U4_Tank_Replacement_Project_Exhibits_03272024.pdf

U4 Tank Replacement Project Geotechnical Investigation

EXHIBIT A-1

Geotechnical Investigation

Exhibit Follows

GEOTECHNICAL

INVESTIGATION

UNIVERSITY TANK 4 REPLACEMENT PROJECT

SANTA CRUZ, CALIFORNIA

FOR

MME ENGINEERING

SANTA CRUZ, CALIFORNIA

CONSULTING GEOTECHNICAL ENGINEERS

2250-SZ59-A41

JULY 2022

www.4pacific-crest.com

G E O T E C H N I C A L | E N V I R O N M E N T A L | C H E M I C AL | M AT E R I A L T E ST I N G | S P E C I A L I N S P E C T I O N S

444 AIRPORT BLVD., SUITE 106 | WATSONVILLE, CA 95076 | PHONE 831-722-9446 | WWW.4PACIFIC-CREST.COM

July 13, 2022 Project No. 2250-SZ59-A41

Mr. Rodney Cahill, PE

MME Engineering

224 Walnut Avenue

Santa Cruz, CA 95060

Subject: Geotechnical Investigation – Design Phase

University Tank 4 Replacement Project

Santa Cruz, California

Dear Mr. Cahill, In accordance with your authorization, we have performed a geotechnical investigation for the replacement of an existing water storage tank at the University Tank Site 4 in Santa Cruz, California.

The accompanying report presents our conclusions and recommendations as well as the results of the geotechnical investigation on which they are based. The conclusions and recommendations presented in this report are contingent upon our review of the plans during the design phase of the project, and our observation and testing during the construction phase of the project.

Very truly yours, PACIFIC CREST ENGINEERING INC.

Matthew Maciel, GE

President/Principal Geotechnical Engineer

GE 3189

Expires 9/30/2022

9/30/22

University Tank 4 Replacement Project Project No. 2250-SZ59-A41

July 13, 2022

444 AIRPORT BLVD., SUITE 106 | WATSONVILLE, CA 95076 | PHONE 831-722-9446 | WWW.4PACIFIC-CREST.COM

TABLE OF CONTENTS

I. INTRODUCTION

PURPOSE AND SCOPE

PROJECT LOCATION

PROPOSED IMPROVEMENTS

II. INVESTIGATION METHODS

EXPLORATORY BORINGS

POTHOLES:

LABORATORY TESTING

III. FINDINGS AND ANALYSIS

GEOLOGIC SETTING

SURFACE CONDITIONS

SUBSURFACE CONDITIONS

FAULTING AND SEISMICITY

GEOTECHNICAL HAZARDS

IV. DISCUSSION AND CONCLUSIONS

GENERAL

PRIMARY GEOTECHNICAL CONSIDERATIONS

V. RECOMMENDATIONS

EARTHWORK

FOUNDATION – RINGWALL FOOTING

PAVEMENT DESIGN

SURFACE DRAINAGE

EROSION CONTROL

PLAN REVIEW

VI. LIMITATIONS AND UNIFORMITY OF CONDITIONS

APPENDIX A

REGIONAL SITE MAP

SITE MAP SHOWING TEST BORINGS

KEY TO SOIL CLASSIFICATION

LOG OF TEST BORINGS

LOG OF TEST PITS

ATTERBERG LIMITS RESULTS

R-VALUE TEST RESULTS

GEOTECHNICAL INVESTIGATION REPORT

University Tank 4 Replacement Project

Santa Cruz, California

I. INTRODUCTION

PURPOSE AND SCOPE

This report describes the geotechnical investigation and presents our conclusions and recommendations for the proposed water storage tank replacement project located at University Tank

Site 4, in Santa Cruz, California. For purposes of this report, “site” refers to the area currently occupied by the existing water storage tank, pump station, and unnamed access road connecting the water storage tank to Empire Grade.

Our scope of services for this project has consisted of:

1. Site reconnaissance to observe the existing conditions.

2. Review of the following published maps:

• Geologic Map of Santa Cruz County, California, Brabb, 1997.

• Preliminary Map of Landslide Deposits in Santa Cruz County, California, Cooper- Clark and Associates, 1975.

• Map Showing Geology and Liquefaction Potential of Quaternary Deposits in Santa Cruz County, California, Dupré, 1975.

• Map Showing Faults and Their Potential Hazards in Santa Cruz County, California, Hall, Sarna-Wojcicki, Dupré, 1974.

• U.S. Geological Survey (and the California Geologic Survey), 2018, Quaternary fault and fold database for the United States, accessed on June 20, 2022, from USGS web site: https://www.usgs.gov/natural-hazards/earthquake-hazards/faults

3. The drilling and logging of 5 test borings.

4. Laboratory analysis of retrieved soil samples.

5. Engineering analysis of the field and laboratory test results.

6. Review of existing plans and sections showing the locations of the existing water storage tank, pump station, and water pipeline prepared by Brown and Caldwell – Consulting

Engineers, dated January 1965.

7. Preparation of this report documenting our investigation and presenting geotechnical recommendations for the design and construction of the project.

PROJECT LOCATION

The subject site is located on the southwestern side of Empire Grade Road near post mile marker 14.65.

