Geotechnical Investigation (revised)

Geotechnical Investigation (revised)

Pacific Tunnel Improvements El Dorado County, California

El Dorado Irrigation District

GHD | 4080 Plaza Goldorado Circle Suite B Cameron Park CA 95682 USA

11136547 | September 2018

Attachment B to Addendum 1

GHD | Geotechnical Investigation | 11136547 | Page i

September 27, 2018

Cary Mutschler, PE El Dorado Irrigation District 2890 Mosquito Road Placerville, California 95667

RE: Geotechnical Investigation, Pacific Tunnel (revised)

GHD is pleased to present the attached report containing the results of our geotechnical investigation for the proposed Pacific Tunnel Improvements project in El Dorado County, California. It is our understanding that the proposed project consists of lining the tunnel and the construction of wingwalls at the upstream and downstream portals. This report supersedes our previous geotechnical investigation report dated February 6, 2017.

The accompanying report presents our findings, conclusions, and recommendations developed from our geotechnical investigation. Contained in the report are geotechnical design criteria and recommendations for design and construction of the proposed improvements. The results of the subsurface exploration and laboratory testing programs, which form the basis of our recommendations, are also included in the report. On the basis of our investigation, the site is suitable, from a geotechnical perspective, to receive the planned improvements provided the recommendations presented in the report are incorporated into the design and construction of the project.

If you have any questions regarding the information contained in this report, or if we may be of further assistance, please do not hesitate to contact us.

Sincerely,

GHD

Christopher D. Trumbull, P.E., G.E., D.GE Senior Geotechnical Engineer

GHD | Geotechnical Investigation | 11136547 | Page ii

Table of Contents

1. Introduction 5

1.1 Project Description ............................................................................................................. 5

1.2 Purpose and Scope of Work .............................................................................................. 5

2. Field Exploration and Laboratory Testing 5

2.1 Field Exploration ................................................................................................................ 5

2.2 Geotechnical Laboratory Testing ....................................................................................... 6

3. Geologic and Subsurface Conditions 7 3.1 Site Conditions ................................................................................................................... 7

3.2 Geologic Conditions ........................................................................................................... 7

3.3 Subsurface Conditions ....................................................................................................... 7

3.3.1 Subsurface Materials ........................................................................................ 7 3.3.2 Groundwater Conditions ................................................................................... 7

4. Conclusions 7

4.1 Ground Shaking ................................................................................................................. 7

5. Recommendations 8

5.1 Site Preparation and Earthwork ......................................................................................... 8 5.1.1 General Subgrade Preparation ......................................................................... 8 5.1.2 Engineered Fill .................................................................................................. 8 5.1.3 Benching and Keying Fills ................................................................................ 9 5.1.4 Compaction ....................................................................................................... 9 5.1.5 Cut Slopes ........................................................................................................ 9 5.1.6 Fill Slopes ......................................................................................................... 9

5.2 Foundations ....................................................................................................................... 9

5.2.1 Wingwall Footings........................................................................................... 10 5.2.2 Passive Resistance ........................................................................................ 10

5.3 Rock Anchors ................................................................................................................... 10

5.4 Lateral Earth Pressures ................................................................................................... 11

5.5 Construction Observation ................................................................................................ 11

6. References 11

7. Limitations 12

Table Index

Table 5.1.2 Import Fill Specifications .................................................................................................... 8

Table 5.2 Foundation Soil Parameters…………………………………………………………………....9

GHD | Geotechnical Investigation | 11136547 | Page iii

Table 5.2.1 Bearing Capacity……………………………………………………………………………10

Appendix Index Appendix A Figures

Appendix B Logs of Test Pits

Appendix C Geotechnical Laboratory Test Results

Appendix D Seismic Refraction Survey Results

Appendix E Tunnel Condition Assessment

GHD | Geotechnical Investigation | 11136547 | Page iv

Distribution

To: El Dorado Irrigation District


2890 Mosquito Road

Placerville, California 95667

From: GHD

Christopher Trumbull, P.E., G.E., D.GE

4080 Plaza Goldorado Circle, Suite B

Cameron Park, CA 95682

GHD | Geotechnical Investigation | 11136547 | Page 5

1. Introduction

This report presents the findings, conclusions, and recommendations developed from our geotechnical engineering investigation. The investigation was conducted in accordance with the Professional Services Agreement *On-Call Contract – Geotechnical Notice to ProceedN1216-291 dated 12/05/16. This report supersedes our previous geotechnical investigation report dated February 6, 2017.

