ATTACHMENT D
ENVIRONMENTAL IMPACT REPORT
APPENDIX E
PRELIMINARY GEOTECHNICAL EVALUATION
APPENDIX E
Preliminary Geotechnical Evaluation
PRELIMINARY
GEOTECHNICAL INVESTIGATION
HUGHES CIRCUITS
SOUTH PACIFIC STREET
SAN MARCOS, CALIFORNIA
PREPARED FOR
OCTOBER 1, 2021
PROJECT NO. G2803-52-01
Project No. G2803-52-01
October 1, 2021
Hughes Circuits, Incorporated
546 South Pacific Street
San Marcos, California 92078
Attention: Mr. Joe Hughes
Subject: PRELIMINARY GEOTECHNICAL INVESTIGATION
HUGHES CIRCUITS
SOUTH PACIFIC STREET
SAN MARCOS, CALIFORNIA
Dear Mr. Hughes:
In accordance with your request and authorization of our Proposal No. LG-21353 dated July 21, 2021, we herein submit the results of our preliminary geotechnical investigation for the subject project. We performed our investigation to evaluate the underlying soil and geologic conditions and potential geologic hazards, and to assist in the design of the proposed commercial building and associated improvements.
The accompanying report presents the results of our study and conclusions and recommendations pertaining to geotechnical aspects of the proposed project. The site is suitable for the proposed building and improvements provided the recommendations of this report are incorporated into the design and construction of the planned project.
Should you have questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Kenneth Haase
Senior Staff Geologist
Shawn Foy Weedon
GE 2714
John Hoobs
CEG 1524
KH:SFW:JH:arm
(e-mail) Addressee
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ................................................................................................................. 1
2. SITE AND PROJECT DESCRIPTION ........................................................................................... 2
3. GEOLOGIC SETTING .................................................................................................................... 4
4. SOIL AND GEOLOGIC CONDITIONS ........................................................................................ 5
4.1 Undocumented Fill (Qudf) .................................................................................................... 5
4.2 Alluvium (Qal and Qya) ........................................................................................................ 5
4.3 Santiago Formation (Tsa) ...................................................................................................... 5
5. GROUNDWATER .......................................................................................................................... 6
6. GEOLOGIC HAZARDS ................................................................................................................. 6
6.1 Regional Faulting and Seismicity .......................................................................................... 6
6.2 Ground Rupture ..................................................................................................................... 8
6.3 Liquefaction ........................................................................................................................... 8
6.4 Storm Surge, Tsunamis, and Seiches ..................................................................................... 8
6.5 Landslides .............................................................................................................................. 8
6.6 Erosion ................................................................................................................................... 9
7. CONCLUSIONS AND RECOMMENDATIONS ......................................................................... 10
7.1 General ................................................................................................................................. 10
7.2 Excavation and Soil Characteristics .................................................................................... 11
7.3 Grading ................................................................................................................................ 12
7.4 Subdrains ............................................................................................................................. 14
7.5 Temporary Excavations ....................................................................................................... 16
7.6 Groundwater and Dewatering .............................................................................................. 16
7.7 Seismic Design Criteria – 2019 California Building Code .................................................. 17
7.8 Shallow Foundations ........................................................................................................... 19
7.9 Concrete Slabs-On-Grade .................................................................................................... 20
7.10 Exterior Concrete Flatwork ................................................................................................. 22
7.11 Retaining Walls ................................................................................................................... 23
7.12 Lateral Loading .................................................................................................................... 27
7.13 Preliminary Pavement Recommendations ........................................................................... 27
7.14 Site Drainage and Moisture Protection ................................................................................ 31
7.15 Grading and Foundation Plan Review ................................................................................. 31
7.16 Testing and Observation Services During Construction ...................................................... 31
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Geologic Map
Figure 2, Geologic Cross Sections
APPENDIX A
FIELD INVESTIGATION
APPENDIX B
LABORATORY TESTING
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
Geocon Project No. G2803-52-01 - 1 - October 1, 2021
PRELIMINARY GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our preliminary geotechnical investigation for a new commercial building located north and east of South Pacific Street in the City of San Marcos, California as shown on the Vicinity Map.
Vicinity Map
The purpose of the preliminary geotechnical investigation is to evaluate the surface and subsurface soil conditions and general site geology, and to identify geotechnical constraints that may affect development of the property including faulting, liquefaction and seismic shaking based on the 2019 CBC seismic design criteria. In addition, this report includes recommendations for remedial grading, temporary excavations, shallow and mat foundations, concrete slab-on-grade, concrete flatwork, pavement and retaining walls.
We also reviewed the plans titled Hughes San Marcos Prelim Site Plan Option #1 & Hughes San Marcos Prelim Site Plan Rev #2, prepared by SCA Architecture, dated August 20, 2021 (Project No. 21019.S50).
The scope of this investigation included reviewing readily available published and unpublished geologic literature (see List of References), performing engineering analyses and preparing this report.
We also advanced 6 exploratory trenches to a maximum depth of about 14 feet, sampled soil and Geocon Project No. G2803-52-01 - 2 - October 1, 2021
performed laboratory testing. Appendix A presents the exploratory trench logs and details of the field investigation. The details of the laboratory tests and a summary of the test results are shown in Appendix B and on the boring logs in Appendix A.
2. SITE AND PROJECT DESCRIPTION
The property is currently undeveloped and consists of sparse to dense vegetation with minor drainages. The site is east and north of South Pacific Street and southwest of a San Diego Water Authority easement along the northeast boundary. Environmentally sensitive habitat exists to the southeast. An existing sewer line crosses the central portion of the site, as shown on the Geologic Map, Figure 1. Existing grades are relatively flat with elevations varying from approximately 524 to 532 feet Mean Sea Level (MSL) across the site. The Existing Site Plan shows the current site conditions.
Existing Site Plan
We understand the project will consist of construction of a 1-story commercial building with warehouse space and associated amenities, surface parking, landscaping and utilities. The Proposed Site Plans show two possible options for the planned building and improvements. One of the proposed plans removes the existing sewer line while the other designs the planned building to avoid the location of the existing sewer line.
Geocon Project No. G2803-52-01 - 3 - October 1, 2021
Proposed Site Plan – Option 1
Proposed Site Plan – Option 2
Geocon Project No. G2803-52-01 - 4 - October 1, 2021
The locations, site descriptions, and proposed development are based on our site reconnaissance, review of published geologic literature, field investigations, and discussions with project personnel. If development plans differ from those described herein, Geocon Incorporated should be contacted for review of the plans and possible revisions to this report.
3. GEOLOGIC SETTING
The site is located in the northeastern portion of the coastal plain within the southern portion of the Peninsular Ranges Geomorphic Province of southern California. The Peninsular Ranges is a geologic and geomorphic province that extends from the Imperial Valley to the Pacific Ocean and from the Transverse Ranges to the north and into Baja California to the south. The coastal plain of San Diego County is underlain by a thick sequence of relatively undisturbed and non-conformable sedimentary rocks that thicken to the west and range in age from Upper Cretaceous through the Pleistocene with intermittent deposition. The sedimentary units are deposited on bedrock Cretaceous to Jurassic age igneous and metavolcanic rocks. Geomorphically, the coastal plain is characterized by a series of 21, stair-stepped marine terraces (younger to the west) that have been dissected by west flowing rivers.
The coastal plain is a relatively stable block that is dissected by relatively few faults consisting of the potentially active La Nacion Fault Zone and the active Rose Canyon Fault Zone. The Peninsular Ranges Province is also dissected by the Elsinore Fault Zone that is associated with and sub-parallel to the San Andreas Fault Zone, which is the plate boundary between the Pacific and North American Plates. The site is composed of Tertiary-age sedimentary rocks consisting of the Santiago Formation.
The Regional Geologic Map shows the geologic units in the area of the site.
Regional Geologic Map
Geocon Project No. G2803-52-01 - 5 - October 1, 2021
4. SOIL AND GEOLOGIC CONDITIONS
We encountered two surficial soil units (consisting of undocumented fill and young alluvium) and one formational unit (consisting of the Santiago Formation). The occurrence, distribution, and description of each unit encountered is shown on the Geologic Map, Figure 1 and on the boring logs in Appendix A. The Geologic Cross-Sections, Figure 2, show the approximate subsurface relationship between the geologic units. We prepared the geologic cross-sections using interpolation between exploratory excavations and observations; therefore, actual geotechnical conditions may vary from those illustrated and should be considered approximate. The surficial soil and geologic units are described herein in order of increasing age.
4.1 Undocumented Fill (Qudf)
We encountered undocumented fill in trench T-2 to a depth of approximately 2 feet. In general, the fill consists of loose to medium dense, moist, silty sand and possesses a “low” to “medium” expansion index (expansion index of 20 or greater). We expect the majority of the fill is located on the southwestern portion of the site and possibly adjacent to the existing roadways. In addition, we expect undocumented fill exists over the existing sewer line that traverses the property. The undocumented fill is not considered suitable in its current condition for the support of foundations or structural fill and remedial grading will required. The undocumented fill can be reused for new compacted fill during grading operations provided if it is free of roots and debris.
4.2 Alluvium (Qal and Qya)
We encountered alluvium in all of our trenches to depths ranging between 3½ and 10 feet. The alluvial deposits typically consist of loose to medium dense, dark olive brown, silty to clayey sand with some stiff to very stiff clay and very dense gravel layers. The upper portion of the alluvium is considered unsuitable for the support of foundations or structural fills and will require remedial grading. The alluvium is considered acceptable for reuse as fill; however, some soil is saturated and will require mixing with drier material or require drying of the soil to obtain a proper moisture content during fill placement and compaction.
4.3 Santiago Formation (Tsa)
Tertiary-age Santiago Formation is present below the undocumented fill and alluvium across the site.
We encountered the Santiago Formation between 3½ and 10 feet below existing grade. The Santiago Formation consists of interbeds of dense to very dense, silty to clayey sandstone and is considered suitable for the support of proposed fill and structural loads. The presence of siltstone and claystone layers and potential BPS within this geologic unit will require slope stabilization methods within proposed cut slopes including buttresses and slope stabilization fills..
Geocon Project No. G2803-52-01 - 6 - October 1, 2021
5. GROUNDWATER
We encountered groundwater during the field investigation in our trench locations between 4 and 10 feet below existing grade as shown on Table 5 and on the Geologic Map, Figure 1. The use of dewatering techniques may be necessary if excavations below the groundwater elevation occur. It is not uncommon for groundwater or seepage conditions to develop where none previously existed.
Groundwater and seepage is dependent on seasonal precipitation, irrigation, land use, among other factors, and varies as a result. Proper surface drainage will be important to future performance of the project. We expect that groundwater levels will fluctuate depending on the rainy season.