The tank site is situated at the end of an unnamed access road approximately ¼ mile south of the

Empire Grade Road. Please refer to the Regional Site Map, Figure No. 1, in Appendix A for the general vicinity of the project site, which has an approximate center located at the following coordinates:

Latitude = 36.999713 degrees

Longitude = -122.069993 degrees

PROPOSED IMPROVEMENTS

Based on our discussions with MME, it is our understanding that the planned improvements will include replacing the existing 400,000-gallon steel water storage tank in kind, improve the access roadway, and construct a 35,000-gallon maintenance water storage tank. The existing 400,000-gallon steel water storage tank is founded upon an 18-inch thick concrete ring foundation embedded into weathered to competent quartz diorite bedrock. It is our understanding that the new 400,000-gallon water storage tank may be founded upon the existing foundation. The composition and footprint of the 35,000-gallon maintenance tank are currently being evaluated by MME, but it is our understanding that the maintenance tank will be generally situated on the northwest side of the larger 400,000-gallon tank.

II. INVESTIGATION METHODS

EXPLORATORY BORINGS

Five, 6-inch diameter borings were drilled at the site on June 1, 2022. The approximate location of the test borings is shown on Figures No. 2A and 2B, in Appendix A. The drilling method used was hydraulically operated continuous flight augers tractor mounted drill rig. A geologist from Pacific Crest

Engineering Inc. was present during the drilling operations to log the soil encountered and to choose sampler type and locations.

Relatively undisturbed soil samples were obtained at various depths by driving a split spoon sampler

18 inches into the ground. This was achieved by dropping a 140 pound hammer a vertical height of 30 inches. The hammer was actuated with a wire winch. The number of blows required to drive the sampler each 6-inch increment and the total number of blows required to drive the last 12 inches was recorded by the field geologist. The outside diameter of the samplers used was 3-inch or 2-inch and is designated on the Boring Logs as “L” or “T”, respectively.

The field blow counts in 6-inch increments are reported on the Boring Logs adjacent to each sample as well as the Standard Penetration Test data (SPT). All SPT data has been normalized to a 2-inch O.D.

sampler and is reported on the Boring Logs as SPT "N" values. The normalization method used was derived from the second edition of the Foundation Engineering Handbook (H.Y. Fang, 1991). The method utilizes a Sampler Hammer Ratio which is dependent on the weight of the hammer, height of hammer drop, outside diameter of sampler, and inside diameter of sample.

The soils encountered in the borings were continuously logged in the field and visually described in accordance with ASTM D2488. The soil classifications were verified upon completion of laboratory testing in general accordance with the Unified Soil Classification System (ASTM D2487). Please refer to the Boring Log Explanations, Figures No. 3 and 4, in Appendix A for a summary of the Unified Soil

Classification System.

Appendix A contains the site plan showing the locations of the test borings, our borings logs and an explanation of the soil classification system used. Stratification lines on the boring logs are approximate as the actual transition between soil types may be gradual.

POTHOLES:

Our investigation included the excavation of two (2) potholes along the northwestern and eastern sides of the existing tank to verify the depth of the foundation elements. The approximate locations of the potholes are illustrated on Figure No. 2A of this report. The approximately 24-inch by 36-inch potholes were excavated with hand digging equipment to a depth that clearly exposed the bottom of the foundation element in the area. The footing embedment depths were measured relative to the existing lowest adjacent grade. Upon completion of the excavation and evaluation process, the excavations were backfilled with native material that was generated during excavation. Refer to our logs presented as Figures 10 and 11 within Appendix A of this report for the findings of our potholing operation.

LABORATORY TESTING

The laboratory testing program was developed to aid in evaluating the engineering properties of the materials encountered at the site. Laboratory tests performed include:

• Moisture Density relationships in accordance with ASTM D2937.

• Gradation testing in accordance with ASTM D1140.

• Atterberg Limits testing in accordance with ASTM D4318.

• "R" Value testing in accordance with California 301.

The results of the laboratory testing are presented on the boring logs opposite the sample tested and/or presented graphically in Appendix A.

III. FINDINGS AND ANALYSIS

GEOLOGIC SETTING

The surficial geology in the area of the project site is mapped as Quartz Diorite (Brabb 1997). Diorite is a coarse-grained igneous rock that typically occurs as a large intrusion and is characterized by a “salt and pepper” appearance. Quartz diorite is a diorite that is composed of between 5% and 20% quartz.

Based upon local geology maps, the quartz diorite grades to granodiorite south and east of Ben Lomond

Mountain. The residual soils that blanket the site are consistent with material derived from completely weathered Quartz Diorite bedrock. The quartz diorite bedrock encountered in our test borings is generally consistent with the above geologic description.

SURFACE CONDITIONS

The subject site consists of an existing 400,000-gallon steel water tank, pump station, and other related infrastructure situated on a building pad that was cut into the hillside. Quartz diorite bedrock is exposed in the cut along the north and northeast sides of the existing water storage tank. The southeast side of the water tank is approximately 12 feet from the top of a steeply descending, vegetated slope. There is an unnamed road that provides access to the subject tank site and related infrastructure. The northwest to southeast trending road ascends to the northwest as it approaches

Empire Grade Road. The southernmost portion of the access road is constructed on a cut/fill slope and is flanked by a vegetated drainage to the west. The existing road pavement is in poor condition, and potholes as well as alligator cracks are visible.