1.1 Project Description

The project site is located south of US Highway 50 in El Dorado County, California as shown on Figure A-1. The proposed project consists primarily of the design and construction of new tunnel lining and wingwalls at both the upstream and downstream portals.

1.2 Purpose and Scope of Work

The purpose of this study was to evaluate the suitability of the project site, from a geotechnical perspective, for the proposed improvements. The main objectives of the investigation were to characterize the subsurface materials, perform engineering analyses, develop geotechnical recommendations and criteria, and document our findings, conclusions, and recommendations in this report.

The scope of our geotechnical investigation included the following tasks:

• A review of published geologic and geotechnical material pertaining to the site vicinity

• A field exploration program consisting of two test pits to a depth of approximately 2 feet below ground surface within the site to characterize the subsurface conditions

• Three seismic refraction surveys to characterize the subsurface materials

• Geotechnical laboratory testing on select soil samples collected from the test pits

• Engineering analyses to develop geotechnical design criteria and recommendations for the proposed project

• Preparation of this report

2. Field Exploration and Laboratory Testing

2.1 Field Exploration

Two test pits were hand excavated on December 22, 2016 at the approximate locations shown on the Exploration Maps, Figures A-2 and A-3. The test pits were placed near the proposed wing wall improvements and were located in the field based on estimated distances from the existing structures. The test pits were excavated to a maximum depth of approximately 2 feet under the supervision of Christopher Trumbull of GHD.


GHD performed three seismic refraction surveys of the existing site; see Figure A-2 in Appendix A for locations. Lines one and two were performed at the upstream portal. Line three was performed in two legs perpendicular to each other at the downstream portal. The lines were based on site improvements, existing conditions, and landslide geometry. The purpose of the surveys was to provide additional subsurface data related to seismic velocity and depth of rock to assist in evaluating the strength of rock for foundation and anchor design.

The seismic refraction lines were acquired using a 12-channel system with geophones spaced at 2-foot intervals to provide adequate detail of the subsurface refractors, and the energy source consisted of an impact tool (16-lb sledge hammer). Shot points were positioned midpoint between each geophone along the length of the line. Seismic data was acquired utilizing a digital, distributed, 24-bit instrument. Color-coded seismic velocity cross-sections were generated for the seismic refraction lines to clearly delineate changes in seismic velocities.

Seismic refraction has its limitations and shall coincide with other methods, such as geotechnical borings, and geological observations. General and specific limitations are listed in ASTM D5777.

Subsurface conditions encountered are summarized in Section 3.3. Logs of the test pits were prepared based on the field logging, visual examination of the soil samples in the laboratory, and the results of laboratory testing. The soil test pit key and the logs of test pits are presented in Appendix B. The results of the seismic refraction surveys are presented in Appendix D.

2.2 Tunnel Inspection

A tunnel inspection was performed on December 22, 2016. The objective of the inspection was to observe and evaluate the current condition of Pacific Tunnel. To achieve this objective, the inspection party performed the condition assessment, including rebound hammer testing, geologic interpretation of the tunnel condition, identification of anomalies, measurement of cross-sectional dimensions, measurement of seeps and water inflow, and photography of conditions. The Tunnel Condition Assessment is presented in Appendix E.

2.3 Geotechnical Laboratory Testing

Laboratory testing was conducted on disturbed soil samples recovered during the site investigation. Samples were classified in general accordance with ASTM D2487. Tests conducted include the following:

• Standard Test Method for Particle-Size Analysis of Soils (ASTM D422)

• Standard Test Method for Laboratory Compaction Characteristics of Soil (ASTM D1557)

• Standard Test Method for Direct Shear Test of Soils (ASTM D3080)

Geotechnical laboratory test results are presented in Appendix C.


3. Geologic and Subsurface Conditions

3.1 Site Conditions

The project is located in El Dorado County, California. The Pacific Tunnel is an approximately 190-foot-long untreated water tunnel in El Dorado Irrigation District’s (EID’s) water delivery system. The tunnel conveys flow along the El Dorado Canal (FERC Project 184) below access road R82. The access road to the tunnel from Park Creek Road consisted of steep grades with erosion, rilling in areas were greater than 12-inches in depth. The approximate 190-foot long tunnel (nominal) is unlined rock over much of its length, with timber lined sections at the inlet and outlet portals. The upstream and downstream portals consist of soil slopes ranging from 2:1 to 1:1 (H:V) with timber cribbing.

