Appendix_B_C24864011.pdf

APPENDIX B

Geotechnical Investigation

MARCH 2021

PREPARED FOR:

CALIFORNIA STATE PARKS –

SOUTHERN SERVICE CENTER

NTC AT LIBERTY STATION, BARRACKS 26

2797 TRUXTON ROAD

SAN DIEGO, CALIFORNIA 92106

PREPARED BY:

GEOCON CONSULTANTS, INC.

3160 GOLD VALLEY DRIVE, SUITE 800

RANCHO CORDOVA, CALIFORNIA 95742

GEOCON PROJECT NO. S1352-05-21

Comfort Station Replacements Huntington State Beach

Orange County, California

GEOTECHNICAL INVESTIGATION

Project No. S1352-05-21 March 17, 2021

VIA EMAIL

Carl Shaffer California State Parks – Southern Service Center NTC at Liberty Station, Barracks 26 2797 Truxtun Road San Diego, California 92106

Subject: GEOTECHNICAL INVESTIGATION

COMFORT STATION REPLACEMENTS

HUNTINGTON STATE BEACH

ORANGE COUNTY, CALIFORNIA

Mr. Sater:

In accordance with Contract C16E0085, Work Order No. 85-160900-17 dated January 31, 2020 we have prepared this geotechnical investigation report for the proposed comfort station (restroom) replacements at Huntington State Beach in Orange County, California.

The accompanying report presents our findings, conclusions, and recommendations pertaining to the geotechnical aspects of designing and constructing the project as presently proposed. This report provides a seismic hazards evaluation and design-level geotechnical recommendations for the proposed improvements. In our opinion, no adverse geotechnical or geologic conditions are present that would preclude construction at the site, provided the recommendations of this report are incorporated into design and construction of the project.

Please contact us if you have any questions concerning the contents of this report. We look forward to reviewing the project plans as they develop further, providing engineering consultation as needed, and performing geotechnical observation and testing services during construction.

Respectfully, GEOCON CONSULTANTS, INC.

Jeremy J. Zorne, PE, GE Jelisa Adams, PE, GE Senior Engineer Senior Engineer

TABLE OF CONTENTS

GEOTECHNICAL INVESTIGATION PAGE

1.0 INTRODUCTION AND SCOPE OF SERVICES

2.0 SITE AND PROJECT DESCRIPTION

3.0 SOIL AND GEOLOGIC CONDITIONS

3.1 Regional and Local Geology

3.2 Concrete

3.3 Fill

3.4 Eolian Deposits

4.0 GROUNDWATER

5.0 GEOLOGIC HAZARDS

5.1 Mapped Geologic Hazard Zones

5.2 Faulting / Ground Rupture

5.3 Ground Shaking

5.4 Liquefaction

5.5 Expansive Soil

5.6 Soil Corrosion Screening

6.0 CONCLUSIONS AND RECOMMENDATIONS

6.1 General Discussion

6.2 Code-Based Seismic Design Values

6.3 Soil and Excavation Characteristics

6.4 Materials for Fill

6.5 Grading and Earthwork

6.6 Foundations

6.7 Interior Slabs-on-Grade

6.8 Retaining Walls

6.9 Concrete Sidewalks and Flatwork

6.10 Site Drainage

7.0 FURTHER GEOTECHNICAL SERVICES

7.1 Plan and Specification Review

7.2 Testing and Observation Services

8.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS

9.0 REFERENCES

FIGURES

1. Vicinity Map 2-1. Site Plan – Comfort Station #2 2-2. Site Plan – Comfort Station #3

APPENDIX A

FIELD EXPLORATION

Figure A1 – Key to Logs Figures A2 through A5 – Boring Logs (B7 through B10) Figures A6 and A7 – CPT Sounding Logs (CPT 1 and CPT2)

TABLE OF CONTENTS (Continued)

LABORATORY TESTING PROGRAM

Figure B1 – Summary of Laboratory Results Figures B2 and B3 – Grain Size Distribution Figure B4 – Corrosivity Test Results

APPENDIX C

LIQUEFACTION ANALYSIS

Geocon Project No. S1352-05-21 - 1 - March 17, 2021

GEOTECHNICAL INVESTIGATION

1.0 INTRODUCTION AND SCOPE OF SERVICES

This report presents the results of our geotechnical investigation for the proposed comfort station (restroom) replacements at Huntington State Beach in Orange County, California. The approximate site location is shown on the Vicinity Map, Figure 1.

The purpose of our investigation was to explore and evaluate subsurface soil, geologic, and seismic conditions at the site and provide conclusions and design-level recommendations for the project as presently proposed.

To prepare this report, we performed the following scope of services:

• Performed a limited geologic literature review to aid in evaluating the geologic conditions present at the site (see References in Section 9.0 of this report).

• Coordinated with State Parks and performed a site reconnaissance to review project limits and mark out exploratory excavation locations for subsequent utility clearance.

• Notified subscribing utility companies via DigAlert/Underground Service Alert (USA) a minimum of two working days (as required by law) prior to performing exploratory excavations at the site.

• Paid required fees and obtain a drilling permit from Orange County Environmental Health (OCEHD).

• Performed two cone penetration test (CPT) soundings (CPT1 and CPT2) using truck-mounted equipment to a depth of approximately 50 feet each.

