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ENGINEERING GEOLOGY AND GEOTECHNICAL ENGINEERING REPORT FOR REPLACMENT WATER TANKS AT WELL SITE 31C/31D, AND WELL SITE 32, TAPO CANYON AREA, VENTURA COUNTY, CALIFORNIA

PROJECT NO.: 303079-001 MAY 16, 2019 (REVISED SEPTEMBER 18, 2019)

PREPARED FOR CANNON ASSOCIATES

BY EARTH SYSTEMS PACIFIC 1731-A WALTER STREET VENTURA, CALIFORNIA Earth Systems 0 1731 Walter Street, Suite A I Ventura, CA 93003 I Ph : 805.642 .6727 I www.earthsystems. com

May 16, 2019 Project No.: 303079-001 (Revised September 18, 2019) Report No.: 19-5-45

Attention: Eric Porkert Cannon Associates 11900 West Olympic Boulevard, Suite 530 Los Angeles, CA 90064

Project: Replacement Water Tanks Well Site 31C/31D and Well Site 32 Tapo Canyon Area Ventura County, California

As authorized, we have performed a geotechnical study for proposed water tanks that would replace aging existing tanks servicing Well Site 31C/31D and Well Site 32 in the Tapo Canyon area of Ventura County, California. The accompanying Engineering Geology and Geotechnical Engineering Report presents the results of our subsurface exploration and laboratory testing programs, as well as our conclusions and recommendations pertaining to geotechnical aspects of project design. This report completes the scope of services described within our Proposal No. VEN -19-02-008 dated February 15, 2019, and authorized by Cannon Standard Task Orders dated May 13, 2019.

We have appreciated the opportunity to be of service to you on this project. Please call if you have any questions, or if we can be of further service.

Respectfully submitted,

EARTH SYSTEMS PACIFIC

Engineering Geologist Geotechnical Engineer

Copies: 4 - Eric Porkert (3 via US mail, 1 via email) 1 - Project File TABLE OF CONTENTS

INTRODUCTION ...... 1 PURPOSE AND SCOPE OF WORK ...... 1 GEOLOGY ...... 2 GEOLOGIC HAZARDS ...... J SEISMIC SHAKING ...... 3 FAULT RUPTURE ...... 6 LANDSLIDING AND ROCK FALL ...... 7 LIQUEFACTION ...... 7 SEISMIC-INDUCED SETTLEMENT OF DRY SANDS ...... 7 FLOODING ...... 8 SOIL CONDITIONS AT WELL SITE 31C/31D ...... 9 SOIL CONDITIONS AT WELL SITE 32 ...... 9 GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS ...... 10 GRADING ...... 12 Pre-Grading Considerations ...... 12 Rough Grading Recommendations ...... 12 Excavations ...... 13 Utility Trenches ...... 14 STRUCTURAL DESIGN ...... 15 Ring Foundations ...... 15 Mat Foundations ...... 15 Frictional and Lateral Coefficients ...... 17 Settlement Considerations ...... 17 ADDITIONAL SERVICES ...... 19 LIMITATIONS AND UNIFORMITY OF CONDITIONS ...... 20 AERIAL PHOTOGRAPHS INTERPRETED FOR THIS STUDY ...... 21 BIBLIOGRAPHY ...... 21 APPENDIX A Vicinity Map Regional Geologic Map Seismic Hazard Zones Map Historic HighGroundwater Map Field Study Geologic Maps Geologic Cross-Sections Logs of Exploratory Borings

EARTH SYSTEMS TABLE OF CONTENTS {Continued)

APPENDIX B Laboratory Testing Laboratory Test Results Table 1809.7 APPENDIX C 2016 CBC & ASCE 7-10 Seismic Parameters US Seismic Design Maps Fault Parameters APPENDIX D Analyses of Liquefaction and Seismic-Induced Settlement of Dry Sands

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INTRODUCTION

This report presents results of an Engineering Geology and Geotechnical Engineering study performed for two proposed bolted steel water tanks in the Tapo Canyon area of Ventura County, California (see Vicinity Map in Appendix A). We understand that a 25,000-gallon, 15.5-foot diameter, 16-foot high tank would replace an existing tank near Simi Wells 31C and 31D, and replace an existing tank near Simi Well 32. The aging existing tanks will be demolished as part of the proposed project.

Given the 16-foot height of both proposed tanks, and a relatively light roof load, total loads generated by the fully loaded tanks are expected to range up to about 1,200 psf. If actual loads vary significantly from these assumed loads, Earth Systems should be notified since reevaluation of the recommendations contained in this report may be required.

The tanks will be situated on existing pads; thus, grading is expected to be limited to preparing near-surface soils to support the new loads generated by the tanks. The tanks are planned to be designed in accordance with current AWWA standards.

PURPOSE AND SCOPE OF WORK

The purpose of the geotechnical study that led to this report was to analyze the geology and soil conditions of the site with respect to the proposed improvements. These conditions include potential geohazards, surface and subsurface soil types, expansion potential, settlement potential, bearing capacity, and the presence or absence of subsurface water. The scope of work included:

1. Reconnaissance and geological mapping of the site. 2. Reviewing aerial photographs taken ofthe site and surrounding areas on October 26, 1945 by Fairchild Aerial Surveys, Inc. 3. Reviewing pertinent geologic literature. 4. Drilling, sampling, and logging two hollow-stem auger borings at each tank site to study geologic, soil, and groundwater conditions. 5. Laboratory testing of soil samples obtained from the subsurface exploration to determine their physical and engineering properties. 6. Consulting with owner representatives and design professionals.