3.2 Geologic Conditions

The site is located within the foothills of the Sierra Nevada geomorphic province. The site is mapped as Tertiary aged Mehrten Formation (Wagner, 1981). Mehrten is a conglomerate or breccia matrix composed of volcanic rocks.

3.3 Subsurface Conditions

3.3.1 Subsurface Materials

The subsurface materials encountered in the investigation consisted of brown and red brown silty sand with gravel to the maximum depth explored of 2 feet. These soils were underlain by Mehrten Formation volcanics. Detailed descriptions of the materials encountered in the test pits are presented in the test pit logs in Appendix B.

3.3.2 Groundwater Conditions

Groundwater was not encountered in the investigation. The depth of groundwater is expected to vary over time due to seasonal changes and other factors such as changes to site drainage.

4. Conclusions

On the basis of our investigation, the site is suitable, from a geotechnical perspective, to receive the planned improvements provided the recommendations presented in the report are incorporated into the design and construction of the project.

4.1 Ground Shaking

The site vicinity is located in an area generally characterized as having low seismicity. Using the USGS Seismic Hazard Tool Website considering the site location, ASCE 7-10/NEHRP, and Type D soils, the Peak Ground Acceleration (PGA) is 0.22 g. Strong ground shaking at the site should not be expected during an earthquake.


4.2 Expansive Soils

Expansive soils are defined as soils that undergo large volume changes (shrink or swell) due to variations in moisture content. Such volume changes may cause damaging settlement and/or heave of foundations, slabs-on-grade, pavements, etc. No evidence of expansive soil was discovered during the subsurface exploration for this project (i.e. soils with a liquid limit greater than 50 or a plasticity index greater than 25).

4.3 Existing Utilities

No underground utilities were discovered during the field exploration and tunnel inspection, though utility field locating was outside of the Project scope. A utility locating investigation would need to be conducted to provide a greater understanding of the potential underground utilities affecting the site

5. Recommendations

5.1 Site Preparation and Earthwork

General site preparation should include the stripping of the existing pavement section. Abandoned underground structures such as culverts should be removed and replaced with engineered fill, placed and compacted as recommended in Section 5.1.4..

5.1.1 General Subgrade Preparation

Any soft, loose areas should be stabilized prior to placement of engineered fill, foundations, pavements, or other structures.

5.1.2 Engineered Fill

Engineered fill should consist of a homogenous mixture of soil and rock free of vegetation, organic material, and rubble. Although not anticipated, highly plastic or organic soils found on site should not be used as engineered fill material.

We anticipate that most of the materials generated from on-site excavations will be suitable for use as engineered fill; however, clay should not be used as engineered fill. Imported material to be used as engineered fill should meet the specifications listed in the table below after compaction.

Table 5.1.2 Import Fill Specifications

Direct Shear (ASTM D3080)

Atterberg Limits (ASTM D4318)

Particle Size

(ASTM C136 or D422)

≥34° PI < 15 LL < 40

100% passing the 6 inch sieve minimum of 85% passing the 2-1/2 inch sieve maximum of 20% passing the #200 sieve

GHD should be provided test results and observe and approve import fill material in writing prior to the material being brought on site.


5.1.3 Benching and Keying Fills

Slopes with inclinations of 6:1 or steeper should be benched during placement of engineered fill. The benches should consist of a level surface excavated at least 4 feet horizontally into native subgrade. The benches should continue progressively up the slope at vertical increments of not greater than 3 feet. Fill placed on slopes that are steeper than 4:1 should be keyed into firm native soil or weathered rock at the toe of the fill slope. The bottom of the keyway should extend a minimum of 3 feet below downslope grade and a have a minimum width of 10 feet (extending beneath the toe of the fill slope). Subdrainage of the keyways may be necessary and should be determined by a qualified GHD representative in the field at the time of construction.

5.1.4 Compaction

Engineered fill should be moisture conditioned as necessary, placed in horizontal loose lifts not exceeding 8 inches in thickness, and compacted to a minimum of 90 percent of the maximum dry density as determined by ASTM D1557 for fills less than 5 feet in thickness. In areas to receive canal improvements, or fills thicker than 5 feet, fill should be compacted to 95 percent of the maximum dry density as determined by ASTM D1557. Placement of fill material should be verified by a qualified geotechnical representative on a continuous basis. Nuclear density testing should be performed every two vertical feet of backfill placement.

