Appendix G2
Geotechnical Investigation Parcel B
LIMITED
GEOTECHNICAL INVESTIGATION
COLLINS AEROSPACE
REDEVELOPMENT SITE PARCEL B
NORTHEAST CORNER OF
H STREET AND MARINA PARKWAY
CHULA VISTA, CALIFORNIA
PREPARED FOR
MARCH 3, 2021
PROJECT NO. G2560-52-01
Project No. G2560-52-01
March 3, 2021
PW Wohl G Street LLC
c/o Wohl Property Group
1081 Camino Del Rio South, Suite 115
San Diego, California 92108
Attention: Mr. Emil Wohl
Subject: LIMITED GEOTECHNICAL INVESTIGATION
COLLINS AEROSPACE REDEVELOPMENT SITE PARCEL B
NORTHEAST CORNER OF H STREET AND MARINA PARKWAY
CHULA VISTA, CALIFORNIA
Dear Mr. Wohl:
In accordance with your request and authorization of our Proposal No. LG-20158 dated June 3, 2020, we herein submit the results of our limited geotechnical investigation for the subject project. We performed our limited investigation to evaluate the underlying soil and geologic conditions and potential geologic hazards, and to assist in the design of the proposed site improvements. The accompanying report presents the results of our study and preliminary conclusions and recommendations pertaining to geotechnical aspects of the proposed 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
Matt Love
RCE 84154
Shawn Foy Weedon
GE 2714
Michael C. Ertwine
CEG 2659
MRL:SFW:MCE:arm
(e-mail) Addressee
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ................................................................................................................. 1
2. SITE AND PROJECT DESCRIPTION ........................................................................................... 2
3. GEOLOGIC SETTING .................................................................................................................... 3
4. SOIL AND GEOLOGIC CONDITIONS ........................................................................................ 4
4.1 Undocumented Fill (Qudf) .................................................................................................... 4
4.2 Bay Deposits (Qb) ................................................................................................................. 5
4.3 Old Paralic Deposits (Qop) .................................................................................................... 5
4.4 San Diego Formation (Tsd) ................................................................................................... 5
5. GROUNDWATER .......................................................................................................................... 5
6. GEOLOGIC HAZARDS ................................................................................................................. 6
6.1 Faulting and Seismicity ......................................................................................................... 6
6.2 Ground Rupture ..................................................................................................................... 7
6.3 Liquefaction Potential and Seismically Induced Settlement ................................................. 7
6.4 Storm Surge, Tsunamis, and Seiches ..................................................................................... 9
6.5 Hazardous Subsurface Materials ......................................................................................... 11
7. CONCLUSIONS AND RECOMMENDATIONS ......................................................................... 12
7.1 General ................................................................................................................................. 12
7.2 Soil Characteristics .............................................................................................................. 13
7.3 Seismic Design Criteria ....................................................................................................... 14
7.4 Site Drainage and Moisture Protection ................................................................................ 16
7.5 Storm Water Management ................................................................................................... 16
7.6 Updated Geotechnical Investigation .................................................................................... 18
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Geologic Map
APPENDIX A
FIELD INVESTIGATION
APPENDIX B
PREVIOUS FIELD INVESTIGATIONS AND LABORATORY TESTING RESULTS
APPENDIX C
LIQUEFACTION ANALYSIS
LIST OF REFERENCES
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LIMITED GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of our limited geotechnical investigation related to the planned improvements to the subject property currently identified as Collins Aerospace – Parcel B in Chula Vista, California (see Vicinity Map).
Vicinity Map
The purpose of this limited 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.
We reviewed the following plans and reports in preparation of this report:
1. Limited Geotechnical Investigation,, Collins Aerospace Redevelopment Site – Parcel A, Chula Vista, California, prepared by Geocon Incorporated, dated October 12, 2020 (Project No. G2559-52-01).
2. Geotechnical Investigation, OMPPA Project on Goodrich Property, Chula Vista, California, prepared by Geocon Incorporated, dated September 12, 2005 (Project No. 07050-22-30).
3. Limited Geotechnical Investigation, B.F. Goodrich Site Development, Chula Vista, California, prepared by Geocon Incorporated, dated June 24, 1999 (Project No. 06327-22-01).