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7. Analyzing the geotechnical data obtained. 8. Preparing this report.

Contained in this report are:

1. Descriptions and results of field and laboratory tests that were performed. 2. Discussions pertaining to the local geologic, soil, and groundwater conditions. 3. Conclusions pertaining to geohazards that could affect the site. 4. Conclusions and recommendations pertaining to site grading and structural design.

GEOLOGY

The site lies within the Simi Hills, which in turn lie within the western Transverse Ranges. The Simi Hills and the Transverse Ranges are characterized by ongoing tectonic activity. In the vicinity of the subject sites, Tertiary and Quaternary sediments have been folded and faulted along predominant east-west structural trends. Although there are several faults located within the region, the nearest known fault of significant activity (i.e. the Santa Susana Fault} is located approximately 4,000 feet north of the subject sites. The project area is not located within any of the "Fault Rupture Hazard Zones" that have been specified by the State of California (C.D .M .G. 1972, Revised 1999).

Near-surface soils underlying both sites are comprised of a combination of artificial fill materials over alluvial deposits. Fill soils consisting of gravelly sands were encountered in the upper 2 to 2.5 feet of the proposed tank area at Well Site 31C/31D, and to depths between 4 and 5 feet at Well Site 32. Alluvial deposits at both sites were found to be pale brown to grayish brown to dark brown sands with variable quantities of grave[.

Bedrock underlying the alluvium is the Saugus Formation (QTs} of Plio-Pleistocene age. The Saugus Formation is comprised of units originating from a combination of shallow marine and non-marine depositional environments. Units encountered in the field study at Well Site 31C/31D included interbedded claystones, siltstones, and sandstones. Units were generally slightly weathered. Finer-grained units were pale olive to olive in color and ranged from very stiff to hard. Sandstones were pale olive brown to orangish brown and very dense. Depth from the existing pad to bedrock was approximately 11.25 to 15 feet at Well Site 31C/31D.

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Units encountered in the field study at Well Site 32 included interbedded siltstones and sandstones. Sandstones had variable quantities of gravels. Units were generally highly to moderately weathered where encountered in Boring 8-3, but moderately to slightly weathered in Boring 8-4. Finer-grained units were pale olive brown to pale brown in color and ranged from stiff to very stiff. Sandstones were pale olive brown to pale brown and dense to very dense. Depth from the existing pad to bedrock at Well Site 32 was approximately 15 feet in both borings.

Strikes of bedding within the Saugus Formation strike northwesterly near Well Site 31C/31D and nearly east-west near Well Site 32. Bedrock dips northward at between about 10° to 25° at both sites.

No faults or landslides were observed to be located on or trending into the subject property during the field study, during reviews of the referenced geologic literature, or during review of the aerial photographs taken of the site.

GEOLOGIC HAZARDS

Geologic hazards that may impact a site include seismic shaking, fault rupture, landsliding, liquefaction and flooding.

A. Seismic Shaking 1. Although the site is not within a State-designated "fault rupture hazard zone", it is located in an active seismic region where large numbers of earthquakes are recorded each year. Historically, major earthquakes (i.e. those with Richter magnitudes greater than 7.0) felt in the vicinity of subject site have originated from faults outside the area. These include the December 21, 1812 "Santa Barbara Region" earthquake, that was presumably centered in the Santa Barbara Channel, the 1857 Fort Tejon earthquake, the 1872 Owens Valley earthquake, and the 1952 Arvin-Tehachapi earthquake.

2. It is assumed that the 2016 CBC and ASCE 7-10 guidelines will apply for the seismic design parameters. The 2016 CBC includes several seismic design parameters that are influenced by the geographic site location with respect to active and potentially active faults, and with respect to subsurface soil or rock conditions. The seismic design parameters presented herein were determined by the U.S. Seismic Design

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Maps "risk-targeted" calculator on the USGS website for the jobsite coordinates (34.3313° North Latitude and 118.7127° West Longitude at Well Site 31C/31D and 34.3338° North Latitude and 118. 7213° West Longitude at Well Site 32). The calculator adjusts for Soil Site Class D (for stiff soils at both sites), and for AWWA Seismic Use Group II (tanks that provide direct service to facilities deemed important to the public welfare). Seismic Use Group II is similar to Special Occupancy buildings, such as public schools, and includes a "Seismic Importance Factor" of 1.25. (A listing of the calculated 2016 CBC and ASCE 7-10 Seismic Parameters is presented below and again in Appendix C.)

The Fault Parameters table (see Appendix C) lists the significant "active" and "potentially active" faults within an approximate 30-mile radius of the subject site. The distance between the site and the nearest portion of each fault is shown, as well as the respective estimated maximum earthquake magnitudes, and the deterministic mean site peak ground accelerations.

