding soil Las Posas, LLC Project No. 3865-SD
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amendments to avoid excessive watering. Leaching a s a method of soil preparation prior to planting is not recommended. An abatement program to control ground-burrowing rodents should be implemented and maintained. This is crit ical as burrowing rodents can decreased the long-term performance of slopes.
It is common for planting to be placed adjacent to structures in planter or lawn areas. This will result in the introduction of water into the ground adjacent to the foundation. This type of landscaping should be avoided. If used, then extre me care should be exercised with regard to the irrigation and drainage in these areas. Waterpr oofing of the foundation and/or subdrains may be warranted and advisable. We could discuss th ese issues, if desired, when plans are made available.
5.5.2 Drainage
The need to maintain proper surface drainage and su bsurface systems cannot be overly emphasized. Positive site drainage should be maint ained at all times. Drainage should not flow uncontrolled down any descending slope. Water shoul d be directed away from foundations and not allowed to pond or seep into the ground. P ad drainage should be directed toward approved area(s) and not be blocked by other improvements.
It is the owner’s responsibility to maintain and clean drainage devices on or contiguous to their lot. In order to be effective, maintenance should be conducted on a regular and routine schedule and necessary corrections made prior to each rainy season.
5.6 PLAN REVIEW AND CONSTRUCTION OBSERVATIONS
We recommend that site grading, specifications, reta ining wall/shoring plans and foundation plans be reviewed by this office prior to construct ion to check for conformance with the recommendations of this report. Additional recomme ndations may be necessary based on these reviews. We also recommend that GeoTek repres entatives be present during site grading and foundation construction to check for pr oper implementation of the geotechnical recommendations. The owner/developer should have G eoTek’s representative perform at least the following duties:
Observe site clearing and grubbing operations for p roper removal of unsuitable materials.
Observe and test bottom of removals prior to fill placement. Evaluate the suitability of on-site and import mate rials for fill placement, and collect soil samples for laboratory testing when necessary.
Observe the fill for uniformity during placement including utility trenches. Observe and test the fill for field density and relative compaction.
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Observe and probe foundation excavations to confirm suitability of bearing materials.
If requested, a construction observation and compac tion report can be provided by GeoTek, which can comply with the requirements of the gover nmental agencies having jurisdiction over the project. We recommend that these agencies be no tified prior to commencement of construction so that necessary grading permits can be obtained.
6. LIMITATIONS
The scope of our evaluation is limited to the area explored that is shown on the Geotechnical Map (Figure 2). This evaluation does not and should in no way be construed to encompass any areas beyond the specific area of proposed construc tion as indicated to us by the client.
Further, no evaluation of any existing site improve ments is included. The scope is based on our understanding of the project and the client’s n eeds, our proposal (Proposal No.
P-1200622-SDCO2) dated April 25, 2023 and geotechni cal engineering standards normally used on similar projects in this region.
The materials observed on the project site appear t o be representative of the area; however, soil and bedrock materials vary in character betwee n excavations and natural outcrops or conditions exposed during site construction. Site conditions may vary due to seasonal changes or other factors. GeoTek, Inc. assumes no responsi bility or liability for work, testing or recommendations performed or provided by others.
Since our recommendations are based on the site con ditions observed and encountered, and laboratory testing, our conclusions and recommendat ions are professional opinions that are limited to the extent of the available data. Obser vations during construction are important to allow for any change in recommendations found to be warranted. These opinions have been derived in accordance with current standards of pra ctice and no warranty is expressed or implied. Standards of practice are subject to change with time.
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7. SELECTED REFERENCES
Alta California Geotechnical Inc., 2021, “Preliminary Geotechnical Investigation, Las Posas Road and Armorlite Drive, City of San Marcos, California,” Proposal No. 1-0371, dated March 31, 2021.
American Society of Civil Engineers (ASCE), 2017, “ Minimum Design Loads for Buildings and Other Structures,” ASCE/SEI 7-16, Third Printing, E rrata Incorporated through February 13, 2019.
ASTM, “Soil and Rock: American Society for Testing and Materials,” volumes 4.08 and 4.09.
Bryant, W.A., and Hart, E.W., 2007, "Fault Rupture Ha zard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquak e Fault Zones Maps," California Geological Survey: Special Publication 42.
California Code of Regulations, Title 24, 2022 “California Building Code,” 2 volumes.
California Geological Survey (CGS, formerly referred to as the California Division of Mines and Geology), 1977, “Geologic Map of California.”
____, 1998, “Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada,” International Conference of Building Officials.
GeoTek, Inc., In-house proprietary information.
Kennedy, M.P., and Tan, S.S., 1996, “Geologic Map o f the Oceanside, San Luis Rey, and San Marcos 7.5’ Quadrangles, San Diego County, California,” DMG Open-File Report 96-02. ____, 2007, “Geologic Map of the Oceanside 30x60-mi nute Quadrangle, California,” California Geological Survey, Regional Geologic Map No. 2, map scale 1:100,000.
Structural Engineers Association of California/California Office of Statewide Health Planning and Development (SEOC/OSHPD), 2019, Seismic Design Maps web interface, accessed May 12, 2019 at
https://seismicmaps.org
1384 Poinsettia Avenue, Suite A, Vista, CA 92081
(760) 599-0509 (phone) / (760) 599-0593 (FAX)
GEOTECHNICAL | ENVIRONMENTAL | MATERIALS
05/2023
FIGURE 1
SITE LOCATION
225 N LAS POSAS RD.
SAN MARCOS, CALIFORNIA
Project No.: Report Date: Drawn By:
3865-SD CDL
Approximate Site
Location
Site
Location
Armorlite
PN: 3865-SD Figure 2
May 2023
Geotechnical Map
SL-1
SL-2
PT-1
PT-2
Explanation
Qal
Kt
T-9
PT-2
PSL-2
Approximate Site Boundary
Approximate Location of Test Pit
Approximate Location of Percolation Test
Approximate Location of Seismic Refraction
Colluvium/Alluvium, undifferentiated
Granitics, Circled Where Buried
Qal
Qal
Kt
Kt
Armorlite
PN: 3865-SD Figure 2
May 2023
Geotechnical Map
PT-1
PT-2
Explanation
Qal
Kt
T-9
PT-2
PSL-2
Approximate Site Boundary
Approximate Location of Test Pit
Approximate Location of Percolation Test
Colluvium/Alluvium, undifferentiated
Granitics, Circled Where Buried
SL-1
SL-2
Qal Kt
Qal Kt
Approximate Location of Seismic Refraction
APPENDIX A
TEST PITS
AND
SEISMIC REFRACTION EVALUATION REPORT
Project No. 1-0371
Date Excavated February 12th, 2021
Logged by JC
Equipment JD 310
TABLE I
LOG OF TEST PITS
Test Pit No. Depth (ft.) USCS Description
TP-1 0.0-1.0
1.0-3.4
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, dark brown, slightly moist, medium
dense, few fine to coarse gravel <3”, some roots
TONALITE (Kt): BEDROCK, fine to medium
grained, slightly orange tan, dry, hard, slightly to
moderately weathered.
@1.8ft. grayish tan, slightly weathered.
TOTAL DEPTH 3.4 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-2 0.0-2.5
2.5-4.0
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, brown, moist, medium dense, some
roots.
@0.4ft. few fine to coarse gravel <3”, few
boulders <2.0ft.
TONALITE (Kt): BEDROCK, fine to coarse grained,
grayish tan, dry, hard, moderately weathered.
@3.4ft. slightly orange tan, slightly weathered.
TOTAL DEPTH 4.0 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-3 0.0-1.5
1.5-3.3
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, brown, moist, medium dense, some
roots.
@0.9ft. slightly orange brown, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
grayish tan, dry, hard, slightly weathered.
TOTAL DEPTH 3.3 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-4 0.0-1.3
1.3-3.7
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, tannish brown, moist, medium dense,
some roots.
@0.7ft. slightly orange brown, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
orange tan, dry, hard, slightly weathered.
TOTAL DEPTH 3.7 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-5 0.0-3.5
3.5-5.2
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, tan, moist, medium dense, some roots.
@1.3ft. slightly orange tan, some pores.
@2.2ft. some fine to coarse gravel <3”.
