VA701-16-B-0085-A00005002 - Geotechnical Report.pdf

GEOTECHNICAL INVESTIGATION

VA LA JOLLA

PARKING STRUCTURE PHASE II

LA JOLLA, CALIFORNIA

PREPARED FOR:

MR. GERARD R. GULPEO

LEO A DALY

550 SOUTH HOPE STREET, 27TH FLOOR

LOS ANGELES, CALIFORNIA 90071-2627

PREPARED BY:

SCST, INC.

6280 RIVERDALE STREET

SAN DIEGO, CALIFORNIA 92120

Providing Professional Engineering Services Since 1959

March 10, 2016 SCST No. 160174F Report No. 1

Mr. Gerard R. Gulpeo Leo A Daly 550 South Hope Street, 27th Floor Los Angeles, California 90071-2627

Subject: GEOTECHNICAL INVESTIGATION

VA LA JOLLA

PARKING STRUCTURE PHASE II

LA JOLLA, CALIFORNIA

Dear Mr. Gulpeo:

SCST, Inc. (SCST) is pleased to present our report describing the geotechnical investigation performed for the subject project. SCST conducted the geotechnical investigation in general conformance with the scope of work presented in our proposal dated December 2, 2014. If you have any questions, please call our office at (619) 280-4321.

Respectfully Submitted, SCST, INC.

W. Lee Vanderhurst, CEG 1125 Principal Geologist

Emil Rudolph, GE 2767 Principal Geotechnical Engineer

WLV: ER:aw

(1) Addressee via e-mail at GRGulpeo@LeoADaly.com

TABLE OF CONTENTS

SECTION PAGE

EXECUTIVE SUMMARY ............................................................................................................. i

1 INTRODUCTION

2 SCOPE OF WORK

2.1 FIELD INVESTIGATION

2.2 LABORATORY TESTING

2.3 ANALYSIS AND REPORT

3 SITE AND SUBSURFACE CONDITIONS

3.1 SITE DESCRIPTION

3.2 SUBSURFACE CONDITIONS

4 GEOLOGIC HAZARDS

4.1 CITY OF SAN DIEGO SEISMIC SAFETY STUDY

4.2 CBC SEISMIC DESIGN PARAMETERS

4.3 FAULTING AND SURFACE RUPTURE

4.4 LIQUEFACTION AND DYNAMIC SETTLEMENT

4.5 LANDSLIDES AND SLOPE STABILITY

4.6 TSUNAMIS, SEICHES AND FLOODING

4.7 SUBSIDENCE

4.8 HYDRO-CONSOLIDATION

5 CONCLUSIONS

6 RECOMMENDATIONS

6.1 SITE PREPARATION AND GRADING

6.1.1 Site Preparation

6.1.2 Earthwork

6.1.3 Expansive Material

6.1.4 Imported Soil

6.1.5 Site Excavation Characteristics

6.1.6 Oversized Material

6.1.7 Temporary Excavations

6.1.8 Temporary Shoring

6.1.9 Temporary Dewatering

6.1.10 Slopes

6.1.11 Surface Drainage

6.1.12 Grading Plan Review

6.2 FOUNDATIONS

6.2.1 Drilled, Cast-in-Place Concrete Piers

6.2.2 Shallow Footings in Scripps Formation

6.2.3 Shallow Footings in Fill

6.2.4 Foundation Plan Review

6.2.5 Foundation Excavation Observations

6.3 SLABS-ON-GRADE

6.3.1 Parking Structure Slab-on-Grade

6.3.2 Exterior Slabs-on-Grade

TABLE OF CONTENTS (Continued)

SECTION PAGE

6.4 CONVENTIONAL RETAINING WALLS

6.4.1 Foundations

6.4.2 Lateral Earth Pressures

6.4.3 Seismic Earth Pressure

6.4.4 Backfill

6.5 MECHANICALLY STABILIZED EARTH RETAINING WALLS

6.6 PAVEMENT SECTION RECOMMENDATIONS

6.7 SOIL CORROSIVITY

7 GEOTECHNICAL ENGINEERING DURING CONSTRUCTION

8 CLOSURE

9 REFERENCES

ATTACHMENTS

FIGURES

Figure 1............................................................................................................. Site Vicinity Map Figure 2........................................................................................................... Geotechnical Map Figure 3..................................................................................... Scripps Formation Contour Map Figure 4.............................................................................................. Seismic Safety Study Map Figure 5................................................................................................... Regional Geology Map Figure 6......................................................................................................... Regional Fault Map Figure 7............................................................................................... Lateral Pressure Diagram Figure 8.......................................................................... Typical Retaining Wall Backdrain Detail Figure 9................................................................. Typical MSE Retaining Wall Backdrain Detail

APPENDICES

Appendix I ....................................................................................................... Field Investigation Appendix II ..................................................................................................... Laboratory Testing

EXECUTIVE SUMMARY

This report presents the results of the geotechnical investigation performed by SCST, Inc. (SCST) for Phase II of the VA La Jolla Parking Structure. We understand that the project will consist of the design and construction of the final phase of a two phase parking garage. Phase I is currently being constructed. Phase II will consist of a one-story parking structure over two levels of underground parking with a finished garage floor elevation of approximately 333 feet for level B2.