SUBSURFACE CONDITIONS

Our subsurface exploration consisted of the advancement five small diameter borings and two potholes. B-1 was drilled in cut on the southeast side of the existing water storage tank as close as possible to the top of the steep bedrock slope. B-2 was advanced in cut on the northeast side of the existing water storage tank. B-3, B-4, and B-5 were drilled along the northwest trending unnamed access road. As previously discussed, the southernmost portion of the access road, where B-3 was advanced, is comprised of cut and fill. Consequently, B-3 was advanced as close as possible to the outboard edge of the unnamed access road to quantify the depth of fill in the area. Our subsurface exploration also included the excavation of two potholes to confirm the depth? of the existing concrete foundation underlying the existing water storage tank. Potholes PH-1 and PH-2 were excavated adjacent to B-1 and B-2, respectively.

Subsurface conditions at the tank site (B-1 and B-2) generally consisted of 1 to 6 feet of weathered quartz diorite underlain by competent quartz diorite to a maximum explored depth of 6 feet, 2½ inches below existing ground surface. Drilling and sampling refusal were encountered within the competent quartz diorite. The weathered quartz diorite was described as dense to very dense, fine to medium grained sand with silt. The sand was sub-angular to sub-rounded shaped, poorly graded, and micaceous. In general, the quartz diorite was slightly weathered and was described as having moderately hard to hard rock hardness. Collected samples were mechanically pulverized and mostly reduced to rock flour with a few competent quartz diorite gravels.

Subsurface conditions encountered along the unnamed access road (B-3, B-4, and B-5) generally consisted of approximately 2 to 3-inches of asphaltic concrete (AC) underlain by approximately 0 to 4 inches of aggregate base. Underlying the road section, areas of non-engineered fill comprised of clayey sand were encountered ranging from 0 to 2½-feet thick. This fill was generally thickest near the southern limits of the roadway. Underlying the fill, we generally encountered sandy clay or clayey sand to the maximum explored depth of 10½-feet. The clay exhibited intermediate to high plasticity characteristics and was generally hard in consistency. The sand was described as fine to medium grained, sub-angular to sub-rounded shaped, poorly graded, and was generally medium dense to very dense in consistency. These materials are generally consistent with weathered quartz diorite.

Based on the findings of our potholing operation, it was determined that the foundation elements for the existing water tank extend approximately 18 inches below the existing grades adjacent to the tank.

The concrete appeared to be in good condition with little to no signs of cracking and deterioration. The ring wall footing was observed to bear upon weathered Quartz Diorite on the south-southeast side of the tank (PH-1) and competent Quartz Diorite on the north-northwest (PH-2) side of the tank.

Groundwater was not encountered in any of the five test borings to the maximum explored depth of

10½-feet. The groundwater conditions described in this report reflect the conditions encountered during our drilling investigation at the specific locations drilled. It must be anticipated that perched and regional groundwater tables may vary with location and could fluctuate with variations in rainfall, runoff, irrigation, and other changes to the conditions encountered at the time our observations were made.

Please refer the Logs of Test Borings in Appendix A, for a more detailed description of the subsurface conditions encountered in each of our test borings at the subject site.

FAULTING AND SEISMICITY

Faulting

Mapped faults which have the potential to generate earthquakes that could significantly affect the subject site are listed in Table No. 1. The fault distances are approximate distances based on the U.S.

Geological Survey and California Geological Survey, Quaternary fault and fold database, accessed June

20, 2022, from the USGS website https://www.usgs.gov/natural-hazards/earthquake-hazards/faults and overlaid onto Google Earth.

Table No. 1 - Distance to Significant Faults

Fault Name Distance

(miles) Direction

Zayante-Vergeles 7½ North-northeast

San Andreas 11 Northeast

Sargent 12 Northeast

Monterey Bay-Tularcitos 7 Southwest

San Gregorio 8 West-Southwest

Seismic Shaking and CBC Design Parameters

Due to the proximity of the site to active and potentially active faults, it is reasonable to assume the site will experience high intensity ground shaking during the lifetime of the project. Structures founded on thick, soft soil deposits are more likely to experience more destructive shaking, with higher amplitude and lower frequency, than structures founded on bedrock. Generally, shaking will be more intense closer to earthquake epicenters. Thick, soft soil deposits large distances from earthquake epicenters, however, may result in seismic accelerations significantly greater than expected in bedrock.

Selection of seismic design parameters should be determined by the project structural designer. The site coefficients and seismic ground motion values provided in Table No. 2 were developed based on

CBC 2019 incorporating the ASCE 7-16 standard, while the values provided in Table No. 3 were determined in accordance with AWWA D100-21.

Table No. 2 - 2019 CBC Seismic Design Parameters Note 1

Seismic Design Parameter ASCE 7-16 Value

Site Class C

Spectral Acceleration for Short Periods Ss = 1.626g

Spectral Acceleration for 1-second Period S1 = 0.624g

Short Period Site Coefficient Fa = 1.2

1-Second Period Site Coefficient Fv = 1.4

MCE Spectral Response Acceleration for Short Period SMS = 1.951g

MCE Spectral Response Acceleration for 1-Second Period SM1 = 0.873

Design Spectral Response Acceleration for Short Period SDS = 1.301g

Design Spectral Response Acceleration for 1-Second Period SD1 = 0.582g

Seismic Design Category 2 D

Note 1: Design values have been obtained by using the ASCE Hazard Tool at https://asce7hazardtool.online

Note 2: The Seismic Design Category assumes that the water tank is a Risk Category IV structure as defined by Table 1604.5 of the 2019 CBC. Pacific Crest Engineering Inc. should be contacted for revised seismic design parameters if the proposed structure has a different occupancy rating than that assumed.