TABLE 5
RECORDED GROUNDWATER ELEVATION
Boring No. Date Recorded
Approximate Depth of
Groundwater Below Existing
Grade (feet)
Approximate Elevation
of Groundwater (in feet
MSL)
T-1 09/01/2021 10 515
T-2 09/01/2021 7 518
T-3 09/01/2021 7 519
T-4 09/01/2021 7 518
T-5 09/01/2021 6 519
T-6 09/01/2021 4 522
6. GEOLOGIC HAZARDS
6.1 Regional Faulting and Seismicity
A review of the referenced geologic materials and our knowledge of the general area indicate that the site is not underlain by active, potentially active, or inactive faults. An active fault is defined by the California Geological Survey (CGS) as a fault showing evidence for activity within the last 11,700 years. The site is not located within a State of California Earthquake Fault Zone.
The USGS has developed a program to evaluate the approximate location of faulting in the area of properties. The following figure shows the location of the existing faulting in the San Diego County and Southern California region. The fault traces are shown as solid, dashed and dotted that represent well-constrained, moderately constrained and inferred, respectively. The fault line colors represent faults with ages less than 150 years (red), 15,000 years (orange), 130,000 years (green), 750,000 years (blue) and 1.6 million years (black).
Geocon Project No. G2803-52-01 - 7 - October 1, 2021
Faults in Southern California
The San Diego County and Southern California region is seismically active. The following figure presents the occurrence of earthquakes with a magnitude greater than 2.5 from the period of 1900 through 2015 according to the Bay Area Earthquake Alliance website.
Earthquakes in Southern California
Considerations important in seismic design include the frequency and duration of motion and the soil conditions underlying the site. Seismic design of structures should be evaluated in accordance with the California Building Code (CBC) guidelines currently adopted by the local agency.
Geocon Project No. G2803-52-01 - 8 - October 1, 2021
6.2 Ground Rupture
Ground surface rupture occurs when movement along a fault is sufficient to cause a gap or rupture where the upper edge of the fault zone intersects the ground surface. The potential for ground rupture is considered to be very low due to the absence of active faults at the subject site.
6.3 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are cohesionless or silt/clay with low plasticity, groundwater is encountered within 50 feet of the surface and soil densities are less than about 70 percent of the maximum dry densities. If the four previous criteria are met, a seismic event could result in a rapid pore water pressure increase from the earthquake-generated ground accelerations. Although groundwater is present near existing grade, liquefaction potential for the site is considered very low due to the very dense nature of the underlying Santiago Formation and the removal of the alluvium and undocumented fill.
6.4 Storm Surge, Tsunamis, and Seiches
Storm surges are large ocean waves that sweep across coastal areas when storms make landfall. Storm surges can cause inundation, severe erosion and backwater flooding along the water front. The site is located approximately 8 miles from the Pacific Ocean and is at an elevation of about 520 feet or greater above Mean Sea Level (MSL). Therefore, the potential of storm surges affecting the site is considered low.
A tsunami is a series of long period waves generated in the ocean by a sudden displacement of large volumes of water. Causes of tsunamis include underwater earthquakes, volcanic eruptions, or offshore slope failures. The potential for the site to be affected by a tsunami is negligible due to the distance from the Pacific Ocean and the site elevation.
A seiche is a run-up of water within a lake or embayment triggered by fault- or landslide-induced ground displacement. The site is located approximately a ½ mile north of Lake San Marcos but is located upstream of the body of water. Therefore, the risk of seiches affecting the site is negligible.
6.5 Landslides
We did not observe evidence of previous or incipient slope instability at the site during our study and the property is relatively flat. Published geologic mapping indicates landslides are not present on or adjacent to the site. Therefore, in our professional opinion, the potential for a landslide is not a significant concern for this project.
Geocon Project No. G2803-52-01 - 9 - October 1, 2021
6.6 Erosion
The site is relatively flat and is not located adjacent to the Pacific Ocean coast. However, the property possesses a free-flowing drainage where active erosion is occurring. Water runoff enters the site from the north and exits the site through a headwall in the southern area of the site. Erosion is occurring within the drainage and near the inlet structure on the southeast. Provided the engineering recommendations herein are followed and the project civil engineer prepares the grading plans in accordance with generally-accepted regional standards, we do not expect erosion to be a major impact to site development. In addition, we expect the proposed development would not increase the potential for erosion if properly designed.
Geocon Project No. G2803-52-01 - 10 - October 1, 2021
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 We did not encounter soil or geologic conditions during our exploration that would preclude the proposed development, provided the recommendations presented herein are followed and implemented during design and construction. We will provide supplemental recommendations if we observe variable or undesirable conditions during construction, or if the proposed construction will differ from that anticipated herein.
7.1.2 With the exception of possible moderate to strong seismic shaking, we did not observe or know of significant geologic hazards to exist on the site that would adversely affect the proposed project.
7.1.3 The undocumented fill, alluvium and upper portion of the Santiago Formation are potentially compressible and unsuitable in their present condition for the support of compacted fill or settlement-sensitive improvements. Due to the presence of groundwater close to existing grade, not all of the surficial materials may be practically removed.
Remedial grading of these materials should be performed as discussed herein. The dense portions of the Santiago Formation are considered suitable for the support of proposed fill and structural loads.
7.1.4 An existing sewer line crosses the site. We understand that if Option 1 is selected for construction, the sewer line will be removed and relocated during grading. If Option 2 is constructed, the sewer line will remain in place.
7.1.5 We encountered groundwater at a depth of approximately 4 to 10 feet below the existing ground surface (approximate elevation of 515 to 522 feet above MSL). Groundwater will likely have a significant influence on construction of utilities and during remedial grading.
Dewatering may be required for excavations near or below the fluctuating groundwater elevation and preliminary recommendations are provided herein.
7.1.6 Excavation of the undocumented fill, alluvium and Santiago Formation should generally be possible with moderate to heavy effort using conventional, heavy-duty equipment during grading and trenching operations. If encountered, we expect very heavy excavation effort will be required within localized areas of strongly cemented portions of the Santiago Formation.
7.1.7 Proper drainage should be maintained in order to preserve the engineering properties of the fill in both the building pads and slope areas. Recommendations for site drainage are provided herein.
Geocon Project No. G2803-52-01 - 11 - October 1, 2021
7.1.8 Based on our review of the preliminary project plans, we opine the planned development can be constructed in accordance with our recommendations provided herein. We do not expect the planned development will destabilize or result in settlement of adjacent properties if properly constructed.
7.1.9 Surface settlement monuments will not be required on this project.
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the in-situ soil should be possible with moderate to heavy effort using conventional heavy-duty equipment. Excavation of the formational materials may require very heavy effort during the grading operations.
7.2.2 The soil encountered in the field investigation is considered to be “non-expansive” to “expansive” (expansion index [EI] of 20 or less and greater than 20, respectively) as defined by 2019 California Building Code (CBC) Section 1803.5.3. We expect a majority of the soil encountered possess a “very low” to “medium” expansion potential (EI of 90 or less) in accordance with ASTM D 4829. Table 7.2 presents soil classifications based on the expansion index.
TABLE 7.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (EI) ASTM D 4829 Expansion
Classification
2019 CBC Expansion
Classification
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive 51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
7.2.3 We performed laboratory tests on samples of the site materials to evaluate the percentage of water-soluble sulfate content. Appendix B presents results of the laboratory water-soluble sulfate content tests. The test results indicate the on-site materials at the locations tested possess “S0” sulfate exposure to concrete structures as defined by 2019 CBC Section 1904 and ACI 318-14 Chapter 19. The presence of water-soluble sulfates is not a visually discernible characteristic; therefore, other soil samples from the site could yield different concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers and other soil nutrients) may affect the concentration.
Geocon Project No. G2803-52-01 - 12 - October 1, 2021
7.2.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, further evaluation by a corrosion engineer may be performed if improvements susceptible to corrosion are planned.
7.3 Grading
7.3.1 Grading should be performed in accordance with the recommendations provided in this report, the Recommended Grading Specifications contained in Appendix C and the City of San Marcos’s Grading Ordinance. Geocon Incorporated should observe the grading operations on a full-time basis and provide testing during the fill placement.
7.3.2 Prior to commencing grading, a preconstruction conference should be held at the site with the city inspector, developer, grading and underground contractors, civil engineer, and geotechnical engineer in attendance. Special soil handling and/or the grading plans can be discussed at that time.
7.3.3 Site preparation should begin with the removal of deleterious material, debris, and vegetation. The depth of vegetation removal should be such that material exposed in cut areas or soil to be used as fill is relatively free of organic matter. Material generated during stripping and/or site demolition should be exported from the site. Asphalt and concrete should not be mixed with the fill soil unless approved by the Geotechnical Engineer.
7.3.4 Abandoned foundations and buried utilities (if encountered) should be removed and the resultant depressions and/or trenches should be backfilled with properly compacted material as part of the remedial grading.
7.3.5 We expect the proposed 1-story building to be supported on a shallow foundation system.
The existing groundwater elevations will affect the potential remedial grading. The proposed building can be graded using the following options:
Option 1 – Full Removal: The existing surficial soils can be excavated to expose competent formational materials prior to compacted fill placement. Water would be encountered and a subdrain would need to be installed on the northern, western and eastern portions of the site to control the water.
Option 2 – Partial Removal: The upper 3 feet of the existing materials or 3 feet below proposed grade (whichever results in a deeper excavation) should be excavated prior to compacted fill placement. In addition, excavations should extend at least 2 feet below foundations and 5 feet laterally from the foundations. The base of the foundation removals Geocon Project No. G2803-52-01 - 13 - October 1, 2021
would likely require stabilization with rock and fabric prior to compacted fill placement. We expect a minimum of 12 inches of 3- to 6-inch rock would be required to stabilize the soil.
The rock would need to be installed with some compactive effort to “bridge” the underlying soft soil. The compactive effort can consist of beating the rock into the underlying soil with the bucket of an excavator. A reinforcement fabric would be required above the rock to help prevent the migration of fines (Mirafi HP370 or equivalent). Planned utility trenches should not be placed in the isolated foundation zones where rock and fabric are placed.
7.3.6 In areas of proposed improvements outside of the building areas, removals should be limited to 2 feet below existing grade or below proposed grade, whichever results in a deeper removal. The removals should extend at least 2 feet outside of the improvement area, where possible. Table 7.3.1 provides a summary of the grading recommendations.
TABLE 7.3.2
SUMMARY OF GRADING RECOMMENDATIONS
Area Removal Requirements
Proposed Building Area – Option 1 (Full
Removal)
Remove Existing Surficial Materials to Competent
Bottom and 3-Feet Below Proposed Grade,
Whichever is Deeper
Proposed Building Area – Option 2 (Partial
Removal)
Remove Upper 3 Feet of Existing Material or 3 Feet
Below Proposed Slab Grade, Whichever is Deeper.