Summary of Seismic Parameters - 2016 CBC Well Site 31C/31D Site Class (Table 20.3-1 of ASCE 7-10 with 2016 update) D AWWA Seismic Use Group II Seismic Design Category E Maximum Considered Earthquake (MCE) Ground Motion Spectral Response Acceleration, Short Period - Ss 2.919 g Spectral Response Acceleration at 1 sec. - S1 0.996 g Site Coefficient - Fa 1.00 Site Coefficient - Fv 1.50 Site-Modified Spectral Response Acceleration, Short Period - SMs 2.919 g Site-Modified Spectral Response Acceleration at 1 sec. - SM1 1.494 g Design Earthquake Ground Motion Short Period Spectral Response - Sos 1.946 g One Second Spectral Response - So1 0.996 g Site Modified Peak Ground Acceleration - PGAM 1.098 g Note: Valu es Appropriate for a 2% Probability of Exceedance in 50 Years

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Summary of Seismic Parameters - 2016 CBC Well Site 32 Site Class (Table 20.3-1 of ASCE 7-10 with 2016 update) D AWWA Seismic Use Group II Seismic Design Category E Maximum Considered Earthquake (MCE) Ground Motion Spectral Response Acceleration, Short Period - Ss 2.941 g Spectral Response Acceleration at 1 sec. - 51 1.009 g Site Coefficient - Fa 1.00 Site Coefficient - Fv 1.50 Site-Modified Spectral Response Acceleration, Short Period - 5Ms 2.941 g Site-Modified Spectral Response Acceleration at 1 sec. - SM1 1.514 g Design Earthquake Ground Motion Short Period Spectral Response - Sos 1.961 g One Second Spectral Response - 501 1.009 g Site Modified Peak Ground Acceleration - PGAM 1.108 g Note: Va lues Appropriate for a 2% Probability of Exceedance in 50 Years

3. Southern Ventura County has been mapped by the California Division of Mines and Geology to delineate areas of varying predicted seismic response. The Saugus Formation that underlies the subject area is mapped as having a probable maximum intensity of earthquake response of approximately VII-VIII on the Modified Mercalli Scale. Historically, the highest observed intensity of ground response has been VIII in the Simi area (C.D.M.G ., 1995).

4. The San Andreas is the dominant active fault in California. The fault extends from the Gulf of California to Cape Mendocino in northern California. That portion of the zone extending southward from Parkfield, California is estimated to have been active for the last 12 million years. As much as 190 miles of right lateral displacement has occurred across the zone (Crowell, 1975). This displacement includes offsets on the actual San Andreas Fault and related faults that include the Imperial, Banning, Mission Creek, and San Jacinto faults.

5. Historically, the Sa n Andreas Fault is responsible for two of the three "great" earthquakes experienced in California. ("Great" earthquakes are defined as having

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Richter magnitudes that are equal to or greater than 8.0.) These are the 1857 Fort Tejon and 1906 San Francisco earthquakes. Each event is credited with approximately 200 miles of surface rupture and horizontal displacements of up to 30 feet. Ground shaking was very intense and damage to man-made structures very wide spread. The 1857 rupture extended along the San Andreas Fault from near Bakersfield to Cajon Pass and was felt throughout most of California. Horizontal displacements of 10 to 13 feet were observed along the fault in the Palmdale area .

6. Recurrence intervals for major earthquakes in southern California are best documented for the San Andreas Fault. It is estimated that a major earthquake has occurred along the southern portion of the San Andreas Fault every 100 to 200 years (Sieh, 1978). The average recurrence interval is estimated to be 140 years. The last major earthquake on the San Andreas Fault in the southern California area occurred in 1857; therefore, the occurrence of a major event in the same general area is considered likely within the estimated lifetime of any new construction.

7. On December 21, 1812, an estimated 7.0 Richter magnitude event occurred in an area believed to be offshore in the western part of the Santa Barbara Channel. This earthquake caused considerable shaking in the area of the proposed project.

8. On March 26, 1872, the greatest recorded earthquake in the western United States, excluding Alaska, occurred along the Owens Valley Fault near Lone Pine. The earthquake is estimated to have had a Richter magnitude of 8.25, and significantly shook most of California.

9. On July 21, 1952, the Arvin-Tehachapi earthquake occurred on the White Wolf Fault. The earthquake registered 7.7 on the Richter Scale and was felt throughout southern California.

B. Fault Rupture Surficial displacement along a fault trace is known as fault rupture. Fault rupture typically occurs along previously existing fault traces. As mentioned in the "Structure" section above, no existing fault traces were observed to be crossing the site. As a result, it is the opinion of this firm that the potential for fault rupture on this site is low.

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C. Landsliding and Rock Fall Neither site is located within any of the Seismic-Induced Landslide areas that have been designated by C.D.M.G. (1997b) as requiring evaluation of slope stability. As mentioned previously, no existing landslides were observed on, or trending into the site. Slopes above the tank sites are not of heights that pose a risk to the tanks, and there are no slopes immediately below the tank pads. Based on these data, it appears that the hazard posed by landsliding is low.

There are no large, loose, rounded rocks on the slopes above the tank pads. Asa result, it appears that the hazard posed by rock fall is low.

D. Liquefaction Earthquake-induced vibrations can be the cause of several significant phenomena, including liquefaction in fine sands and silty sands. Liquefaction results in a loss of strength and can cause structures to settle or even overturn if it occurs in the bearing zone. Liquefaction is typically limited to the upper 50 feet of soils underlying a site.

Fine sands and silty sands that are poorly graded and lie below the groundwater table are the soils most susceptible to liquefaction. Soils with plasticity indices greater than 7, sufficiently dense soils, and/or soils located above the groundwater table are not generally susceptible to liquefaction.

Groundwater was not encountered within the subsurface of either site, and Saugus Formation bedrock was encountered at depths of 11.25 feet at Well Site 31C/31D and 15 feet at Well Site 32. Bedrock is sufficient dense to prevent liquefaction from occurring.