• Performed four exploratory borings (B7 through B101) using a truck-mounted drill rig equipped with direct-push sampling tooling to depths of approximately 15 feet.

• Obtain representative soil samples from the borings.

• Logged the borings in accordance with the Unified Soil Classification System.

• Upon completion, backfilled the borings with neat cement grout in accordance with OCEHD permit requirements.

• Performed laboratory tests to evaluate pertinent geotechnical parameters.

• Prepared this report summarizing our findings, conclusions, and recommendations regarding the geotechnical aspects of designing and constructing the project as presently proposed.

Approximate locations of the subsurface explorations are shown on the Site Plans, Figures 2 and 3.

Details of our field exploration program, including exploration logs, are presented in Appendix A.

Details of our laboratory testing program and test results are summarized in Appendix B. Results of our liquefaction analysis are presented in Appendix C.

1 Borings B1 through B6 were performed as part of the current ADA Improvements project, presented under separate cover.

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2.0 SITE AND PROJECT DESCRIPTION

The project will replace two comfort stations (restroom buildings) at Huntington State Beach which were damage/lost due to fire (arson). Other improvements will include accessibility upgrades to parking spaces serving the buildings and path of travel (ramp and stairs) from the parking lot to the buildings. Specific improvements are as follows:

Comfort Station #2 (Southeast of Brookhurst Street entrance)

• Demolish the fire-damaged Comfort Station #2 and replace with new comfort station.

• New comfort station to be roughly similar in size to original building, to include 50% accessible toilet rooms with baby changing stations, lavatories in all accessible and standard toilet rooms, no outdoor lavatories, no dressing/changing rooms, and no alcoves or partially enclosed shaded areas on building exterior.

• Reconstruct the existing sidewalk/ramp and railing from parking lot to building plaza to current accessibility standards.

• Modify the existing stair from multipurpose trail to building plaza to current accessibility standards; at a minimum, stripe stair nosings and install new handrails.

• Restripe four existing accessible parking stalls adjacent to comfort station plaza and multiuse trail, and provide signage. Stripe two stalls as van accessible and restripe section of parking lot between accessible stalls as “no parking” for access to Spencer Ramp. Restripe original stalls for conventional parking.

Comfort Station #3 (Northwest of Brookhurst Street entrance)

• Demolish the building slab, footings and utilities remaining from demolished (fire-damaged) comfort station and construct new comfort station.

• New comfort station to be roughly similar in size to original building, to include 50% accessible toilet rooms with baby changing stations, lavatories in all accessible and standard toilet rooms, no outdoor lavatories, no dressing/changing rooms, and no alcoves or partially enclosed shaded areas on building exterior.

• Reconfigure plaza and planter areas for accessibility and compatibility with new building.

• Reconstruct existing sidewalk/ramp and railing from parking lot to building plaza (two sides) to current accessibility standards.

• Reconstruct or modify existing stair from multipurpose trail to building plaza to current accessibility standards; at a minimum, stripe stair nosings and install new handrails.

• Modify and restripe existing accessible parking stalls as necessary for compliance with current accessibility standards.

Comfort Station #2 is located approximately 500 feet southeast of the intersection of Brookhurst Street and the Pacific Coast Highway (PCH). The existing comfort station building consists of a concrete masonry building with several individual restrooms. The building was damaged by fire (arson) and is currently out of service and closed to the public. The comfort station is located within an “island” in the parking lot adjacent to the beach. The island contains concrete flatwork, concrete benches, and elevated landscaped areas contained by concrete masonry landscape retaining walls on the order of 4

Geocon Project No. S1352-05-21 - 3 - March 17, 2021 feet high or less. Site-specific topography/survey information was not available for our review. Based on satellite imagery topographic information (Google Earth Pro, July 11, 2018, WGS84 EGM96 Geoid), the topography of the site is relatively flat-lying at elevations between approximately 10 to 15 feet. The site configuration is shown on the Site Plan, Figure 2.

Comfort Station #3 is located approximately 550 feet northwest of the intersection of Brookhurst Street and the PCH. The former comfort station building was damaged by fire (arson) and has been removed;

however, the concrete slab remains. The former comfort station is located within an “island” in the parking lot adjacent to the beach. The island contains concrete flatwork, concrete benches, and elevated landscaped areas contained by concrete masonry landscape retaining walls on the order of 4 feet high or less. Site-specific topography/survey information was not available for our review. Based on satellite imagery topographic information (Google Earth Pro, July 11, 2018, WGS84 EGM96 Geoid), the topography of the site is relatively flat-lying at elevations between approximately 10 to 15 feet. The site configuration is shown on the Site Plan, Figure 3.

Based on the original design plans (State of California, Department of Transportation, 1982) provided by State Parks, foundations for the former/existing comfort station buildings consist of continuous perimeter and wall footings and isolated column footings at the ends of the buildings. The perimeter and wall footings are reportedly 12 inches and 15 inches wide, respectively, and the column footings are 26 inches square. All footings are 12 inches deep.

The proposed new buildings will likely be of concrete masonry construction supported on conventional shallow foundations with interior concrete slabs-on-grade. Basements or other below-grade improvements are not planned. Grading plans are not yet available; however, due to the relatively flat site topography, we anticipate grading will include minor cuts and fills on the order of 5 feet or less.