Excavate 2 Feet Below Foundations and Stabilize
Bottom with 1 Foot of Crushed Rock
Site Development Limit Remedial Grading to 2 Below Existing Grade Grading Limits 5 Feet Outside of Foundation Zones/2 Feet Outside of Improvement Areas, Where Possible
7.3.7 The contractor should be careful during the remedial grading operations to avoid a “pumping” condition at the base of the removals. Where recompaction of the excavated bottom will result in a “pumping” condition, the bottom of the excavation should be tracked with low ground pressure earthmoving equipment prior to placing fill. If needed to improve the stability of the excavation bottoms, reinforcing fabric or 3- to 6-inch crushed rock can be placed prior to placement of compacted fill. A representative of Geocon should be on-site during removals to evaluate the limits of the remedial grading.
7.3.8 Some areas of overly wet and saturated soil could be encountered due to the existing landscape and pavement areas. The saturated soil would require additional effort prior to placement of compacted fill or additional improvements. Stabilization of the soil would include scarifying and air-drying, removing and replacement with drier soil, use of stabilization fabric (e.g. Tensar TX7 or other approved fabric), or chemical treating (i.e. cement or lime treatment).
Geocon Project No. G2803-52-01 - 14 - October 1, 2021
7.3.9 The site should then be brought to final subgrade elevations with fill compacted in layers. In general, soil native to the site is suitable for use from a geotechnical engineering standpoint as fill if relatively free from vegetation, debris and other deleterious material. However, significant drying or mixing with drier material may be required due to the existing high moisture contents. Layers of fill should be about 6 to 8 inches in loose thickness and no thicker than will allow for adequate bonding and compaction. Fill, including backfill and scarified ground surfaces, should be compacted to a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content in accordance with ASTM Test Procedure D 1557. Fill materials placed below optimum moisture content may require additional moisture conditioning prior to placing additional fill. The upper 12 inches of subgrade soil underlying pavement should be compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content shortly before paving operations.
7.3.10 Import fill (if necessary) should consist of the characteristics presented in Table 7.3.3. Geocon Incorporated should be notified of the import soil source and should perform laboratory testing of import soil prior to its arrival at the site to determine its suitability as fill material.
TABLE 7.3.3
SUMMARY OF IMPORT FILL RECOMMENDATIONS
Soil Characteristic Values
Expansion Potential “Very Low” to “Medium” (Expansion Index of 90 or less) Particle Size Maximum Dimension Less Than 3 Inches
Generally Free of Debris
7.4 Subdrains
7.4.1 Due to the presence of near surface groundwater, the design and implementation of additional drainage mechanisms may be necessary. We recommend the use of a subdrain system to divert water away/around the proposed building. A subdrain system should be installed within the high side of the site, the north corner. The subdrain should be routed around the proposed building and connected to the existing storm drain system on the south side of the site.
7.4.2 Subdrains should be at least 6-inch diameter, Schedule 40 PVC (or equivalent) and sloped at a minimum of 1 percent. The actual subdrain locations should be evaluated in the field during the remedial grading operations. The project civil engineer should survey the pipe locations and elevations after installation. Appropriate subdrain outlets should be evaluated prior to finalizing 40-scale grading plan.
Geocon Project No. G2803-52-01 - 15 - October 1, 2021
7.4.3 Prior to outletting, the final 20-foot segment of a subdrain that will not be extended during future development should consist of non-perforated drainpipe. At the non- perforated/perforated interface, a seepage cutoff wall should be constructed on the downslope side of the junction as shown herein.
Typical Cutoff Wall Detail
7.4.4 Subdrains that discharge into a natural drainage course or open space area should be provided with a permanent headwall structure as shown herein.
Typical Headwall Detail
7.4.5 The final grading plans should show the location of the proposed subdrains. Upon completion of remedial excavations and subdrain installation, the project civil engineer should survey the drain locations and prepare an “as-built” map depicting the existing conditions. The final outlet and connection locations should be determined during grading. The grading contractor should consider videoing the subdrains shortly after burial to check proper installation and to check that the pipe has not been crushed. The contractor is responsible for the performance of the drains.
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7.5 Temporary Excavations
7.5.1 The recommendations included herein are provided for stable excavations. It is the responsibility of the contractor and their competent person to ensure all excavations, temporary slopes and trenches are properly constructed and maintained in accordance with applicable OSHA guidelines in order to maintain safety and the stability of the excavations and adjacent improvements. These excavations should not be allowed to become saturated or to dry out. Surcharge loads should not be permitted to a distance equal to the height of the excavation from the top of the excavation. The top of the excavation should be a minimum of 15 feet from the edge of existing improvements. Excavations steeper than those recommended or closer than 15 feet from an existing surface improvement should be shored in accordance with applicable OSHA codes and regulations.
7.5.2 The stability of the excavations is dependent on the design and construction of the shoring system and site conditions. Therefore, Geocon Incorporated cannot be responsible for site safety and the stability of the proposed excavations.
7.6 Groundwater and Dewatering
7.6.1 We observed groundwater during site exploration at depths of approximately 4 to 10 feet below the ground surface (approximate elevations of 515 to 525 feet MSL). Table 7.6 presents the information where we encountered groundwater. Excavations near and below these elevations should be expected to encounter the groundwater table and seepage. We also expect that the groundwater level will fluctuate during the rainy season.
TABLE 7.6
RECORDED GROUNDWATER ELEVATION
Boring
No.
Date
Recorded
Approximate Depth of Groundwater
Below Existing Grade (feet)
Approximate Elevation of
Groundwater (in feet MSL)
T-1 09/01/2021 10 515
T-2 09/01/2021 7 518
T-3 09/01/2021 7 519
T-4 09/01/2021 7 518
T-5 09/01/2021 6 519
T-6 09/01/2021 4 522
7.6.2 The contractor should be prepared to accommodate seepage and/or groundwater in project excavations with one or more of the following conventional measures. Where minor seepage is encountered during excavation, sloping excavation bottoms to a sump and pumping from the sump can be utilized. In this case, an approximately 1-foot-thick layer of Geocon Project No. G2803-52-01 - 17 - October 1, 2021
freely draining gravel or crushed rock placed on the excavation bottom would help groundwater to flow toward the sump and provide a working pad.
7.6.3 If more than heavy seepage is encountered during excavation work, a dewatering system using well points should be utilized. Temporary dewatering consisting of perimeter wells with interior well points may not be completely effective due to the presence of fine-grained soils and inability of a well to produce groundwater draw-down in its vicinity. It is our opinion that if wells are ineffective, the water may be collected and controlled within the excavation through the use of gravel filled trenches (French drains). The number and locations of the French drains can be adjusted during excavation activities as necessary to collect and control encountered seepage. The French drains could then direct the collected seepage to a sump where it will be pumped out of the excavation. It is likely that due to the soft soils expected at the excavation bottom, a gravel blanket may be required for this project for stabilization. This gravel blanket may also be utilized for dewatering purposes as necessary.
7.6.4 The dewatering system should be designed by an experienced, qualified contractor and the plans should be reviewed by the contractor’s geotechnical engineer. Appropriate permits should be obtained and possible treatment may be required to discharge water generated by dewatering.
7.6.5 Following construction and completion of dewatering, groundwater flow and migration patterns should return to approximately the original direction and flow rates as a result of the proposed construction techniques.
7.7 Seismic Design Criteria – 2019 California Building Code
7.7.1 Table 7.7.1 summarizes site-specific design criteria obtained from the 2019 California Building Code (CBC; Based on the 2018 International Building Code [IBC] and ASCE 7- 16), Chapter 16 Structural Design, Section 1613 Earthquake Loads. We used the computer program U.S. Seismic Design Maps , provided by the Structural Engineers Association (SEA) to calculate the seismic design parameters. The short spectral response uses a period of 0.2 second. We evaluated the Site Class based on the discussion in Section 1613.2.2 of the 2019 CBC and Table 20.3-1 of ASCE 7-16. The values presented herein are for the risk- targeted maximum considered earthquake (MCER). Sites designated as Site Class D, E and F may require additional analyses if requested by the project structural engineer and client.
Geocon Project No. G2803-52-01 - 18 - October 1, 2021
TABLE 7.7.1
2019 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2019 CBC Reference
Site Class C Section 1613.2.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS
0.897g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1
0.331g Figure 1613.2.1(2)
Site Coefficient, FA 1.200 Table 1613.2.3(1)
Site Coefficient, FV 1.500* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response
Acceleration (short), SMS
1.077g Section 1613.2.3 (Eqn 16-36)
Site Class Modified MCER Spectral Response
Acceleration – (1 sec), SM1
0.496g* Section 1613.2.3 (Eqn 16-37)
5% Damped Design
Spectral Response Acceleration (short), SDS
0.718g Section 1613.2.4 (Eqn 16-38)
5% Damped Design
Spectral Response Acceleration (1 sec), SD1
0.331g* Section 1613.2.4 (Eqn 16-39)
*Note: Using the code-based values presented in this table, in lieu of a performing a ground motion hazard analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed by the project structural engineer. Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis should be performed for projects for Site Class “E” sites with Ss greater than or equal to 1.0g and for Site Class “D” and “E” sites with S1 greater than 0.2g. Section 11.4.8 also provides exceptions which indicates that the ground motion hazard analysis may be waived provided the exceptions are followed.
7.7.2 Table 7.7.2 presents the mapped maximum considered geometric mean (MCE G) seismic design parameters for projects located in Seismic Design Categories of D through F in accordance with ASCE 7-16.
TABLE 7.7.2
ASCE 7-16 PEAK GROUND ACCELERATION
Parameter Value ASCE 7-16 Reference
Mapped MCEG Peak Ground Acceleration, PGA 0.388g Figure 22-9 Site Coefficient, FPGA 1.200 Table 11.8-1
Site Class Modified MCEG Peak Ground
Acceleration, PGAM
0.465g Section 11.8.3 (Eqn 11.8-1)
7.7.3 Conformance to the criteria in Tables 7.7.1 and 7.7.2 for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur in the event of a large earthquake. The primary goal of seismic design is to protect life, not to avoid all damage, since such design may be economically prohibitive.
7.7.4 The project structural engineer and architect should evaluate the appropriate Risk Category and Seismic Design Category for the planned structures. The values presented herein Geocon Project No. G2803-52-01 - 19 - October 1, 2021
assume a Risk Category of II and resulting in a Seismic Design Category D. Table 7.7.3 presents a summary of the risk categories in accordance with ASCE 7-16.