Based on these data, it is the opinion of this firm that a potential for liquefaction does not exist at either site.

E. Seismic-Induced Settlement of Dry Sands Dry sands tend to settle and densify when subjected to earthquake shaking. The amount of settlement is a function of relative density, cyclic shear strain magnitude, and the number of strain cycles. Procedures to evaluate this type of settlement were developed by Seed and Silver (1972) and later modified by Pyke, et al. (1975). Tokimatsu and Seed (1987) presented a simplified procedure that has been reduced to a series of equations

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by Pradel (1998). For this study, the Tokimatsu and Seed procedure, as implemented by Pradel, was used to eva luate seismically-induced settlement at each site.

For Well Site 31(/ 310, the site acceleration and earthquake magnitude used in the analysis were 1.098g and 7.2 Mw, respectfully, as discussed in the Seismic Shaking section of this report. It has been assumed that the bedrock encountered below a depth of 15 feet is not susceptible to seismic-induced settlement. The calculations (see Appendix D) using this procedure and blow count data from Boring B-1 indicate that seismically-induced settlement could range up to about 2.6 inches. Approximately 2.4 inches of this settlement would occur between depths of 5 and 10 feet, with another nearly 0.2 inches between depths of 10 and 15 feet. Differential settlement across the tank footprint could range up to about 1.3 inches without mitigation.

For Well Site 32, the site acceleration and earthquake magnitude used in the analysis were 1.108 g and 7.2 Mw, respectfully, as discussed in the Seismic Shaking section of this report. It has been assumed that the bedrock encountered below a depth of 15 feet is not susceptible to seismic-induced settlement. The calculations (see Appendix D) using this procedure and blow count data from Boring B-4 indicate that seismically-induced settlement could range up to about 1.0 inch. All but about 0.2 inches would occur between depth"'s of 5 and 15 feet. Differential settlement across the tank footprint could range up to about 0.5 inches without mitigation.

F. Flooding Earthquake-induced flooding types include tsunamis, seiches, and reservoir failure. Due to the inland location of the site, hazards from tsunamis and seiches are considered extremely unlikely. Any nearby reservoir that may fail would normally drain into established major drainage channels, and away from the site; therefore, flooding should not be considered a potential hazard.

Both sites are located within areas designated by the FEMA Flood Map Service Center website as Zone X, which are designated as "areas of minimal flood hazard". As a result, it appears that the hazard posed by storm-induced flooding is low.

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SOIL CONDITIONS AT WELL SITE 31C/31D

Near~surface soils underlying the proposed tank location at Well Site 31C/31D include approximately 2 feet of artificial fill over about 9.25 to 13 feet of alluvium. Saugus Formation bedrock underlies the alluvium. The fill and alluvium are comprised of slightly silty sands with variable percentages of gravels. So ils encountered at approximate bearing depths are characterized by moderate to low blow counts, low to moderate in-place densities, and high compressibilities. Testing indicates that anticipated bearing soils lie in the "very low" expansion range of Table 1809. 7 because the expansion index was found to be 0. [A locally adopted version of the classification of soil expansion ranges is included in Appendix B of this report.] It appears that soils can be cut by normal grading equipment.

Groundwater was not encountered to the maximum depth of exploration, which was 26.5 feet below the existing pad elevation.

Samples of near-surface soils were tested for pH, resistivity, soluble sulfates, and soluble chlorides. The test results provided in Appendix B should be distributed to the design team for their interpretations pertaining to the corrosivity or reactivity of various construction materials (such as concrete and piping) with the soils. It should be noted that sulfate contents (700 mg/Kg) are in the "SO" ("negligible") exposure class of Table 19.3.1.1 of ACI 318-14; therefore, it appears that special concrete designs will not be necessary for the measured sulfate contents.

Based on criteria established by the County of Los Angeles (2013), measurements of resistivity of near-surface soils (1,700 ohms-cm) indicate that they are "corrosive" to ferrous metal (i.e. cast iron, etc.) pipes.

As noted previously, soils underlying Well Site 31C/31D are potentially susceptible to seismic induced settlement of dry sands. Without mitigation, total seismic-induced settlement could range up to 2.6 inches, and differential settlement across the tank footprint could range up to about 1.3 inches.

SOIL CONDITIONS AT WELL SITE 32

Near-surface soils underlying the proposed tank location at Well Site 32 approximately 2.5 feet of artificial fill over about 12.5 feet of alluvium. Saugus Formation bedrock underlies the alluvium.

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The fill and alluvium are comprised of slightly silty sands with variable percentages of gravels. Soils encountered at approximate bearing depths are characterized by moderate to low blow counts, low in-place densities, and high compressibilities. Testing indicates that anticipated bearing soils lie in the "very low" expansion range of Table 1809.7 because the expansion index was found to be 0. [A locally adopted version of the classification of soil expansion ranges is included in Appendix B of this report.] It appears that soils can be cut by normal grading equipment.

Groundwater was not encountered to the maximum depth of exploration, which was 26.5 feet below the existing pad elevation.

Samples of near-surface soils were tested for pH, resistivity, soluble sulfates, and soluble chlorides. The test results provided in Appendix B should be distributed to the design team for their interpretations pertaining to the corrosivity or reactivity of various construction materials (such as concrete and piping) with the soils. It should be noted that sulfate contents (8.7 mg/Kg) are in the "SO" ("negligible") exposure class of Table 19.3.1.1 of ACI 318-14; therefore, it appears that special concrete designs will not be necessary for the measured sulfate contents.