3.0 SOIL AND GEOLOGIC CONDITIONS

We identified soil and geologic conditions by observing exploratory borings, reviewing the referenced geotechnical information for nearby sites, and reviewing the referenced geologic literature (Section 9.0). The soil descriptions provided in this report include the Unified Soil Classification System (USCS) symbol where applicable.

3.1 Regional and Local Geology

Based on our review of published geologic maps of the area (USGS, 2004), the site is located in the Peninsular Ranges geomorphic province of California on the coast of the Pacific Ocean. The site and local vicinity are underlain wind-blown (eolian) sand deposits (Qe). These deposits generally consist of beach sand and wind-blown sand.

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3.2 Concrete

Borings B7 through B10 were performed within the existing concrete flatwork areas within/near the comfort station building areas. At each boring location, the concrete was approximately 5 inches thick and was placed directly on soil (e.g. no aggregate/gravel underlayment).

3.3 Fill

Below the concrete, we encountered existing fill to depths ranging from approximately 1 to 1½ feet.

The fill generally consisted of loose to medium dense silty sand (SM). Since we do not know the compaction and placement history of the fill, excavation and re-compaction will be required during site grading. Specific recommendations are provided in this report.

3.4 Eolian Deposits

Below the fill, we encountered native eloian deposits to the maximum depth explored of approximately 50 feet. The eolian deposits generally consist of interbedded layers of poorly graded and (SP) and silty sand (SM). Relative density generally increases with depth and ranges from loose (near the ground surface) to medium dense to dense.

Soil conditions described in the previous paragraphs are generalized. The exploratory boring logs included in Appendix A detail soil type, color, moisture, consistency, and USCS classification of the soils encountered at specific locations and elevations. The CPT logs in Appendix A provide an indication of relative density with depth.

4.0 GROUNDWATER

We encountered groundwater in Borings B7 through B10 at depths ranging from approximately 9 to 10½ feet on December 4, 2020.

Review of the Seismic Hazard Zone Report for the Anaheim and Newport Beach 7.5-Minute Quadrangle (CGS, 1997) indicates that seasonal depth to groundwater in the vicinity of the site is approximately 3 feet. Based on this information, we expect that depth to groundwater fluctuates seasonally and is influenced by tidal action and precipitation/flow in the nearby rivers and drainage channels. Therefore, it is possible that groundwater may be higher or lower than the level observed during our investigation and may be encountered during construction.

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5.0 GEOLOGIC HAZARDS

5.1 Mapped Geologic Hazard Zones

The site is located in a mapped liquefaction hazard zone (CGS, 1997).

5.2 Faulting / Ground Rupture

Based on our research, analyses, and observations, the site is not located on any known “active” earthquake fault trace. In addition, the site is not located within an Alquist-Priolo Earthquake Fault Zone (Hart and Bryant, 2007). Therefore, we consider the potential for ground rupture due to onsite active faulting to be low.

The dominant sources of potential earthquake ground motions at the site include the Newport- Inglewood-Rose Canyon fault zone located approximately one-half mile east, the San Joaquin Hills thrust fault located approximately three miles northeast, and the Palos Verdes fault zone located (offshore) approximately 4 miles west of the site.

5.3 Ground Shaking

We used the United States Geological Survey (USGS) Unified Hazard Tool (https://earthquake.usgs.gov/hazards/interactive/) to determine the deaggregated seismic source parameters, including controlling magnitude and fault distance. The USGS estimated modal magnitude is 6.9 and the estimated Peak Ground Acceleration (PGA) for the Maximum Considered Earthquake (MCE) with a 2,475-year return period is 0.67g.

5.4 Liquefaction

Liquefaction is a phenomenon in which saturated cohesionless soils are subject to a temporary loss of shear strength due to pore pressure buildup under the cyclic shear stresses associated with earthquakes.

Primary factors that trigger liquefaction are strong ground shaking (seismic source), relatively clean, loose granular soils (primarily poorly graded sands and silty sands), and saturated soil conditions.

As previously mentioned, the site is located in a mapped liquefaction hazard zone (CGS, 1997) which indicates that soil and groundwater conditions exist at the site that may be susceptible to seismic-induced liquefaction under the design-level seismic event.

We analyzed the potential for liquefaction in general accordance with the Recommended Procedures for Implementation of DMG Special Publication 117A, Guidelines for Analyzing and Mitigating Liquefaction in California. We used the computer software program CLiq (Version 1.7, Geologmiski) and the in-situ soil parameters measured in our CPT soundings. The software utilizes the 1998 National Center for Earthquake Engineering Research (NCEER) method of analysis that was developed with the broad consensus of national geotechnical and earthquake engineering experts. We assumed an average

Geocon Project No. S1352-05-21 - 6 - March 17, 2021 groundwater depth of 10 feet, an earthquake moment magnitude of 6.9, and a PGA of 0.67g (PGAM adjusted for Site Class per ASCE 7-16, Eq. 11.8-1). Based on the results of our analyses, there is the potential for liquefaction at the site within sandy soil layers generally present between depths of approximately 10 and 25 feet. Results of our liquefaction analysis are presented in Appendix C.