TONALITE (Kt): BEDROCK, fine to coarse grained,
orange tan, slightly moist, hard, moderately
weathered.
@4.4ft. grayish tan, slightly weathered.
TOTAL DEPTH 5.2 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-6 0.0-1.8
1.8-3.0
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, brown, moist, medium dense, some
roots.
@0.5ft. trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
reddish brown, dry, hard, moderately weathered.
@2.7ft. tannish gray, very hard.
TOTAL DEPTH 3.0 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-7 0.0-1.9
1.9-3.5
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, brown, moist, medium dense, some
roots.
@010ft. reddish brown, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
reddish brown, dry, hard, moderately weathered.
@2.4ft. tan, slightly weathered.
TOTAL DEPTH 3.5 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-8 0.0-3.1
3.1-4.7
SM
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, dark brown, moist, loose, some roots.
@0.5ft. medium to coarse grained, dry, medium
dense, trace pores.
@1.2ft. orange tan.
@2.8ft. trace clay.
TONALITE (Kt): BEDROCK, fine to coarse grained,
reddish brown, dry, hard, moderately weathered.
@3.6ft. slightly weathered.
TOTAL DEPTH 4.7 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
TP-9 0.0-2.5
2.5-3.8
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, tannish brown, moist, medium dense,
some roots.
@0.7ft. slightly orange brown, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
orange tan, dry, hard, slightly weathered.
TOTAL DEPTH 3.8 FEET
NO GROUNDWATER ENCOUNTERED
SLIGHT CAVING ABOVE 4.0 FEET
Test Pit No. Depth (ft.) USCS Description
PT-1 0.0-1.4
1.4-4.0
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, tannish brown, moist, medium dense,
some roots.
@0.7ft. slightly orange brown, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
orange tan, dry, hard, slightly weathered.
TOTAL DEPTH 4.0 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
Test Pit No. Depth (ft.) USCS Description
PT-2 0.0-2.1
2.1-4.5
SM
ALLUVIUM(Qal): SILTY SAND, very fine to fine
grained, tannish brown, moist, medium dense,
some roots.
@1.5ft. slightly orange brown, few fine gravel
<3/4”, trace pores.
TONALITE (Kt): BEDROCK, fine to coarse grained,
orange tan, dry, hard, slightly weathered.
TOTAL DEPTH 4.5 FEET
NO GROUNDWATER ENCOUNTERED
NO CAVING OBSERVED
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/16 /15 /3 □ /5 /3 /32 /5 /20 /21 /12 /15 /21 /5 /11 /3 □ /30 /12 /2 /15 /21 /2 /12 □ /21 /17 /15 /3 □ /29 /90 /91 □ /5 /3 /18 /17 /2 /14 □ /1 /2 /12 □ /17 /11 /26 /12 □ /25/2 □ /15 /20 /20 /11 /89 /2 /4 □ /89 /5 /21 /17 /11 /26 /21 □ /5 /3 /18 /12 /2 /15 /14 /5 /3 /30 □ /12 /5 /14 /19 □ /11 /32 □ /30 /2 /11 /21 /2 /18 /17 /3 /5 /18 /15 /20 □ /17 /15 /31 /15 /12 /4 /14 □ /129 /14 /20/11 /1 /2 □ /14 /21 /15 /25 /5 /20 /5 /21 /27 /130 □ /30 /12 /11 /26 /3 /4 /89 /15 /21 /2 /12 □ /13 /11 /26 /3 /4 /5 /3 /30 /130 □ /26 /21 /5 /20 /5 /21 /5 /2 /14 /130 □ /11 /12 □ /11 /21 /17 /2/12 □ /32 /15 /18 /21 /11 /12 /14 /131 □ /21 /17 /15 /21 □ /18 /15 /3 /3 /11 /21 □ /25 /2 □ /13 /5 /21 /5 /30 /15 /21 /2 /4 □ /21 /11 □ /15 /3 □ /15 /18 /18 /2 /1 /21 /15 /25 /20 /2 □ /20 /2 /132 /2 /20 /92 □ /93 /94/95 □ /96 /95 /97 /98 /99 /100 /97 /95 □ /101 /99 □ /101 /94 /102 /97 □ /103 /104 /96 /95 /95 /100 /102 /100 /105 □ /106 /107 /95 /97 /101 /102 /99 /100 □ /97 /94 /108 /109 /109 □ /110 /95 □ /110 /108 /97 /95 /111 □/99 /100 □ /108 □ /104 /99 /112 /98 /96 /95 /94 /95 /100 /97 /102 /113 /95 □ /95 /113 /108 /109 /107 /108 /101 /102 /99 /100 □ /99 /114 □ /101 /94 /95 □ /114 /108 /104 /101 /99 /96 /97 □ /98 /96 /95 /97 /95 /100 /101 /95 /111 □ /102/100 □ /115 /98 /98 /95 /100 /111 /102 /116 □ /117 /118 /119 /118 □
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/121 /96 /99 /113 /102 /111 /95 □ /110 /108 /97 /102 /97 /122 □ □
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/103 /107 /112 /112 /108 /96 /102 /123 /95 □ /114 /102 /100 /111 /102 /100 /105 /97 □ /99 /114 □ /97 /101 /107 /111 /102 /95 /97 /124 □ /98 /96 /99 /113 /102 /111 /95 □ /96 /95 /114 /95 /96 /95 /100 /104 /95 □ /101 /99□ /97 /101 /107 /111 /102 /95 /97 /125 □ /104 /108 /109 /104 /107 /109 /108 /101 /102 /99 /100 /97 /125 □ /112 /108 /98 /97 /125 □ /111 /108 /101 /108 □ /97 /99 /107 /96 /104 /95 /97 /125 □ /95 /101 /104 /118 □ /121 /96/99 /113 /102 /111 /95 □ /100 /108 /96 /96 /108 /101 /102 /113 /95 □ /111 /102 /97 /104 /107 /97 /97 /102 /99 /100 □ /99 /114 □ /97 /101 /107 /111 /126 /127 /111 /108 /101 /108 □ /97 /99 /107 /96 /104 /95 □ /108 /98 /98 /109 /102 /104 /108 /110 /102/109 /102 /101 /126 /118 □ □ □
X
An infiltration testing evaluation was performed at the site, by borehole method to obtain percolation rates that were converted to infiltration rates via Porchet method.
Site specific testing resulted in rates of 0.1 and 0.4 inches per hour.
GeoTek, Inc. "Preliminary Geotechnical Evaluation, Eastern Portion of 225 N. Las Posas Road, San Marcos, California 92069," Project No. 3685-SD, dated May 30, 2023. /0 /1 /1 /2 /3 /4 /5 /6 □ /8 /9 □ /10 /11 /12 /13 /14 □ /15 /3 /4 □ /16 /17 /2 /18 /19 /20 /5 /14 /21 /14□ □
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/64 /11 □ /14 /11 /5 /20 □ /15 /3 /4 □ /33 /2 /11 /20 /11 /33 /5 /18 □ /18 /11 /3 /4 /5 /21 /5 /11 /3 /14 □ /15 /20 /20 /11 /42 □ /34 /11 /12 □ /5 /3 /34 /5 /20 /21 /12 /15 /21/5 /11 /3 □ /5 /3 □ /15 /3 /27 □ /15 /1 /1 /12 /2 /18 /5 /15 /25 /20 /2 □ /12 /15 /21 /2 □ /11 /12 □ /37 /11 /20 /26 /13 /2 /44 □ /65 /66 /49 □ /46 /49 /57 /67 /58 /53 /57 /49 □ /48 /58 □ /48 /66 /47 /57 □ /51 /52/46 /49 /49 /53 /47 /53 /54 □ /55 /56 /49 /57 /48 /47 /58 /53 □ /57 /66 /50 /68 /68 □ /69 /49 □ /69 /50 /57 /49 /70 □ /58 /53 □ /50 □ /52 /58 /71 /67 /46 /49 /66 /49 /53 /57 /47 /72 /49 □ /49 /72 /50 /68 /56 /50 /48 /47/58 /53 □ /58 /73 □ /48 /66 /49 □ /73 /50 /52 /48 /58 /46 /57 □ /67 /46 /49 /57 /49 /53 /48 /49 /70 □ /47 /53 □ /74 /67 /67 /49 /53 /70 /47 /75 □ /45 /76 /77 □ /50 /53 /70 □ /74 /67 /67 /49 /53 /70 /47 /75 □ /78 /76 □ □ □
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An infiltration testing evaluation was performed at the site, by borehole method to obtain percolation rates that were converted to infiltration rates via Porchet method.