5.1.5 Cut Slopes

Cut slopes at the portals should be excavated as not to exceed a 2:1 (H:V) inclination in native soil, or 1:1 in rock. A v-ditch should be constructed at the perimeter to prevent water from entering the cut slope area.

5.1.6 Fill Slopes

Fill slopes should be constructed at an inclination no steeper than 2:1, should be laterally over-built at least one foot, and the slope face trimmed back to firm, compacted material

5.1.7 Erosion Control

Erosion control measures should be implemented for exposed surfaces potentially subject to soil erosion particularly cut and fill slopes. Best Management Practices to reduce erosion and transport of soil particles or turbid water into the drainage course flowing from the construction site must be employed. All conditions of existing water quality regulatory agency permits must be adhered to.

5.2 Foundations

Provided herein are the soil parameters to be used for the foundations and retaining walls. The parameters are based on materials encountered in the test pits, laboratory testing of collected samples (See Appendix B and D) and engineering judgement.


Table 5.2 Foundation Soil Parameters

Parameters Soil Rock Unit Weight (pcf), γt 93 150

Internal Friction Angle, ø 34 40 Cohesion (psf), c 0 0

5.2.1 Wingwall Footings

Footings for the new portal wingwalls should be designed with maximum allowable bearing capacities in Table 5.2.1 below. The allowable bearing capacity can be increased by one-third for all loads including wind and seismic. The proposed footings should be excavated to a minimum depth of 18 inches below the lowest adjacent grade and have a minimum width of 24 inches. Total settlement should be less than 1 inch and differential settlement across the structure should be less than 1/2 inch.

Table 5.2.1 Maximum Allowable Bearing Capacity

Bearing Material Bearing Capacity (psf) Dead Load Dead + Live Loads

Soil 2,300 3,500 Rock 4,000 6,000

5.2.2 Passive Resistance

Passive earth resistance or passive earth pressure is the amount of resistance provided by the soil in response to a movement of a structure resulting in a compressive force upon the soil. A passive earth pressure of 350 pounds per cubic foot should be used if the upper foot of soils is ignored. A friction coefficient of 0.35 is recommended. If the foundation is poured against neatly excavated soil without the use of forms, both the friction coefficient and the passive resistance may be used in design. Passive earth pressures provided herein assume that the zone of interest is above groundwater table and on a relatively level surface. If these conditions are not met in any of the foundation locations, GHD should be contacted to provide a reduced passive earth pressure value.

5.3 Rock Anchors

To achieve stability of the wingwalls, permanent rock anchors may be required. Rebound hammer readings within the tunnel ranged from 200 psi to 4,150 psi with an average reading of approximately 2,000 psi. Considering the rebound hammer values and the seismic velocities, an allowable bond strength of 200 psi (10% of the ultimate capacity) should be used for design.

Rock anchors shall be 1”, 150 ksi epoxy coated all-thread bar. A non-shrink cement grout such as Masterflow 555 grout or equivalent is recommended. The grout should be mixed in accordance with


the manufacturer’s specifications and tremmied from the bottom of the anchor hole. Grout cylinders 2 inches in diameter and 4 inches long should be cast at the time of grouting. For each day’s grouting, cylinders will be broken at 24 hours, 2 days, 7 days, and 2 at 28 days (with one hold, e.g. collect 6 samples). Stressing of rock anchors may commence once the grout has achieved a compressive strength of 2,000 psi.

Proof testing of rock anchors should be accomplished by applying a sustained proof load to a rock anchor and measuring anchor movement over a specified period of time. A minimum of 15 percent of the anchors should be proof tested to a minimum of 133 percent of the design capacity. A load cell capable of providing a capacity of two times the design capacity of the anchors should be used. The load cell should have been calibrated by a certified laboratory within the last six months, and the certificate should be submitted to GHD prior to testing.

5.4 Lateral Earth Pressures

We assume the wingwalls will be in a restrained (at-rest) and undrained condition. An undrained at-rest equivalent fluid pressure of 85 pcf should be used for design.

5.5 Invert Slab

Due to the probe depth measured at the invert in the tunnel condition assessment, it is recommended that the tunnel receive an invert slab to reduce future erosion and improve flow through the tunnel.

5.6 Tunnel Liner

Due to the scour observed at the ribs in the tunnel condition assessment, and to improve flow characteristic to accommodate for future flows, it is recommended that the tunnel receive lining of the ribs with reinforced air-placed concrete. The Mehrten rock that comprises the tunnel ribs and back may be considered equivalent to un-reinforced concrete with an unconfined compressive strength of 2,000 pounds per square inch (psi) for design.