Consequences of liquefaction may include loss of bearing capacity, ground surface settlement, ground loss (sand boils), and lateral slope displacements (lateral spreading). For loss of bearing capacity, the liquefiable layer must be close to the ground surface and within the zone of influence of the foundation.

The shallowest potentially liquefiable layer is approximately 10 feet deep, which is well below the zone of influence of the proposed foundations. Therefore, loss of bearing capacity is not expected. For liquefaction-induced sand boils or fissures to occur, pore water pressure induced within liquefied strata must exert a large enough force to break through overlying, non-liquefiable layers. Based on work by Youd and Garris (1995), which modified and advanced the work of Ishihara (1985), a capping layer of non-liquefiable soil can prevent the occurrence of sand boils or fissures. An apparently continuous, non-liquefiable stratum approximately 10 feet thick is present across the site. In our opinion, this layer is sufficiently thick enough to reduce the potential for ground loss due to sand boils or fissures.

Because the site topography is generally flat and level and there is not an adjacent free-face or sloping geometry, lateral spreading is not anticipated.

Therefore, ground surface settlement is the likely consequence of potential liquefaction at the site.

Dynamic settlement of the soils that experience liquefaction may occur after earthquake shaking has ceased. We estimated post-liquefaction settlement under the MCE and design-level ground motions using the CLiq software following the methodology of Zhang et al (2002), which is generally based on case histories of liquefaction of hydraulic fills in the San Francisco Bay Area, and are considered conservative for this site. In estimating post-liquefaction settlement at the site, we implemented a depth-dependent weighting factor for volumetric strain proposed by Cetin (2009). Development of this weighting factor is based on 49 high-quality, cyclically-induced, ground settlement case histories from seven different earthquakes. The weighting procedure was used to calibrate the analytical model to better fit actual surface settlement measurements at liquefaction sites. Additional rationale behind the use of a depth-dependent weighting factor is based on the following: 1) upward seepage, triggering void ratio redistribution and resulting in unfavorably higher void ratios for the shallower sublayers of soil layers; 2) reduced induced shear stresses and number of shear stress cycles transmitted to deeper soil layers due to initial liquefaction of surficial layers; and 3) arching effects due to non-liquefied soil layers. These factors generally reduce the contribution of volumetric settlement of deeper soil layers to the overall ground surface settlement (Cetin, 2009). The results of the analysis are summarized in Table 5.4A.

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TABLE 5.4A

ESTIMATED LIQUEFACTION SETTLEMENT

CPT Location

Estimated Total Liquefaction Settlement

MCE Ground Motion (PGAM = 0.67g)

CPT1 1.1 inches CPT2 1.1 inches

As detailed in Table 5.4A, estimated total liquefaction settlement of just over one inch is possible at the site under the maximum level earthquake event. Based on the distribution and magnitude of total liquefaction settlements, Table 5.4B presents the expected differential liquefaction settlement in terms of settlement over length (“L”) and deflection ratio.

TABLE 5.4B

DIFFERENTIAL LIQUEFACTION SETTLEMENT FOR DESIGN

Differential Liquefaction Settlement Deflection Ratio

½ inch over 30 feet 0.0014L

The magnitude of differential settlement is less than one-quarter of the differential settlement threshold allowed for Risk Category I or II buildings of any construction type Per Table 12.13-3 in Section

12.13.9 of ASCE 7-16. Therefore, shallow foundations may be used for this project with no special design with respect to liquefaction differential settlement.

5.5 Expansive Soil

Near-surface soil at the site is predominantly granular (sandy) and is considered essentially non-expansive. Mitigation and specific design measures with respect to expansive soil are not necessary.

5.6 Soil Corrosion Screening

We performed a soil corrosion potential screening by conducting laboratory testing on a representative near-surface soil sample. The laboratory test results and published screening levels are presented in Appendix B.

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6.0 CONCLUSIONS AND RECOMMENDATIONS

6.1 General Discussion

6.1.1 No soil or geologic conditions were encountered during our investigation that would preclude the proposed project as presently planned, provided the recommendations contained in this report are incorporated into the design and construction of the project.

6.1.2 Conclusions and recommendations provided in this report are based on our review of referenced literature, analysis of data obtained from our exploratory field exploration program, laboratory testing program, and our understanding of the proposed development at this time.

6.1.3 Geocon should be retained to review the project plans as they develop further, provide engineering consultation as-needed, and perform geotechnical observation and testing services during construction. The recommendations contained in this report are preliminary until verified during construction by representatives of our firm.

6.2 Code-Based Seismic Design Values

6.2.1 Seismic design of the proposed structures will be performed in accordance with the provisions of the 2019 California Building Code (CBC), the seismic provisions of which are based on the American Society of Civil Engineers (ASCE)/Structural Engineering Institute (SEI) publication: ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures (ASCE/SEI, 2017). We used the Structural Engineers Association of California (SEAOC) and Office of Statewide Health Planning and Development (OSHPD) web application Seismic Design Maps (https://seismicmaps.org/) to evaluate code-based seismic design parameters in accordance with ASCE 7-16.

6.2.2 For seismic design purposes, sites are classified as Site Class “A” through “F” as follows:

• Site Class A – Hard Rock;

• Site Class B – Rock;

• Site Class C – Very Dense Soil and Soft Rock;

• Site Class D – Stiff Soil;

• Site Class E – Soft Clay Soil; and

• Site Class F – Soils Requiring Site Response Analysis.