Based on criteria established by the County of Los Angeles (2013), measurements of resistivity of near-surface soils (13,000 ohms-cm) indicate that they are "mildly corrosive" to ferrous metal (i.e. cast iron, etc.) pipes.

As noted previously, soils underlying Well Site 32 are potentially susceptible to seismic-induced settlement of dry sands. Without mitigation, total seismic-induced settlement could range up to 1.0 inch, and differential settlement across the tank footprint could range up to about 0.5 inches.

GEOTECHNICAL CONCLUSIONS AND RECOMMENDATIONS

The site is suitable for the proposed development from Engineering Geology and Geotechnical Engineering standpoints provided that the recommendations contained in this report are successfully implemented into the project.

Of primary concern is the potential for both static and seismic-induced settlements. The alluvial soils in the upper 15 feet are generally at a low density, highly compressible, and susceptible to seismic-induced settlement during a design seismic event. As previously discussed, seismically-

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induced settlements in the upper 15 feet were estimated to about 2.6 inches at the location of Well 31C/31D and about 1 inch at the location of Well 32. As such, recompacting the upper 5 feet of soil will not mitigate a significant amount of the potential seismic-induced settlement that could occur in the native soils between the depths of 5 and 15 feet.

Because the proposed tank zone at each site has been surcharged by the existing tank for years, settlements for tanks at the exact location as the existing tanks are expected to be less than estimated. However, the extent of the settlement that has occurred in the soils underlying the existing tanks is unknown. Should the replacement tank be located at a different location than the existing tank it's replacing at the Well 32 site, we estimated that a total static settlement of about 2.4 inches in the center of the tank and about 0.5 inches near the perimeter of the tank. Hence, differential settlement between the center column foundation and edge of the new tank at the Well 32 site is estimated to be about 1.9 inches. Should the replacement tank be located at a different location than the existing tank at the Well 31C/31D site, we estimated that a total static of about 2.9 inches in the center of the tank and about 0.8 inches near the perimeter of the tank. Hence, differential settlement between the center and edge of the new tank at the Well 31C/31D site is estimated to be about 2.1 inches. The static settlements presented above are based on a bearing pressure of 1,200 psf. These static settlements, along with the liquefaction induced settlements discussed above, should be accounted for during the design of the new tanks.

Because of the estimated total and differential settlements (i.e., static and seismic-induced) may be excessive, remedial grading or ground improvemE:nt may be required to reduce the settlements to values that are tolerable for the proposed tank foundations. Remedial grading may consist of removing and replacing the native soils to a depth where the settlement is manageable, whereas the compressible in-place soils can be improved (densified) through ground improvement methods such as compaction grouting. Estimated settlements for various depths of remedial grading and/or ground improvement are presented on Page 17 of this report.

Alternatively, rammed aggregate piers (RAPs) could be installed beneath the proposed tanks to transfer the loads to bedrock, arid not the underlying compressible soils. RAPs are a patented ground improvement system that is designed by the Geopier Foundation Company, but there are similar competing proprietary systems. The actual number of RAP and their depths would need to be determined by the Geopier Foundation Company based on the settlement the foundation

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Both compaction grouting and RAPs will densify the soils to reduce the potential for seismic induced settlement of dry sands and static settlement under the load of the tanks.

A. Grading 1. Pre-Grading Considerations a. Plans and specifications should be provided to Earth Systems prior to grading. Plans should include the grading plans, foundation plans, and foundation details. b. Final site grade should be designed so that all water is diverted away from the tanks over paved surfaces, or over landscaped surfaces in accordance with current codes. Water should not be allowed to pond anywhere on the pad . c. Shrinkage of soils affected by compaction is estimated to be about 15% based on an anticipated average compaction of 92 percent of the maximum dry density. d. It is recommended that Earth Systems be retained to provide Geotechnical Engineering services during site development and grading, and foundation construction phases of the work to observe compliance with the design concepts, specifications and recommendations, and to allow design changes in the event that subsurface conditions differ from those anticipated prior to the start of construction. e. Compaction tests shall be made to determine the relative compaction of the fills in accordance with the following minimum guidelines: one test for each two foot vertical lift; one test for each 1,000 cubic yards of material placed; and two tests at finished subgrade elevation in each tank pad.

2. Rough Grading Recommendations a. Grading at a minimum should conform to appropriate sections of the 2016 California Building Code. b. If the proposed tanks will be constructed in the exact same location of the existing tanks, removal of the tank and related underground utilities at each site will disturb the soils immediately below the pad. Soils disturbed by the removal process should be completely removed.