The purpose of our work is to provide conclusions and recommendations regarding the geotechnical aspects of Phase II of the parking garage.

SCST explored the subsurface conditions adjacent to the Phase II parking garage by drilling eight borings to depths between about 20 feet and 30½ feet below the existing ground surface using a truck-mounted drill rig equipped with a hollow stem auger. An SCST geologist logged the borings and collected samples of the materials encountered for laboratory testing. SCST tested selected samples from the borings to evaluate pertinent soil classification and engineering properties to assist in developing geotechnical conclusions and recommendations. Ten exploratory borings drilled for earlier geotechnical investigations for the Phase I and Phase II parking garage were utilized to supplement the subsurface information obtained during our investigation.

The materials encountered in the borings consist of undocumented fill and Scripps Formation.

The undocumented fill consists of medium dense to very dense silty fine sand and clayey sand.

The fill ranges from 3-feet to 33-feet thick. The deeper fill was encountered in the southern portion of the proposed garage. The fill is considered compressible and unsuitable for support of the planned structure. The Scripps Formation underlies the fill. The Scripps Formation consists of hard, moderately to strongly cemented sandy claystone, claystone, siltstone, sandy siltstone and silty sandstone. The formation is moderately fractured and contains concretions up to several feet in diameter. The Scripps Formation is considered suitable for support of the planned fill or structural loads. While groundwater was not encountered in the borings, seepage could be encountered during construction as a result of irrigation and rainfall runoff.

The main geotechnical considerations affecting the planned development are the presence of potentially compressible fill, expansive soil, and difficult excavations. It is our understanding that the garage will be supported by foundations bearing in Scripps Formation (as is the Phase I portion of the garage). This will result in deep (drilled cast-in-place concrete pier foundations) in areas where fills underlie the lowest levels of below grade parking. To mitigate expansive soils, the interior slab should be underlain by at least 2 feet of material with an expansion index of 50 or less. Exterior slabs outside the limits of the underground parking structure should be underlain by at least 2 feet of compacted fill with an expansion index of 50 or less. Contract documents should specify that the contractor mobilize equipment capable of excavating material with concretions.

Oversized rock will be generated during grading that will be unsuitable for reuse as fill.

Temporary dewatering may be necessary during construction. The grading and foundation recommendations presented herein may need to be updated once final plans are developed.

1 INTRODUCTION

This report presents the results of the geotechnical investigation performed by SCST, Inc. (SCST) for Phase II of the VA La Jolla Parking Structure. We understand that the project will consist of the design and construction of the final phase of a two phase parking garage. Phase I is currently being constructed. Phase II will consist of a one-story parking structure over two levels of underground parking with a finished garage floor elevation of approximately 333 feet for level B2.

The purpose of our work is to provide conclusions and recommendations regarding the geotechnical aspect of Phase II of the parking garage. Figure 1 presents a site vicinity map.

2 SCOPE OF WORK

2.1 FIELD INVESTIGATION

SCST explored the subsurface conditions adjacent to the Phase II parking garage by drilling eight borings to depths between about 20 feet and 30½ feet below the existing ground surface using a truck-mounted drill rig equipped with a hollow stem auger. An SCST geologist logged the borings and collected samples of the materials encountered for laboratory testing. SCST tested selected samples from the borings to evaluate pertinent soil classification and engineering properties to assist in developing geotechnical conclusions and recommendations. Ten exploratory borings drilled for earlier geotechnical investigations for the Phase I and Phase II (Ninyo & Moore, 2013; SCS&T, 2010) were utilized to supplement the subsurface information obtained during our investigation. Figure 2 shows the approximate locations of the borings. The logs of the borings drilled for this investigation and earlier (Ninyo

& Moore, 2013; SCS&T, 2010) are presented in Appendix I. Soils are classified according to the Unified Soil Classification System illustrated on Figure I-1.

2.2 LABORATORY TESTING

Selected samples obtained from the borings were tested to evaluate pertinent soil classification and engineering properties and enable development of geotechnical conclusions and recommendations. The laboratory tests consisted of:

Grain Size Distribution

Atterberg Limits

R-Value

Expansion Index

Corrosivity

Direct Shear

The results of the laboratory tests, and brief explanations of test procedures, are presented in

Appendix II.

2.3 ANALYSIS AND REPORT

The results of the field and laboratory tests were evaluated to develop conclusions and recommendations regarding:

Leo A Daly March 10, 2016 VA La Jolla Parking Structure Phase II SCS&T No. 160174F-1 La Jolla, California Page 2

Subsurface conditions beneath the site

Potential geologic hazards

Criteria for seismic design in accordance with the 2013 California Building Code (CBC)

Site preparation and grading

Excavation characteristics

Appropriate alternatives for foundation support along with geotechnical engineering criteria for design of the foundations

Estimated foundation settlements

Support for concrete slabs-on-grade

Lateral pressures for the design of retaining walls

Pavement sections

Corrosion potential

3 SITE AND SUBSURFACE CONDITIONS

3.1 SITE DESCRIPTION

The site is located at just south of the VA Medical Center in La Jolla California, in a paved parking lot. The centroid of the site is located at latitude 32.81068°; longitude -117.06625°.