Table No. 3 – 2021 AWWA Seismic Design Parameters

Seismic Design Parameter 2021 AWWA Value

Seismic Use Group IV

Seismic Importance Factor 1.5

Site Class C

Spectral Acceleration for Short Periods Ss = 1.626g

Spectral Acceleration for 1-second Period S1 = 0.624g

Short Period Site Coefficient Fa = 1.0

1-Second Period Site Coefficient Fv = 1.3

MCE Spectral Response Acceleration for Short Period SMS = 1.626g

MCE Spectral Response Acceleration for 1-Second Period SM1 = 0.8111g

Design Spectral Response Acceleration for Short Period SDS = 1.084g

Design Spectral Response Acceleration for 1-Second Period SD1 = 0.541g

Response Modification Factors – Impulse Response Note1 Ri = 3.0

Response Modification Factors – Convective Response Rc = 1.5

Note 1: Values assume mechanically anchored tank.

The recommendations of this report are intended to reduce the potential for structural damage to an acceptable risk level, however strong seismic shaking could result in damage to improvements and the need for post-earthquake repairs.

GEOTECHNICAL HAZARDS

A quantitative analysis of geotechnical hazards was beyond our scope of services for this project. In general, however, the geotechnical hazards associated with the project site include seismic shaking

(discussed above), ground surface fault rupture, liquefaction, lateral spreading, landsliding, and expansive soils. A qualitative discussion of these hazards is presented below.

Ground Surface Fault Rupture

Pacific Crest Engineering Inc. has not performed a specific investigation for the presence of active faults at the project site. Based upon our review of the Santa Cruz County GIS Hazard Maps, the project site is not mapped within a fault hazard zone.

Ground surface fault rupture typically occurs along the surficial traces of active faults during significant seismic events. Since the nearest known active, or potentially active fault trace is mapped approximately 7-miles from the site, it is our opinion that the potential for ground surface fault rupture to occur at the site may be considered low.

Liquefaction and Lateral Spreading

Based upon our review of the Santa Cruz County GIS Hazard Maps, the project site is not mapped within a liquefaction hazard zone.

Liquefaction tends to occur in loose, saturated fine-grained sands and coarse silt, or clays with low plasticity. We did not encounter potentially liquefiable soils, nor did we encounter groundwater during our field investigation. Consequently, it is our opinion that the potential for liquefaction to occur at the subject site may be considered low.

Liquefaction induced lateral spreading occurs when a liquefied soil mass fails toward an open slope face or fails on an inclined topographic slope. Our analysis indicates that the site has a low potential for liquefaction, consequently the potential for lateral spreading may also be considered low.

Landsliding

An investigation to determine whether the proposed project is located on an existing landslide or the potential for a deep-seated landslide to occur and adversely affect the project was beyond our scope of services for this project and was not performed.

Based upon our review of the Santa Cruz County GIS App which utilizes the map entitled, “Preliminary

Landslide Map of Santa Cruz County,” (Cooper-Clark and Associates, 1975), the site is mapped outside of known or questionable landslide deposits.

Slope failures can also occur where surface drainage is allowed to concentrate onto unprotected slopes such as the steep slope south of the existing water storage tank as well as the drainage that runs roughly parallel to the west side of the unnamed access road. Appropriate landscaping and good control of surface drainage around the project area becomes very important to reduce potential for shallow slumping of slopes. Erosion control measures should be implemented and maintained. Under no circumstances should surface runoff be directed toward, or discharged upon, any topographic slopes.

Expansive Soils

The northern part of the unnamed access road is underlain by a relatively thick layer of sandy clay, which generally exhibits an intermediate to high expansive potential. It is possible there are additional expansive soil layers that were not detected in our subsurface investigation. Expansive soils tend to heave during the rainy season and contract during the summer and this shrink/swell action extends down to the depth of seasonal moisture change. When this cyclical volume change occurs on sloping ground it results in “soil creep” due to the downward vector of the shrink/swell action. Seasonal moisture fluctuation and subsequent expansion and contraction of these types of soils typically occurs more near the ground surface where the seasonal moisture fluctuation is the greatest and decreases with depth below ground surface.

IV. DISCUSSION AND CONCLUSIONS

GENERAL

1. The results of our investigation indicate that the proposed improvements are feasible from a geotechnical engineering standpoint, provided our recommendations are included in the design and construction of the project.

2. Grading and foundation plans should be reviewed by Pacific Crest Engineering Inc. during their preparation and prior to contract bidding.

3. Pacific Crest Engineering Inc. should be notified at least four (4) working days prior to any site clearing and grading operations on the property to observe the stripping and disposal of unsuitable materials, and to coordinate this work with the grading contractor. During this period, a pre-construction conference should be held on the site, with at least the client or their representative, the grading contractor, a City representative and one of our engineers present. At this meeting, the project specifications and the testing and inspection responsibilities will be outlined and discussed.