6.2.3 We evaluated seismic Site Class in accordance with Chapter 20 of ASCE 7-16. As discussed in Section 5.4 of this report, there is low potential for liquefaction and associated ground failure or collapse (sand boils/ground loss); therefore, Site Class “F” does not apply. Based on the subsurface conditions at the site, the three required criteria for Site Class “E” (Section

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20.3.2 of ASCE 7-16) do not apply. Therefore, we evaluated seismic Site Class on the basis of penetration resistance correlated from the CPT data. Based on this analysis, the site is classified as Site Class “D” (“Stiff Soil”) per Table 20.3-1 of ASCE 7-16.

6.2.4 For the purposes of evaluating code-based seismic parameters for design, we assumed a seismic Risk Category II (per the CBC) for the project. Results are summarized in Table 6.2.4.

TABLE 6.2.4

ASCE 7-16 (CODE-BASED) SEISMIC DESIGN PARAMETERS

SITE CLASS “D” – STIFF SOIL

Parameter Value ASCE 7-16 Reference

MCER Ground Motion Spectral Response Acceleration – Class B (short), SS 1.389g Figure 22-1

MCER Ground Motion Spectral Response Acceleration – Class B (1 sec), S1 0.498g Figure 22-2

Site Coefficient, FA 1.0 Table 11.4-1 Site Coefficient, FV 1.802* Table 11.4-2

Site Class Modified MCER Spectral Response Acceleration (short), SMS 1.389g Eq. 11.4-1

Site Class Modified MCER Spectral Response Acceleration (1 sec), SM1 0.898g* Eq. 11.4-2

5% Damped Design Spectral Response Acceleration (short), SDS 0.926g Eq. 11.4-3

5% Damped Design Spectral Response Acceleration (1 sec), SD1 0.598g* Eq. 11.4-4

Long Period Transition Period, TL 8 Seconds Figs. 22-14 through 22-

TS = SD1 / SDS 0.65 Seconds Chapter 11

* Per Section 11.4.8 of ASCE/SEI 7-16, a ground motion hazard analysis (GMHA) shall be performed for projects on Site Class “D” sites with long-period spectral acceleration (S1) greater than or equal to 0.2g, which is true for this site. However, Section 11.4.8 also provides exceptions which indicates that the ground motion hazard analysis may be waived provided the exceptions are followed. Using the code based values presented in the table above, in lieu of a performing a ground motion hazard analysis, requires the exceptions outlined in ASCE 7-16 Section 11.4.8 be followed.

Specifically for this site/project, Exception No. 2 would apply which states that a GMHA is not required for:

Structures on Site Class D sites with S1 greater than or equal to 0.2, provided the value of the seismic response coefficient Cs is determined by Eq. (12.8-2) for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with either Eq. (12.8-3) for TL ≥ T > 1.5Ts or Eq. (12.8-4) for T > TL.

6.2.5 Table 6.2.5 presents the mapped maximum considered geometric mean (MCEG) seismic design parameters for projects located in Seismic Design Categories of D through F, in accordance with ASCE 7-16.

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TABLE 6.2.5

ASCE 7-16 PEAK GROUND ACCELERATION PARAMETERS

Parameter Value ASCE 7-16 Reference

Mapped MCEG Peak Ground Acceleration, PGA 0.607g Figure 22-7 Site Coefficient, FPGA 1.1 Table 11.8-1

Site Class Modified MCEG Peak Ground Acceleration, PGAM 0.67g Section 11.8.3 (Eq. 11.8-1)

6.2.6 Conformance to the criteria presented in Tables 6.2.4 and 6.2.5 for seismic design does not constitute any kind of guarantee or assurance that significant structural damage or ground failure will not occur if a maximum level earthquake occurs. The primary goal of seismic design is to protect life and not to avoid structural damage, as such design may be economically prohibitive.

6.3 Soil and Excavation Characteristics

6.3.1 In our opinion, excavations at the site may be accomplished with light to moderate effort using typical heavy-duty grading/excavation equipment. We do not anticipate that excavations will produce oversized materials (greater than 6 inches in maximum dimension) which would require special handling or placement.

6.3.2 Based on the predominantly granular, near-surface soils, we anticipate temporary excavations, such as utility trenches, may experience sloughing/caving. It is the contractor’s responsibility to provide sufficient and safe excavation support as well as protecting nearby utilities, structures, and other improvements which may be damaged by earth movements.

6.3.3 Temporary excavation slopes must meet Cal-OSHA requirements as appropriate. Excavation sloping, benching, the use of trench shields, and the placement of trench spoils should conform to the latest applicable Cal-OSHA standards. The contractor should have a Cal- OSHA-approved “competent person” onsite during excavation to evaluate trench conditions and to make appropriate recommendations where necessary. It is the contractor’s responsibility to provide sufficient and safe excavation support as well as protecting nearby utilities, structures, and other improvements which may be damaged by earth movements.

6.3.4 The excavation support recommendations provided by Cal/OSHA are generally geared toward protecting human life and not necessarily toward preventing damage to nearby structures or surface improvements. The contractor is responsible for using the proper active shoring systems or underpinning measures to prevent damage to any structure or improvements located near excavations.