Site specific testing resulted in rates of 0.1 and 0.4 inches per hour.
GeoTek, Inc. "Preliminary Geotechnical Evaluation, Eastern Portion of 225 N. Las Posas Road, San Marcos, California 92069," Project No. 3685-SD, dated May 30, 2023.
X
X
Based on the underlying geology, granitic rock is shallow and will create a groundwater mounding affect.
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X
No
Infiltration
Based on the underlying geology, granitic rock is shallow and will create a shallow ground water condition. A review of Geotracker.com did not reveal environmental concerns immediately adjacent to the property.
Although GeoTek does not practice in water rights consultation, infiltration of surface waters into the subsurface does not appear to violate downstream water rights. /0 /1 /1 /2 /3 /4 /5 /6 □ /8 /9 □ /10 /11 /12 /13 /14 □ /15 /3 /4 □ /16 /17 /2 /18 /19 /20 /5 /14 /21 /14□ □
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/48 /45 /49 /50 /46 /52 □ /82 /52 /75 /50 /61 /41 /43 /39 /41 /50 /42 /52 □ /80 /39 /41 /45 /76 □ /50 /52 /74 /56 /43 /76 □ /83/54 /45 /49 /50 /46 /52 □/65 □ /83/42 /68 /49 /45 /43 /63 /45 /54□ /74 □ /67/41 /42 /41 /39 /61□ □ /32 /26 /1 /1 /11 /12 /21 /5 /3 /34 □ /33 /15 /21 /15 □ /78 /43 /50 /45 /75 /61 /47 □ /54 /45 /49 /40 /43 /50 /68 /45 □ /50 /52 /75 /50 /61 /41 /43 /39 /41 /50 /42 /52 □ /41 /45 /49 /41 □ /39 /52 /54 □ /51 /43 /42 /63 /50 /54 /45 □ /43 /45 /75 /45/43 /45 /52 /40 /45 □ /41 /42 □ /41 /45 /49 /41 □ /75 /42 /43 /69 /49 /85 □ □
□
□
□
□
□ □
2 2
1 1
0.5 0.5
0.25 0.25
1.5 To
Be
Determined
by
Civil
Engineer
0.1 inches per hour
An infiltration testing evaluation was performed at the site, by borehole method to obtain percolation rates that were converted to infiltration rates via Porchet method.
GeoTek, Inc. "Preliminary Geotechnical Evaluation, Eastern Portion of 225 N. Las Posas Road, San Marcos, California 92069," Project No. 3685-SD, dated May 30, 2023.
SEISMIC REFRACTION STUDY
1244 ARMORLITE DRIVE
San Marcos, California
PREPARED FOR:
Alta California Geotechnical Inc.
170 North Maple Street, Suite 108
Corona, California 92880
PREPARED BY:
Atlas Technical Consultants
6280 Riverdale Street
San Diego, California 92120
March 30, 2021
6280 Riverdale Street
San Diego, CA 92120
(877) 215-4321 | oneatlas.com
March 30, 2021
Atlas No. 121096SWG
Report No. 1
MR. JAMES COYNE
ALTA CALIFORNIA GEOTECHNICAL INC.
170 NORTH MAPLE STREET, SUITE 108
CORONA, CALIFORNIA 92880
Subject: Seismic Refraction Study
1244 Armorlite Drive
San Marcos, California
Dear Mr. Coyne:
In accordance with your authorization, Atlas Technical Consultants has performed a seismic refraction study pertaining to the 1244 Armorlite Drive project located in San Marcos, California.
Specifically, our evaluation consisted of performing two seismic P-wave refraction traverses at the project site. The purpose of our study was to develop subsurface velocity profiles of the areas studied, and to assess the depth to bedrock and apparent rippability of the subsurface materials.
Our field services were conducted on March 12, 2021. This data report presents our methodology, equipment used, analysis, and results.
If you have any questions, please call us at (619) 280-4321.
Respectfully submitted,
Atlas Technical Consultants LLC
Thomas M. Bouleanu Patrick F. Lehrmann, P.G., P.Gp.
Senior Staff Geophysicist Principal Geologist/Geophysicist TMB:KJA:MDE:PFL:ds
Distribution: Mr. James Coyne at [email protected]
Atlas No. 121096SWG
Report No. 1
Page | i
CONTENTS
1. INTRODUCTION ............................................................................................................ ....... 1
2. SCOPE OF SERVICES ......................................................................................................... 1
3. SITE AND PROJECT DESCRIPTION ................................................................................... 1
4. STUDY METHODOLOGY ..................................................................................................... 1
5. DATA ANALYSIS .................................................................................................................. 3
6. RESULTS AND CONCLUSIONS .......................................................................................... 3
7. LIMITATIONS ........................................................................................................................ 3
8. SELECTED REFERENCES .................................................................................................. 4
TABLE
Table 1 – Rippability Classification ............................................................................................... 2
FIGURES
Figure 1 Site Location Map
Figure 2 Seismic Line Location Map
Figure 3 Site Photographs
Figure 4a P-Wave Profile, SL-1
Figure 4b P-Wave Profile, SL-2
Atlas No. 121096SWG
Report No. 1
Page | 1
1. INTRODUCTION
In accordance with your authorization, Atlas Technical Consultants has performed a seismic refraction study pertaining to the 1244 Armorlite Drive project located in San Marcos, California.
Specifically, our evaluation consisted of performing two seismic P-wave refraction traverses at the project site. The purpose of our study was to develop subsurface velocity profiles of the areas studied, and to assess the depth to bedrock and apparent rippability of the subsurface materials.
Our field services were conducted on March 12, 2021. This data report presents our methodology, equipment used, analysis, and results.
2. SCOPE OF SERVICES
Our scope of services included:
Performance of two seismic P-wave refraction traverse at the project site. Compilation and analysis of the data collected.
Preparation of this data report presenting our results and conclusions.
3. SITE AND PROJECT DESCRIPTION
The project site is located in an undeveloped lot located at 1244 Armorlite Drive in San Marcos, California (Figure 1). The seismic traverses were performed at locations provided at your specified locations. The area is an undeveloped lot with a perimeter fence and thick, waist high vegetation.
Figures 2 and 3 depict the general site conditions in the area of the seismic traverses.
Based on our discussions with you, it is our understanding that the results of our study may be used in the formulation of design and construction parameters for the project.
4. STUDY METHODOLOGY
A seismic P-wave (compression wave) refraction study was conducted at the project to develop subsurface velocity profiles of the areas studied, and to assess the depth to bedrock and apparent rippability of the subsurface materials. The seismic refraction method uses first-arrival times of refracted seismic waves to estimate the thicknesses and seismic velocities of subsurface layers.
Seismic P-waves generated at the surface, using a hammer and plate, are refracted at boundaries separating materials of contrasting velocities. These refracted seismic waves are then detected by a series of surface vertical component 14-Hz geophones and recorded with a 24-channel Geometrics Geode seismograph. The travel times of the seismic P-waves are used in conjunction with the shot-to-geophone distances to obtain thickness and velocity information on the subsurface materials.
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Two seismic traverses (SL-1 and SL-2) were conducted in the study area. The general location and length of the lines were determined by surface conditions, site access, and your requested depth of investigation. Shot points (signal generation locations) were conducted along the lines at the ends, midpoint, and intermediate points between the ends and the midpoint.
The seismic refraction theory requires that subsurface velocities increase with depth. A layer having a velocity lower than that of the layer above will not generally be detectable by the seismic refraction method and, therefore, could lead to errors in the depth calculations of subsequent layers. In addition, lateral variations in velocity, such as those caused by core stones, intrusions, or boulders can also result in the misinterpretation of the subsurface conditions. In general, the effective depth of evaluation for a seismic refraction traverse is approximately one-third to one- fifth of the length of the spread.