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c. Due to the presence of fairly low-density soils at the bearing depth, overexcavation and recompaction of soils in the tank areas will be necessary to decrease the potential for differential settlement and provide more uniform bearing conditions. The depth of overexcavation will depend on the differential settlement the foundation system can tolerate. Estimated settlements for various depths of remedial grading and/or ground improvement are presented on Page 17 of this report. The lateral extension of the overexcavation outside the perimeter of the tank should be equal to the depth of removal beneath the foundation of the tank. The exposed surface at the bottom of the remedial excavation should then be scarified an additional 6 inches, moisture conditioned to above the optimum moisture content, and recompacted to at least 90% ofthe maximum dry density. d. Areas outside of the tank area to receive fill, exterior slabs-on-grade, or paving should be overexcavated until all existing artificial fill soils are completely removed. The resulting surface should then be scarified an additional 6 inches, moisture conditioned, and recompacted. e. The bottom of all excavations should be observed by a representative oft his firm prior to processing or placing fill. f. The excavated soils may be used for fill once they are cleaned of all organic material, rock, debris and irreducible material larger than 8 inches. g. Fill and backfill placed above the optimum moisture content in layers with loose thickness not greater than 8 inches should be compacted to a minimum of 90% of the maximum dry density obtainable by the ASTM D 1557 test method. h. Import soils used to raise site grade should be equal to, or better than, on-site soils in strength, expansion, and compressibility characteristics. Import soil can be evaluated, but will not be prequalified by the Geotechnical Engineer. Final comments on the characteristics of the import will be given after the material is at the project site.

3. Excavations a. Excavations anticipated for site grading for proposed improvements in the tank pad areas will typically encounter silty sands and poorly- to well-graded sands. These materials should be able to be excavated with conventional earthmoving equipment.

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b. Temporary unshared, unsurcharged, open excavations above the groundwater level may be cut vertically to a maximum height of no more than 4 feet. Excavations extending higher than 4 vertical feet should be sloped back above the 4-foot vertical cut to at least 1.5H:1V (horizontal to vertical} or flatter provided the adjacent ground is not subject to surcharge loading. If excavations dry out, sloughing will occur. No excavation should be made within a 1:1 line projected downward from the outside edge at the base of any existing footing or slab. c. During the time excavations are open, no heavy grading equipment or other surcharge loads (i.e. excavation spoils} should be allowed within a horizontal distance from the top of any slope equal to the depth of the excavation (both distances measured from the top of the excavation slope}. d. Adequate measures should be taken to protect any structural foundations, pavements, or utilities adjacent to any excavations. e. All open cuts should be in compliance with applicable Occupational Safety Health Administration (OSHA} regulations (California Construction Safety Orders, Title 8} and should be monitored for evidence of incipient instability. Standard construction techniques should be sufficient for temporary site excavations. Project safety is the responsibility of the Contractor and the Owner. Earth Systems will not be responsible for project safety.

4. Utility Trenches a. Utility trench backfill should be governed by the provisions of this report relating to minimum compaction standards. In general, on-site service lines may be backfilled with native soils compacted to 90% of maximum density. Backfill of offsite service lines will be subject to the specifications of the jurisdictional agency or this report, whichever are greater. b. Utility trenches running parallel to footings should be located at least 5 feet outside the footing line, or above a 1:1 (horizontal to vertical} projection downward from the outside edge of the bottom of the footing. c. Compacted native soils should be util,ized for backfill below the tanks. Sand should not be used under structures because it provides a conduit for water to migrate under foundations. d. Backfill operations should be observed and tested by the Geotechnical Engineer to monitor compliance with these recommendations:

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B. Structural Design 1. Ring Foundations a. Ring footings may be used to help support the tanks. b. Footings should bear into firm recompacted soils, as recommended elsewhere in this report. Foundation excavations should be observed by a representative of this firm after excavation, but prior to placing of reinforcing steel or concrete, to verify bearing conditions. c. Ring footings for either tank may be designed based on an allowable bearing value of 3,000 psf for an assumed depth of 12 inches and width of 18 inches. This value is based on a factor of safety of 3. d. Allowable bearing values are net (weight of footing and soil surcharge may be neglected) and are applicable for dead plus reasonable live loads. e. Bearing values may be increased by one-third when transient loads such as wind and/or seismicity are included. f. Lateral loads may be resisted by soil friction on foundations and by passive resistance of the soils acting on ring footings. g. Soils should be lightly moistened prior to placing concrete; however, testing of premoistening is not required.

2. Mat Foundations a. As an alternative a ring foundation system, a structural mat slab may be used to support the tanks. b. The mat foundation may be a conventionally reinforced slab system designed for the anticipated differential settlements. c. The mat foundation should bear into firm recompacted soils, as recommended elsewhere in this report. Foundation excavations should be observed by a representative of this firm after excavation, but prior to placing of reinforcing steel or concrete, to verify bearing conditions. d. To limit the maximum total settlement at the center of the tank under static conditions to about 1 inch at the Well 31C/31D site, an allowable "net" bearing capacity of 550 pounds per square foot (psf), for loads distributed over the full footprint of the mat foundation, may be utilized for dead and sustained live loads for design of the mat foundation. For the Well 32 site, an allowable "net" bearing capacity of 750 psf should be used to limit the maximum total settlement under static conditions to about 1 inch. [These values assume that

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remedial grading or ground improvement has not been performed.] Use of a higher bearing pressure will result in static settlements greater than 1 inch as discussed on Page 11 of this report. e. Allowable bearing values are net (weight of footing and soil surcharge may be neglected} and are applicable for dead plus reasonable live loads. f. Bearing values may be increased by one-third when transient loads such as wind and/or seismicity are included. g. The estimated static settlements are long-term settlements of the soils within the zone of stress influence, a depth of which is typically 2 to 2.5 times the foundation width/diameter. These settlements are inelastic, and because the subsurface stress distribution follows Boussinesq's principles, the settlement is "bowl-shaped". Conversely, the modulus of subgrade reaction is an elastic reaction of the subgrade under a load. In order to match the sub grade modulus value to the estimated static settlements, the following values should be used for Well 31C/31D depending on the depth of remedial grading and the bearing pressure. For Bearing Pressure of 1,200 psf