4. Soil Investigation, Sauder Furnace Foundation, Building No. 1, Column E11-F11, Chula Vista, California, prepared by Geocon Incorporated, dated July 14, 1980 (Project No. 02080-02-02).
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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 5 exploratory Cone Penetrometer Tests (CPTs) to a maximum depth of 80 feet.
Appendix A presents the CPT soundings and details of the field investigation. Appendix B presents the exploratory boring logs and laboratory testing from investigations previously performed on or adjacent to the property. The locations of the current CPTs and previous borings/CPTs at the property are shown on the Geologic Map, Figure 1. Appendix C presents the results of our current liquefaction analysis along with pertinent results from the Parcel A site.
2. SITE AND PROJECT DESCRIPTION
The Collins Aerospace – Parcel B property consists of the western portion of the existing Collins Aerospace facility (also identified as Rohr Industries, B. F. Goodrich and/or UTC Aerospace property). The Existing Site Map shows the current site conditions.
Existing Site Map
The property is bounded by H Street to the south, Marina Parkway and the future Gaylord Chula Vista Hotel and Convention Center to the west, and the remainder of the Collins Aerospace facility to the east and north. An existing rail line is present along the eastern border of the property. The site is currently occupied by a large industrial warehouse building along with several small ancillary buildings and structures, and an on-grade asphalt concrete and Portland Cement concrete parking lots along with other associated improvements. Additionally, a San Diego Gas & Electric substation is Geocon Project No. G2560-52-01 - 3 - March 3, 2021
located on the northeast corner of the property. Existing grades are relatively flat with elevations of approximately 8 to 12 feet Mean Sea Level (MSL) on the west and east, respectively.
Based on discussions with you, we understand the proposed development will consist of demolition of the existing warehouse building and ancillary structures and construction of new concrete-tilt-up style warehouse buildings and a hotel building along with other associated improvements. We do not expect the site will require storm water management devices. No other information is known at this time. We will need to prepare an updated geotechnical investigation once the site plans are developed.
3. GEOLOGIC SETTING
Regionally, the site is located in the Peninsular Ranges geomorphic province. The province is bounded by the Transverse Ranges to the north, the San Jacinto Fault Zone on the east, the Pacific Ocean coastline on the west, and the Baja California on the south. The province is characterized by elongated northwest-trending mountain ridges separated by straight-sided sediment-filled valleys. The northwest trend is further reflected in the direction of the dominant geologic structural features of the province that are northwest to west-northwest trending folds and faults, such as the nearby Rose Canyon fault zone.
Locally, the site is within the coastal plain of San Diego County. The coastal plain is underlain by a thick sequence of relatively undisturbed and non-conformable sedimentary bedrock units that thicken to the west and range in age from Upper Cretaceous age through the Pleistocene age which have been deposited on Cretaceous to Jurassic age igneous and volcanic bedrock. 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 site is located on the western portion of the coastal plain. Artificial fill, young alluvial flood-plain deposits (Bay Deposits), and marine sedimentary units consisting of Pleistocene-age Old Paralic Deposits (formerly known as the Bay Point Formation) make up the geologic sequence at the site. The Old Paralic Deposits are shallow marine deposits generally consisting of sand and silty sand units interfingered with layers of silt and clay. Based on published geologic information, we expect this unit to be in excess of 150 to 160 feet deep and extend below the current sea level. The mapped geologic conditions at the site is presented on the Regional Geologic Map.
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Regional Geologic Map
4. SOIL AND GEOLOGIC CONDITIONS
Based on our review of published geologic maps, and the current and previous investigations at the site, we expect the site is underlain by two surficial soil types (consisting of undocumented fill and Holocene-age Bay Deposits) and two formational unit (consisting of Old Paralic Deposits and the San Diego 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 B. The geologic units are discussed herein in order of increasing age.
4.1 Undocumented Fill (Qudf)
We expect that undocumented fill associated with the existing site improvements is present across the majority of the site to depths of about 5 to 10 feet. In general, the fill consists of loose to medium dense, moist to wet, silty sand and possesses a “very low” to “low” expansion index (expansion index of 50 or less). The fill located below the groundwater elevation possesses a potential for liquefaction.