In general, the seismic P-wave velocity of a material can be correlated to rippability (see Table 1 below), or to some degree “hardness.” Table 1 is based on published information from the Caterpillar Performance Handbook (Caterpillar, 2018) , as well as our experience with similar materials, and assumes that a Caterpillar D-9 dozer ripping with a single shank is used. We emphasize that the cutoffs in this classifi cation scheme are approximate and that rock characteristic, such as fracture spacing and orientation, play a significant role in determining rock quality or rippability. The rippability of a mass is also dependent on the excavation equipment used and the skill and experience of the equipment operator.
For trenching operations , the rippability values should be scaled downward. For example, velocities as low as 3,500 feet/second may indicate difficult ripping during trenching operations.
In addition, the presence of boulders, which can be troublesome in narrow trenching operations, should be anticipated.
Table 1 – Rippability Classification
Seismic P-wave Velocity Rippability
0 to 2,000 feet/second Easy
2,000 to 4,000 feet/second Moderate
4,000 to 5,500 feet/second Difficult, Possible Blasting 5,500 to 7,000 feet/second Very Difficult, Probable Blasting Greater than 7,000 feet/second Blasting Generally Required
It should be noted that the rippability cutoffs presented in Table 1 are slightly more conservative than those published in the Caterpillar Performance Handbook. Accordingly, the above classification scheme should be used with discretion, and contractors should not be relieved of making their own independent evaluation of the rippability of the on-site materials prior to submitting their bids.
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5. DATA ANALYSIS
The collected data was processed using SIPwin (Rimrock Geophysics, 2003), a seismic interpretation program, and analyzed using SeisOpt Pro (Optim, 2008). SeisOpt Pro uses first arrival picks and elevation data to produce subsurface velocity models through a nonlinear optimization technique called adaptive simulated annealing. The resulting velocity model provides a tomography image of the estimated geologic conditions. Both vertical and lateral velocity information is contained in the tomography m odel. Changes in layer velocity are revealed as gradients rather than discrete contacts, which typically are more representative of actual conditions.
6. RESULTS AND CONCLUSIONS
As previously indicated, two seismic traverses were performed at your specified locations. Figures 4a and 4b present the P-wave velocity models generated from our analysis. The results from our seismic study revealed distinct layers/zones in the near surface that might represent soil overlying granitic bedrock with varying degrees of weathering. Distinct vertical and lateral velocity variations are evident in the models. These inhomogeneities are likely related to the presence of remnant boulders, intrusions, and differential weathering of the bedrock materials. It is also evident in the tomography models that the depth to bedrock is variable across the site.
Based on the refraction results, variability in the excavatability (including depth of rippability) of the subsurface materials should be expected across the project area. Furthermore, blasting may be required depending on the excavation, depth, location, equipment used, and desired rate of production. In addition, oversized materials should be expected. A contractor with excavation experience in similarly difficult conditions should be consulted for expert advice on excavation methodology, equipment, and production rate.
7. LIMITATIONS
The field evaluation and geophysical analyses presented in this report have been conducted in general accordance with current practice and the standard of care exercised by consultants performing similar tasks in the project area. No warranty, express or implied, is made regarding the conclusions, recommendations, and opinions presented in this report. There is no evaluation detailed enough to reveal every subsurface condition. Variations may exist and conditions not observed or described in this report may be present. Uncertainties relative to subsurface conditions can be reduced through additional subsurface exploration. Additional subsurface surveying will be performed upon request.
This document is intended to be used only in its entirety. No portion of the document, by itself, is designed to completely represent any aspect of the project described herein. Atlas should be contacted if the reader requires additional information or has questions regarding the content, interpretations presented, or completeness of this document. This report is intended exclusively
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for use by the client. Any use or reuse of the findings, conclusions, and/or recommendations of this report by parties other than the client is undertaken at said parties’ sole risk.
8. SELECTED REFERENCES
Caterpillar, Inc., 2018, Caterpillar Performance Handbook, Edition 48, Caterpillar, Inc., Peoria, Illinois.
Mooney, H.M., 1976, Handbook of Engineering Geophysics, dated February.
Optim, Inc., 2008, SeisOpt Pro, V-5.0.
Rimrock Geophysics, 2003, Seismic Refraction Interpretation Program (SIPwin), V-2.76.
Telford, W.M., Geldart, L.P., Sheriff, R.E., and Keys, D.A., 1976, Applied Geophysics, Cambridge University Press.
SITE LOCATION MAP
Figure 1
1244 Armorlite Drive
San Marcos, California
Project No.: 121096SWG Date: 03/21
APPROXIMATE SEISMIC
LINE LOCATIONS
W
est M
ission Road
North Las Posas Road
Figure 2
SEISMIC LINE
LOCATION MAP
Project No.: 121096SWG
1244 Armorlite Drive
San Marcos, California
Date: 03/21
approximate scale in feet
100 2000
Seismic Line
LEGEND
SL-2
1500
Figure 3
1244 Armorlite Drive
San Marcos, California
Project No.: 121096SWG Date: 03/21
SITE PHOTOGRAPHS
SL-1
SL-2
SEISMIC PROFILE
(SL-1)
Figure 4a
Project No.: 121096SWG Date: 03/21
TOMOGRAPHY MODEL
SL-1
Note: Contour Interval = 1,000 feet per second
Velocity (ft/s)
Distance (ft)
Relative Elevation (ft)
1244 Armorlite Drive
San Marcos, California
0 20 40 60 80 100 120 140 160 180 200 220 240
-40
-20
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
SL-2 Transect
SEISMIC PROFILE
(SL-2)
Figure 4b
Project No.: 121096SWG Date: 03/21
TOMOGRAPHY MODEL
SL-2
Note: Contour Interval = 1,000 feet per second
Velocity (ft/s)
Distance (ft)
Relative Elevation (ft)
1244 Armorlite Drive
San Marcos, California
0 1 02 03 04 05 06 07 08 09 0 1 0 0 1 1 0 1 2 0 1 3 0 1 4 0 1 5 0 -30
-20
-10
0 10
20 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
SL-1 Transect
APPENDIX B
RESULTS OF LABORATORY TESTING
Project Number 1‐0371 Page C‐1
March 31, 2021
ALTA CALIFORNIA GEOTECHNICAL, INC.
LABORATORY TESTING
The following laboratory tests were performed on representative samples in accordance with the applicable latest standards or methods from the ASTM, California Building Code (CBC) and California Department of Transportation.
Classification
Soils were classified with respect to the Unified Soil Classification System (USCS) in accordance with ASTM D‐2487 and D‐2488.
Particle Size Analysis
Modified hydrometer testing was conducted to aid in classification of the soil. The results of the particle size analysis are presented in Table 7‐1 and Table C.
Expansion Index Tests
One (1) expansion index test was performed to evaluate the expansion potential of typical on‐ site soil. Testing was carried out in general conformance with ASTM Test Method D‐4829. The results are presented in Table C.
Chemical Analyses
Chemical testing was performed on one select sample. The results of this test (sulfate content, resistivity, chloride content and pH) is presented on Table C.
Boring/Pit No.
Depth (Feet)
Soil Description
Group Symbol - Unified
Soil Classification System
Maximum Density (pcf)
Optimum Moisture (%)
Direct Shear
Gravel (% + No. 4 Screen)
% Sand
%Silt (0.074 to 0.005mm)
% Clay (-0.005 mm)
Expansion Index
Sulfate Content (%)
Consolidation
Other Tests Remarks
T-3 2 Bedrock (Kt) - - - - 0 56 29 15 1 ND -
Min. Resistivity: 7,600 OHM-CM
Chloride: 20ppm
PH: 6.37
TABLE C
SUMMARY OF LABORATORY TEST DATA
P.N. 1-0371
Maximum Dry Density Grain Size Analysis
Alta California Geotechnical, Inc.
APPENDIX C
GENERAL EARTHWORK GRADING GUIDELINES
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 1
GENERAL GRADING GUIDELINES
Guidelines presented herein are intended to address general construction procedures for earthwork construction. Specific situations and conditions o ften arise which cannot reasonably be discussed in general guidelines, when anticipated these are disc ussed in the text of the report. Often unanticipated conditions are encountered which may necessitate modification or changes to these guidelines. It is our hope that these will assist the contractor to more efficiently complete the project by providing a reasonable understanding of the procedures that would be expected during earthwork and the testing and observation used to evaluate those procedures.