Depth of R&R Center of Tank) (Perimeter of Tank) 0 2.9 pci 10.4 pci 5 4.4 pci 13.9 pci 10 10.4 pci 20.3 pci 15 83.3 pci 83.3 pci

For Bearing Pressure of 550 psf

Depth of R&R Center of Tank) (Perimeter of Tank) 0 3.8 pci 9.5 pci 5 4.8 pci 12.7 pci 10 9.5 pci 19.1 pci 15 38.2 pci 38.2 pci

With the reduction in the tank diameter at Well Site 32 (30-foot to 15.5-foot}, an allowable "net" bearing capacity of 750 psf should be used to limit the maximum total settlement under static conditions to about 1 inch. In order to match the subgrade modulus value to the estimated static settlements, the following values should be used for Well 32 depending on the depth of remedial grading and the bearing pressure.

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For Bearing Pressure of 1,200 psf

Depth of R&R Center of Tank) {Perimeter of Tank) 0 3.5 pci 16.7 pci 5 4.4 pci 16.7 pci 10 9.3 pci 20.8 pci 15 83.3 pci 83.3 pci

For Bearing Pressure of 750 psf

Depth of R&R Center of Tank) {Perimeter of Tank) 0 5.2 pci 17.4 pci 5 6.5 pci 17.4 pci 10 10.4 pci 26.0 pci 15 52.1 pci 52.1 pci

f. Lateral loads may be resisted by soil friction acting on the base of foundations and by passive resistance of the soils acting on the foundation sides embedded in compacted nati~e soil. g. Soils should be lightly moistened prior to placing concrete; however, testing of premoistening is not required.

3. Frictional and Lateral Coefficients a. Resistance to lateral loading may be provided by friction acting on the bases of foundations. A coefficient of friction of 0.65 may be applied to dead load forces. This value does not include a factor of safety. b. Passive resistance acting on the sides of foundation stems equal to 425 pcf of equivalent fluid weight may be included for resistance to lateral load. This value does not include a factor of safety. c. A minimum factor of safety of 1.5 should be used when designing for sliding or overturning. d. Passive resistance may be combined with frictional resistance provided that a one-third reduction in the coefficient of friction is used.

4. Settlement Considerations a. Without remedial grading or ground improvement performed at the Wel l 32 site, maximum static settlements of about 2.4 inches in the center of the tank and

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about 0.5 inches near the perimeter of the tank are estimated for a bearing pressure of 1,200 psf. Maximum static settlements of 2.9 inches in the center of the tank and about 0.8 inches near the perimeter of the tank are anticipated at the Well 31C/31D site without remedial grading or ground improvement being performed and a bearing pressure of 1,200 psf. b. Without remedial grading or ground improvement performed at either well site, seismically-induced settlements in the upper 15 feet were estimated to about 2.6 inches at the location of Well 31C/31D and about 1 inch at the location of Well 32. c. With remedial grading or ground improvement performed, the following settlements have been estimated:

Well Site Depth of Remedial Seismic-Induced Estimated Static Settlement 31C/31D Grading/Ground Settlement (inches) Improvement (inches) Bearing Pressure Bearing Pressure (feet) 1,200 psf 550 psf 0 2.6 2.9 (center) 1.0 (center) 0.8 (perimeter) 0.4 (perimeter) 5 2.6 1.9 (center) 0.8 (center) 0.6 (perimeter) 0.3 (perimeter) 10 0.2 0.8 (center) 0.4 (center) 0.4 (perimeter) 0.2 (perimeter) 15 0.0 0.5 (center) <0.1 (center) 0.1 (perimeter) <0.1 (perimeter)

Well Site Depth of Remedial Seismic-Induced Estimated Static Settlement 32 Grading/Ground Settlement (inches) Improvement (inches) Bearing Pressure Bearing Pressure (feet) 1,200 psf 750 psf 0 1.0 2.4 (center) 1.0 (center) 0.5 (perimeter) 0.3 (perimeter) 5 0.8 1.9 (center) 0.8 (center) 0.5 (perimeter) 0.3 (perimeter) 10 0.7 0.9 (center) 0.5 (center) 0.4 (perimeter) 0.2 (perimeter)

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15 0.0 0. 5 (center) <0.1 (center) 0.1 (perimeter) <0.1 (perimeter) d. Estimated differential static settlements from the center of the tank to the perimeter of the tank will be as follows:

Well Site Depth of Remedial Estimated Static 31C/31D Grading/Ground Differential Settlement'1l (inches) Improvement Bearing Pressure Bearing Pressure (feet) 1,200 psf 550 psf 0 2.1 0.6 5 1.3 0.5 10 0.4 0.2 15 0.4 0.0

Well Site Depth of Remedial Estimated Static 32 Grading/Ground Differential Settlement(1l (inches) Improvement Bearing Pressure Bearing Pressure (feet) 1,200 psf 750 psf 0 1.9 0.7 5 1.4 0.5 10 0.5 0.3 15 0.4 0.0 (1)- Seismic-induced settlement of dry sands and static settlements are not additive. The differential settlement given in the table above is the maximum difference of the estim ated total and seism ic-induced settlements.