TABLE 7.7.3
ASCE 7-16 RISK CATEGORIES
Risk Category Building Use Examples
I Low risk to Human Life at Failure Barn, Storage Shelter II Nominal Risk to Human Life at Failure
(Buildings Not Designated as I, III or IV)
Residential, Commercial and Industrial
Buildings
III Substantial Risk to Human Life at
Failure
Theaters, Lecture Halls, Dining Halls,
Schools, Prisons, Small Healthcare
Facilities, Infrastructure Plants, Storage
for Explosives/Toxins
IV Essential Facilities
Hazardous Material Facilities,
Hospitals, Fire and Rescue, Emergency
Shelters, Police Stations, Power
Stations, Aviation Control Facilities,
National Defense, Water Storage
7.8 Shallow Foundations
7.8.1 The proposed structure can be supported on a shallow foundation system founded in the compacted fill/formational materials. Foundations for the structure should consist of continuous strip footings and/or isolated spread footings. Footings should be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally from the face of the slope. Table 7.8 provides a summary of the foundation design recommendations.
TABLE 7.8
SUMMARY OF FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Continuous Foundation Width, WC 12 inches
Minimum Isolated Foundation Width, WI 24 inches
Minimum Foundation Depth, D 24 Inches Below Lowest Adjacent Grade Minimum Steel Reinforcement 4 No. 5 Bars, 2 at the Top and 2 at the Bottom Allowable Bearing Capacity 2,000 psf
Bearing Capacity Increase 500 psf per Foot of Depth
300 psf per Foot of Width
Maximum Allowable Bearing Capacity 3,500 psf
Estimated Total Settlement 1 Inch (Grading Option 1)
2 Inches (Grading Option 2)
Estimated Differential Settlement ½ Inch in 40 Feet (Grading Option 1) 1 Inch in 40 Feet (Grading Option 2)
Footing Size Used for Settlement 8-Foot Square
Design Expansion Index 50 or less
Geocon Project No. G2803-52-01 - 20 - October 1, 2021
7.8.2 The foundations should be embedded in accordance with the recommendations herein and the Wall/Column Footing Dimension Detail. The embedment depths should be measured from the lowest adjacent pad grade for both interior and exterior footings. Footings should be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally from the face of the slope (unless designed with a post-tensioned foundation system as discussed herein).
Wall/Column Footing Dimension Detail
7.8.3 The bearing capacity values presented herein are for dead plus live loads and may be increased by one-third when considering transient loads due to wind or seismic forces.
7.8.4 We should observe the foundation excavations prior to the placement of reinforcing steel and concrete to check that the exposed soil conditions are similar to those expected and that they have been extended to the appropriate bearing strata. Foundation modifications may be required if unexpected soil conditions are encountered.
7.8.5 Geocon Incorporated should be consulted to provide additional design parameters as required by the structural engineer.
7.9 Concrete Slabs-On-Grade
7.9.1 Concrete slabs-on-grade for the structures should be constructed in accordance with Table 7.9.
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TABLE 7.9
MINIMUM CONCRETE SLAB-ON-GRADE RECOMMENDATIONS
Parameter Value
Minimum Concrete Slab Thickness 5 inches
Minimum Steel Reinforcement No. 4 Bars 18 Inches on Center, Both Directions Typical Slab Underlayment 3 to 4 Inches of Sand/Gravel/Base Design Expansion Index 90 or less
7.9.2 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture- sensitive materials should be underlain by a vapor retarder. The vapor retarder design should be consistent with the guidelines presented in the American Concrete Institute’s (ACI) Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In addition, the membrane should be installed in accordance with manufacturer’s recommendations and ASTM requirements and installed in a manner that prevents puncture.
The vapor retarder used should be specified by the project architect or developer based on the type of floor covering that will be installed and if the structure will possess a humidity controlled environment.
7.9.3 The bedding sand thickness should be determined by the project foundation engineer, architect, and/or developer. It is common to have 3 to 4 inches of sand in the southern California region. However, we should be contacted to provide recommendations if the bedding sand is thicker than 6 inches. The foundation design engineer should provide appropriate concrete mix design criteria and curing measures to assure proper curing of the slab by reducing the potential for rapid moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation design engineer present the concrete mix design and proper curing methods on the foundation plans. It is critical that the foundation contractor understands and follows the recommendations presented on the foundation plans.
7.9.4 Concrete slabs should be provided with adequate crack-control joints, construction joints and/or expansion joints to reduce unsightly shrinkage cracking. The design of joints should consider criteria of the American Concrete Institute (ACI) when establishing crack-control spacing. Crack-control joints should be spaced at intervals no greater than 12 feet.
Additional steel reinforcing, concrete admixtures and/or closer crack control joint spacing should be considered where concrete-exposed finished floors are planned.
7.9.5 Special subgrade presaturation is not deemed necessary prior to placing concrete; however, the exposed foundation and slab subgrade soil should be moisturized to maintain a moist condition as would be expected in any such concrete placement.
Geocon Project No. G2803-52-01 - 22 - October 1, 2021
7.9.6 The concrete slab-on-grade recommendations are based on soil support characteristics only.
The project structural engineer should evaluate the structural requirements of the concrete slabs for supporting expected loads.
7.9.7 The recommendations of this report are intended to reduce the potential for cracking of slabs due to expansive soil (if present), differential settlement of existing soil or soil with varying thicknesses. However, even with the incorporation of the recommendations presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of concrete shrinkage cracks is independent of the supporting soil characteristics. Their occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper concrete placement and curing, and by the placement of crack control joints at periodic intervals, in particular, where re-entrant slab corners occur.
7.10 Exterior Concrete Flatwork
7.10.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in accordance with the recommendations presented in Table 7.10. The recommended steel reinforcement would help reduce the potential for cracking.
TABLE 7.10
MINIMUM CONCRETE FLATWORK RECOMMENDATIONS
Expansion
Index, EI Minimum Steel Reinforcement* Options Minimum
Thickness
EI < 90
6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh
4 Inches
No. 3 Bars 18 inches on center, Both Directions
*In excess of 8 feet square.
7.10.2 The subgrade soil should be properly moisturized and compacted prior to the placement of steel and concrete. The subgrade soil should be compacted to a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content in accordance with ASTM D 1557.
7.10.3 Even with the incorporation of the recommendations of this report, the exterior concrete flatwork has a potential to experience some uplift due to expansive soil beneath grade. The steel reinforcement should overlap continuously in flatwork to reduce the potential for vertical offsets within flatwork. Additionally, flatwork should be structurally connected to the curbs, where possible, to reduce the potential for offsets between the curbs and the flatwork.
Geocon Project No. G2803-52-01 - 23 - October 1, 2021
7.10.4 Concrete flatwork should be provided with crack control joints to reduce and/or control shrinkage cracking. Crack control spacing should be determined by the project structural engineer based upon the slab thickness and intended usage. Criteria of the American Concrete Institute (ACI) should be taken into consideration when establishing crack control spacing. Subgrade soil for exterior slabs not subjected to vehicle loads should be compacted in accordance with criteria presented in the grading section prior to concrete placement.
Subgrade soil should be properly compacted and the moisture content of subgrade soil should be verified prior to placing concrete. Base materials will not be required below concrete improvements.
7.10.5 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should be dowelled into the structure’s foundation stemwall. This recommendation is intended to reduce the potential for differential elevations that could result from differential settlement or minor heave of the flatwork. Dowelling details should be designed by the project structural engineer.
7.10.6 The recommendations presented herein are intended to reduce the potential for cracking of exterior slabs as a result of differential movement. However, even with the incorporation of the recommendations presented herein, slabs-on-grade will still crack. The occurrence of concrete shrinkage cracks is independent of the soil supporting characteristics. Their occurrence may be reduced and/or controlled by limiting the slump of the concrete, the use of crack control joints and proper concrete placement and curing. Crack control joints should be spaced at intervals no greater than 12 feet. Literature provided by the Portland Concrete Association (PCA) and American Concrete Institute (ACI) present recommendations for proper concrete mix, construction, and curing practices, and should be incorporated into project construction.
7.11 Retaining Walls
7.11.1 Retaining walls should be designed using the values presented in Table 7.11.1. Soil with an expansion index (EI) of greater than 90 should not be used as backfill material behind retaining walls.
Geocon Project No. G2803-52-01 - 24 - October 1, 2021
TABLE 7.11.1
RETAINING WALL DESIGN RECOMMENDATIONS
Parameter Value
Active Soil Pressure, A (Fluid Density, Level Backfill) 40 pcf Active Soil Pressure, A (Fluid Density, 2:1 Sloping Backfill) 55 pcf Seismic Pressure, S 15H psf
At-Rest/Restrained Walls Additional Uniform Pressure (0 to 8 Feet High) 7H psf At-Rest/Restrained Walls Additional Uniform Pressure (8+ Feet High) 13H psf Expected Expansion Index for the Subject Property EI< 90 H equals the height of the retaining portion of the wall
7.11.2 The project retaining walls should be designed as shown in the Retaining Wall Loading Diagram.
Retaining Wall Loading Diagram
7.11.3 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals the height of the retaining portion of the wall) at the top of the wall. Where walls are restrained from movement at the top (at-rest condition), an additional uniform pressure should be applied to the wall. For retaining walls subject to vehicular loads within a horizontal distance equal to two-thirds the wall height, a surcharge equivalent to 2 feet of fill soil should be added.
Geocon Project No. G2803-52-01 - 25 - October 1, 2021
7.11.4 The structural engineer should determine the Seismic Design Category for the project in accordance with Section 1613.3.5 of the 2019 CBC or Section 11.6 of ASCE 7-10. For structures assigned to Seismic Design Category of D, E, or F, retaining walls that support more than 6 feet of backfill should be designed with seismic lateral pressure in accordance with Section 1803.5.12 of the 2019 CBC. The seismic load is dependent on the retained height where H is the height of the wall, in feet, and the calculated loads result in pounds per square foot (psf) exerted at the base of the wall and zero at the top of the wall.
7.11.5 Retaining walls should be designed to ensure stability against overturning sliding, and excessive foundation pressure. Where a keyway is extended below the wall base with the intent to engage passive pressure and enhance sliding stability, it is not necessary to consider active pressure on the keyway.
7.11.6 Drainage openings through the base of the wall (weep holes) should not be used where the seepage could be a nuisance or otherwise adversely affect the property adjacent to the base of the wall. The recommendations herein assume a properly compacted granular (EI of 90 or less) free-draining backfill material with no hydrostatic forces or imposed surcharge load.
The retaining wall should be properly drained as shown in the Typical Retaining Wall Drainage Detail. If conditions different than those described are expected, or if specific drainage details are desired, Geocon Incorporated should be contacted for additional recommendations.
Typical Retaining Wall Drainage Detail
7.11.7 The retaining walls may be designed using either the active and restrained (at-rest) loading condition or the active and seismic loading condition as suggested by the structural engineer. Typically, it appears the design of the restrained condition for retaining wall loading may be adequate for the seismic design of the retaining walls. However, the active earth pressure combined with the seismic design load should be reviewed and also considered in the design of the retaining walls.