5.7 Construction Observation

Our conclusions and recommendations are contingent upon GHD being retained to provide intermittent observation and appropriate field and laboratory testing during site preparation to evaluate if the subsurface conditions are as anticipated. If the subsurface conditions are observed to be different from those described in this report, we should be notified immediately so that the changed conditions can be evaluated and our recommendations revised, if appropriate. The recommendations in this report are contingent upon our notification and review of changed conditions. The services proposed above would be performed on an as-needed basis under a supplemental task order.

6. References

Wagner, et all. 1981. “Geologic Map of the Sacramento Quadrangle, California, 1:250,000”


Jennings, Charles W. 2010. “Geologic Map of California: California Division of Mines and Geology, scale 1:750,000.”

Post-Tensioning Institute, 2014, “Recommendations for Prestressed Rock and Soil Anchors.”

California Building Standards Commission, 2016, “California Building Code.”

7. Limitations

This Geotechnical Investigation (“Report”):

• Has been prepared by GHD for the El Dorado Irrigation District (the District) under the professional supervision of those senior partners and/or senior staff whose seals and signatures appear herein

• May only be used and relied on by the District, which is responsible to ensure that all relevant parties to the project, including designers, contractors, subcontractors, etc., are made aware of this report in its entirety

• Must not be copied to, used by, or relied on by any person other than the District without the prior written consent of GHD

• May only be used for the purpose of engineering design of the proposed storm drain improvements at the project site described in this report (and must not be used for any other purpose)

GHD and its servants, employees and officers otherwise expressly disclaim responsibility to any person other than the District arising from or in connection with this Report.

To the maximum extent permitted by law, all implied warranties and conditions in relation to the services provided by GHD and the Report are excluded unless they are expressly stated to apply in this Report.

The services undertaken by GHD in connection with preparing this Report:

• In regard to site exploration and testing:

– Site exploration and testing characterizes subsurface conditions only at the locations where the explorations or tests are performed; actual subsurface conditions between explorations may be different than those described in this report. Variations of subsurface conditions from those analyzed or characterized in this report are not uncommon and may become evident during construction. In addition, changes in the condition of the site can occur over time as a result of either natural processes (such as earthquakes, flooding, or changes in ground water levels) or human activity (such as construction adjacent to the site, dumping of fill, or excavating). If changes to the site’s surface or subsurface conditions occur since the performance of the field work described in this report, or if differing subsurface conditions are encountered, we should be contacted immediately to evaluate the differing conditions to assess if the opinions, conclusions, and recommendations provided in this report are still applicable or should be amended.


• In regard to limitations:

– Our scope of services was limited to the proposed work described in this report, and did not address other items or areas.

– The geotechnical investigation upon which this report is based was conducted for the proposed structures at the project site described in this report. The conclusions and recommendations contained in this report are not valid for other structures and/or project sites. If the proposed project is modified or relocated, or if the subsurface conditions found during construction differ from those described in this report, GHD should be provided the opportunity to review the new information or changed conditions to determine if our conclusions and recommendations need revision.

• Did not include evaluation or investigation of the presence or absence of wetlands

• Did not include a landslide evaluation

• Did not include a fault investigation

GHD expressly disclaims responsibility for any error in, or omission from, this Report arising from or in connection with any of the Assumptions being incorrect. There is no warranty, either expressed or implied. GHD accepts no liability regarding completeness or accuracy of the information presented and/or provided to us, or any conclusions and decisions which may be made by the client or others regarding the subject site/project. Verification of our conclusions and recommendations is subject to our review of the project plans and specifications, and our observations of construction.

Subject to the paragraphs in this section of the Report, the interpretations of data, findings, conclusions, recommendations and professional opinions in this Report are based on the information reviewed, site conditions encountered, and samples collected during our field exploration and were developed in accordance with generally accepted geotechnical engineering principles and practices and as prescribed by the client. This Report is considered valid for the proposed project for a period of two years from the report date provided that the site conditions and development plans remain unchanged. With the passage of time, changes in the conditions of a property can occur due to natural processes or the works of man on this or adjacent properties. Legislation or the broadening of knowledge may result in changes in applicable standards. Depending on the magnitude of any changes, GHD may require that additional studies (at additional cost) be performed and that an updated report be issued. Additional studies may disclose information which may significantly modify the findings of this report. GHD will retain untested samples collected during our field investigation for a period not to exceed 60 days unless other arrangements are made with the client. After a period of two years from the report date, GHD expressly disclaims responsibility for any error in, or omission from, this Report arising from or in connection with those opinions, conclusions and any recommendations.