General
Grading should be performed to at least the minimum requirements of governing agencies, the California Building Code, CBC (2022) and the guidelines presented below.
Preconstruction Meeting
A preconstruction meeting should be held prior to site earthwork. Any questions the contractor has regarding our recommendations, general site conditi ons, apparent discrepancies between reported and actual conditions and/or differences in procedu res the contractor intends to use should be brought up at that meeting. The contractor (including the main onsite representative) should review our report and these guidelines in advance of the m eeting. Any comments the contractor may have regarding these guidelines should be brought up at that meeting.
Grading Observation and Testing
1. Observation of the fill placement should be provide d by our representative during grading.
Verbal communication during the course of each day will be used to inform the contractor of test results. The contractor should receive a copy of the "Daily Field Report" indicating results of field density tests that day. If our re presentative does not provide the contractor with these reports, our office should be notified.
2. Testing and observation procedures are, by their na ture, specific to the work or area observed and location of the tests taken, variabili ty may occur in other locations. The contractor is responsible for the uniformity of the grading operations; our observations and test results are intended to evaluate the contracto r’s overall level of efforts during grading.
The contractor’s personnel are the only individuals participating in all aspect of site work.
Compaction testing and observation should not be co nsidered as relieving the contractor’s responsibility to properly compact the fill.
3. Cleanouts, processed ground to receive fill, key ex cavations, and subdrains should be observed by our representative prior to placing any fill. It will be the contractor's responsibility to notify our representative or offi ce when such areas are ready for observation.
4. Density tests may be made on the surface material to receive fill, as considered warranted by this firm.
5. In general, density tests would be made at maximum intervals of two feet of fill height or every 1,000 cubic yards of fill placed. Criteria w ill vary depending on soil conditions and size of the fill. More frequent testing may be performe d. In any case, an adequate number of field density tests should be made to evaluate the required compaction and moisture content is generally being obtained.
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6. Laboratory testing to support field test procedures will be performed, as considered warranted, based on conditions encountered (e.g. ch ange of material sources, types, etc.) Every effort will be made to process samples in the laboratory as quickly as possible and in progress construction projects are our first priori ty. However, laboratory workloads may cause in delays and some soils may require a minimum of 48 to 72 hours to complete test procedures . Whenever possible, our representative(s) should be informed in advance of operational changes that might result in different source areas for materials.
7. Procedures for testing of fill slopes are as follows:
a) Density tests should be taken periodically during grading on the flat surface of the fill, three to five feet horizontally from the face of the slope. b) If a method other than over building and cutting back to the compacted core is to be employed, slope compaction testing during construct ion should include testing the outer six inches to three feet in the slope face to determine if the required compaction is being achieved.
8. Finish grade testing of slopes and pad surfaces sho uld be performed after construction is complete.
Site Clearing
1. All vegetation, and other deleterious materials, sh ould be removed from the site. If material is not immediately removed from the site it should be stockpiled in a designated area(s) well outside of all current work areas and delineated wi th flagging or other means. Site clearing should be performed in advance of any grading in a specific area.
2. Efforts should be made by the contractor to remove all organic or other deleterious material from the fill, as even the most diligent efforts ma y result in the incorporation of some materials. This is especially important when gradi ng is occurring near the natural grade. All equipment operators should be aware of these effort s. Laborers may be required as root pickers.
3. Nonorganic debris or concrete may be placed in deep er fill areas provided the procedures used are observed and found acceptable by our repre sentative. Typical procedures are similar to those indicated on Plate G-4.
Treatment of Existing Ground
1. Following site clearing, all surficial deposits of alluvium and colluvium as well as weathered or creep effected bedrock, should be removed (see Plat es G-1, G-2 and G-3) unless otherwise specifically indicated in the text of this report.
2. In some cases, removal may be recommended to a spec ified depth (e.g. flat sites where partial alluvial removals may be sufficient). The contractor should not exceed these depths unless directed otherwise by our representative.
3. Groundwater existing in alluvial areas may make exc avation difficult. Deeper removals than indicated in the text of the report may be necessary due to saturation during winter months.
4. Subsequent to removals, the natural ground should b e processed to a depth of six inches, moistened to near optimum moisture conditions and compacted to fill standards.
5. Exploratory back hoe or dozer trenches still remain ing after site removal should be excavated and filled with compacted fill if they can be located.
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Page C - 3
Subdrainage
1. Subdrainage systems should be provided in canyon bo ttoms prior to placing fill, and behind buttress and stabilization fills and in other areas indicated in the report. Subdrains should conform to schematic diagrams G-1 and G-5, and be acceptable to our representative.
2. For canyon subdrains, runs less than 500 feet may use six-inch pipe. Typically, runs in excess of 500 feet should have the lower end as eight-inch minimum.
3. Filter material should be clean, 1/2 to 1-inch gravel wrapped in a suitable filter fabric. Class 2 permeable filter material per California Department of Transportation Standards tested by this office to verify its suitability, may be used without filter fabric. A sample of the material should be provided to the Soils Engineer by the con tractor at least two working days before it is delivered to the site. The filter should be clean with a wide range of sizes.
4. Approximate delineation of anticipated subdrain loc ations may be offered at 40-scale plan review stage. During grading, this office would ev aluate the necessity of placing additional drains.
5. All subdrainage systems should be observed by our r epresentative during construction and prior to covering with compacted fill.
6. Subdrains should outlet into storm drains where pos sible. Outlets should be located and protected. The need for backflow preventers should be assessed during construction.
7. Consideration should be given to having subdrains located by the project surveyors.
Fill Placement
1. Unless otherwise indicated, all site soil and bedro ck may be reused for compacted fill; however, some special processing or handling may be required (see text of report).
2. Material used in the compacting process should be e venly spread, moisture conditioned, processed, and compacted in thin lifts six (6) to e ight (8) inches in compacted thickness to obtain a uniformly dense layer. The fill should be placed and compacted on a nearly horizontal plane, unless otherwise found acceptable by our representative.
3. If the moisture content or relative density varies from that recommended by this firm, the contractor should rework the fill until it is in accordance with the following:
a) Moisture content of the fill should be at or above optimum moisture. Moisture should be evenly distributed without wet and dry po ckets. Pre-watering of cut or removal areas should be considered in addition to w atering during fill placement, particularly in clay or dry surficial soils. The a bility of the contractor to obtain the proper moisture content will control production rates.
b) Each six-inch layer should be compacted to at least 90 percent of the maximum dry density in compliance with the testing method speci fied by the controlling governmental agency. In most cases, the testing me thod is ASTM Test Designation D 1557.
4. Rock fragments less than eight inches in diameter may be utilized in the fill, provided:
a) They are not placed in concentrated pockets;
b) There is a sufficient percentage of fine-grained material to surround the rocks; c) The distribution of the rocks is observed by, and acceptable to, our representative.
5. Rocks exceeding eight (8) inches in diameter should be taken off site, broken into smaller fragments, or placed in accordance with recommendat ions of this firm in areas designated suitable for rock disposal (see Plate G-4). On pro jects where significant large quantities of oversized materials are anticipated, alternate guid elines for placement may be included. If
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 4
significant oversize materials are encountered during construction, these guidelines should be requested.
6. In clay soil, dry or large chunks or blocks are com mon. If in excess of eight (8) inches minimum dimension, then they are considered as over sized. Sheepsfoot compactors or other suitable methods should be used to break up b locks. When dry, they should be moisture conditioned to provide a uniform condition with the surrounding fill.
Slope Construction
1. The contractor should obtain a minimum relative com paction of 90 percent out to the finished slope face of fill slopes. This may be ac hieved by either overbuilding the slope and cutting back to the compacted core, or by direct co mpaction of the slope face with suitable equipment.
2. Slopes trimmed to the compacted core should be over built by at least three (3) feet with compaction efforts out to the edge of the false slo pe. Failure to properly compact the outer edge results in trimming not exposing the compacted core and additional compaction after trimming may be necessary.