The site is bordered by the medical center on the north, the Phase I parking garage on the west, and parking lots on the south and east. Existing site improvements consist of asphalt paved parking, landscaped medians, and light standards. The site slopes gently to the south with site elevations ranging from about 330 feet to about 343 feet above mean sea level

(MSL). The location of the site is shown on Figure 1, Vicinity Map and Figure 2, Geotechnical

Map.

3.2 SUBSURFACE CONDITIONS

The materials encountered in the borings consist of undocumented fill and Scripps Formation.

Descriptions of the materials are presented below. Figure 2 presents the site-specific geology. Figure 3 presents a contour map showing the estimated elevation of the top of the

Scripps Formation. Figure 5 presents the regional geology in the vicinity of the site.

Undocumented Fill - The undocumented fill consists of medium dense to very dense silty fine sand and clayey sand. The fill ranges from 3 feet to 33 feet thick. The deeper fill was encountered in the southern portion of the proposed garage. The fill is considered compressible and unsuitable for support of the planned structure.

Subsurface exploration data, construction data from the Phase I parking garage, old topographic maps and aerial photographs were used to estimate the elevation of the top of the

Scripps Formation (Figure 3, Scripps Formation Contour Map). By subtracting the elevation of the top of the Scripps Formation from existing or planned grades, the approximate thickness of fill can be calculated.

La Jolla, California Page 3

Scripps Formation - The Scripps Formation underlies the fill. The Scripps Formation consists of hard, moderately to strongly cemented sandy claystone, claystone, siltstone, sandy siltstone and silty sandstone. The formation is moderately fractured and contains concretions up to several feet in diameter. The Scripps Formation is considered suitable for support of the planned fill or structural loads.

Groundwater - Groundwater was not encountered in the borings. Seepage could be encountered during construction as a result of irrigation and rainfall runoff.

4 GEOLOGIC HAZARDS

4.1 CITY OF SAN DIEGO SEISMIC SAFETY STUDY

The site is located in Geologic Hazard Category 51 and 52 on the City of San Diego Seismic

Safety Study, Map Sheet 34. Geologic Hazard Category 51 is assigned to areas of nominal risk with level mesas underlain by terrace deposits and bedrock. Hazard Category 52 is assigned to areas considered to have favorable geologic structure and are considered to be low risk. A portion of the City of San Diego Seismic Safety Study is presented on Figure 4.

4.2 CBC SEISMIC DESIGN PARAMETERS

A geologic hazard likely to affect the project is groundshaking as a result of movement along an active fault zone in the vicinity of the subject site. The site coefficients and adjusted maximum considered earthquake spectral response accelerations in accordance with the

2013 CBC are presented below:

Site Coordinates: Latitude 32.81068° Longitude -117.06625° Site Class: C Site Coefficients, Fa = 1.000 Fv = 1.336 Mapped Spectral Response Acceleration at Short Periods, Ss = 1.199g Mapped Spectral Response Acceleration at 1-Second Period, S1 = 0. 464g SDS = 0.800g SD1 = 0.413g PGAM = 0.525g

4.3 FAULTING AND SURFACE RUPTURE

A regional fault map is presented in Figure 6. The site is not located in an Alquist-Priolo

Earthquake Fault Zone. No active faults are known to underlie or project toward the site. The closest active fault to the site is the Rose Canyon fault located approximately 3.3 kilometers west of the site. Additionally, the Elsinore fault is located approximately 39 kilometers northeast of the site at its closest approach. Several unnamed potentially active faults have been mapped to the north, south and east of the site (Figures 4 and 6). The faults appear

La Jolla, California Page 4 overlain by unfaulted Quaternary aged deposits. The probability of fault rupture at the site is low.

4.4 LIQUEFACTION AND DYNAMIC SETTLEMENT

Liquefaction occurs when loose, saturated, generally fine sands and silts are subjected to strong ground shaking. The soils lose shear strength and become liquid, potentially resulting in large total and differential ground surface settlements as well as possible lateral spreading during an earthquake. Given the relatively dense nature of the materials beneath the site, the potential for liquefaction and dynamic settlement to occur is low.

4.5 LANDSLIDES AND SLOPE STABILITY

The site is relatively flat and evidence of landslides or slope instabilities was not observed. A review of aerial photographs of the site and immediate vicinity prior to development do not show evidence of slope instability. The potential for landslides or slope instabilities to occur at the site is considered low.

4.6 TSUNAMIS, SEICHES AND FLOODING

The site is not located within a mapped area on the State of California Tsunami Inundation

Maps (Cal EMA, 2009); therefore, damage due to tsunamis is considered low. Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays, or reservoirs. The site is not located adjacent to any lakes or confined bodies of water; therefore, the potential for a seiche to affect the site is considered low. The site is not located within a flood zone or dam inundation area (County of San Diego, 2012).

4.7 SUBSIDENCE

The site is not located in an area of known subsidence associated with fluid withdrawal

(groundwater or petroleum); therefore, the potential for subsidence due to the extraction of fluids is negligible.

4.8 HYDRO-CONSOLIDATION

Hydro-consolidation can occur in recently deposited (less than 10,000 years old) sediments that were deposited in a semi-arid environment. Examples of such sediments are aolian sands, alluvial fan deposits, and mudflow sediments deposited during flash floods. The pore space between particle grains can re-adjust when inundated by groundwater causing the material to consolidate. The relatively dense materials underlying the site are not susceptible to hydro-consolidation.