Additionally, we understand that a zone of debris fill is located along the previous shoreline of the bay (along the western edge of the property). These materials are composed of concrete and trash debris mixed with soil that extend to depths of 5 to 10 feet. The upper portion of the undocumented fill is likely unsuitable for the support of proposed structures or structural fill and will require remedial grading. However, we expect the remedial grading operations will be limited to the groundwater elevation and/or saturated soil conditions.
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4.2 Bay Deposits (Qb)
The Bay Deposits (bay mud) exist below the undocumented fill or at-grade to a maximum depth of approximately 15 to 20 feet on the western portion of the site and 20 to 30 feet on the eastern portion of the site. The bay deposits generally consist of very loose to medium dense, silty and clayey sand and soft, wet to saturated, sandy silt and clay. Sandy portions of the Bay Deposits are potentially liquefiable when subjected to strong ground motion. Additionally, the soft muds within the Bay Deposits are subject to consolidation settlement. The amount of settlement that could occur is a function of how thick the layer is, how compressible the layer is and the magnitude of the new vertical load (weight of new fill or future building loads). We consider these materials unsuitable for the support of structures or structural fill in their present condition.
4.3 Old Paralic Deposits (Qop)
The Quaternary-age Old Paralic Deposits (formally called the Bay Point Formation) exist below the undocumented fill and/or Bay Deposits across the site. The Old Paralic Deposits consist of medium dense to very dense sand layers interbedded with stiff clay and silt layers. The Old Paralic Deposits are considered suitable for the support of the proposed structures. However, we do not expect the Old Paralic Deposits will be encountered during the construction of the planned improvements.
4.4 San Diego Formation (Tsd)
Based on published geologic information, we expect the San Diego Formation underlies the Old Paralic Deposits. Based on our experience in the area, the top of the San Diego Formation is at about 150 to 160 feet deep (an elevation of -140 to -150 MSL). The San Diego Formation consists of dense to very dense silty, to clayey sandstone and siltstone. We do not expect to encounter the San Diego Formation during the construction of the planned improvements.
5. GROUNDWATER
We previously encountered groundwater at depths ranging from about 8 to 20 feet below the existing ground surface (approximate elevation of 1 to 7 feet above MSL). In addition, we encountered groundwater during our current study within the CPTs at depths ranging from approximately 5 to 8 feet below the existing ground surface (approximate elevation of 2 to 5 feet above MSL). Several groundwater monitoring wells have been installed on and adjacent to the property. Based on review of our existing information in the vicinity of the site, the groundwater depths range from about 3 to 11 feet below grade. The water elevations fluctuate due to tidal influences. The groundwater should be considered brackish due to the close proximity to the San Diego Bay and Pacific Ocean. Groundwater will be a factor in development especially in liquefaction remediation, deep foundation design and construction, grading operations and utility installation. A groundwater elevation of 6 feet above MSL should be incorporated into the design and construction operations. In addition, the soil about 2 to Geocon Project No. G2560-52-01 - 6 - March 3, 2021
3 feet above the groundwater elevation may be saturated. Groundwater and seepage is dependent on seasonal precipitation, tidal influence, irrigation, land use, among other factors, and varies as a result.
Proper surface drainage will be important to future performance of the project.
6. GEOLOGIC HAZARDS
6.1 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).
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.
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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.
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 Potential and Seismically Induced Settlement 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.
The surficial soil (undocumented fill and Bay Deposits) at the site is generally loose/soft and considered to possess a potential for liquefaction below the groundwater elevation. The Multi- Jurisdictional-Hazard Mitigation Plan (2017) maps the site as having zones of liquefiable layers.
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Liquefaction Hazard Map
The current standard of practice, as outlined in the Recommended Procedures for Implementation of DMG Special Publication 117A, Guidelines for Analyzing and Mitigating Liquefaction in California requires liquefaction analysis to a depth of 50 feet below the lowest portion of the proposed structure.
Liquefaction typically occurs in areas where the soils below the water table are composed of poorly consolidated, fine to medium-grained, primarily sandy soil. In addition to the requisite soil conditions, the ground acceleration and duration of the earthquake must also be of a sufficient level to induce liquefaction.
We performed liquefaction analyses with our CPT soundings using the program CLiq (Version 3.0).