Geocon Project No. G2803-52-01 - 26 - October 1, 2021
7.11.8 In general, wall foundations should be designed in accordance with Table 7.11.2. The proximity of the foundation to the top of a slope steeper than 3:1 could impact the allowable soil bearing pressure. Therefore, retaining wall foundations should be deepened such that the bottom outside edge of the footing is at least 7 feet horizontally from the face of the slope.
TABLE 7.11.2
SUMMARY OF RETAINING WALL FOUNDATION RECOMMENDATIONS
Parameter Value
Minimum Retaining Wall Foundation Width 12 inches
Minimum Retaining Wall Foundation Depth 12 Inches
Minimum Steel Reinforcement Per Structural Engineer
Allowable Bearing Capacity 2,000 psf
Estimated Total Settlement 1 Inch
Estimated Differential Settlement ½ Inch in 40 Feet
7.11.9 The recommendations presented herein are generally applicable to the design of rigid concrete or masonry retaining walls. In the event that other types of walls (such as mechanically stabilized earth [MSE] walls, soil nail walls, or soldier pile walls) are planned, Geocon Incorporated should be consulted for additional recommendations.
7.11.10 It is common to see retaining walls constructed in the areas of the elevator pits. The retaining walls should be properly drained and designed in accordance with the recommendations presented herein. If the elevator pit walls are not drained, the walls should be designed with an increased active pressure with an equivalent fluid density of 90 pcf. It is also common to see seepage and water collection within the elevator pit. The pit should be designed and properly waterproofed to prevent seepage and water migration into the elevator pit.
7.11.11 Unrestrained walls will move laterally when backfilled and loading is applied. The amount of lateral deflection is dependent on the wall height, the type of soil used for backfill, and loads acting on the wall. The retaining walls and improvements above the retaining walls should be designed to incorporate an appropriate amount of lateral deflection as determined by the structural engineer.
7.11.12 Soil contemplated for use as retaining wall backfill, including import materials, should be identified in the field prior to backfill. At that time, Geocon Incorporated should obtain samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures Geocon Project No. G2803-52-01 - 27 - October 1, 2021
may be necessary if the backfill soil does not meet the required expansion index or shear strength. City or regional standard wall designs, if used, are based on a specific active lateral earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may or may not meet the values for standard wall designs. Geocon Incorporated should be consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall designs will be used.
7.12 Lateral Loading
7.12.1 Table 7.12 should be used to help design the proposed structures and improvements to resist lateral loads for the design of footings or shear keys. The allowable passive pressure assumes a horizontal surface extending at least 5 feet, or three times the surface generating the passive pressure, whichever is greater. The upper 12 inches of material in areas not protected by floor slabs or pavement should not be included in design for passive resistance.
TABLE 7.12
SUMMARY OF LATERAL LOAD DESIGN RECOMMENDATIONS
Parameter Value
Passive Pressure Fluid Density 350 pcf
Coefficient of Friction (Concrete and Soil) 0.35
Coefficient of Friction (Along Vapor Barrier) 0.2 to 0.25* *Per manufacturer’s recommendations.
7.12.2 The passive and frictional resistant loads can be combined for design purposes. The lateral passive pressures may be increased by one-third when considering transient loads due to wind or seismic forces.
7.13 Preliminary Pavement Recommendations
7.13.1 We calculated the flexible pavement sections in general conformance with the Caltrans Method of Flexible Pavement Design (Highway Design Manual, Section 608.4) using an estimated Traffic Index (TI) of 5.0, 5.5, 6.0, and 7.0 for parking stalls, driveways, medium truck traffic areas, and heavy truck traffic areas, respectively. The project civil engineer and owner should review the pavement designations to determine appropriate locations for pavement thickness. The final pavement sections for the parking lot should be based on the R-Value of the subgrade soil encountered at final subgrade elevation. We have assumed an R-Value of 19 (based on lab testing) and 78 for the subgrade soil and base materials, respectively, for the purposes of this preliminary analysis. Table 7.13.1 presents the preliminary flexible pavement sections.
Geocon Project No. G2803-52-01 - 28 - October 1, 2021
TABLE 7.13.1
PRELIMINARY FLEXIBLE PAVEMENT SECTION
Location
Assumed
Traffic
Index
Assumed
Subgrade
R-Value
Asphalt
Concrete
(inches)
Class 2
Aggregate
Base (inches)
Parking stalls for automobiles
and light-duty vehicles 5.0 19 3 7
Driveways for automobiles
and light-duty vehicles 5.5 19 3 9
Medium truck traffic areas 6.0 19 3.5 10
Driveways for heavy truck traffic 7.0 19 4 12
7.13.2 Prior to placing base materials, the upper 12 inches of the subgrade soil should be scarified, moisture conditioned as necessary, and recompacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content as determined by ASTM D 1557. Similarly, the base material should be compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Asphalt concrete should be compacted to a density of at least 95 percent of the laboratory Hveem density in accordance with ASTM D 2726.
7.13.3 Base materials should conform to Section 26-1.028 of the Standard Specifications for The State of California Department of Transportation (Caltrans) with a ¾-inch maximum size aggregate. The asphalt concrete should conform to Section 203-6 of the Standard Specifications for Public Works Construction (Greenbook).
7.13.4 The base thickness can be reduced if a reinforcement geogrid is used during the installation of the pavement. Geocon should be contacted for additional recommendations, if required.
7.13.5 A rigid Portland cement concrete (PCC) pavement section should be placed in roadway aprons and cross gutters. We calculated the rigid pavement section in general conformance with the procedure recommended by the American Concrete Institute report ACI 330R-08 Guide for Design and Construction of Concrete Parking Lots using the parameters presented in Table 7.13.2
Geocon Project No. G2803-52-01 - 29 - October 1, 2021
TABLE 7.13.2
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Concrete Compressive Strength 3,000 psi
Traffic Category, TC A and C
Average daily truck traffic, ADTT 10 and 100
7.13.6 Based on the criteria presented herein, the PCC pavement sections should have a minimum thickness as presented in Table 7.13.3.
TABLE 7.13.3
RIGID VEHICULAR PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Parking Stalls (TC=A, ADTT=10) 6.0
Driveways (TC=C, ADTT=100) 7.5
7.13.7 The PCC vehicular pavement should be placed over subgrade soil that is compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content.
7.13.8 Reinforcing steel will not be necessary within the concrete for geotechnical purposes with the possible exception of dowels at construction joints as discussed herein.
7.13.9 To control the location and spread of concrete shrinkage cracks, crack-control joints (weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should be sealed with an appropriate sealant to prevent the migration of water through the control joint to the subgrade materials. The depth of the crack-control joints should be determined by the referenced ACI report.
7.13.10 The rigid pavement should also be designed and constructed incorporating the parameters presented in Table 7.13.4.
Geocon Project No. G2803-52-01 - 30 - October 1, 2021
TABLE 7.13.4
ADDITIONAL RIGID PAVEMENT RECOMMENDATIONS
Subject Value
Thickened Edge
1.2 Times Slab Thickness
Minimum Increase of 2 Inches
4 Feet Wide
Crack Control Joint Spacing
30 Times Slab Thickness
Max. Spacing of 12 feet for 5.5-Inch-Thick
Max. Spacing of 15 Feet for Slabs 6 Inches and Thicker
Crack Control Joint Depth
Per ACI 330R-08
1 Inch Using Early-Entry Saws on Slabs Less Than 9 Inches Thick Crack Control Joint Width
¼-Inch for Sealed Joints
⅜-Inch is Common for Sealed Joints
1/10- to 1/8-Inch is Common for Unsealed Joints
7.13.11 To provide load transfer between adjacent pavement slab sections, a butt-type construction joint should be constructed. The butt-type joint should be thickened by at least 20 percent at the edge and taper back at least 4 feet from the face of the slab. As an alternative to the butt- type construction joint, dowelling can be used between construction joints for pavements of 7 inches or thicker. As discussed in the referenced ACI guide, dowels should consist of smooth, 1-inch-diameter reinforcing steel 14 inches long embedded a minimum of 6 inches into the slab on either side of the construction joint. Dowels should be located at the midpoint of the slab, spaced at 12 inches on center and lubricated to allow joint movement while still transferring loads. In addition, tie bars should be installed as recommended in Section 3.8.3 of the referenced ACI guide. The structural engineer should provide other alternative recommendations for load transfer.
7.13.12 Concrete curb/gutter should be placed on soil subgrade compacted to a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Cross-gutters that receives vehicular should be placed on subgrade soil compacted to a dry density of at least 95 percent of the laboratory maximum dry density near to slightly above optimum moisture content. Base materials should not be placed below the curb/gutter, or cross-gutters so water is not able to migrate from the adjacent parkways to the pavement sections. Where flatwork is located directly adjacent to the curb/gutter, the concrete flatwork should be structurally connected to the curbs to help reduce the potential for offsets between the curbs and the flatwork.
Geocon Project No. G2803-52-01 - 31 - October 1, 2021
7.14 Site Drainage and Moisture Protection
7.14.1 Adequate site drainage is critical to reduce the potential for differential soil movement, erosion and subsurface seepage. Under no circumstances should water be allowed to pond adjacent to footings. The site should be graded and maintained such that surface drainage is directed away from structures in accordance with 2019 CBC 1804.4 or other applicable standards. In addition, surface drainage should be directed away from the top of slopes into swales or other controlled drainage devices. Roof and pavement drainage should be directed into conduits that carry runoff away from the proposed structure.
7.14.2 In the case of basement walls or building walls retaining landscaping areas, a water-proofing system should be used on the wall and joints, and a Miradrain drainage panel (or similar) should be placed over the waterproofing. The project architect or civil engineer should provide detailed specifications on the plans for all waterproofing and drainage.
7.14.3 Underground utilities should be leak free. Utility and irrigation lines should be checked periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
7.14.4 Landscaping planters adjacent to paved areas are not recommended due to the potential for surface or irrigation water to infiltrate the pavement's subgrade and base course. Area drains to collect excess irrigation water and transmit it to drainage structures or impervious above- grade planter boxes can be used. In addition, where landscaping is planned adjacent to the pavement, construction of a cutoff wall along the edge of the pavement that extends at least 6 inches below the bottom of the base material should be considered.
7.14.5 We should prepare a storm water infiltration feasibility report if storm water management devices are planned.
7.15 Grading and Foundation Plan Review
7.15.1 Geocon Incorporated should review the grading and building foundation plans for the project prior to final design submittal to evaluate if additional analyses and/or recommendations are required. We should update this preliminary report once grading plans and a final building design have been prepared.