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6.3.5 Permanent cut and fill slopes (if any) should be constructed no steeper than 2H:1V (horizontal to vertical). To mitigate potential erosion, slopes should be vegetated as soon as possible and surface drainage should be directed away from the tops of slopes.

6.4 Materials for Fill

6.4.1 Excavated near-surface soils generated from cut operations at the site are suitable for use as engineered fill in structural areas, provided that they do not contain deleterious matter, organic material, tree roots, or rocks larger than 6 inches in maximum dimension.

6.4.2 Import fill material should be primarily granular with a “low” expansion potential

(Expansion Index less than 50), a Plasticity Index less than 15, be free of organic material and construction debris, and not contain rock larger than 6 inches in greatest dimension.

Import soil should also contain a sufficient amount of fines (generally more than 10%) to provide “binder” and reduce potential caving when excavated.

6.4.3 Environmental characteristics and corrosion potential of import soil materials should also be considered. Proposed import materials should be sampled, tested, and approved by Geocon prior to their transportation to the site.

6.5 Grading and Earthwork

6.5.1 Earthwork operations should be observed and fills tested for recommended compaction and moisture content by a representative of our firm.

6.5.2 References to relative compaction and optimum moisture content in this report are based on the American Society for Testing and Materials (ASTM) D1557 Test Procedure. Structural building pad areas should be considered as areas extending a minimum of feet horizontally beyond the outside dimensions of the buildings.

6.5.3 Prior to commencing grading, a pre-construction conference with representatives of the client, grading contractor, and Geocon should be held at the site. Site preparation, soil handling and/or the grading plans should be discussed at the pre-construction conference.

6.5.4 Site preparation should begin with complete removal of the existing comfort station structures including all foundations, underground utilities, surrounding flatwork, and pavements.

6.5.5 Excavations or depressions resulting from site clearing operations, or other existing excavations or depressions, should be restored with engineered fill in accordance with the recommendations of this report.

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6.5.6 Because of the disturbance that will be caused by removing the existing buildings, the new building pad should be over-excavated to at least the depth of the deepest former footing or underground utility, whichever is deeper. Existing footings are reported to be 12 inches deep based on the original design plans. Excavation should also be conducted as-necessary to remove all existing artificial fill. We note that groundwater may be encountered at relatively shallow depths. Therefore, the over-excavation depth should be limited to 2 to 3 feet maximum. The bottom of the over-excavated area should be scarified 8 inches, uniformly moisture-conditioned at or near optimum moisture content and compacted to at least 90% relative compaction. Over-excavation and re-compaction operations should be performed in the presence of a Geocon representative to evaluate performance of the subgrade under compaction equipment loading.

6.5.7 Engineered fill consisting of excavated soil or approved import should be compacted in horizontal lifts not exceeding 8 inches (loose thickness) and brought to final subgrade elevations. Each lift should be moisture-conditioned at or near optimum moisture content and compacted to at least 90% relative compaction.

6.5.8 Underground utility trenches within structural areas should be backfilled with properly compacted material. Pipe bedding, shading and backfill should conform to the requirements of the appropriate utility authority. Material excavated from trenches should be adequate for use as general backfill above shading provided it does not contain deleterious matter, vegetation or cementations larger than 6 inches in maximum dimension. Trench backfill should be placed in loose lifts not exceeding 8 inches. Lifts should be compacted to a minimum of 90% relative compaction at or above optimum moisture content.

6.6 Foundations

6.6.1 Provided the building pads are graded in accordance with the recommendations of this report, the proposed buildings may be supported on conventional shallow foundations bearing on engineered fill.

6.6.2 To reduce potential for moisture variations beneath buildings, foundations should include continuous perimeter footings with continuous wall footings or interior spread footings.

Perimeter footings should be continuous around the entire perimeter of the structure without breaks or discontinuities.

6.6.3 Continuous footings should be at least 12 inches wide and spread footings should be at least

18 inches square. All footings should be embedded at least 12 inches below pad grade.

Underground utilities running parallel to footings should not be constructed in the zone of influence of footings. The zone of influence may be taken to be the area beneath the footing and within a 1:1 plane extending out and down from the bottom of the footing.

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6.6.4 Continuous footings should be reinforced with at least four No. 4 reinforcement bars, two each placed near the top and bottom of the footing to allow footings to span isolated soil irregularities. The reinforcement recommended here is for soil characteristics only and is not intended to replace reinforcement required for structural considerations. The project structural engineer should evaluate the need for additional reinforcement.

6.6.5 Shallow foundations for the new building may be designed using an allowable bearing capacity of 2,000 pounds per square foot (psf) for dead plus live load conditions with a one-third increase for short-term transient loading such as wind and seismic.

6.6.6 Allowable passive pressure used to resist lateral movement of the footings may be assumed to be equal to a fluid weighing 300 pounds per cubic foot (pcf). The coefficient of friction to resist sliding is 0.35 for concrete against soil. Combined passive resistance and friction may be utilized for design, provided that the frictional resistance is reduced by 50%.

6.6.7 Foundations designed in accordance with the recommendations above should experience total post-construction settlement due to building loads of less than one inch and differential settlement of ½ inch or less over a distance of 50 feet. The majority of settlement will be immediate and occur as the building is constructed. This settlement is in addition to the potential liquefaction settlement estimated in Section 5.4.