4. The findings, conclusions and recommendations provided in this report are based on the understanding that Pacific Crest Engineering will remain as Geotechnical Engineer of Record throughout the design and construction phase of the project. The validity of the findings, conclusions and recommendations contained in this report are dependent upon our review of project plans as well as an adequate testing and observation program during the construction phase. Field observation and testing must therefore be provided by a representative of Pacific Crest Engineering Inc., to enable us to form an opinion as to whether the extent of work related to earthwork or foundation excavation complies with the project plans, specifications and our geotechnical recommendations. Pacific Crest

Engineering assumes no responsibility for any site work that is performed without the full knowledge and direct observation of Pacific Crest Engineering Inc.

PRIMARY GEOTECHNICAL CONSIDERATIONS

5. Based upon the results of our investigation, it is our opinion that the primary geotechnical issues associated with the design and construction of the proposed project are the following:

a. Slope Creep and Erosion: Improvements are proposed near or on relatively steep slopes with gradients as steep as 1½:1. Surficial soils on steep slopes may be subject to erosion and/or soil creep, potentially undermining foundation elements and hardscape. To reduce this risk of this hazard to foundation elements, all foundation elements should be set back from the crest of the slope and embedded into bedrock. Detailed recommendations are presented in the

Foundations section of this report.

b. Remnant Effects of Demolition Operation: The initial preparation of the site may include the demolition of the existing water tank and associated foundation elements. As a result of these activities, it is likely that the upper 1 to 2 feet of surficial soil across the site will be highly disturbed. These soils will need to be sub-excavated and recompacted as engineered fill. Refer to the Site Preparation section of this report for recommendations.

c. Shallow Hard Bedrock: Relatively hard bedrock conditions were encountered near the ground surface in the vicinity of the proposed improvements. The earthwork contractor should be aware of these conditions and employ the appropriate earthwork equipment to assure excavation to the design depths. Refer to the Logs of Test Borings, in Appendix A for detailed bedrock conditions at each boring location.

d. Surface Drainage: The loose cohesionless surficial soils that blanket the slopes around the proposed development area are highly susceptible to erosion. Consequently, the collection and discharge of storm water must be conducted in a controlled manner. Refer to the Surface

Drainage and Erosion Control section of the report for additional recommendations.

e. Non-Engineered Fills: The outboard edge of the unnamed access road is underlain by approximately 2½ feet of non-engineered fill in the vicinity of B-3. Portions of the roadway underlain by non-engineered fill may be subject to settlement and distress when traversed by heavy construction equipment. If the risk of settlement and distress of the subject roadway segment is not acceptable to the city or if the roadway is rendered impassible due to significant settlement, then the non-engineered fill should be completely removed and replaced with properly compacted engineered fill. Refer to the Site Preparation section of this report for recommendations.

f. Expansive Soils: The native clay soils underly portions of the unnamed access road are moderate to highly expansive. Seasonal shrinking and swelling of these soils could result in heave or settlement and damage to the new roadway section. To reduce this potential, we recommend that the new roadway section incorporate the full HMA and baserock thicknesses specified in the Pavement Design section of this report.

g. Strong Seismic Shaking: The project site is located within a seismically active area and strong seismic shaking is expected to occur within the design lifetime of the project. Improvements should be designed and constructed in accordance with the most current CBC/AWWA and the recommendations of this report to minimize reaction to seismic shaking. Structures built in accordance with the latest edition of the CBC/AWWA have an increased potential for experiencing relatively minor damage which should be repairable, however strong seismic shaking could result in damage to improvements and the need for post-earthquake repairs.

V. RECOMMENDATIONS

EARTHWORK

Clearing and Stripping

1. The initial preparation of the site may consist of demolition of portions of any existing structures and their foundations, and removal of designated trees and debris. All foundation elements from existing tank must be completely removed from development area. Tree removal should include the entire stump and root ball. Septic tanks and leaching lines, if found, must be completely removed. The extent of this soil removal will be designated by a representative of Pacific Crest Engineering Inc. in the field. This material must be removed from the site.

2. Any voids created by the removal of old structures and their foundations, tree and root balls, septic tanks, and leach lines must be backfilled with properly compacted engineered fill which meets the requirements of this report.

3. Any wells encountered shall be capped in accordance with the requirements and approval of the

County Health Department. The strength of the cap shall be equal to the adjacent soil and shall not be located within 5 feet of a structural footing.

4. Any remaining surface vegetation, tree roots and organically contaminated topsoil should then be removed (“stripped”) from the area to be graded. In addition, any remaining debris or large rocks must also be removed (this includes asphalt or rocks greater than 2 inches in greatest dimension). This material may be stockpiled for future landscaping.

5. Given the past development of the tank site, it is anticipated that minimal stripping will be required. Final required depth of stripping must be based upon visual observations by a representative of Pacific Crest Engineering Inc., in the field. The required depth of stripping will vary based upon the type and density of vegetation across the project site and with the time of year.

Subgrade Preparation

6. As previously discussed, areas of non-engineered fill were encountered within B-3, which was advanced on the outboard side of the existing unnamed access road. Should the City determine that settlement of the non-engineered fill as discussed above is unacceptable, then we recommend that the fill be completely removed and replaced with engineered fill placed in accordance with the recommendations of this report. It is possible that there are additional areas of man-made fill at the site that our field investigation did not detect. Additional areas of man-made fill, if encountered, will need to be completely excavated to undisturbed native material. The excavation process should be observed, and the extent designated by a representative of Pacific Crest Engineering Inc., in the field.