5 CONCLUSIONS

The main geotechnical considerations affecting the planned development are the presence of potentially compressible fill, expansive soil, and difficult excavations. It is our understanding that

La Jolla, California Page 5 the garage will be supported by foundations bearing in Scripps Formation (as is the Phase I portion of the garage). This will result in deep (drilled cast-in-place concrete pier foundations) in areas where fills underlie the lowest levels of below grade parking.

To mitigate expansive soils, the interior slab should be underlain by at least 2 feet of material with an expansion index of 50 or less. Exterior slabs outside the limits of the underground parking structure should be underlain by at least 2 feet of compacted fill with an expansion index of 50 or less.

Contract documents should specify that the contractor mobilize equipment capable of excavating and processing material with concretions. Oversized rock will be generated during grading that will be unsuitable for reuse as fill. Temporary dewatering may be necessary during construction.

The grading and foundation recommendations presented herein may need to be updated once final plans are developed.

6 RECOMMENDATIONS

6.1 SITE PREPARATION AND GRADING

6.1.1 Site Preparation

Site preparation should begin with the removal of existing improvements, vegetation and debris. The existing fill and Scripps Formation should be excavated at least 2 feet below finish basement grade where interior slabs-on-grade will be used. No overexcavation is recommended for areas where interior slabs will be supported by piers and grade beams.

Soil beneath exterior slabs and pavements should be excavated to at least 2 feet below subgrade. Excavations should extend at least 2 feet outside the planned hardscape and pavements, or up to temporary shoring or existing improvements, whichever is less. An

SCST representative should observe conditions exposed in the bottom of the excavation to determine if additional excavation is required.

6.1.2 Earthwork

Excavated material, except for roots, debris and rocks greater than 6 inches, can be used as compacted fill provided the material has an expansion index of 50 or less determined in accordance with ASTM D4829. Interior and exterior slabs-on-grade, hardscape, and pavements should be underlain by at least 2 feet of material with an expansion index of 50 or less. We expect that most of the onsite materials will not meet the expansion index criteria. Therefore, import may be required. Fill should be moisture conditioned to near optimum moisture content and compacted to at least 90% relative compaction. Fill should be placed in horizontal lifts at a thickness appropriate for the equipment spreading, mixing, and compacting the material, but generally should not exceed 8 inches in loose thickness.

The maximum dry density and optimum moisture content for the evaluation of relative compaction should be determined in accordance with ASTM D 1557. Utility trench backfill

La Jolla, California Page 6 beneath structures, pavements and hardscape should be compacted to at least 90% relative compaction. The top 12 inches of subgrade beneath pavements should be compacted to at least 95% relative compaction.

6.1.3 Expansive Material

The onsite materials tested have a low to medium expansion potential. The grading and foundation recommendations presented in this report reflect a low expansion potential.

6.1.4 Imported Soil

Imported soil should consist of predominately granular soil free of organic matter and rocks greater than 6 inches. Imported soil should have an expansion index of 50 or less and should be inspected and, if appropriate, tested by SCST prior to transport to the site.

6.1.5 Site Excavation Characteristics

It is anticipated that excavations in fill and Scripps Formation can be achieved with conventional earthwork equipment in good working order. However, difficult excavation should be anticipated in concretions and strongly cemented layers. Additionally, excavations in the Scripps Formation may generate oversized material that will require extra effort to crush or haul offsite. Contract documents should specify that the contractor mobilize equipment capable of excavating and compacting material with concretions and hard rock.

6.1.6 Oversized Material

Excavations may generate oversized material. Oversized material is defined as rocks or cemented clasts greater than 6 inches in largest dimension. Based on the planned construction, there does not appear to be suitable space onsite for disposal of oversized material within fills. Oversized material should be broken down to no greater than 6 inches in largest dimension for use in fill, used as landscape material, or disposed offsite.

6.1.7 Temporary Excavations

Temporary excavations 3 feet deep or less can be made vertically. Deeper temporary excavations in fill should be laid back no steeper than 1:1 (horizontal:vertical). Deeper temporary excavations in Scripps Formation should be laid back no steeper than ½:1

(horizontal:vertical). An SCST Geologist should observe temporary cut slopes to evaluate whether adverse conditions are present. The faces of temporary slopes should be inspected daily by the contractor’s Competent Person before personnel are allowed to enter the excavation. Any zones of potential instability, sloughing or raveling should be brought to the attention of the Engineer and corrective action implemented before personnel begin working in the excavation. Excavated soils should not be stockpiled behind temporary excavations within a distance equal to the depth of the excavation.

La Jolla, California Page 7

SCST should be notified if other surcharge loads are anticipated so that lateral load criteria can be developed for the specific situation. If temporary slopes are to be maintained during the rainy season, berms are recommended along the tops of slopes to prevent runoff water from entering the excavation and eroding the slope faces. Slopes steeper than those described above will require shoring. A shoring system consisting of soldier piles, lagging and tie-back anchors (if needed) can be used.

Existing fill should be classified as Type C soils in accordance with CalOSHA guidelines.

The Scripps Formation can be classified as a Type B soil in accordance with the CalOSHA guidelines.