3. If fill slopes are built "at grade" using direct compaction methods, then the slope construction should be performed so that a constant gradient is maintained throughout construction. Soil should not be "spilled" over the slope face nor sho uld slopes be "pushed out" to obtain grades. Compaction equipment should compact each l ift along the immediate top of slope.
Slopes should be back rolled or otherwise compacted at approximately every 4 feet vertically as the slope is built.
4. Corners and bends in slopes should have special att ention during construction as these are the most difficult areas to obtain proper compaction.
5. Cut slopes should be cut to the finished surface. Excessive undercutting and smoothing of the face with fill may necessitate stabilization.
Keyways, Buttress and Stabilization Fills
Keyways are needed to provide support for fill slope and various corrective procedures.
1. Side-hill fills should have an equipment-width key at their toe excavated through all surficial soil and into competent material and tilted back in to the hill (Plates G-2, G-3). As the fill is elevated, it should be benched through surficial so il and slopewash, and into competent bedrock or other material deemed suitable by our re presentatives (See Plates G-1, G-2, and G-3).
2. Fill over cut slopes should be constructed in the following manner:
a) All surficial soils and weathered rock materials sh ould be removed at the cut-fill interface.
b) A key at least one and one-half (1.5) equipment wid th wide (or as needed for compaction), and tipped at least one (1) foot into slope, should be excavated into competent materials and observed by our representative. c) The cut portion of the slope should be excavated prior to fill placement to evaluate if stabilization is necessary. The contractor should be responsible for any additional earthwork created by placing fill prior to cut exca vation. (see Plate G-3 for schematic details.)
3. Daylight cut lots above descending natural slopes m ay require removal and replacement of the outer portion of the lot. A schematic diagram for this condition is presented on Plate G-
2. GENERAL GRADING GUIDELINES APPENDIX C
Page C - 5
4. A basal key is needed for fill slopes extending ove r natural slopes. A schematic diagram for this condition is presented on Plate G-2.
5. All fill slopes should be provided with a key unles s within the body of a larger overall fill mass. Please refer to Plate G-3 for specific guidelines.
Anticipated buttress and stabilization fills are di scussed in the text of the report. The need to stabilize other proposed cut slopes will be evaluat ed during construction. Plate G-5 shows a schematic of buttress construction.
1. All backcuts should be excavated at gradients of 1: 1 or flatter. The backcut configuration should be determined based on the design, exposed c onditions, and need to maintain a minimum fill width and provide working room for the equipment.
2. On longer slopes, backcuts and keyways should be ex cavated in maximum 250 feet long segments. The specific configurations will be determined during construction.
3. All keys should be a minimum of two (2) feet deep a t the toe and slope toward the heel at least one foot or two (2%) percent, whichever is greater.
4. Subdrains are to be placed for all stabilization sl opes exceeding 10 feet in height. Lower slopes are subject to review. Drains may be requir ed. Guidelines for subdrains are presented on Plate G-5.
5. Benching of backcuts during fill placement is required.
Lot Capping
1. When practical, the upper three (3) feet of materia l placed below finish grade should be comprised of the least expansive material available . Preferably, highly and very highly expansive materials should not be used. We will at tempt to offer advice based on visual evaluations of the materials during grading, but it must be realized that laboratory testing is needed to evaluate the expansive potential of soil. Minimally, this testing takes two (2) to four (4) days to complete.
2. Transition lots (cut and fill) both per plan and th ose created by remedial grading (e.g. lots above stabilization fills, along daylight lines, ab ove natural slopes, etc.) should be capped with a minimum three foot thick compacted fill blanket.
3. Cut pads should be observed by our representative(s ) to evaluate the need for overexcavation and replacement with fill. This may be necessary to reduce water infiltration into highly fractured bedrock or other permeable zo nes, and/or due to differing expansive potential of materials beneath a structure. The ov erexcavation should be at least three feet.
Deeper overexcavation may be recommended in some cases.
ROCK PLACEMENT AND ROCK FILL GUIDELINES
If large quantities of oversize material would be g enerated during grading, it’s likely that such materials may require special handling for burial. Although alternatives may be developed in the field, the following methods of rock disposal are recommended on a preliminary basis.
Limited Larger Rock
When materials encountered are principally soil wit h limited quantities of larger rock fragments or boulders, placement in windrows is recommended. The following procedures should be applied:
1. Oversize rock (greater than 8 inches) should be placed in windrows. a) Windrows are rows of single file rocks placed to avoid nesting or clusters of rock.
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Page C - 6
b) Each adjacent rock should be approximately the same size (within ~one foot in diameter).
c) The maximum rock size allowed in windrows is four feet
2. A minimum vertical distance of three feet between l ifts should be maintained. Also, the windrows should be offset from lift to lift. Rock windrows should not be closer than 15 feet to the face of fill slopes and sufficient space mus t be maintained for proper slope construction (see Plate G-4).
3. Rocks greater than eight inches in diameter should not be placed within seven feet of the finished subgrade for a roadway or pads and should be held below the depth of the lowest utility. This will allow easier trenching for utility lines.
4. Rocks greater than four feet in diameter should be broken down, if possible, or they may be placed in a dozer trench. Each trench should be ex cavated into the compacted fill a minimum of one foot deeper than the largest diameter of rock. a) The rock should be placed in the trench and granula r fill materials (SE>30) should be flooded into the trench to fill voids around the rock.
b) The over size rock trenches should be no closer tog ether than 15 feet from any slope face.
c) Trenches at higher elevation should be staggered an d there should be a minimum of four feet of compacted fill between the top of the one trench and the bottom of the next higher trench.
d) It would be necessary to verify 90 percent relative compaction in these pits. A 24 to 72 hour delay to allow for water dissipation should be anticipated prior to additional fill placement.
Structural Rock Fills
If the materials generated for placement in structural fills contains a significant percentage of mate rial more than six (6) inches in one dimension, then pla cement using conventional soil fill methods with isolated windrows would not be feasible. In such cases the following could be considered:
1. Mixes of large rock or boulders may be placed as ro ck fill. They should be below the depth of all utilities both on pads and in roadways and b elow any proposed swimming pools or other excavations. If these fills are placed withi n seven (7) feet of finished grade, they may affect foundation design.
2. Rock fills are required to be placed in horizontal layers that should not exceed two feet in thickness, or the maximum rock size present, which ever is less . All rocks exceeding two feet should be broken down to a small er size, windrowed (see above), or disposed of in non-structural fill areas. Localized larger rock up to 3 feet in largest dimension may be placed in rock fill as follows:
a) individual rocks are placed in a given lift so as t o be roughly 50% exposed above the typical surface of the fill ,
b) loaded rock trucks or alternate compactors are worked around the rock on all sides to the satisfaction of the soil engineer,
c) the portion of the rock above grade is covered with a second lift.
3. Material placed in each lift should be well graded. No unfilled spaces (voids) should be permitted in the rock fill.
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Page C - 7
Compaction Procedures
Compaction of rock fills is largely procedural. Th e following procedures have been found to generally produce satisfactory compaction.
1. Provisions for routing of construction traffic over the fill should be implemented. a) Placement should be by rock trucks crossing the lif t being placed and dumping at its edge.
b) The trucks should be routed so that each pass acros s the fill is via a different path and that all areas are uniformly traversed.
c) The dumped piles should be knocked down and spread by a large dozer (D-8 or larger suggested). (Water should be applied before and during spreading.)
2. Rock fill should be generously watered (sluiced)
a) Water should be applied by water trucks to the:
i) dump piles,
ii) front face of the lift being placed and,
iii) surface of the fill prior to compaction.
b) No material should be placed without adequate water. c) The number of water trucks and water supply should be sufficient to provide constant water.
d) Rock fill placement should be suspended when water trucks are unavailable:
i) for more than 5 minutes straight, or,
ii) for more than 10 minutes/hour.
3. In addition to the truck pattern and at the discret ion of the soil engineer, large, rubber tired compactors may be required.
a) The need for this equipment will depend largely on the ability of the operators to provide complete and uniform coverage by wheel rolling with the trucks. b) Other large compactors will also be considered by t he soil engineer provided that required compaction is achieved.