This program utilizes the 2001 NCEER method of analysis. We used a static groundwater elevation of 6 feet MSL, a modal magnitude of 6.12 earthquake (attributed to the Rose Canyon Fault), and a peak horizontal site acceleration, PGA
M, of 0.636g calculated from ASCE 7-16 Section 11.8.3. This semi- empirical method is based on correlations with the data collected from the CPT soundings and field performance data.
The liquefaction analyses (included in Appendix C) indicate the surficial soils to depths between approximately 5 and 30 feet below the existing grade at the locations the CPTs could be prone to between 0.2 and 1.3 inches during ground motion resulting in an average of about 0.5 to 0.75 inches.
Additionally, relatively thin and isolated lenses of soil within the Old Paralic Deposits between 30 and 50 feet are potentially liquefiable.
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Sand boils occur where liquefiable soil is extruded upward through the soil deposit to the ground surface. Providing an increase in overburden pressure and a compacted fill mat can mitigate surface manifestation. Research presented by Ishihara (1985) indicates that the presence of a non-liquefiable surface layer typically results in the effects of at-depth liquefaction from reaching the surface.
Modifications to Ishihara’s chart have been made to include higher ground accelerations (Ishihara’s 1985 chart was based on a 0.25g ground acceleration) by Youd and Garris (1995). Based on Youd’s modified curves and the thickness of the non-liquefiable soil layer (layer above the assumed groundwater table), the potential for surface manifestation is possible unless ground improvements are performed.
Lateral spreading occurs when liquefiable soil is in the immediate vicinity of a free face such as a slope. Factors controlling lateral displacement include earthquake magnitude, distance from the earthquake epicenter, thickness of liquefiable soil layer, grain size characteristics, fines content of the soil and SPT blow counts. Bartlett and Youd (1995) have concluded that lateral spreading is restricted to sediments with corrected SPT blow counts of 15 or less for earthquake magnitudes less than or equal to 8.0. The potential of lateral spreading in the liquefiable soil below the groundwater table is not considered an adverse impact to the proposed development due to relatively flat topography of the site and distance to the San Diego Bay from the site.
The mitigation of potential hazards due to liquefaction can be accomplished by the densification or removal of the potentially liquefiable soil or the use of foundation systems that still provide acceptable structural support should liquefaction occur. Soil densification can be accomplished by compaction grouting, vibrocompaction, soil mixing, and deep dynamic compaction (among others). We understand the use of vibrocompaction or stone columns may be unacceptable due to the creation of potential vertical pathways for contamination and potential distress to existing structures. Soil densification is generally used to increase the density and provide liquefaction mitigation of sensitive soil to relatively shallow depths over large areas. Deep foundation systems may be used to transmit structural loads to bearing depths below the liquefiable zones and may consist of driven piles or drilled piles. Deep foundations are designed to mitigate damage to the structures supported on the piles; however, they do not generally reduce the potential for damage to underground utilities and peripheral site improvements. The effects of differential settlement between ridged structures and attached settlement-sensitive surface improvements can be mitigated by designing the utilities to accommodate differential movement at the connections.
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 800 feet from San Diego Bay, is at an elevation of about 10 feet or greater above Mean Sea Level (MSL) and is protected from ocean waves by the Silver Strand to the west.
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Based on historic and predicated wave heights and runout lengths, the proposed site elevation with neighboring topographic features is likely sufficient to mitigate the risk; 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 first-order driving force for locally generated tsunamis offshore southern California is expected to be tectonic deformation from large earthquakes (Legg, et al., 2002). Historically, tsunami wave heights have ranged up to 3.7 feet in the San Diego area. Wave heights and run-up elevations from tsunamis along the San Diego Coast have historically fallen within the normal range of the tides. The Multi-Jurisdictional Hazard Mitigation Plan (2017) maps zones of possible tsunami inundation for coastal areas throughout the county. The site is not included within one of these high- risk hazard areas. Therefore, we consider the risk of a tsunami hazard at the site to be low.
Tsunami Inundation Map
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 800 feet from San Diego Bay, is at an elevation of about 10 feet or greater above Mean Sea Level (MSL) and is protected from ocean waves by the Silver Strand to the west. Based on historic and predicated wave heights and runout lengths, we expect the proposed site elevation is sufficient to mitigate the risk; therefore, we consider the potential for seiches to impact the site low.