6.6.8 A Geocon representative should observe foundation excavations prior to placing reinforcing steel or concrete to observe that the exposed soil conditions are consistent with those anticipated. If unanticipated soil conditions are encountered, foundation modifications may be required.

6.7 Interior Slabs-on-Grade

6.7.1 Conventional interior concrete slabs-on-grade are suitable for the building pads prepared as recommended in this report. Slab thickness and reinforcement should be determined by the structural engineer based on anticipated loading. However, slabs should be at least 4 inches thick and be reinforced with at least No. 3 reinforcing bars placed 18 inches on center, each way.

Control joints should be provided at periodic intervals in accordance with American Concrete Institute (ACI) or Portland Cement Association (PCA) recommendations, as appropriate.

6.7.2 If building pad soils become dry, they should be re-moistened prior to concrete slab-on-grade construction. Building pads should be moistened to at least optimum moisture content, at least 48 hours before placing the vapor barrier. Moisture content should be verified by Geocon prior to placing the vapor barrier.

Geocon Project No. S1352-05-21 - 14 - March 17, 2021

6.7.3 Migration of moisture through concrete slabs-on-grade or moisture otherwise released from slabs is not a geotechnical issue. However, for the convenience of the owner and design team, we are providing the following general suggestions for consideration by the owner, architect, structural engineer, and contractor. The suggested procedures may reduce the potential for moisture-related floor covering failures on concrete slabs-on-grade, but moisture problems may still occur even if the procedures are followed. If more detailed recommendations are desired, we recommend consulting a specialist in this field.

6.7.4 For slabs that receive floor coverings, a minimum 10-mil-thick vapor barrier meeting ASTM

E1745-97 Class C requirements may be placed directly below the slab, without a sand cushion. To reduce the potential for punctures, a higher quality vapor barrier (15 mil, Class A or B) may be used. The vapor barrier, if used, should extend to the edges of the slab and should be sealed at all seams and penetrations. At least 4 inches of ½- or ¾-inch crushed rock, with no more than 5% passing the No. 200 sieve, may be placed below the vapor barrier to serve as a capillary break.

6.7.5 The concrete water/cement ratio should be as low as possible. The water/cement ratio should not exceed 0.45 for concrete placed directly on the vapor barrier. Midrange plasticizers could be used to facilitate concrete placement and workability.

6.7.6 Proper finishing, curing, and moisture vapor emission testing should be performed in accordance with the latest guidelines provided by the ACI, PCA, and ASTM.

6.8 Retaining Walls

6.8.1 Design of retaining walls and buried structures may be based on the lateral earth pressures (equivalent fluid pressure) summarized in Table 6.8.1.

TABLE 6.8.1

RECOMMENDED LATERAL EARTH PRESSURES

Condition Equivalent Fluid Density

Active 35 pcf At-Rest 55 pcf Passive 300 pcf

Seismic Earth Pressure1 20 pcf

1. Applicable for walls that support more than 6 feet of backfill in accordance with the 2019 CBC. Conventional triangular distribution. Should be combined with ACTIVE lateral earth pressure for seismic case analysis.

Geocon Project No. S1352-05-21 - 15 - March 17, 2021

6.8.2 Unrestrained walls should be designed using the active case. Unrestrained walls are those that are allowed to rotate more than 0.001H (where H is the height of the wall). Walls restrained from movement should be designed using the at-rest case. The soil pressures listed in Table 6.8.1 are based on the assumption that that the backfill material within an area bounded by the wall and a 1:1 plane extending upward from the base of the wall will be composed of the existing onsite soils.

6.8.3 Retaining wall foundations with a minimum depth of 18 inches may be designed using the allowable bearing capacity of 2,000 psf. To resist lateral movement of retaining wall foundations, an allowable passive earth pressure equivalent to a fluid density of 300 pcf for footings or shear keys poured neat against properly compacted engineered fill soils or undisturbed natural soils. This allowable passive pressure is based on the assumption that a horizontal surface extends at least 5 feet or three times the depth of the footing or shear key, whichever is greater, beyond the face of the retaining wall foundation. If this surface is not protected by floor slabs or pavement, the upper 12 inches of material should not be included in the design for lateral resistance. An allowable friction coefficient of 0.35 may be used for resistance to sliding between soil and concrete. Combined passive resistance and friction may be utilized for design provided that the frictional resistance is reduced by 50%.

6.8.4 Retaining walls taller than 2 feet should be provided with a drainage system and waterproofed as required by the project architect. Positive drainage for retaining walls should consist of a vertical layer of permeable material positioned between the retaining wall and the soil backfill. The permeable material may be composed of a composite drainage geosynthetic or a natural permeable material (such as crushed gravel) at least 12 inches thick and capped with at least 12 inches of native soil. A geosynthetic filter fabric should be placed between the gravel and the soil backfill. Provisions for removal of collected water should be provided for either system by installing a perforated drainage pipe along the bottom of the permeable material which leads to suitable drainage facilities.

6.9 Concrete Sidewalks and Flatwork

6.9.1 Onsite exterior concrete flatwork may be supported directly on properly moisture-conditioned and compacted subgrade soil.