Any voids created by fill removal must be backfilled with properly compacted engineered fill.

7. After clearing and stripping and removing non-engineered fill as discussed above, the surficial soils disturbed by the demolition operation should be completely sub-excavated to undisturbed native material.

8. Final depth of subexcavation should be determined by a representative of Pacific Crest

Engineering Inc., in the field.

9. Hard bedrock may be encountered in the excavations. All grading contractors should be made aware of hard bedrock conditions.

10. Care must be taken not to undermine the foundation system beneath existing structures.

Excavations made adjacent to existing footings must not extend below a line drawn outward at a gradient of 2:1 (H:V) from the bottom outside edge of the footing.

11. Following clearing, stripping and any necessary subexcavations, the exposed subgrade material that is to support (concrete slabs-on-grade, foundations, pavements) should then be scarified 8 inches, and the soil moisture conditioned and compacted as outlined below. This requirement may be waved at the sole discretion of a Pacific Crest Engineering field representative.

12. While not anticipated, if wet or unstable subgrades are encountered, they may need to be further subexcavated and replaced with stabilization fabric, crushed rock, or other materials to create a stable working surface. The depth of over-excavations should be determined in the field at the time of construction. All subexcavations should be observed by a representative of Pacific Crest Engineering

Inc. and modified as necessary to establish a firm and stable subgrade.

Material for Engineered Fill

13. Native or imported soil proposed for use as engineered fill should meet the following requirements:

a. free of organics, debris, and other deleterious materials,

b. free of “recycled” materials such as asphaltic concrete, concrete, brick, etc.,

c. granular in nature, well graded, and contain sufficient binder to allow utility trenches to stand open,

d. free of rocks in excess of 2 inches in size.

14. In addition to the above requirements, import fill should have a Plasticity Index between 4 and 12, and a minimum Resistance “R” Value of 30, and be non-expansive.

15. Samples of any proposed imported fill planned for use on this project should be submitted to

Pacific Crest Engineering Inc. for appropriate testing and approval not less than ten (10) working days before the anticipated jobsite delivery. This includes proposed import trench sand, drain rock and for aggregate base materials. Imported fill material delivered to the project site without prior submittal of samples for appropriate testing and approval must be removed from the project site.

Engineered Fill Placement and Compaction

16. Following any necessary subexcavations and/or subgrade preparation, areas should be brought up to design grades with engineered fill that is moisture conditioned and compacted according to the recommendations of this report.

17. Engineered fill should be placed in maximum 8-inch lifts, before compaction, at a water content which is within 1 to 3 percent of the laboratory optimum value. Expansive subgrade soils should be moisture conditioned to between 3 to 5 percent of laboratory optimum.

18. The soil on the project site should be compacted as follows:

a. In pavement areas the upper 8 inches of subgrade, and all aggregate subbase and aggregate base, should be compacted to a minimum of 95% of its maximum dry density,

b. In pavement areas all utility trench backfill should be compacted to 95% of its maximum dry density,

c. All remaining soil on the project site should be compacted to a minimum of 90% of its maximum dry density.

19. The maximum dry density will be obtained from a laboratory compaction curve run in accordance with ASTM Procedure #D1557. This test will also establish the optimum moisture content of the material. Field density testing will be performed in accordance with ASTM Test #D6938 (nuclear method).

20. We recommend field density testing be performed in maximum 1-foot elevation differences. In general terms, we recommend at least one compaction test per 200 linear feet of utility trench, and at least one compaction test per 500 square feet of building or structure area. This is a subjective value and may be changed by the geotechnical engineer based on a review of the final project layout and exposed field conditions.

21. Engineered fill placed on existing slopes that are steeper than 5:1 (H:V) should be keyed and benched into competent native material. Toe keys should be constructed at the base of the fill slope with a minimum 10-foot-wide width and sloped negatively at least 2% into the bank. The depth of the keyways will vary, depending on the materials encountered.

Cut and Fill Slopes

22. Should the non-engineered fill along the outboard edge of the access road in the vicinity of B-3 be removed as discussed above, then the subject fill slope should be reconstructed with engineered fill meeting the minimum requirements of this report and have a gradient no steeper than 2:1 (H:V). Fill slopes should not exceed 15 feet in vertical height unless specifically reviewed by Pacific Crest

Engineering Inc.

23. It is our understanding that the existing cut slope to the north-northwest of the tank site may be modified to accommodate the proposed 35,000-gallon maintenance water tank. The subject cut slope is predominantly comprised of Quartz Diorite bedrock and is capped with several feet of native colluvial/residual soil. Permanent cut slopes in the colluvial/residual soil cap shall not exceed a 2.5:1

(H:V) gradient. Permanent cut slopes in that Quartz Diorite bedrock shall not exceed a 1.5:1 (H:V) gradient. All cut slopes should not exceed a 15 foot vertical height unless specifically reviewed by a representative of Pacific Crest Engineering Inc.

24. The above slope gradients are based on the strength characteristics of the materials under conditions of normal moisture content that would result from rainfall falling directly on the slope, and do not take into account the additional activating forces applied by seepage from spring areas or subsurface groundwater. Therefore, in order to maintain stable slopes at the recommended gradients, it is important that any seepage forces and accompanying hydrostatic pressure (if encountered) be relieved by adequate drainage. Drainage facilities may include subdrains, gravel blankets, rock fill surface trenches or horizontally drilled drains. Configurations and type of drainage will be determined by a representative of Pacific Crest Engineering Inc. during the grading operations.