4. Placement and compaction of the rock fill is largel y procedural. Observation by trenching should be made to check:
a) the general segregation of rock size,
b) for any unfilled spaces between the large blocks, and c) the matrix compaction and moisture content.
5. Test fills may be required to evaluate relative com paction of finer grained zones or as deemed appropriate by the soil engineer.
a) A lift should be constructed by the methods proposed, as proposed
6. Frequency of the test trenching is to be at the dis cretion of the soil engineer. Control areas may be used to evaluate the contractor’s procedures.
7. A minimum horizontal distance of 15 feet should be maintained from the face of the rock fill and any finish slope face. At least the outer 15 f eet should be built of conventional fill materials.
Piping Potential and Filter Blankets
Where conventional fill is placed over rock fill, t he potential for piping (migration) of the fine gra ined material from the conventional fill into rock fills will need to be addressed.
The potential for particle migration is related to the grain size comparisons of the materials present and in contact with each other. Provided that 15 p ercent of the finer soil is larger than the effecti ve
GENERAL GRADING GUIDELINES APPENDIX C
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pore size of the coarse soil, then particle migrati on is substantially mitigated. This can be accomplished with a well-graded matrix material for the rock fill and a zone of fill similar to the matrix above it. The specific gradation of the fil l materials placed during grading must be known to evaluate the need for any type of filter that may b e necessary to cap the rock fills. This, unfortunately, can only be accurately determined during construction.
In the event that poorly graded matrix is used in t he rock fills, properly graded filter blankets 2 to 3 feet thick separating rock fills and conventional f ill may be needed. As an alternative, use of two layers of filter fabric (Mirafi 700 x or equivalent ) could be employed on top of the rock fill. In or der to mitigate excess puncturing, the surface of the r ock fill should be well broken down and smoothed prior to placing the filter fabric. The first laye r of the fabric may then be placed and covered with relatively permeable fill material (with respect to overlying material) 1 to 2 feet thick. The relati ve permeable material should be compacted to fill stan dards. The second layer of fabric should be placed and conventional fill placement continued.
Subdrainage
Rock fill areas should be tied to a subdrainage sys tem. If conventional fill is placed that separates the rock from the main canyon subdrain, then a secondar y system should be installed. A system consisting of an adequately graded base (3 to 4 per cent to the lower side) with a collector system and outlets may suffice.
Additionally, at approximately every 25 foot vertic al interval, a collector system with outlets should be placed at the interface of the rock fill and the conventional fill blanketing a fill slope.
Monitoring
Depending upon the depth of the rock fill and other factors, monitoring for settlement of the fill areas may be needed following completion of grading . Typically, if rock fill depths exceed 40 feet, monitoring would be recommend prior to construction of any settlement sensitive improvements.
Delays of 3 to 6 months or longer can be expected prior to the start of construction.
UTILITY TRENCH CONSTRUCTION AND BACKFILL
Utility trench excavation and backfill is the contr actor’s responsibility. The geotechnical consultan t typically provides periodic observation and testing of these operations. While efforts are made to make sufficient observations and tests to verify th at the contractors’ methods and procedures are adequate to achieve proper compaction, it is typica lly impractical to observe all backfill procedures.
As such, it is critical that the contractor use consistent backfill procedures.
Compaction methods vary for trench compaction and e xperience indicates many methods can be successful. However, procedures that “worked” on p revious projects may or may not prove effective on a given site. The contractor(s) shoul d outline the procedures proposed, so that we may discuss them prior to construction. We will offer comments based on our knowledge of site conditions and experience.
1. Utility trench backfill in slopes, structural areas , in streets and beneath flat work or hardscape should be brought to at least optimum moi sture and compacted to at least 90 percent of the laboratory standard. Soil should be moisture conditioned prior to placing in the trench.
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 9
2. Flooding and jetting are not typically recommended or acceptable for native soils. Flooding or jetting may be used with select sand having a Sa nd Equivalent (SE) of 30 or higher. This is typically limited to the following uses:
a) shallow (12 + inches) under slab interior trenches and, b) as bedding in pipe zone.
The water should be allowed to dissipate prior to pouring slabs or completing trench compaction.
3. Care should be taken not to place soils at high moi sture content within the upper three feet of the trench backfill in street areas, as overly w et soils may impact subgrade preparation.
Moisture may be reduced to 2% below optimum moistur e in areas to be paved within the upper three feet below sub grade.
4. Sand backfill should not be allowed in exterior tre nches adjacent to and within an area extending below a 1:1 projection from the outside b ottom edge of a footing, unless it is similar to the surrounding soil.
5. Trench compaction testing is generally at the discr etion of the geotechnical consultant.
Testing frequency will be based on trench depth and the contractor’s procedures. A probing rod would be used to assess the consistency of comp action between tested areas and untested areas. If zones are found that are consid ered less compact than other areas, this would be brought to the contractor’s attention.
JOB SAFETY
General
Personnel safety is a primary concern on all job si tes. The following summaries are safety considerations for use by all our employees on mult i-employer construction sites. On ground personnel are at highest risk of injury and possibl e fatality on grading construction projects. The company recognizes that construction activities wil l vary on each site and that job site safety is the contractor's responsibility. However, it is, imper ative that all personnel be safety conscious to avo id accidents and potential injury.
In an effort to minimize risks associated with geot echnical testing and observation, the following precautions are to be implemented for the safety of our field personnel on grading and construction projects.
1. Safety Meetings: Our field personnel are directed t o attend the contractor's regularly scheduled safety meetings.
2. Safety Vests: Safety vests are provided for and are to be worn by our personnel while on the job site.
3. Safety Flags: Safety flags are provided to our fiel d technicians; one is to be affixed to the vehicle when on site, the other is to be placed atop the spoil pile on all test pits.
In the event that the contractor's representative o bserves any of our personnel not following the above, we request that it be brought to the attention of our office.
Test Pits Location, Orientation and Clearance
The technician is responsible for selecting test pi t locations. The primary concern is the technician 's safety. However, it is necessary to take sufficient tests at various locations to obtain a representative sampling of the fill. As such, efforts will be mad e to coordinate locations with the grading contractors authorized representatives (e.g. dump m an, operator, supervisor, grade checker, etc.),
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 10
and to select locations following or behind the est ablished traffic pattern, preferably outside of current traffic. The contractors authorized repres entative should direct excavation of the pit and safety during the test period. Again, safety is the paramount concern.
Test pits should be excavated so that the spoil pil e is placed away from oncoming traffic. The technician's vehicle is to be placed next to the te st pit, opposite the spoil pile. This necessitates that the fill be maintained in a drivable condition. Alternatively, the contractor may opt to park a piece of equipment in front of test pits, particularly in small fill areas or those with limited access.
A zone of non-encroachment should be established fo r all test pits (see diagram below). No grading equipment should enter this zone during the test pr ocedure. The zone should extend outward to the sides approximately 50 feet from the center of the test pit and 100 feet in the direction of traff ic flow. This zone is established both for safety and to avoid excessive ground vibration, which typically decreases test results.
50 ft Zone of
Non-Encroachment
50 ft Zone of
Non-Encroachment
Traffic Direction
Vehicle
parked here Test Pit Spoil
pile
Spoil
pile
Test Pit
SIDE VIEW
PLAN VIEW
TEST PIT SAFETY PLAN
10 0 ft Zone of
Non-Encroachment
Slope Tests
When taking slope tests, the technician should park their vehicle directly above or below the test location on the slope. The contractor's representative should effectively keep all equipment at a safe operation distance (e.g. 50 feet) away from the slope during testing.
The technician is directed to withdraw from the active portion of the fill as soon as possible following testing. The technician's vehicle should be parked at the perimeter of the fill in a highly visible location.
Trench Safety
It is the contractor's responsibility to provide sa fe access into trenches where compaction testing is needed. Trenches for all utilities should be excav ated in accordance with CAL-OSHA and any other applicable safety standards. Safe conditions will be required to enable compaction testing of the trench backfill.
GENERAL GRADING GUIDELINES APPENDIX C
Page C - 11
All utility trench excavations in excess of 5 feet deep, which a person enters, are to be shored or laid back. Trench access should be provided in accordan ce with OSHA standards. Our personnel are directed not to enter any trench by being lowered or "riding down" on the equipment.