7.16 Testing and Observation Services During Construction
7.16.1 Geocon Incorporated should provide geotechnical testing and observation services during the grading operations, foundation construction, utility installation, retaining wall backfill Geocon Project No. G2803-52-01 - 32 - October 1, 2021
and pavement installation. Table 7.16 presents the typical geotechnical observations we would expect for the proposed improvements.
TABLE 7.16
EXPECTED GEOTECHNICAL TESTING AND OBSERVATION SERVICES
Construction Phase Observations Expected Time Frame
Grading
Base of Removal Part Time During
Removals
Geologic Logging Part Time to Full Time
Fill Placement and Soil Compaction Full Time
Soldier Piles Solder Pile Drilling Depth Part Time
Foundations
Drilling Operations for Piles Full Time
Foundation Excavation Observations Part Time
Utility Backfill Fill Placement and Soil Compaction Part Time to Full Time Retaining Wall Backfill Fill Placement and Soil Compaction Part Time to Full Time Subgrade for Sidewalks,
Curb/Gutter and Pavement Soil Compaction Part Time
Pavement Construction
Base Placement and Compaction Part Time
Asphalt Concrete Placement and
Compaction Full Time
Geocon Project No. G2803-52-01 October 1, 2021
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. The firm that performed the geotechnical investigation for the project should be retained to provide testing and observation services during construction to provide continuity of geotechnical interpretation and to check that the recommendations presented for geotechnical aspects of site development are incorporated during site grading, construction of improvements, and excavation of foundations. If another geotechnical firm is selected to perform the testing and observation services during construction operations, that firm should prepare a letter indicating their intent to assume the responsibilities of project geotechnical engineer of record. A copy of the letter should be provided to the regulatory agency for their records. In addition, that firm should provide revised recommendations concerning the geotechnical aspects of the proposed development, or a written acknowledgement of their concurrence with the recommendations presented in our report. They should also perform additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
2. The recommendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate from those disclosed in the investigation. If any variations or undesirable conditions are encountered during construction, or if the proposed construction will differ from that anticipated herein, Geocon Incorporated should be notified so that supplemental recommendations can be given. The evaluation or identification of the potential presence of hazardous or corrosive materials was not part of the scope of services provided by Geocon Incorporated.
3. This report is issued with the understanding that it is the responsibility of the owner or his representative to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plans, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field.
4. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years.
T-6T-5
T-4T-3T-2T-1
(4.5')[4'](3.5')[6']
(4.5')[7'](5')[7'](7')[7'](10')[10']
Qal/
Qudf/
PROPOSEDDEVELOPMENT AREA
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22'
1'
1 APPROX. LOCATION OFEXISTING SEWER LINE
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GEOLOGIC MAPTHE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT ISNOT INTENDED FOR CLIENT'S USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENTSHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULTOF SUCH USE OR RELIANCE BY CLIENT. 1 HUGHES CIRCUITSSAN MARCOS, CALIFORNIA
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974PHONE 858 558-6900 - FAX 858 558-6159PROJECT NO. G2803 - 52 - 01DATE 10 - 01 - 2021FIGURE GEOTECHNICAL ENVIRONMENTAL MATERIALS Plotted:10/01/2021 2:18PM | By:JONATHAN WILKINS | File Location:Y:\PROJECTS\G2803-52-01 Hughes Circuit\SHEETS\G2803-52-01 GeologicMAP.dwg T-6?
GEOCON LEGEND........UNDOCUMENTED FILLQudf
........APPROX. LOCATION OF TRENCH
........APPROX. LOCATION OF GEOLOGIC CONTACT (Queried Where Uncertain)........APPROX. LOCATION OF GEOLOGIC CROSS-SECTION22' ........ALLUVIUM (Dotted Where Buried)Qal........SANTIAGO FORMATION (Dotted Where Buried)Tsa(10')........APPROX. DEPTH OF FORMATIONAL MATERIAL (In Feet)[10']........APPROX. DEPTH OF WATER/SEEPAGE (In Feet)
ELEVATION (MSL)
ELEVATION (MSL)
DISTANCE (FEET)SCALE: 1" = 20' (Vert. = Horiz.)GEOLOGIC CROSS-SECTION 1-1' 485
505
525
545
565
585
485
505
525
545
565
585
0 20406080100120140160180200220240260280300320340360380380
ELEVATION (MSL)
ELEVATION (MSL)
DISTANCE (FEET)SCALE: 1" = 20' (Vert. = Horiz.)GEOLOGIC CROSS-SECTION 2-2' 485
505
525
545
565
585
485
505
525
545
565
585
0 20406080100120140160180200220240260280300320340360380400420440445 2 2'
1 1'
S PACIFIC STREET
APPROX.SITE LIMITS APPROX.SITE LIMITS
EXISTING GRADE
SECTION 1-1'
T-3(PROJECTED29' NE) T-4(PROJECTED15' S) T-1(PROJECTED126' N) Tsa Tsa Tsa QalQalQal
T-4(PROJECTED80' S) T-5(PROJECTED84' E)
S PACIFIC STREETAPPROX.SITE LIMITS APPROX.SITE LIMITS
EXISTING GRADE
SAN DIEGO COUNTYWATER AUTHORITY EASEMENT
TsaQal Qal QalTsa Tsa
SECTION 2-2'
N66W
N25E
QudfAPPROX. LOCATION OFEXISTING SEWER LINE
?APPROX. LOCATION OFEXISTING SEWER LINEQudf
?
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974PHONE 858 558-6900 - FAX 858 558-6159SHEET OFPROJECT NO.SCALEDATEFIGURE Plotted:10/01/2021 3:16PM | By:JONATHAN WILKINS | File Location:Y:\PROJECTS\G2803-52-01 Hughes Circuit\SHEETS\G2803-52-01 Cross-Section.dwgGEOTECHNICAL ENVIRONMENTAL MATERIALS1" = GEOLOGIC CROSS - SEC8IONS HUGHES CIRCUITSSAN MARCOS, CALIFORNIA20'10 - 01 - 2021G2803 - 52 - 011 12 ?
GEOCON LEGEND
........YOUNG ALLUVIUMQal
........APPROX. LOCATION OF GEOLOGIC CONTACT (Queried Where Uncertain)........SANTIAGO FORMATIONTsa........APPROX. ELEVATION OF GROUNDWATER........APPROX. LOCATION OF TRENCHT-6 ........UNDOCUMENTED FILLQudf
APPENDIX A
Geocon Project No. G2803-52-01 October 1, 2021
APPENDIX A
FIELD INVESTIGATION
We performed the trenching operations on September 1, 2021 to depths ranging from approximately 9 to 14 feet below existing grade using a John Deere 310L EP back-hoe with MCM Construction performing the work. Trenches were extended to maximum depth of approximately 14 feet. The locations of the current exploratory trenches are shown on the Geologic Map, Figure 1. The trench logs are presented in this Appendix. We located the trenches in the field using a measuring tape and existing reference points; therefore, actual boring locations may deviate slightly.
We obtained disturbed bulk and chunk samples during our subsurface exploration in the trenches. We obtained the samples at appropriate depths, placed them in moisture-tight containers, and transported them to the laboratory for testing. The type of sample is noted on the exploratory trench logs. We estimated elevations shown on the trench logs either from a topographic map or by using a benchmark.
Each excavation was backfilled as noted on the trench logs.
We visually examined, classified, and logged the soil encountered in the trenches in general accordance with American Society for Testing and Materials (ASTM) practice for Description and Identification of Soils (Visual-Manual Procedure D 2488). The logs depict the soil and geologic conditions observed and the depth at which samples were obtained.
ALLUVIUM (Qal)Medium dense, damp, light brown, Silty, fine to coarse SAND; trace roots Dense, moist, brown to dark brown, Clayey, fine to medium SAND -Caving between 9.5-10 feet, groundwater at 10 feetSANTIAGO FORMATION (Tsa)Soft, moist to saturated, greenish-gray, CLAYSTONE; highly weathered-Becomes stiff, moderately weathered TRENCH TERMINATED AT 13.5 FEETGroundwater at 10 feet, caving between 9.5-10 feet SM
SC
CL
T1-1
T1-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 10
12 Figure A-1,Log of Trench T 1, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 1
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)525'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
UNDOCUMENTED FILL (Qudf)Medium dense, moist, brown, Silty, fine to medium SAND, trace deleteriousmaterialALLUVIUM (Qal)Loose to medium dense, moist, light brown to brown, Silty, fine to mediumSANDDense, moist, dark brown to gray, Clayey, fine to medium SAND -Becomes saturated at 7 feet, caving at 6.5 feetSANTIAGO FORMATION (Tsa)Medium dense, saturated, light gray, Clayey to Silty, fine- to medium-grainedSANDSTONE with yellowish brown staining, highly weathered, friable -Becomes denser, moderately weathered
TRENCH TERMINATED AT 14 FEETGroundwater at 7 feet, caving at 6.5 feet SM
SM
SC
SC
110.0 17.9T2-1T2-2
T2-3
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 10
12 14Figure A-2,Log of Trench T 2, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 2
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)525'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
ALLUVIUM (Qal)Medium dense, moist, brown, Silty, fine to medium SAND Medium dense, moist, dark brown to gray, Clayey, fine to medium SAND SANTIAGO FORMATION (Tsa)Dense, moist to saturated, yellowish brown, Clayey, fine- to coarse-grainedSANDSTONE; highly weathered/friable-Groundwater at 7 feet, caving at 7 feet-Becomes saturated, light gray to yellowish brown, moderately weathered -Becomes very dense, yellowish brown, slightly weathered TRENCH TERMINATED AT 14 FEETGroundwater at 7 feet
SM
SC
SCT3-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 10
12 14Figure A-3,Log of Trench T 3, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 3
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)526'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
ALLUVIUM (Qal)Medium dense, moist, light brown to light gray, Silty, fine to medium SANDMedium dense, moist, dark brown, Clayey, fine to medium SAND SANTIAGO FORMATION (Tsa)Dense, moist to saturated, yellowish brown, Clayey, fine- to medium-grainedSANDSTONE-Caving at 4.5 feet-Groundwater at 7 feetDense, saturated, light gray to yellowish brown, Silty, fine- to coarse-grainedSANDSTONE; slightly weatheredVery dense, saturated, light gray, Clayey, fine- to coarse-grainedSANDSTONE; moderately cementedTRENCH TERMINATED AT 10.5 FEETGroundwater at 7 feet, caving at 4.5 feet SM
SC
SC
SM
SC
T4-1
T4-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 10
Figure A-4,Log of Trench T 4, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 4
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)525'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
ALLUVIUM (Qal)Medium dense, moist, brown, Clayey SAND; some roots SANTIAGO FORMATION (Tsa)Dense, moist, yellowish brown, Clayey, fine- to coarse- grainedSANDSTONE; moderately weathered-Caving at 5.5 feet-Becomes saturated, groundwater at 6 feet -From 8.5-9.5 feet becomes dense to very denseTRENCH TERMINATED AT 9.5 FEETGroundwater at 6 feet, caving at 5.5 feet SC
SCT5-1
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 Figure A-5,Log of Trench T 5, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 5
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)525'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
ALLUVIUM (Qal)Loose, moist, Clayey SAND; trace gravel
-Becomes medium dense-Caving at 3.5 feet-Groundwater at 4 feetSANTIAGO FORMATION (Tsa)Dense, saturated, yellowish brown to gray, Clayey, fine- to coarse-grainedSANDSTONE; highly weathered-Becomes very dense TRENCH TERMINATED AT 9 FEETGroundwater at 4 feet, caving at 3.5 feet SC
SC
T6-1
T6-2
... DISTURBED OR BAG SAMPLE
GEOCON
DEPTHINFEET
0 2
4 6
8 Figure A-6,Log of Trench T 6, Page 1 of 1
DRY DENSITY(P.C.F.)