6.1.8 Temporary Shoring

Slopes steeper than those described above will require shoring. Soldier piles and lagging, sheet piles, internally braced shoring, anchor tieback walls, or a combination of shoring types could be used.

Recommended earth pressure values for cantilever shoring (soldier piles and lagging and sheet piles without tie-back anchors) and for shoring with multiple levels of bracing

(internally braced or tie-back) are shown on Figure 7. The surcharge loads on shoring from traffic and light construction equipment working adjacent to the excavation can be modeled by assuming an additional 2 feet of soil behind the wall. Excavated materials should not be stockpiled behind temporary shoring within a distance equal to the depth of the excavation. SCST should be notified if other surcharge loads are anticipated, so that lateral load criteria can be developed for the specific situation.

The excavation support system should be inspected daily by the contractor’s Competent

Person before personnel start working in the installation. In addition, survey marks for monitoring horizontal and vertical deflection should be established on top of the shoring and on the ground surface 10 and 20 feet behind the shoring at intervals of 50 feet.

Survey marks also should be established on existing nearby structures. The survey marks should be monitored daily for the first 2 weeks after installation and then at least once a week thereafter. Any indication of deflection or distress should be brought to the attention of the Engineer immediately.

6.1.9 Temporary Dewatering

Groundwater seepage may occur locally due to local irrigation or following heavy rain.

Groundwater should be anticipated in the planned basement excavations. Temporary dewatering can be accomplished by sloping the excavation bottom to a sump and pumping from the sump. A layer of gravel about 6 inches thick placed in the bottom of the excavation will facilitate groundwater flow and can be used as a working platform.

La Jolla, California Page 8

6.1.10 Slopes

All permanent slopes should be constructed no steeper than 2:1 (horizontal:vertical).

Faces of fill slopes should be compacted either by rolling with a sheep-foot roller or other suitable equipment, or by overfilling and cutting back to design grade. All slopes are susceptible to surficial slope failure and erosion. Water should not be allowed to flow over the top of slopes. Additionally, slopes should be planted with vegetation that will reduce the potential for erosion.

6.1.11 Surface Drainage

Final surface grades around structures should be designed to collect and direct surface water away from the structure and toward appropriate drainage facilities. The ground around the structure should be graded so that surface water flows rapidly away from the structure without ponding. In general, we recommend that the ground adjacent to the structure slope away at a gradient of at least 2%. Densely vegetated areas where runoff can be impaired should have a minimum gradient of at least 5% within the first 5 feet from the structure. Roof gutters with downspouts that discharge directly into a closed drainage system are recommended on structures.

Drainage patterns established at the time of fine grading should be maintained throughout the life of the proposed structures. Site irrigation should be limited to the minimum necessary to sustain landscape growth. Should excessive irrigation, impaired drainage, or unusually high rainfall occur, saturated zones of perched groundwater can develop.

6.1.12 Grading Plan Review

SCST should review the grading plans and earthwork specifications to ascertain whether the intent of the recommendations contained in this report have been implemented, and that no revised recommendations are needed due to changes in the development scheme.

6.2 FOUNDATIONS

6.2.1 Drilled, Cast-in-Place Concrete Piers

Drilled, cast-in-place concrete piers are considered the most appropriate foundation system for the new structures where the Scripps Formation is below a depth of about 5 feet below typical footing bottom levels. The piers should extend at least 10 feet into the very dense and hard Scripps Formation. Based on the conditions encountered in the borings, it is anticipated that piers will extend between about 10 and 35 feet below the existing ground surface. In areas where fills are between 0 and 5 feet deep, shallower piers could be used if these would be more efficient than excavating deepened footings.

Preliminary axial capacities for 24-inch, 30-inch and 36-inch diameter piers are summarized below. Total and differential settlements of the structure supported on drilled

La Jolla, California Page 9 piers, or a combination of drilled piers and shallow foundations in Scripps Formation, are expected to be less than ¼ inch.

Vertical Capacity of Cast-In-Place Piers

(kips)

Pier Tip Penetration into Formation

(feet)

Pier Diameter (inches)

18 24 30 36

10 150 230 315 400

15 200 300 405 510

20 240 365 490 615

The preliminary lateral load causing ¼-inch deflection at the top of the pier is summarized below. The lateral load can be increased linearly with deflection up to a maximum deflection of 1 inch.

Lateral Loads Causing ¼ Deflection at Top of Pier

Free Head Condition

(kips)

Pier Tip Penetration into Formation

(feet)

Pier Diameter (inches)

18 24 30 36

10(1)

12 20 28 36

(1) Minimum depth of penetration into Scripps Formation.

Lateral Loads Causing ¼ Deflection at Top of Pier

Fixed Head Condition

(kips)

Pier Tip Penetration into Formation

(feet)

Pier Diameter (inches)

18 24 30 36

10(1)

22 44 65 86

(1) Minimum depth of penetration into Scripps Formation.

Because the pier lengths are controlled by end bearing in Scripps Formation, lateral loads causing the calculated deflection do not increase with increasing depth beyond the minimum.

Uplift Capacity of Cast-In-Place Piers

La Jolla, California Page 10

(kips)

Pier Tip Penetration into Formation

(feet)

Pier Diameter (inches)

18 24 30 36

10 80 110 140 170

15 110 150 190 230

20 140 185 230 275

The values above do not include the weight of the pier itself.