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6.5 Hazardous Subsurface Materials
We understand contaminated soil and groundwater have been encountered at locations in the vicinity of the property associated with past and current uses as an industrial facility (AECOM, 2017). Where proposed remedial grading, installation of utilities or other improvements extend into areas identified as containing contaminated soil and/or contaminated groundwater, special provisions may be required for the health and safety of workers and to limit movement of the contamination in accordance with the project environmental consultant. Construction techniques to limit movement of contaminates may be required. Additionally, we understand the use of certain ground improvement techniques (i.e. stone columns or wick drains, modifying the use of pipe bedding and certain types of deep foundations) may be restricted due to the existing contaminated soil.
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7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 From a geotechnical engineering standpoint, we opine the subject site is suitable for proposed improvements provided the preliminary recommendations presented herein are implemented in design and construction of the project. We should be contacted to prepare an updated geotechnical investigation to provide recommendations for the planned buildings and improvements once design plans are available.
7.1.2 The site may be subject to geologic hazards, including moderate to strong seismic shaking, liquefaction, seismically induced settlement and consolidation settlement. From a geotechnical engineering standpoint, we opine soil or geologic conditions do not exist at the subject site that is considered adverse to proposed improvements at the site, assuming they are designed to accommodate the potential geologic hazards at the site or be mitigated during the construction operations.
7.1.3 Based on a review of the referenced documents and our experience in the area, we expect the site is underlain by undocumented fill and Bay Deposits overlying Old Paralic Deposits and San Diego Formation. The existing formational units are considered suitable for support of structural loads from the proposed development. However, remedial grading and possible ground modification of the surficial materials situated may need to be performed.
7.1.4 We encountered groundwater at a depth of approximately 5 to 8 feet below the existing ground surface (approximate elevation of 2 to 5 feet above MSL). Groundwater will likely have a significant influence on construction of deep utilities (if constructed), and during remedial grading. Dewatering will likely be required for excavations below the fluctuating groundwater elevation. The project should be designed with a groundwater elevation of 6 feet MSL.
7.1.5 We expect that grading of the site will consist of removal of the upper portions of the surficial materials (undocumented fill and/or bay deposits) within areas that are to receive new fill or structures supported on shallow foundations. These removals will likely be limited to within 2 to 3 feet above groundwater elevations due to saturated soil conditions.
Removals within the proposed pavement areas can likely be limited to the upper 1 to 2 feet of existing soil.
7.1.6 We should provide foundation recommendations in future studies. Proposed ancillary structures may be supported on a shallow foundation system bearing in compacted fill, assuming that the estimated seismic and static load settlements can be accommodated by the Geocon Project No. G2560-52-01 - 13 - March 3, 2021
structure. Alternatively, we expect the settlement-sensitive structures would be supported by a deep foundation system or by a shallow foundation system over ground that has been modified to mitigate the liquefaction potential (i.e. ground improvements).
7.1.7 Excavation of the fill, Bay Deposits and Old Paralic Deposits should generally be possible with moderate to heavy effort using conventional, heavy-duty equipment during grading and trenching operations.
7.1.8 Adequate drainage provisions are imperative to the performance of the development. Site drainage should be maintained to direct surface runoff into controlled drainage devices.
Positive site drainage should be maintained away from structures and pavements and tops of slopes and directed to storm drain facilities.
7.2 Soil Characteristics
7.2.1 Based on the soil encountered during previous investigations for the site, we expect the soil is considered to be “non-expansive” and “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. Table 7.2.1 presents soil classifications based on the expansion index. We expect a majority of the soil encountered possess a “very low” to “low” expansion potential (EI of 50 or less).
TABLE 7.2.1
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
0 – 20 Very Low Non-Expansive
21 – 50 Low
Expansive
51 – 90 Medium
91 – 130 High
Greater Than 130 Very High
7.2.2 Previously reported laboratory water-soluble sulfate content test results indicate the on-site materials possess “S0” to “S2” sulfate exposure to concrete structures as defined by 2019 CBC Section 1904 and ACI 318-14 Chapter 19. Table 7.2.2 presents a summary of concrete requirements set forth by 2019 CBC Section 1904 and ACI 318. 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.