... DRIVE SAMPLE (UNDISTURBED)
BACKHOE JOHN DEERE 310L
PENETRATIONRESISTANCE(BLOWS/FT.)TRENCH T 6
... CHUNK SAMPLE
DATE COMPLETED
... SAMPLING UNSUCCESSFUL
SOILCLASS(USCS)GROUNDWATERD. THOMAS
CONTENT (%)SAMPLENO. 09-01-2021
SAMPLE SYMBOLS
MOISTUREBY:EQUIPMENTELEV. (MSL.)526'
G2803-52-01.GPJ
MATERIAL DESCRIPTION
LITHOLOGY
... STANDARD PENETRATION TEST... WATER TABLE OR... SEEPAGENOTE:
PROJECT NO.
THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. ITIS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
G2803-52-01
APPENDIX B
Geocon Project No. G2803-52-01 October 1, 2021
APPENDIX B
LABORATORY TESTING
We performed laboratory tests in accordance with generally accepted test methods of the American Society for Testing and Materials (ASTM) or other suggested procedures. We tested selected soil samples maximum density/optimum moisture content, expansion index, water-soluble sulfate, R-Value, consolidation and direct shear strength. The results of our current laboratory tests are presented herein.
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Sample No. Description
Maximum
Dry Density
(pcf)
Optimum
Moisture Content
(% dry wt.)
T4-1 Light to dark brown, Silty, fine to medium SAND 125.5 10.4 T5-1 Yellowish brown, Clayey, fine to coarse SAND 122.4 11.8
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829
Sample
No.
Moisture Content (%) Dry
Density
(pcf)
Expansion
Index
2019 CBC
Expansion
Classification
ASTM Soil
Expansion
Classification
Before
Test After Test
T2-2 11.0 24.3 105.3 56 Expansive Medium
T4-1 8.5 15.9 114.0 10 Non-Expansive Very Low
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST NO. 417
Sample No. Depth (feet) Geologic Unit Water-Soluble
Sulfate (%)
ACI 318 Sulfate
Exposure
T2-2 5-6 Qal 0.028 S0
T4-1 0-3 Qal 0.011 S0
SUMMARY OF LABORATORY RESISTANCE VALUE (R-VALUE) TEST RESULTS ASTM D 2844
Sample No. Depth (Feet) Description (Geologic Unit) R-Value T4-1 0-3 Light to dark brown, Silty, fine to medium SAND (Qal) 19 SAMPLE NO.: Qal
SAMPLE DEPTH (FT):
PROJECT NO.: G2803-52-01
17.9%
INITIAL DRY DENSITY (PCF):
INITIAL WATER CONTENT (%):
SAMPLE SATURATED AT (KSF):
INITIAL SATURATION (%):
2.0 93.8%
CONSOLIDATION CURVE - ASTM D 2435
HUGHES CIRCUITS
T2-1
4-5
GEOLOGIC UNIT:
TEST INFORMATION
110.0
-2.0
0.0 2.0
4.0 6.0
8.0 10.0
0.10 1.00 10.00
VERTICAL STRAIN (%)
APPLIED PRESSURE (KSF)
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
10.5 9.7 10.0 10.1
112.6 113.3 113.3 113.1
1 K 2 K 4 K AVERAGE
15.4 15.9 16.3 15.9
952 1631 2885 --
952 1631 2885 --
460
29 460
29 COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
T4-1
G2803-52-01
HUGHES CIRCUITS
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
Qal
0-3
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
R
0 500
1000
1500
2000
2500
3000
3500
0.000 0.050 0.100 0.150 0.200 0.250 0.300
SHEAR STRESS (PSF)
HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1 K
0 1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000
SHEAR STRESS (PSF)
NORMAL STRESS (PSF)
SAMPLE NO.: GEOLOGIC UNIT:
SAMPLE DEPTH (FT): NATURAL/REMOLDED:
1 K 2 K 4 K AVERAGE
890 2030 4300 --
11.1 11.2 11.1 11.2
111.2 110.8 111.4 111.1
1 K 2 K 4 K AVERAGE
16.5 16.5 16.1 16.4
971 1622 2809 --
971 1622 2790 --
500
28 500
28 COHESION, C (PSF)
DRY DENSITY (PCF):
AFTER TEST CONDITIONS
T5-1
G2803-52-01
HUGHES CIRCUITS
COHESION, C (PSF)
FRICTION ANGLE (DEGREES)
DIRECT SHEAR - ASTM D 3080
PROJECT NO.:
FRICTION ANGLE (DEGREES)
NORMAL STRESS TEST LOAD
ACTUAL NORMAL STRESS (PSF):
WATER CONTENT (%):
ULTIMATE
RESULTS
PEAK
Tsa
5-7
NORMAL STRESS TEST LOAD
WATER CONTENT (%):
PEAK SHEAR STRESS (PSF):
ULT.-E.O.T. SHEAR STRESS (PSF):
INITIAL CONDITIONS
R
0 500
1000
1500
2000
2500
3000
0.000 0.050 0.100 0.150 0.200 0.250 0.300
SHEAR STRESS (PSF)
HORIZONTAL DEFORMATION (IN)
1 K 2 K 4 K
1 K PEAK 2 K PEAK 4 K PEAK
1 K ULTIMATE 2 K ULTIMATE 4 K ULTIMATE
4 K
2 K
1 K
0 1000
2000
3000
4000
5000
6000
7000
0 1000 2000 3000 4000 5000 6000
SHEAR STRESS (PSF)
NORMAL STRESS (PSF)
APPENDIX C
APPENDIX C
RECOMMENDED GRADING SPECIFICATIONS
FOR
HUGHES CIRCUITS
SOUTH PACIFIC STREET
SAN MARCOS, CALIFORNIA
PROJECT NO. G2803-52-01
GI rev. 07/2015
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended G rading Specifications shall be used in conjunction with the Geotechnical Report for the project prepared by Geocon. The recommendations contained in the text of the Geotechnical Report are a part of the earthwork and grading specifications and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be employed for the purpose of observing earthwork procedures and testing the fills for substantial conformance with the recommendations of the Geotechnical Report and these specifications. The Consultant should provide adequate testing and observation services so that they may assess whether, in their opinion, the work was performed in substa ntial conformance with these specifications. It shall be the responsibility of the Contractor to assist the Consultant and keep them apprised of work schedules and changes so that personnel may be scheduled accordingly.
1.3 It shall be the so le responsibility of the Contractor to provide adequate equipment and methods to accomplish the work in accordance with applicable grading codes or agency ordinances, these specifications and the approved grading plans. If, in the opinion of the Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture condition, inadequate compaction, and/or adverse weather result in a quality of work not in conformance with these specifications, the Consultant will be empowered to reject the work and recommend to the Owner that grading be stopped until the unacceptable conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading work is being p erformed and who has contracted with the Contractor to have grading performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California l icensed Civil Engineer or consulting firm responsible for preparation of the grading plans, surveying and verifying as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner, who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be responsible for having qualified representatives on-site to observe and test the Contractor's work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained by the Owner to p rovide geologic observations and recommendations during the site grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include a geologic reconnaissance or geologic investigation that was prepared spe cifically for the development of the project for which these Recommended Grading Specifications are intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or imported to the site that, in the opinion of the Consultant, is suitable for use in construction of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as defined below.
3.1.1 Soil fills are defined as fills containi ng no rocks or hard lumps greater than 12 inches in maximum dimension and containing at least 40 percent by weight of material smaller than ¾ inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than 4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow for proper compaction of soil fill around the rock fragments or hard lumps as specified in Paragraph 6.2. Oversize rock is defined as material greater than 12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet in maximum dimension and containing little or no fines. Fines are defined as material smaller than ¾ inch in maximum dimension. The quantity of fines shall be less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on -site, shall not contain hazardous materials as defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9 GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall not be responsible for the identi fication or analysis of the potential presence of hazardous materials. However, if observations, odors or soil discoloration cause Consultant to suspect the presence of hazardous materials, the Consultant may request from the Owner the termination of gradi ng operations within the affected area. Prior to resuming grading operations, the Owner shall provide a written report to the Consultant indicating that the suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of properly compacted soil fill materials approved by the Consultant. Rock fill may extend to the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This procedure may be utilized provided it is acceptable to the governing agency, Owner and Consultant.
3.5 Samples of soil mater ials to be used for fill should be tested in the laboratory by the Consultant to determine the maximum density, optimum moisture content, and, where appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the Geotechnical Report may be encountered by the Contractor. The Consultant shall be notified immediately to evaluate the significance of the unanticipated condition.
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of complete removal above the ground surface of trees, stumps, brush, vegetation, man -made structures, and sim ilar debris. Grubbing shall consist of removal of stumps, roots, buried logs and other unsuitable material and shall be per formed in areas to be graded. Roots and other projections exceeding 1½ inches in diameter shall be removed to a depth of 3 feet below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly disposed at an approved off-site facility or in an acceptable area of the project evaluated by Geocon and the property owner . Concrete fragments that are free of reinforcing steel may be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this document.
GI rev. 07/2015
4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or porous soils shall be removed to the depth recom mended in the Geotechnical Report. The depth of removal and compaction should be observed and approved by a repr esentative of the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth of 6 inches and until the surface is free from uneven features that would tend to prevent uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5:1 (horizontal:vertical), or where recommended by the Consultant, the original ground should be benched in accordance with the following illustration.