The lateral and vertical capacities above are preliminary and are based on the limited current project data. These values may need to be modified when more detailed structural information is available.

The vertical and uplift capacities can be increased by ⅓ when considering the total of all loads, including wind or seismic forces. Lateral loads will be partially resisted by passive pressure on the face of the pier cap. Passive pressure can be computed using 350 pounds per square foot (psf) per foot of depth. This value is considered an ultimate, and an appropriate factor of safety should be incorporated into the imposed load values.

Passive pressure on the pier cap can be added to the lateral resistance of the pier.

Groundwater seepage could occur, depending on local irrigation and rainfall. In addition, difficult drilling conditions in cobble, boulders and debris might be encountered in the undocumented fill. The Scripps Formation is very dense and hard, and a heavy-duty drill rig will be needed to penetrate the formational material. Caving could occur in loose zones in the fill. Drilling fluid or casing might be required to maintain an open hole in the fill.

It is recommended that the lower level building floor be structurally supported on the drilled piers. Detailed design should be prepared by the project structural engineer.

6.2.2 Shallow Footings in Scripps Formation

Portions of the structures will be in or near the Scripps Formation. These portions of the structure can be supported on shallow foundations that take their support from bearing in the formation. Spread footings should be at least 18 inches wide, have bottom levels at least 18 inches below the lowest adjacent grade and extend at least 6 inches into very dense and hard formation. Where such formational materials are not present in footing excavations, the excavations can be deepened and backfilled with a 2-sack sand-cement slurry to footing grade. Spread footings in the formation can be designed to impose an allowable bearing pressure of 5,000 psf for dead plus long term live loads. The allowable

La Jolla, California Page 11 bearing capacity can be increased by 500 psf for each foot of depth or by 250 psf for each foot of width beyond the 18 inch by 18 inch dimension, up to 7,500 psf. This value can be increased by ⅓ when considering the total of all loads, including wind or seismic forces.

Lateral loads will be resisted by friction along the base of the foundations and by passive resistance on the faces of footings and other structural elements below grade. A friction factor of 0.35 can be used. A passive resistance value of 350 psf per foot of depth can be applied. The upper 12 inches of soil should not be relied upon for lateral support unless pavements or slabs extend adjacent to the foundations.

A design modulus of subgrade reaction (K) of 230 pounds per cubic inch (pci) may be used for the subgrade soils in evaluating deflections. This value may be considered on ultimate value and is based on a unit square foot area and should be adjusted for footing dimension. Adjusted values of the modulus of subgrade reaction (Kv) can be obtained from the following equation of footings of various widths:

Kv=K[(B=1)/2B]^2 (pci); for B<20 feet; where B is the width of the footing in feet.

6.2.3 Shallow Footings in Fill

Structures independent of the main garage structure and underlain by undocumented fill may be supported by shallow spread footings if all the fill is removed and replaced with compacted fill. The planned structures can be supported on shallow spread footings with bottom levels in the new compacted fill. Footings should have bottom levels at a minimum depth of 24 inches below the lowest adjacent finished grade. A minimum width of 18 inches is recommended for continuous footings. Isolated footings should be at least 24 inches wide. A bearing capacity of 2,500 psf can be used. This value can be increased by

⅓ when considering the total of all loads, including wind or seismic forces.

Lateral loads will be resisted by friction between the bottoms of footings and passive pressure on the faces of footings and other structural elements below grade. A friction factor of 0.35 can be used. Passive pressure can be computed using a lateral pressure value of 350 psf per foot of depth below the ground surface. The upper 1 foot of soil should not be relied on for passive support unless the ground is covered with pavements or slabs.

Total footing settlements are expected to be less than 1 inch. Differential settlements between adjacent footings, and between the middle and ends of continuous footings, are expected to be less than ½ inch.

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6.2.4 Foundation Plan Review

SCST should review the foundation plans to ascertain that the intent of the recommendations in this report has been implemented and that revised recommendations are not necessary as a result of changes after this report was completed.

6.2.5 Foundation Excavation Observations

A representative from SCST should observe the foundation excavations prior to forming or placing reinforcing steel.

6.3 SLABS-ON-GRADE

6.3.1 Parking Structure Slab-on-Grade

The top 2 feet of material below exterior concrete slabs-on-grade should have an expansion index of 50 or less determined in accordance with ASTM D4829. Portland cement concrete pavement for the parking structure should have a minimum thickness of

6 inches and be underlain by at least 6 inches of aggregate base. The pavements should be reinforced with at least No. 4 reinforcing bars placed at 18 inches on center each way.

Reinforcement should be placed approximately at mid-height of the pavement. Concrete should have a minimum compressive strength of 3,250 pounds per square inch (psi) for the rigid pavements.

A vapor barrier should be placed beneath slabs-on-grade where moisture sensitive floor coverings or equipment are planned. If plastic is used, a minimum 10-mil is recommended.

The plastic should comply with ASTM E1745. Installation should comply with ASTM

E1643. Current construction practice typically includes placement of a 2-inch thick sand cushion between the bottom of the concrete slab and the moisture vapor retarder/barrier.

This cushion can provide some protection to the vapor retarder/barrier during construction, and may assist in reducing the potential for edge curling in the slab during curing.