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TABLE 7.2.2
REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
S0 SO4<0.10 No Type
Restriction n/a 2,500
S1 0.10<SO4<0.20 II 0.50 4,000
S2 0.20<SO4<2.00 V 0.45 4,500
S3 SO4>2.00 V+Pozzolan or
Slag 0.45 4,500
1 Maximum water to cement ratio limits do not apply to lightweight concrete
7.2.3 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 Seismic Design Criteria
7.3.1 Table 7.3.1 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. However, we expect the proposed buildings will possess a period of less than 0.5 second; therefore, the building improvements can be designed based on the soil conditions (ASCE 7-16, Section 20.3.1). The values presented herein are for the risk-targeted maximum considered earthquake (MCE R). Sites designated
as Site Class D, E and F may require additional analyses if requested by the project structural engineer and client.
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TABLE 7.3.1
2019 CBC SEISMIC DESIGN PARAMETERS
Site Class E Section 1613.2.2
MCER Ground Motion Spectral Response
Acceleration – Class B (short), SS
1.234g Figure 1613.2.1(1)
MCER Ground Motion Spectral Response
Acceleration – Class B (1 sec), S1
0.411g Figure 1613.2.1(2)
Site Coefficient, FA 1.200 Table 1613.2.3(1)
Site Coefficient, FV 2.377* Table 1613.2.3(2)
Site Class Modified MCER Spectral Response
Acceleration (short), SMS
1.481g Section 1613.2.3 (Eqn 16-36)
Site Class Modified MCER Spectral Response
Acceleration – (1 sec), SM1
0.978g* Section 1613.2.3 (Eqn 16-37)
5% Damped Design
Spectral Response Acceleration (short), SDS
0.987g Section 1613.2.4 (Eqn 16-38)
5% Damped Design
Spectral Response Acceleration (1 sec), SD1
0.652g* Section 1613.2.4 (Eqn 16-39)
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.
7.3.2 Table 7.3.2 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 7.3.2
ASCE 7-16 PEAK GROUND ACCELERATION
Mapped MCEG Peak Ground Acceleration, PGA 0.556g Figure 22-7 Site Coefficient, FPGA 1.144 Table 11.8-1
Site Class Modified MCEG
Peak Ground Acceleration, PGAM
0.636g Section 11.8.3 (Eqn 11.8-1)
7.3.3 Conformance to the criteria in Tables 7.3.1 and 7.3.2 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.
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7.4 Site Drainage and Moisture Protection
7.4.1 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.
7.4.2 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.
7.4.3 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. We recommend that area drains to collect excess irrigation water and transmit it to drainage structures or impervious above-grade planter boxes be used. In addition, where landscaping is planned adjacent to the pavement, we recommend construction of a cutoff wall along the edge of the pavement that extends at least 6 inches below the bottom of the base material.
7.5 Storm Water Management
7.5.1 The United States Department of Agriculture (USDA), Natural Resources Conservation Services, possesses general information regarding the existing soil conditions for areas within the United States. The USDA website also provides the Hydrologic Soil Group.
Table 7.5 presents the descriptions of the hydrologic soil groups. If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. In addition, the USDA website also provides an estimated saturated hydraulic conductivity for the existing soil.
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TABLE 7.5
HYDROLOGIC SOIL GROUP DEFINITIONS
A
Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands.
These soils have a high rate of water transmission.
B
Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission.
C
Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission.
D
Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet.
These consist chiefly of clays that have a high shrink-swell potential, soils that have a high-water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.
7.5.2 Based on information from the USDA, the eastern portion of the property is designated as Huerohuero Urban Land Complex (2 to 9 percent slopes) and is classified as Soil Group D with a saturated hydraulic conductivity rate of 0.00 to 0.06 inches per hour, as shown on the USDA Hydrologic Soil Group Map. The western edge of the property is designated as Made Land which does not have a corresponding saturated hydraulic conductivity from USDA.
USDA Hydrologic Soil Group Map
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7.5.3 We should provide storm water infiltration recommendations if storm water management devices are planned.
7.6 Updated Geotechnical Investigation
7.6.1 We should be contacted to provide an updated geotechnical investigation for the project once the grading and building foundation are available. We should provide review of the project plans prior to final design submittal to evaluate if additional analyses and/or recommendations are required.
Geocon Project No. G2560-52-01 March 3, 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.