6.9.2 Exterior concrete flatwork should be structurally independent of building foundations except at doorways where it should be dowelled into the adjacent slab. To reduce the potential for concrete cracking, exterior concrete flatwork could be reinforced with No. 3 reinforcing bars spaced 24 inches center to center, each way. Consideration should be given to providing adequate control joints in accordance with ACI or PCA guidelines.

Geocon Project No. S1352-05-21 - 16 - March 17, 2021

6.10 Site Drainage

6.10.1 Proper site drainage is critical to reduce the potential for differential soil movement, soil expansion, erosion and subsurface seepage. Under no circumstances should water be allowed to pond adjacent to building foundations. The site should be graded and maintained such that surface drainage is directed away from structures in accordance with the 2019 CBC or other applicable standards. In addition, surface drainage should be directed away from the top of slopes into swales or other controlled drainage devices.

6.10.2 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.

6.10.3 Experience has shown that even with these provisions, subsurface seepage may develop in areas where no such water conditions existed prior to site development. This is particularly true where a substantial increase in surface water infiltration has resulted from an increase in landscape irrigation.

7.0 FURTHER GEOTECHNICAL SERVICES

7.1 Plan and Specification Review

7.1.1 We should review the improvement plans and specifications prior to final design submittal to assess whether our recommendations have been properly implemented and to evaluate if additional analysis and/or recommendations are required.

7.2 Testing and Observation Services

7.2.1 The recommendations provided in this report are based on the assumption that Geocon will continue as Geotechnical Engineer of Record throughout the construction phase and provide construction observation and testing services. Providing these services during construction is important to maintain continuity of geotechnical interpretation and confirm that field conditions encountered are similar to those anticipated during design. If we are not retained for these services, we cannot assume any responsibility for other’s interpretation of our recommendations and, therefore, the future performance of the project.

Geocon Project No. S1352-05-21 - 17 - March 17, 2021

8.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS

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, we should be notified so that supplemental recommendations can be given. The evaluation or identification of the potential presence of hazardous materials or environmental contamination was not part of our scope of services.

This report is issued with the understanding that it is the responsibility of the owner or their representative to ensure that the information and recommendations contained herein are brought to the attention of the design team for the project and incorporated into the plans and specifications, and the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field.

The recommendations contained in this report are preliminary until verified during construction by representatives of our firm. Changes in the conditions of a property can occur with the passage of time, whether they are due to natural processes or the works of man on this or adjacent properties.

Additionally, 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 partially or wholly by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years.

Our professional services were performed, our findings obtained, and our recommendations prepared in accordance with generally accepted geotechnical engineering principles and practices used in the site area at this time. No warranty is provided, express or implied.

Geocon Project No. S1352-05-21 - 18 - March 17, 2021

9.0 REFERENCES

1. American Concrete Institute, ACI 318-14, Building Code Requirements for Structural Concrete and Commentary, 2014.

2. American Society of Civil Engineers / Structural Engineering Institute, ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, 2017.

3. Bryant, W.A., and E.W. Hart, Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zone Maps, California Geological, Special Publication 42, Interim Revision 2007.

4. California Building Standards Commission, 2019 California Building Code.

5. California Department of Transportation, Huntington State Beach Comfort Station, Foundation Plan (Sheet S3.1), July 1982.

6. California Geological Survey, State of California Seismic Hazard Zones, Newport Beach Quadrangle, Official Map, Liquefaction Zone Released: April 17, 1997; Landslide Zone Released: April 15, 1998.

7. Cetin, K.O., Bilge, H.T., Wu, J., Kammerer, A.M., and Seed, R.B., Probabilistic Model for the Assessment of Cyclically Induced Reconsolidation (Volumetric) Settlements, ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vo. 135, No. 3, March 1, 2009.

8. GeoLogismiki, CLiq V1.07 – Cone Penetration Test based soil liquefaction assessment software, 2014.

9. Jennings, C.W. (compiler), Fault Map of California, California Division of Mines and Geology, 1982.

10. National Center for Earthquake Engineering Research, Evaluation of Liquefaction Resistance of Soils, December 1997.

11. Portland Cement Association, Concrete Floors on Ground, 2001.

12. Seed, H.B. and Tokimatsu, K., Simplified Procedures for the Evaluation of Settlements in Sands due to Earthquake Shaking, Earthquake Engineering, 1987.

13. Southern California Earthquake Center, University of Southern California, Recommended Procedures for Implementation of DMG Special Publication 117A, Guidelines for Analyzing and Mitigating Liquefaction in California, March 1999.

14. Structural Engineers Association of California (SEAOC) and Office of Statewide Health Planning and Development (OSHPD), Seismic Design Maps, https://seismicmaps.org/.

15. United States Geological Survey, Unified Hazard Tool, https://earthquake.usgs.gov/hazards/interactive.

16. United States Geological Survey, Geologic Map of the San Bernardino and Santa Ana 30’ x 60’ Quadrangles, California, 2006.

17. Unpublished reports, aerial photographs, and maps on file with Geocon.

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PROJECT

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Comfort Station #3

Comfort Station #2

Comfort Station #3

Comfort Station #2

Pl ac en tia

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Newport Beach

Newport Beach

Comfort Station Replacements Huntington State Beach

Huntington Beach, California

VICINITY MAP

March 2021 Figure 1S1352-05-21

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