Our personnel are directed not to enter any excavation which;
1. is 5 feet or deeper unless shored or laid back,
2. exit points or ladders are not provided,
3. displays any evidence of instability, has any loose rock or other debris which could fall into the trench, or
4. displays any other evidence of any unsafe conditions regardless of depth.
If the contractor fails to provide safe access to t renches for compaction testing, our company policy requires that the soil technician withdraws and not ifies their supervisor. The contractor’s representative will then be contacted in an effort to affect a solution. All backfill not tested due to safety concerns or other reasons is subject to reprocessing and/or removal.
Procedures
In the event that the technician's safety is jeopardized or compromised as a result of the contractor's failure to comply with any of the above, the technician is directed to inform both the developer's and contractor's representatives. If the condition is not rectified, the technician is required, by compa ny policy, to immediately withdraw and notify their su pervisor. The contractor’s representative will then be contacted in an effort to affect a solution . No further testing will be performed until the situation is rectified. Any fill placed in the int erim can be considered unacceptable and subject to reprocessing, recompaction or removal.
In the event that the soil technician does not comp ly with the above or other established safety guidelines, we request that the contractor bring th is to technician’s attention and notify our project manager or office. Effective communication and coo rdination between the contractors' representative and the field technician(s) is stron gly encouraged in order to implement the above safety program and safety in general.
The safety procedures outlined above should be disc ussed at the contractor's safety meetings. This will serve to inform and remind equipment operators of these safety procedures particularly the zone of non-encroachment.
The safety procedures outlined above should be disc ussed at the contractor's safety meetings. This will serve to inform and remind equipment operators of these safety procedures particularly the zone of non-encroachment.
1384 Poinsettia Avenue, Suite A
Vista, California 92083
TYPICAL CANYON
CLEANOUT
STANDARD GRADING
GUIDELINES
ALTERNATES
Original Ground
3’
Loose Surface Materials
PLATE G-1
Finish Grade
3’
Suitable
Material
Suitable
Material
6” Perforated Pipe in 9 cubic feet per Lineal
Foot Clean Gravel Wrapped in Filter Fabric
Construct Benches
where slope exceeds 5:1
Bottom of Cleanout to Be At
Least 1.5 Times the Width of
Compaction Equipment
4 feet typical
Slope to Drain
Original Ground
Loose Surface Materials
Finish Grade
Suitable
MaterialConstruct Benches
where slope exceeds 5:1
Bottom of Cleanout to Be At
Least 1.5 Times the Width of
Compaction Equipment
4 feet typical
Slope to Drain
6” Perforated Pipe in 9 cubic feet
per Lineal Foot Clean Gravel
Wrapped in Filter Fabric
TREATMENT ABOVE
NATURAL SLOPES
STANDARD GRADING
GUIDELINES
TYPICAL FILL SLOPE OVER
NATURAL DESCENDING SLOPE
Topsoil
Bedrock
PLATE G-2
Finish Grade
Fill Slope
Daylight Cut
Line per Plan
Project Removal
at 1 to 1
Min. 3 Feet
Compacted Fill
Colluvium
Creep Zone
Minimum 15 Feet Wide
or 1.5 Equipment
Widths for Compaction
Toe of Fill Slope
per Plan
DAYLIGHT CUT AREA OVER
NATURAL DESCENDING SLOPE
Topsoil
Structural Setback
Without Corrective Work
Project Removal
at 1 to 1
Colluvium
Creep Zone
Min.
2 Feet
Minimum 15 Feet Wide
or 1.5 Equipment
Widths for Compaction
Finish Grade
Bedrock
Min. 3 Feet
Compacted Fill
Min.
2 Feet
Compacted Fill
Compacted Fill
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
Topsoil
Colluvium
Creep Zone
COMMON FILL
SLOPE KEYS
STANDARD GRADING
GUIDELINES
TYPICAL FILL SLOPE OVER
CUT SLOPE
Topsoil
Bedrock
PLATE G-3
Finish Grade
2: 1 Fill Slope
4’ Typical
Colluvium
Creep Zone
Minimum 15 Feet Wide
or 1.5 Equipment
Widths for Compaction
Toe of Fill Slope
per Plan
TYPICAL FILL SLOPE
Bedrock or
Suitable Dense Material
Minimum compacted fill required
to provide lateral support.
Excavate key if width or depth
less than indicated in table above
Cut Slope
SLOPE
HEIGHT
MIN. KEY
WIDTH
MIN. KEY
DEPTH
5 10
15 20
25 >25
7 10
15 15
15 SEE TEXT
1 1.5
2 2.5
3 CONTRACTOR TO VERIFY
WITH SOIL ENGINEER
PRIOR TO CONSTRUCTION
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
NOTES:
1) SOIL FILL OVER WINDROW SHOULE BE 7 FEET OR PER JURISDUICTIONAL STANDARDS AND SUFFICIENT
FOR FUTURE EXCAVATIONS TO AVOID ROCKS
2) MAXIMUM ROCK SIZE IN WINDROWS IS 4 FEET MINIMUM DIAMETER 3) SOIL AROUND WINDROWS TO BE SANDY MATERIAL SUBJECT TO SOIL ENGINEER ACCEPTANCE 4) SPACING AND CLEARANCES MUST BE SUFFICIENT TO ALLOW FOR PROPER COMPACTION 5) INDIVDUAL LARGE ROCKS MAY BE BURIED IN PITS.
ROCK BURIAL
DETAILS
STANDARD GRADING
GUIDELINES
PLATE G-4
SEE NOTE 1
15’
MIN.
3’ MIN.
3’ MIN.
MINIMUM 15’ CLEAR OR
1.5 EQUIPMENT WIDTHS
FOR COMPACTION
STAGGER ROWS
HORIZONTALLY
NO ROCKS IN
THIS ZONE
CROSS SECTIONAL VIEW
FINISH GRADE
FILL SLOPE
PLAN VIEW
FILL SLOPE
MINIMUM 15’ CLEAR OR 1.5 EQUIPMENT
WIDTHS FOR COMPACTION
MINIMUM 15’ CLEAR OR 1.5 EQUIPMENT
WIDTHS FOR COMPACTION
PLACE ROCKS END TO END
DO NOT PILE OR STACK ROCKS
SOIL TO BE PLACE AROUND AND OVER ROCKS THEN FLOODED INTO VOIDS. MUST COMPACT AROUND AND OVER EACH ROCK WINDROW
1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505
6” Perforated Pipe in 6 cubic
feet per lineal foot clean gravel
wrapped in filter fabric outlet
pipe to gravity flow
BEDROCK COMPACTED FILL
MIN. 3 FEET
COMPACTED FILL
TERRACE DRAIN
AS REQUIRED
2 1
MIN. 15 FEET WIDE OR 1.5 EQUIPMENT
WIDTHS FOR COMPACTION
MIN. 2 FEET
EMBEDDMENT
1384 Poinsettia Avenue, Suite A
Vista, California 92083
Typical Buttress and
Stabilization Fill PLATE G-5
4” or 6” Perforated Pipe in 6 cubic
feet per lineal foot clean gravel
wrapped in filter fabric outlet pipe
to gravity flow at 2% min.
TRANSITION &
UNDERCUT LOTS PLATE G-6
TRANSITION LOT
PROPSED FINISH GRADE
COMPETENT MATERIAL
4’ MIN.
OVEREXCAVATE AND
RECOMPACT
PROPOSED STRUCTURE
COMPACTED FILL
3 1
OVEREXCAVATION AND BENCHING NOT
TO EXCEED INCLINATION OF 3:1 (H:V)
UNDERCUT LOT
PROPSED FINISH GRADE
PROPOSED STRUCTURE
4’ MIN.
COMPETENT MATERIAL
COMPACTED FILL
OVEREXCAVATE AND
RECOMPACT
OVEREXCAVATION TO HAVE 1%
FALL TOWARD FRONT OF LOT
Notes:
1. Removed/overexcavated soils should be recompacted in accordance with recommendations included in the text of the report.
2. Location of cut/fill transition should verified in the field during site grading.
STANDARD GRADING
GUIDELINES1384 Poinsettia Avenue, Suite A
Vista, California 92081-8505