25. The above recommended gradients do not preclude periodic maintenance of the slopes, as minor sloughing and erosion may take place.

26. All flatwork should be set back at least 5 feet horizontally from the top of cut and fill slopes. All foundations should be set back at least 10 feet horizontally from the top of cut and fill slopes.

Soil Moisture and Weather Conditions

27. If earthwork activities are done during or soon after the rainy season, the on-site soils and other materials may be too wet in their existing condition to be used as engineered fill. These materials may require a diligent and active drying and/or mixing operation to reduce the moisture content to the levels required to obtain adequate compaction as an engineered fill. If the on-site soils or other materials are too dry, water may need to be added. In some cases, the time and effort to dry the on-site soil may be considered excessive, and the import of aggregate base may be required.

Utility Trench Backfill

28. Utility trenches that are parallel to the sides of the building should be placed so that they do not extend below a line sloping down and away at a 2:1 (horizontal to vertical) slope from the bottom outside edge of all footings.

29. Utility pipes should be designed and constructed so that the top of pipe is a minimum of 24 inches below the finish subgrade elevation of any road or pavement areas. Any pipes within the top 24 inches of finish subgrade should be concrete encased, per design by the project civil engineer.

30. For the purpose of this section of the report, backfill is defined as material placed in a trench starting one foot above the pipe, and bedding is all material placed in a trench below the backfill.

31. Unless concrete bedding is required around utility pipes, free-draining clean sand should be used as bedding. Sand bedding should be compacted to at least 95 percent relative compaction. Clean sand is defined as 100 percent passing the #4 sieve, and less than 5 percent passing the #200 sieve.

32. Approved imported clean sand or native soil should be used as utility trench backfill. Backfill in trenches located under and adjacent to structural fill, foundations, concrete slabs and pavements should be placed in horizontal layers no more than 8 inches thick. This includes areas such as sidewalks, patios, and other hardscape areas. Each layer of trench backfill should be water conditioned and compacted to the relative compaction values provided above.

33. Utility trenches which carry “nested” conduits (stacked vertically) should be backfilled with a control density fill (such as 2-sack sand\cement slurry) to an elevation one foot above the nested conduit stack. The use of pea gravel or clean sand as backfill within a zone of nested conduits is not recommended.

34. A representative from our firm should be present to observe the bottom of all trench excavations, prior to placement of utility pipes and conduits. In addition, we should observe the condition of the trench prior to placement of sand bedding, and to observe compaction of the sand bedding, in addition to any backfill planned above the bedding zone.

35. Jetting of the trench backfill is not recommended as it may result in an unsatisfactory degree of compaction.

36. Trenches must be shored as required by the local agency and the State of California Division of

Industrial Safety construction safety orders.

Excavations and Shoring

37. It should be understood that on-site safety is the sole responsibility of the Contractor, and that the Contractor shall designate a competent person (as defined by CAL-OSHA) to monitor the slope excavation prior to the start of each workday, and throughout the workday as conditions change. The competent person designated by the Contractor shall determine if flatter slope gradients are more appropriate, or if shoring should be installed to protect workers in the vicinity of the slope excavation.

Refer to Title 8, California Code of Regulations, Sections 1539-1543.

38. All excavations must meet the requirements of 29 CFR 1926.651 and 1926.652 or comparable

OSHA approved state plan requirements.

39. The “top” of any temporary cut slope and excavations should be set-back at least ten feet

(measured horizontally) from any nearby structure or property line. Any excavations which cannot meet this requirement will need to have a shoring system designed to support steeper sidewall gradients.

40. Temporary shoring is not currently anticipated for this project. Should these requirements change, please contact our office for additional recommendations.

FOUNDATION – RINGWALL FOOTING

41. The following recommendations assume that the proposed new 400,000-gallon tank will occupy the same footprint as the existing tank, and that the 35,000-gallon maintenance tank be founded into conditions similar to those in the vicinity of the existing water storage tank. If the proposed locations change, we request the opportunity to review proposed plans to confirm if these recommendations still apply.

42. It is our understanding that the existing foundation for the 400,000-gallon water tank may be reused for the new tank. Evaluation of the existing ring foundation may utilize the geotechnical design criteria in this section of the report.

43. We recommend both water storage tanks be founded on a reinforced concrete ringwall foundation system embedded into undisturbed quartz diorite that predominates the site. This system should consist of a continuous perimeter footing, in conjunction with isolated interior foundations to support the roof of the tank.

44. All new footings must be trenched into undisturbed quartz diorite or at least 24 inches below lowest adjacent grade, which ever results in a greater depth.

45. New/existing footings may be designed/evaluated using the following parameters.

a. Allowable bearing capacity = 2,500 psf for dead plus live loading with a 1/3rd increase for seismic or wind loading.

b. Ultimate friction coefficient between foundations and underlying soil subgrade = 0.35.

c. Ultimate passive resistance = 450 pounds per cubic foot.

46. The upper 1 foot of soil should be ignored when calculating passive soil resistance.

47. Passive resistance between the sides of the footing and the adjacent soil is only applicable where concrete is placed neat against the quartz diorite and/or engineered fill. Voids created by concrete forms should be backfilled with compacted engineered fill or concrete.