However, the sand layer also provides a source of moisture to the underside of the slab that can increase the time required to reduce vapor emissions to limits acceptable for the type of floor covering placed on top of the slab. The slab can be placed directly on the vapor retarder/barrier. The floor covering manufacturer should be contacted to determine the volume of moisture vapor allowable and any treatment needed to reduce moisture vapor emissions to acceptable limits for the particular type of floor covering installed.

Where the slab is supported by pier and grade beams, the structural slab should be designed by the structural engineer.

6.3.2 Exterior Slabs-on-Grade

The top 2 feet of material below exterior concrete slabs-on-grade should have an expansion index of 50 or less determined in accordance with ASTM D4829. Exterior slabs

La Jolla, California Page 13 should have a minimum thickness of 4 inches and be reinforced with at least No. 3 bars at

18 inches on center each way. Slabs should be provided with weakened plane joints.

Joints should be placed in accordance with the American Concrete Institute (ACI) guidelines. The project architect should select the final joint patterns.

A 1-inch maximum size aggregate mix is recommended for concrete for exterior slabs.

The corrosion potential of on-site soils with respect to reinforced concrete will need to be taken into account in concrete mix design. Coarse and fine aggregate in concrete should conform to the “Greenbook” Standard Specifications for Public Works Construction.

6.4 CONVENTIONAL RETAINING WALLS

6.4.1 Foundations

The recommendations provided in the foundation section of this report are also applicable to conventional retaining walls.

6.4.2 Lateral Earth Pressures

The at-rest earth pressure for the design of restrained earth retaining structures with level backfills can be taken as equivalent to the pressure of a fluid weighing 60 pcf for granular backfill or 80 pcf for the onsite clays retained by temporary shoring. The active earth pressure for the design of unrestrained earth retaining structures with level backfills can be taken as equivalent to the pressure of a fluid weighing 40 pcf for granular backfill or 60 pcf for the onsite clays. An additional 20 pcf should be added to these values for walls with a

2:1 (horizontal: vertical) sloping backfill. An increase in earth pressure equivalent to an additional 2 feet of retained soil can be used to account for surcharge loads from light traffic. The above values do not include a factor of safety. Appropriate factors of safety should be incorporated into the design. If any other surcharge loads are anticipated, SCST should be contacted for the necessary increase in soil pressure.

Retaining walls should be designed to resist hydrostatic pressures or be provided with a backdrain to reduce the accumulation of hydrostatic pressures. Backdrains may consist of a 2-foot wide zone of ¾-inch crushed rock. The backdrain should be separated from the adjacent soils using a non-woven filter fabric, such as Mirafi 140N or equivalent. Weep holes should be provided or a perforated pipe (Schedule 40 PVC) should be installed at the base of the backdrain and sloped to discharge to a suitable storm drain facility. As an alternative, a geocomposite drainage system such as Miradrain 6000 or equivalent placed behind the wall and connected to a suitable storm drain facility can be used. The project architect should provide waterproofing specifications and details. Figure 8 shows typical conventional retaining wall backdrain details.

La Jolla, California Page 14

6.4.3 Seismic Earth Pressure

If required, the seismic earth pressures can be taken as equivalent to the pressure of a fluid weighing 13 pcf. These values are for level backfill conditions and do not include a factor of safety. Appropriate factors of safety should be incorporated into the design. This pressure is in addition to the un-factored static active pressures. The allowable passive pressure and bearing capacity can be increased by ⅓ in determining the seismic stability of the wall.

6.4.4 Backfill

All backfill soils should be compacted to at least 90% relative compaction. Expansive or clayey soil should not be used for backfill material. Additionally, fill within 3 feet from the back of the wall should not contain rocks greater than 3 inches in any dimension. The wall should not be backfilled until the grout has reached an adequate strength.

6.5 MECHANICALLY STABILIZED EARTH RETAINING WALLS

The following soil parameters can be used for design of mechanically stabilized earth (MSE) retaining walls. The reinforced soil should consist of granular material with a SE of 20 or more.

MSE Wall Design Parameters

Soil Parameter Reinforced Soil Retained Soil Foundation Soil

Internal Friction Angle 32° 28° 28°

Cohesion 0 0 0

Moist Unit Weight 125 pcf 120 pcf 120 pcf

The bottom of MSE walls should extend to such a depth that a total of 5 feet exists between the bottom of the wall and the face of the slope. Figure 9 presents a typical MSE retaining wall backdrain detail.

6.6 PAVEMENT SECTION RECOMMENDATIONS

The pavement support characteristics of the soils encountered during our investigation are considered poor. An R-value of 5 was assumed for design of preliminary pavement sections.

The actual R-value of the subgrade soils should be determined after grading and final pavement sections be provided. Based on an R-value of 5, the following pavement structural sections are recommended for the assumed Traffic Indices.

Flexible Pavement Sections

La Jolla, California Page 15

Traffic Type Traffic Index Asphalt Concrete

(inches)

Aggregate Base*

(inches)

Parking Stalls 4.5 3 8

Drive Lanes 6.0 4 12

Heavy Traffic Areas 7.0 5 14

*Aggregate Base should conform to Class 2 Aggregate Base in accordance with the Caltrans Standard Specifications or Crushed Miscellaneous Base in accordance with the Standard Specifications for Public Works Construction.