GHD | Geotechnical Investigation | 11110191 | Appendix A

Appendix A Figures

DateRevision No.

Project No.

Plot Date: 6 February 2017 - 9:39 AM Filename: \\ghdnet\ghd\us\cameron park\projects\111\11136547\06-CAD\Figures\Exhibits\Geotech Exploration Logs.dwg

El Dorado Irrigation DistrictPacific Tunnel ImprovementsEl Dorado County, CA

11136547001/03/2017

A-1Vicinity Map

PROJECTLOCATION

NTS

9

12

SRL-3

TP-2

11

10

87

65

DateRevision No.

Project No.



11136547001/03/2017

LEGEND

Approximate Location of Test Pit by GHD

Approximate Location of Seismic Refraction Line (SRL) by GHD

0 4'1"=4'

2'

A-2Exploration MapWest (Downstream) Portal

23

45678

8

2

PACIFIC TUNNEL

SRL-2

SRL-1

TP-1

3

4

7

6

5

LEGEND

Approximate Location of Test Pit by GHD

Approximate Location of Seismic Refraction Line (SRL) by GHD

0 4'1"=4'

2'Date

Revision No.Project No.



11136547001/03/2017

A-3Exploration MapEast (Upstream) Portal

GHD | Geotechnical Investigation | 11110191 | Appendix B

Appendix B Logs of Test Pits


1113654702/6/2017

Test Pit Key

SYMBOLS

SANDSWITH FINES

WELL-GRADED GRAVELS, GRAVEL -SAND MIXTURES, LITTLE OR NO FINES

INORGANIC CLAYS OF LOW TO MEDIUMPLASTICITY, GRAVELLY CLAYS, SANDY CLAYS,

SILTY CLAYS, LEAN CLAYS

COARSEGRAINED SOIL

SAMPLE SYMBOLS

GENERAL NOTES

WELL SYMBOLS WATER LEVEL SYMBOLS

Water level measured at a specified time after drilling and sampling or wellcompletion.

Water level at time of drilling.

POORLY GRADED - PREDOMINATELY ONE GRAIN SIZE, OR HAVING A RANGE OF SIZES WITH SOME INTERMEDIATE SIZES MISSING

MORE THAN 50%OF MATERIAL ISSMALLER THANNO. 200 SIEVE

SIZE

APPRECIABLEAMOUNT OF FINES

LITTLE OR NO FINES

APPRECIABLEAMOUNT OF FINES

LITTLE OR NO FINES

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PT

CLEAN SANDS

GRAVELS WITHFINES

CLEAN GRAVELS

LIQUID LIMITGREATER THAN

50

MORE THAN 50%OF MATERIAL ISLARGER THANNO. 200 SIEVE

SIZE

1. Soil classifications are based on the Unified Soil Classification System. Soil descriptions and stratum linesare interpretive, and actual changes may be gradual. Field descriptions may have been modified to reflectresults of laboratory tests.

2. Descriptions on these logs apply only at the specific boring locations and at the time the borings wereadvanced. They are not warranted to be representative of subsurface conditions at other locations.