48. In computing the pressures transmitted to the soil by the footings, the embedded weight of the footing may be neglected.

49. Provided our recommendations are followed, under static loading conditions, we estimate that total post-construction foundation settlement will be less than 1 inch, and post-construction differential foundation set

Table No. 4, Recommended Pavement Sections

Material Traffic Index

4½ 5 5½ 6

Asphalt Concrete 2.5 inches 3.0 inches 3.5 inches 3.5 inches

Class 2 Aggregate Base, R=78 min.

6.0 inches 7.0 inches 8.0 inches 9.0 inches

58. To have the selected pavement sections perform to their greatest efficiency, it is very important that the following items be considered:

a. Properly scarify and moisture condition the upper 8 inches of the subgrade soil and compact it to a minimum of 95% of its maximum dry density, at a moisture content of 1 to 3% over the optimum moisture content for the soil.

b. Provide sufficient gradient to prevent ponding of water.

c. Use only quality materials of the type and thickness (minimum) specified. All aggregate base and subbase must meet Caltrans Standard Specifications for Class 2 materials and be angular in shape. All Class 2 aggregate base should be ¾ inch maximum in aggregate size.

d. Compact the base uniformly to a minimum of 95% of its maximum dry density.

e. Place the asphaltic concrete only during periods of fair weather when the free air temperature is within prescribed limits by Cal Trans Specifications.

f. Porous pavement systems which consist of porous paving blocks, asphaltic concrete or concrete are generally not recommended due to the potential for saturation of the subgrade soils and resulting increased potential for a shorter pavement life. At a minimum, porous pavement systems should include a layer of Mirafi HP370 geotextile fabric placed on the subgrade soil beneath the porous paving section. These pavement systems should only be used with the understanding by the Owner of the increased potential for pavement cracking, rutting, potholes, etc.

g. Maintenance should be undertaken on a routine basis.

SURFACE DRAINAGE

59. Surface water drainage is the responsibility of the project civil engineer. The following should be considered by the civil engineer in design of the project.

60. Surface water must not be allowed to pond or be trapped adjacent to foundations, or on building pads and parking areas.

61. All roof eaves should be guttered, with the outlets from the downspouts provided with adequate capacity to carry the storm water away from structures to reduce the possibility of soil saturation and erosion. The connection should be in a closed conduit which discharges at an approved location away from structures and graded areas.

62. Slope failures can occur where surface drainage is allowed to concentrate on unprotected slopes.

Under no circumstances should surface water be allowed to cascade onto the slopes that border the proposed development area. Appropriate landscaping and surface drainage control around the project area is imperative in order to minimize the potential for shallow slope failures and erosion. Stormwater discharge locations should not be located at the top or on the face of any slope.

63. Final grades should be provided with positive gradient away from all foundation elements. Soil grades should slope away from foundations at least 5 percent for the first 10 feet. Impervious surfaces should slope away from foundations at least 2 percent for the first 10 feet. Concentrations of surface runoff should be handled by providing structures, such as paved or lined ditches, catch basins, etc.

64. Irrigation activities at the site should be done in a controlled and reasonable manner.

65. Following completion of the project we recommend that storm drainage provisions and performance of permanent erosion control measures be closely observed through the first season of significant rainfall, to determine if these systems are performing adequately and, if necessary, resolve any unforeseen issues.

66. Drainage facilities must not be altered, nor any filling or excavation work performed in the area without first consulting Pacific Crest Engineering Inc. Surface drainage improvements developed by the project civil engineer must be maintained by the property owner at all times, as improper drainage provisions can produce undesirable affects.

EROSION CONTROL

67. The surface soils are classified as having a moderate potential for erosion. Therefore, the finished ground surface should be planted with ground cover and continually maintained to minimize surface erosion. For specific and detailed recommendations regarding erosion control on and surrounding the project site, the project civil engineer or an erosion control specialist should be consulted.

68. The surfaces of all cut and fill slopes should be prepared and maintained to reduce erosion. This work, at a minimum, should include track rolling of the slope and effective planting. The protection of the slopes should be installed as soon as practicable so that a sufficient growth will be established prior to inclement weather conditions. It is vital that no slope be left standing through a winter season without the erosion control measures having been provided.

PLAN REVIEW

69. We respectfully request an opportunity to review the project plans and specifications during preparation and before bidding to verify that the recommendations of this report have been included and to provide additional recommendations, if needed. These plan review services are also typically required by the reviewing agency. Misinterpretation of our recommendations or omission of our requirements from the project plans and specifications may result in changes to the project design during the construction phase, with the potential for additional costs and delays in order to bring the project into conformance with the requirements outlined within this report. Services performed for review of the project plans and specifications are considered “post-report” services and billed on a

“time and materials” fee basis in accordance with our latest Standard Fee Schedule.

VI. LIMITATIONS AND UNIFORMITY OF CONDITIONS

1. This Geotechnical Investigation was prepared specifically for MME and for the specific project and location described in the body of this report. This report and the recommendations included herein should be utilized for this specific project and location exclusively. This Geotechnical Investigation should not be applied to nor utilized on any other project or project site.

2. The recommendations of this report are based upon the assumption that the soil conditions do not deviate from those disclosed in the borings.