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974 PHONE 858 558-6900 - FAX 858 558-6159
Geocon Project No. G2560-52-01 March 3, 2021
APPENDIX A
FIELD INVESTIGATION
We performed our field investigation on February 11, 2021 that consisted of performing 5 CPTs (CPT-7 through -11). The CPTs extended to a maximum depth of approximately 80 feet, and the locations of the CPTs are shown on the Geologic Map, Figure 1. The CPT soundings are presented herein. We located the CPTs in the field using a measuring tape and existing reference points; therefore, actual locations may deviate slightly.
Kehoe Testing & Engineering performed the CPTs. The soil conditions encountered during the field investigation were automatically logged in a nearly continuous profile of penetration resistance as each CPT sounding was being conducted. The recorded tip stress, sleeve stress, and pore pressure of the soil is used to develop a stratigraphic interpretation of the soil profile.
APPENDIX B
PREVIOUS BORING LOGS AND LABORATORY TESTING RESULTS
FOR
COLLINS AEROSPACE REDEVELOPMENT SITE PARCEL B
NORTHEAST CORNER OF H STREET AND MARINA PARKWAY
CHULA VISTA, CALIFORNIA
PROJECT NO. G2560-52-01
APPENDIX C
LIQUEFACTION ANALYSIS
FOR
COLLINS AEROSPACE REDEVELOPMENT SITE PARCEL B
NORTHEAST CORNER OF H STREET AND MARINA PARKWAY
CHULA VISTA, CALIFORNIA
PROJECT NO. G2560-52-01
Geocon Project No. G2560-52-01 March 3, 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 Society of Civil Engineers (ASCE ), ASCE 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, 2017.
3. AECOM, Report of Annual Groundwater Monitoring and Sampling – 2017, Rohr Inc., North Campus, Chula Vista, California, dated October 18, 2017 (Project No. 60509378).
4. California Department of Conservation, Division of Mines and Geology, Probabilistic Seismic Hazard Assessment for the State of California, Open File Report 96-08, 1996.
5. California Geological Survey, Seismic Shaking Hazards in California, Based on the USGS/CGS Probabilistic Seismic Hazards Assessment (PSHA) Model, 2002 (revised April 2003). 10% probability of being exceeded in 50 years.
http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamain.html
6. County of San Diego, San Diego County Multi Jurisdiction Hazard Mitigation Plan, San Diego, California – Final Draft, dated October 2017.
7. Geocon Incorporated, 2020, Limited Geotechnical Investigation, Collins Aerospace Redevelopment Site – Parcel A, Chula Vista, California , dated October 12, 2020 (Project No. G2559-52-01).
8. Geocon Incorporated, 2020, Geotechnical Reconnaissance, Collins Aerospace Redevelopment Site – Parcel A, Chula Vista, California, dated June 25, 2020 (Project No. G2559-52-01).
9. Geocon Incorporated, 2005, Geotechnical Investigation, OMPPA Project on Goodrich Property, Chula Vista, California, dated September 12, 2005 (Project No. 07050-22-30).
10. Geocon Incorporated, 1999, Limited Geotechnical Investigation, B.F. Goodrich Site Development, Chula Vista, California, dated June 24, 1999 (Project No. 06327-22-01).
11. Geocon Incorporated, 1980, Soil Investigation, Sauder Furnace Foundation, Building No. 1, Column E11-F11, Chula Vista, California, dated July 14, 1980 (Project No. 02080-02-02).
12. Historical Aerial Photos. http://www.historicaerials.com
13. 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.
14. Kennedy, M. P., and S. S. Tan, 2008, Geologic Map of the San Diego 30’x60’ Quadrangle, California, USGS Regional Map Series Map No. 3, Scale 1:100,000.
15. Legg , M. R., J. C. Borrero, and C. E. Synolakis (2002), Evaluation of Tsunami Risk to Southern California Coastal Cities, 2002 NEHRP Professional Fellowship Report, dated January.
16. Special Publication 117A, Guidelines For Evaluating and Mitigating Seismic Hazards in California 2008, California Geological Survey, Revised and Re-adopted September 11, 2008.
17. Unpublished reports, aerial photographs, and maps on file with Geocon Incorporated.
18. USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra, http://geohazards.usgs.gov/designmaps/us/application.php.
19. Unpublished reports and maps on file with Geocon Incorporated.