Portland Cement Concrete Pavement Sections

Traffic Type Traffic Index

JPCP*

(inches)

Aggregate Base*

(inches)

Parking Stalls 4.5 6 6

Drive Lanes 6.0 7 6

Heavy Traffic Areas 7.0 7 6

*Jointed Plain Concrete Pavement

The top 12 inches of subgrade should be scarified, moisture conditioned to near optimum moisture content, and compacted to at least 95% relative compaction. All soft or yielding areas should be removed and replaced with compacted fill. The aggregate base material should be compacted to at least 95% relative compaction. All materials and methods of construction should conform to good engineering practices and the minimum standards of the

City of San Diego.

6.7 SOIL CORROSIVITY

Representative samples of the onsite soils were tested to evaluate corrosion potential. The test results are presented in Appendix II. The project design engineer can use the sulfate results in conjunction with ACI 318 to specify the water/cement ratio, compressive strength and cementitious material types for concrete exposed to soil. A corrosion engineer should be contacted to provide specific corrosion control recommendations, if needed.

7 GEOTECHNICAL ENGINEERING DURING CONSTRUCTION

The geotechnical engineer should review project plans and specifications prior to bidding and construction to check that the intent of the recommendations in this report has been incorporated.

Observations and tests should be performed during construction. If the conditions encountered during construction differ from those anticipated based on the subsurface exploration program, the presence of the geotechnical engineer during construction will enable an evaluation of the exposed conditions and modifications of the recommendations in this report or development of additional recommendations in a timely manner.

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8 CLOSURE

SCST should be advised of any changes in the project scope so that the recommendations contained in this report can be evaluated with respect to the revised plans. Changes in recommendations will be verified in writing. The findings in this report are valid as of the date of this report. Changes in the condition of the site can, however, occur with the passage of time, whether they are due to natural processes or work on this or adjacent areas. In addition, changes in the standards of practice and government regulations can occur. Thus, the findings in this report may be invalidated wholly or in part by changes beyond our control. This report should not be relied upon after a period of two years without a review by us verifying the suitability of the conclusions and recommendations to site conditions at that time.

In the performance of our professional services, we comply with that level of care and skill ordinarily exercised by members of our profession currently practicing under similar conditions and in the same locality. The client recognizes that subsurface conditions may vary from those encountered at the boring locations, and that our data, interpretations, and recommendations are based solely on the information obtained by us. We will be responsible for those data, interpretations, and recommendations, but shall not be responsible for interpretations by others of the information developed. Our services consist of professional consultation and observation only, and no warranty of any kind whatsoever, express or implied, is made or intended in connection with the work performed or to be performed by us, or by our proposal for consulting or other services, or by our furnishing of oral or written reports or findings.

9 REFERENCES

American Concrete Institute (ACI) (2012), Building Code Requirements for Structural Concrete (ACI 318-11) and Commentary, August.

California Emergency Management Agency, California Geological Survey, University of Southern California (Cal EMA) (2009), Tsunami Inundation Map for Emergency Planning.

Caltrans (2010), Standard Specifications.

City of San Diego (2008), Seismic Safety Study, Geologic Hazards and Faults, Grid Tile: 34, Development Services Department, April 3.

County of San Diego (2012), SanGIS Interactive Map.

International Code Council (2012), 2013 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2, Based on the 2012 International Existing Building Code, Effective Date: January 1, 2014.

Ninyo & Moore (2013), Geotechnical Evaluation, Phase 2 Parking Structure, Veteran Affairs Medical Center, La Jolla Village Drive, San Diego, California, Project No. 107600001, October 21.

Public Works Standards, Inc. (2011), “Greenbook,” Standard Specifications for Public Works Construction, 2012 Edition.

La Jolla, California Page 17

Southern California Soil & Testing (2010), Geotechnical Investigation, VA Medical Center, Phase 1, 400 Space Parking Structure, La Jolla, California, SCS&T No. 0916026F, Report No. 4, October 5.

United States Department of Agriculture (1953), Stereo Aerial Photographs, Flight AXN, Line 4M, Frames 85 and 86, March 31.

Figure:

VA La Jolla Parking Structure Phase II La Jolla, California

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VA La Jolla Parking Structure Phase II

La Jolla, California

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160174F-1

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Job Number: Figure: 8160174F-1

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VA LA JOLLA PARKING STRUCTURE PHASE II

La Jolla, California

Reinforced Soil

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160174F

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March, 2016TYPICAL MSE WALL DETAIL

VA La Jolla Parking Structure Phase II

La Jolla, California

APPENDIX I

FIELD INVESTIGATION

Our field investigation consisted of drilling eight borings on January 24, 2015 to depths between about 20 feet and 30½ feet below the existing ground surface using a truck-mounted drill rig equipped with a hollow stem auger. Figure 2 shows the approximate locations of the borings.

The field investigation was performed under the observation of an SCST geologist who also logged the borings and obtained samples of the materials encountered. Relatively undisturbed samples were obtained using a modified California (CAL) sampler, which is ring-lined split tube sampler with a 3-inch outer diameter and 2½-inch inner diameter. Standard Penetration Tests

(SPT) were performed using a 2-inch outer diameter and 1⅜-inch inner diameter split tube sampler.