TYPICAL BENCHING DETAIL
Remove All
Unsuitable Material
As Recommended By
Consultant
Finish Grade Original Ground
Finish Slope Surface
Slope To Be Such That
Sloughing Or Sliding
Does Not Occur Varies
“B”
See Note 1
No Scale
See Note 2
1 2
DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit complete coverage with the compaction equipment used. The base of the key should be graded horizontal, or inclined slightly into the natural slope. (2) The outside of the key should be below the topsoil or unsuitable surficial material and at least 2 feet into dense forma tional material. Where hard rock is exposed in the bottom of the key, the depth and configuration of the key may be modified as approved by the Consultant.
4.5 After areas to receive fill have been cleared and scarified, the surface should be moisture conditioned to achieve the proper moisture content, and compacted as recommended in Section 6 of these specifications.
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5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel wheeled rollers, vibratory rollers, multiple -wheel pneumatic-tired rollers, or other types of acceptable com paction equipment. Equipment shall be of such a design that it will be capable of compacting the soil or soil-rock fill to the specified relative compaction at the specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with the following recommendations:
6.1.1 Soil fill shall be placed by the Contractor in layers that, when compacted, should generally not exceed 8 inches. Each layer shall be spread evenly and shall be thoroughly mixed during spreading to obtain uniformity of material and moisture in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock materials greater than 12 inches in maximum dimension shall be placed in accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a m oisture content at or above the optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant, water shall be added by the Contractor until the moisture content is in the rang e specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by the Contractor by blading/mixing, or other satisfactory methods until th e moisture content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ra tio (expressed in percent) of the in -place dry density of the compacted fill to the maximum laboratory dry density as determined in accordance with ASTM D 1557. Compaction shall be continuous over the entire area, and compaction equipment shall make sufficient passes so that the specified minimum relative compaction has been achieved throughout the entire fill.
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6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed at least 3 feet below finish pad grade and should be compact ed at a moisture content generally 2 to 4 percent greater than the optimum moisture content for the material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To achieve proper compaction, it is recommended that fill sl opes be over -built by at least 3 feet and then cut to the design grade. This procedure is considered preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over -building of slopes, slope faces may be back -rolled with a heavy-duty loaded sheepsfoot or vibratory roller at maximum 4 -foot fill height intervals. Upon completion, slopes should then be track -walked with a D -8 dozer or similar equipment, such that a dozer track covers all slope surfaces at least twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be incorporated into the compacted soil fill, but shall be limited to the area measured 15 feet minimum horizontally from the slope face and 5 feet below finish grade or 3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximu m dimension may either be individually placed or placed in windrows. Under certain conditions, rocks or rock fragments up to 10 feet in maximum dimension may be placed using similar methods. The acceptability of placing rock materials greater than 4 feet i n maximum dimension shall be evaluated during grading as specific cases arise and shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in properly compacted soil fill. Trenches should be approximately 5 feet wide and 4 feet deep in maximum dimension. The voids around and beneath rocks should be filled with approved granular soil having a Sand Equivalent of 30 or greater and should be compacted by flooding. Windrows may also be placed utilizing an "open-face" method in lieu of the trench procedure, however, this method should first be approved by the Consultant.
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6.2.5 Windrows should generally be parallel to each other and may be placed either parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center -to-center with a 5 -foot stagger or offset from lower courses to next overlying course. The minimum vertical spacing between windrow courses shall be 2 feet from the top of a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2 percent). The surface shall slope toward suitable subdrainage outlet facilities. The rock fills shall be provided with subdrains during construction so that a hydrostatic pressure buildup does not develop. The subdrains shall be permanently connected to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock trucks traversing previously placed lifts and dumping at the edge of the currently placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the rock. The rock fill shall be watered heavily during placement. Watering shall consist of water trucks traversing in front of the current rock lift face and spraying water continuously during rock placement. Compaction equipment with compactive energy comparable to or greater than that of a 20 -ton steel vibratory roller or other compaction eq uipment providing suitable energy to achieve the required compaction or deflection as recommended in Paragraph 6.3.3 shall be utilized. The number of passes to be made should be determined as described in Paragraph 6.3.3. Once a rock fill lift has been cov ered with soil fill, no additional rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both the compacted soil fill and in the rock fill to aid in determining the required minimum number of passes of the compaction equipment. If performed, a minimum of three plate bearing tests should be performed in the properly compacted soil fill (minimum relative compaction of 90 percent). Plate bearing tests shall then be performed on area s of rock fill having two passes, four passes and six passes of the compaction equipment, respectively. The number of passes required for the rock fill shall be determined by comparing the results of the plate bearing tests for the soil fill and the rock fill and by evaluating the deflection GI rev. 07/2015
variation with number of passes. The required number of passes of the compaction equipment will be performed as necessary until the plate bearing deflections are equal to or less than that determined for the properly compacted soil fill. In no case will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to observe that the minimum number of “passes” have been obtained, that water is being properly applied and that specified procedures are being followed. The actual number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that, in their opinion, sufficient water is present and that voids between large rocks are properly filled with smaller rock material. In -place density testing will not be required in the rock fills.
6.3.6 To reduce the potential for “piping” of fines into the rock fill from overlying soil fill material, a 2 -foot layer of graded filter material shall be placed above the uppermost lift of rock fill. The need to place graded filter material below the rock should be determined by the Consultant prior to commencing gr ading. The gradation of the graded filter material will be determined at the time the rock fill is being excavated. Materials typical of the rock fill should be submitted to the Consultant in a timely manner, to allow design of the graded filter prior to t he commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fr acture systems that could be susceptible under certain conditions to seepage. The use of canyon subdrains may be necessary to mitigate the potential for adverse impacts associated with seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500 feet in length should use 6-inch-diameter pipes.
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TYPICAL CANYON DRAIN DETAIL
7.2 Slope drains within stability fill keyways should use 4-inch-diameter (or lager) pipes.
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TYPICAL STABILITY FILL DETAIL
7.3 The actual subdrain locations will be evaluated in the field during the remedial grading operations. Additional drains may be necessary depending on the conditio ns observed and the requirements of the local regulatory agencies. Appropriate subdrain outlets should be evaluated prior to finalizing 40-scale grading plans.
7.4 Rock fill or soil-rock fill areas may require subdrains along their down-slope perimeters to mitigate the potential for buildup of water from construction or landscape irrigation. The subdrains should be at least 6-inch-diameter pipes encapsulated in gravel and filter fabric .
Rock fill drains should be constructed using the same requirements as canyon subdrains.
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7.5 Prior to outletting, the final 20 -foot segment of a subdrain that will not be extended during future development should consist of non -perforated drainpipe. At the non -perforated/ perforated interface, a see page cutoff wall should be constructed on the downslope side of the pipe.
TYPICAL CUT OFF WALL DETAIL
7.6 Subdrains that discharge into a natural drainage course or open space area should be provided with a permanent headwall structure.
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TYPICAL HEADWALL DETAIL
7.7 The final grading plans should show the location of the proposed subdrains. After completion of remedial excavations and subdrain installation, the project civil engineer should survey the drain locations and prep are an “as -built” map showing the drain locations. The final outlet and connection locations should be determined during grading operations. Subdrains that will be extended on adjacent projects after grading can be placed on formational material and a vertical riser should be placed at the end of the subdrain. The grading contractor should consider videoing the subdrains shortly after burial to check proper installation and functionality. The contractor is responsible for the performance of the drains.
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8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner’s representative to observe and perform tests during clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in vertical elevation of soil or soil-rock fill should be placed without at least one field density test being performed within that interval. In addition, a minimum of one field density test should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill material is compacted as specified. Density tests sh all be performed in the compacted materials below any disturbed surface. When these tests indicate that the density of any layer of fill or portion thereof is below that specified, the particular layer or areas represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant should request the e xcavation of observation pits and may perform plate bearing tests on the placed rock fills. The observation pits will be excavated to provide a basis for expressing an opinion as to whether the rock fill is properly seated and sufficient moisture has been applied to the material. When observations indicate that a layer of rock fill or any portion thereof is below that specified, the affected layer or area shall be reworked until the rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of rock fill placement. The specific design of the monitoring program shall be as recommended in the Conclusions and Recommendations section of the project Geotechnical Report or in the final report of testing and observation services performed during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In -Place By the Sand-Cone Method.
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8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density Relations of Soils and Soil -Aggregate Mixtures Using 10 -Pound Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide positive drainag e and prevent ponding of water. Drainage of surface water shall be controlled to avoid damage to adjoining properties or to finished work on the site. The Contractor shall take remedial measures to prevent erosion of freshly graded areas until such time as permanent drainage and erosion control features have been installed. Areas subjected to erosion or sedimentation shall be properly prepared in accordance with the Specifications prior to placing additional fill or structures.
9.2 After compl etion of grading as observed and tested by the Consultant, no further excavation or filling shall be conducted except in conjunction with the services of the Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot horizontally of the positions shown on the grading plans. After installation of a section of subdrain, the project Civil Engineer should survey its location and prepare an as-built plan of the subdrain location. The project Civil Engineer should verify the proper outlet for the subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as -graded soil and geologic report satisfactory to the appropriate govern ing or accepting agencies. The as -graded report should be prepared and signed by a California licensed Civil Engineer experienced in geotechnical engineering and by a California Certified Engineering Geologist, indicating that the geotechnical aspects of t he grading were performed in substantial conformance with the Specifications or approved changes to the Specifications.
Geocon Project No. G2803-52-01 October 1, 2021
LIST OF REFERENCES
1. 2019 California Building Code, California Code of Regulations, Title 24, Part 2, based on the 2018 International Building Code , prepared by California Building Standards Commission, dated July 2019.
2. American Concrete Institute, ACI 318-11, Building Code Requirements for Structural Concrete and Commentary, dated August, 2011.
3. American Concrete Institute, ACI 330-08, Guide for the Design and Construction of Concrete Parking Lots, dated June, 2008.
4. American Society of Civil Engineers (ASCE), ASCE 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, 2017.
5. County of San Diego, San Diego County Multi Jurisdiction Hazard Mitigation Plan, San Diego, California – Final Draft, dated 2017.
6. Geocon, Incorporated Preliminary Geotechnical Investigation, High Tech High – North County Elementary School, San Marcos, California, dated December 21, 2012 (Project No. 07732-42-07).
7. Historical Aerial Photos. http://www.historicaerials.com
8. Jennings, C. W., 1994, California Division of Mines and Geology, Fault Activity Map of California and Adjacent Areas, California Geologic Data Map Series Map No. 6.
9. Kennedy, M. P., and S. S. Tan, 2007, Geologic Map of the Oceanside 30’x60’ Quadrangle, California, USGS Regional Map Series Map No. 2, Scale 1:100,000.
10. Special Publication 117A, Guidelines For Evaluating and Mitigating Seismic Hazards in California 2008, California Geological Survey, Revised and Re-adopted September 11, 2008.
11. Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated.
12. USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra, http://geohazards.usgs.gov/designmaps/us/application.php.