ADDITIONAL SERVICES

This report is based on the assumption that an adequate program of monitoring and testing will be performed by Earth Systems during construction to check compli ance with the recommendations given in this report. The recommended tests and observations include, but are not necessarily limited to the following:

1. Review of the foundation and grading plans during the design phase of the project.

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2. Observation and testing during site preparation, grading, placing of engineered fill, and foundation construction. 3. Consultation as required during construction.

LIMITATIONS AND UNIFORMITY OF CONDITIONS

The analysis and recommendations submitted in this report are based in part upon the data obtained from the borings drilled on the two sites. The nature and extent of variations between and beyond the borings may not become evident until construction. If variations then appear evident, it will be necessary to reevaluate the recommendations of this report.

The scope of services did not include any environmental assessment or investigation for the presence or absence of wetlands, hazardous or toxic materials in the soil, surface water, groundwater or air, on, below, or around this site. Any statements in this report or on the soil boring logs regarding odors noted, unusual or suspicious items or conditions observed, are strictly for the information of the client.

Findings of this report are valid as of this date; however, changes in conditions of a property can occur with passage oftime whether they be due to natural processes or works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur whether they result from legislation or broadening of knowledge. Accordingly, findings of this report may be invalidated wholly or partially by changes outside the control of this firm. Therefore, this report is subject to review and should not be relied upon after a period of one year.

In the event that any changes in the nature, design, or locations of the tanks and other improvements are planned, the conclusions and recommendations contained in this report shall not be considered valid unless the changes are reviewed and conclusions of this report modified or verified in writing.

This report is issued with the understanding that it is the responsibility of the Owner, or of his representative to ensure that the information and recommendations contained herein are called to the attention of the Architect and Engineers for the project and incorporated into the plan and that the necessary steps are taken to see that the Contractor and Subcontractors carry out such recommendations in the field.

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As the Geotechnical Engineers for this project, Earth Systems has striven to provide services in accordance with generally accepted geotechnical engineering practices in this community at this time. No warranty or guarantee is expressed or implied. This report was prepared for the exclusive use of the Client for the purposes stated in this document for the referenced project only. No third party may use or rely on this report without express written authorization from Earth Systems for such use or reliance.

It is recommended that Earth Systems be provided the opportunity for a general review of final design and specifications in order that earthwork and foundation recommendations may be properly interpreted and implemented in the design and specifications. If Earth Systems is not accorded the privilege of making this recommended review, it can assume no responsibility for misinterpretation of the recommendations.

AERIAL PHOTOGRAPHS INTERPRETED FOR THIS STUDY

Fairchild Aerial Surveys, October 25, 1945, Frame Nos. C9800-5-457 and 458, Scale 1-inch equals 1,200 feet.

BIBLIOGRAPHY

American Concrete Institute (ACI}, 2009, ACI 318-14.

American Water Works Association (AWWA}, July 1, 2011 (Effective Date}, Welded Carbon Steel Tanks for Water Storage.

California Building Standards Commission, 2016, California Building Code, California Code of Regulations Title 24.

California Division of Mines and Geology (C.D.M.G.}, 1972 (Revised 1999}, Fault Rupture Hazard Zones in California, Special Publication 42.

C.D.M.G., 1975, Seismic Hazards Study of Ventura County, California, Open File Report 76-5-LA.

EARTH SYSTEMS May 15, 2019 22 Project No.: 303079-001 (Revised September 18, 2019) Report No.: 19-5-45

C.D.M.G., 1995, The Northridge, California, Earthquake of 17 January 1994, Special Publication 116.

C.D.M .G., 1997a, Seismic Hazard Zone Report for the Simi Valley East and Simi Valley West 7.5-Minute Quadrangles, Ventura and Los Angeles Counties, California, Seismic Hazard Zone Report 002.

C.D.M.G., 1997b, State of California Seismic Hazard Zones, Simi Valley East Quadrangle, Official Map, April 7, 1997.

California Geological Survey (C.G.S.), 2008, Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117 A.

County of Los Angeles Department of Public Works, July 2013, Manual for Preparation of Geotechnical Reports.

Crowell, John C., 1975, San Andreas Fault in Southern California, C.D.M .G. Special Report 118.

Dibblee, Jr., Thomas W., 1992, Geologic Map of the Santa Susana Quadrangle, Ventura and Los Angeles Counties, California, Dibblee Foundation Map No. DF-38.

Federal Emergency Management Agency {FEMA), 2019, FEMA Flood Map Service Center Website

GeoDynamics, Inc., December 2018, Geotechnical Investigation Report, Grading Adjacent Proposed Water Well, Gillibrand Basin, Ventura County, California.

Jennings, C.W. and W.A. Bryant, 2010, Fault Activity Map of California, C.G.S. Geologic Data Map No. 6.

NCEER, 1997, Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils, Technical Report NCEER-97-0022.

Sieh, Kerry E., 1978, Earthquake Intervals, San Andreas Fault, Palmdale, California, C.D.M.G .. California Geology, June 1978.

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Southern California Earthquake Center (SCEC), 1999, Recommended Procedures for Implementation of DMG Special Publication 117, Guidelines for Analyzing and Mitigating Liquefaction in California.

Ventura County Planning Department, October 22, 2013, Ventura County General Plan Hazards Appendix.

Weber, F. Harold, Jr. and others, 1973, Geology and Mineral Resources of Southern Ventura County, California, C.D.M.G ., Preliminary Report 14.

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