NOTE: DUAL SYMBOLS ARE USED TO INDICATE BORDERLINE SOIL CLASSIFICATIONS

SILTS ANDCLAYS

LIQUID LIMIT LESSTHAN 50

POORLY-GRADED GRAVELS, GRAVEL -SAND MIXTURES, LITTLE OR NO FINES

BOULDERSCOBBLES

GRAVEL: COARSEGRAVEL: FINE

SAND: COARSESAND: MEDIUM

SAND: FINESILTCLAY

WELL GRADED - HAVING WIDE RANGE OF GRAIN SIZES AND APPRECIABLE AMOUNTS OF ALL INTERMEDIATE PARTICLE SIZES

UNIFIED SOIL CLASSIFICATION AND SYMBOL CHARTDESCRIPTIONS

MORE THAN 50%OF COARSEFRACTION

RETAINED ON NO.4 SIEVE

MORE THAN 50%OF COARSEFRACTION

PASSING ON NO. 4SIEVE

SILTS ANDCLAYS

FINE GRAINEDSOIL

CLAYEY GRAVELS, GRAVEL - SAND -CLAY MIXTURES

WELL-GRADED SANDS, GRAVELLYSANDS, LITTLE OR NO FINES

POORLY-GRADED SANDS, GRAVELLYSAND, LITTLE OR NO FINES

SAND ANDSANDY SOIL

PARTICLE SIZE IDENTIFICATION

HIGHLY ORGANIC SOIL

SILTY SANDS, SAND - SILT MIXTURES

CLAYEY SANDS, SAND - CLAY MIXTURES

ORGANIC SILTS AND ORGANIC SILTYCLAYS OF LOW PLASTICITY

INORGANIC SILTS, MICACEOUS ORDIATOMACEOUS FINE SAND OR SILTY

SOILS

PEAT, HUMUS, SWAMP SOILS WITHHIGH ORGANIC CONTENTS

INORGANIC CLAYS OF HIGH PLASTICITY

MAJOR DIVISIONS

INORGANIC SILTS AND VERY FINE SANDS, ROCKFLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY

SILTS WITH SLIGHT PLASTICITY

ORGANIC CLAYS OF MEDIUM TO HIGHPLASTICITY, ORGANIC SILTS

SILTY GRAVELS, GRAVEL - SAND - SILTMIXTURES

>12 in3 - 12 in3/4 - 3 in

No.4 - 3/4 inNo.10 - No.4No.40 - No.10No.200 - No.40

0.002 mm - No.200<0.002 mm

Cement Grout

Filter Sand

Bentonite

Screen in filter sand

RX (Bedrock)

SloughShelby Tube

No Recovery

California Modified(2.5-inch I.D.)

California(2.0-inch I.D.)

GRAVEL ANDGRAVELLY SOIL

Auger Sample

3. Abbreviations: CD = TX-CD CN = Consolidation CR = Corrosivity CU = TX-CU DS = Direct Shear EI = Expansion Index MDD = Maximum Density

NR = No RecoveryPR = PermeabilityRV = R-ValueTC = Cyclic TriaxialUC = Unconfined CompressionUU = TX-UU (quick)ATD= At Time of Drilling

SPT(1.375 I.D.)

0 - 45 - 1011 - 3031 - 50

>50

Very LooseLoose

Medium DenseDense

Very Dense

*ASTM D 1586; number of blows of 140 pound hammer falling 30 inches to drive a 2-inch-O.D., 1.4-inch-I.D. sampler one foot.

Unconfined Compressive Strength (tons/sq ft)

N Value * (Blows/ft)

FINEGRAINED

SOIL

EMPIRICAL CORRELATIONS WITH STANDARD PENETRATION RESISTANCE N VALUES*N Value *

(Blows/ft) ConsistencyRelative Density

<0.250.25 - 0.500.50 - 1.001.00 - 2.002.00 - 4.00

>4.00

0 - 23 - 45 - 89 - 1516 - 30

>30

Very SoftSoft

Medium StiffStiff

Very StiffHard

COARSEGRAINED

SOIL

* T _ *

PLAS

TIC

ITY

IND

EX

LIQUID LIMIT (LL) (%)0 10

A LINE=0.73(LL-20)

20 30 40 50 60 70 80 90 1000

10

20

30

40

50

60

CL

CH

ML & OL

MH & OH

CL-ML

PLASTICITY CHART

Project No.Revision No.

Date

TEST PIT KEY 11136547 EID PACIFIC TUNNEL.GPJ

MDDDS18BK 72

Brown silty SAND (SM) with gravel, dry

Test pit terminated at 2 ft bgs

ExcavatingMethod: Hand Tools

Start Date: 12/22/16

Excavator:

LoggedBy: Chris Trumbull

Remarks:

ReviewedBy: K. JermstadBorehole

Backfill: spoils

Bucket Notes:

ExcavationContractor:

Total DepthDrilled (ft bgs): 2.0

Arbitrary GroundSurface Elevation: 3833

Other:

CompactionMethod:

TP-1

Elev

atio

n (ft

)

Dep

th (f

t)

Log of Test Pit

Oth

er T

ests

* T _ *


Date

1113654709/27/2018


TEST PIT 11136547 EID PACIFIC TUNNEL.GPJ

% P

assi

ngN

o. 2

00 S

ieve

Gra

phic

Log

Sam

ple

Type

% P

assi

ng N

o. 4

Sie

ve

MATERIALDESCRIPTION

3832.5

3832.0

3831.5

3831.0

3830.5

0.5

1.0

1.5

2.0

2.5

MDDDS29BK 85

Red-brown silty SAND (SM) with gravel

Test pit terminated at 2 ft bgs

ExcavatingMethod: Hand Tools

Start Date: 12/22/16

Excavator:

LoggedBy: Chris Trumbull

Remarks:

ReviewedBy: K. JermstadBorehole

Backfill: spoils

Bucket Notes:

ExcavationContractor:

Total DepthDrilled (ft bgs): 2.0

Arbitrary GroundSurface Elevation: 3837

Other:

CompactionMethod:

TP-2

Elev

atio

n (ft

)

Dep

th (f

t)

Log of Test Pit

Oth

er T

ests

* T _ *


Date

1113654709/27/2018


TEST PIT 11136547 EID PACIFIC TUNNEL.GPJ

% P

assi

ngN

o. 2

00 S

ieve

Gra

phic

Log

Sam

ple

Type

% P

assi

ng N

o. 4

Sie

ve

MATERIALDESCRIPTION

3836.0

3835.5

3835.0

3834.5

3834.0

0.5

1.0

1.5

2.0

2.5

GHD | Geotechnical Investigation | 11110191 | Appendix C

Appendix C Geotechnical Laboratory Test Results

TP-1 0.0 Brown silty SAND (SM) with gravel 19 18 MDD, DS

TP-2 1.0 Red-brown silty SAND (SM) with gravel 19 29 MDD, DS

Summary of Laboratory Results

BoringID

Depth(ft) Description

WaterContent

(%)

DryDensity

(pcf)

MaximumSize(mm)

%<#200Sieve

LiquidLimit

PlasticLimit

PlasticityIndex Other Tests

C-1* T _ *

LABSUM TEST 11136547 EID PACIFIC TUNNEL.GPJ



Date

1113654702/6/2017

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

0.0010.010.1110100

HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS

SILT OR CLAY

Classification

60

PER

CEN

T FI

NER

BY

WEI

GH

T

6 16 20 30 40 501.5 2006 8 10 1441 3/43 24

GRAIN SIZE IN MILLIMETERS

1/2 3/8 3 100 140

54.0

55.2

0.0

1.0

Brown silty SAND (SM) with gravel


%Silt%Sand%Gravel

Specimen Identification LL

17.9

29.4

PI

11.063

7.091

8.448

4.913

D50 D15 %Clay

0.0

1.0

25.2

14.5

Specimen Identification

PL

fine

Cu

19

19

1.483

0.284

coarse fine coarse medium

Cc

TP-1

TP-2

TP-1

TP-2

COBBLESGRAVEL SAND

D100 D10D90 D85

Sieve Analysis C-2* T _ *



Date

1113654702/6/2017

SIEVE MOD 11136547 EID PACIFIC TUNNEL.GPJ

50

55

60

65

70

75

80

85

90

95

100

10 15 20 25 30 35 40 45

DR

Y D

ENSI

TY, p

cf

WATER CONTENT, %

Brown silty SAND (SM) with gravel


Sample ID Classification Method MDD (pcf) OWC (%)

87

82

25

27

D1557 B

D1557 B

TP-1

TP-2

Moisture-Density Relationship C-3* T _ *



Date

1113654702/6/2017

COMPACTION 11136547 EID PACIFIC TUNNEL.GPJ

Lines of 100% Saturation

SG = 2.6

SG = 2.7

SG = 2.8

Tested By: AST

Client: GHD

Project: EID Pacific Tunnel Portal

Location: TP-1

Sample Number: TP-1 Depth: 0-1'

Proj. No.: 11136547 Date Sampled:

Sample Type: Remolded 1" by 2.49" ring.

Description:

Assumed Specific Gravity= 2.55Remarks: Strain rate in/min: .00125

Appendix

Sample No.

Water Content, %Dry Density, pcfSaturation, %Void RatioDiameter, in.Height, in.Water Content, %Dry Density, pcfSaturation, %Void RatioDiameter, in.Height, in.

Normal Stress, tsfFail. Stress, tsf Strain, %Ult. Stress, tsf Strain, %Strain rate, in./min.

Initi

alA

t Tes

t

She

ar S

tress

, tsf

0

0.25

0.5

0.75

1

1.25

1.5

Strain, %

0 5 10 15 20

1

2

3

Fail.

Stre

ss, t

sf

0

0.5

1

1.5

Normal Stress, tsf

0 0.5 1 1.5 2 2.5 3

C, tsf , deg Tan()

Results0.084

41.70.89

1

30.4

72.564.9

1.19482.49

1.0042.9

73.493.6

1.16852.490.99

0.2500.319

2.8

0.00

2

30.4

72.464.7

1.19852.49

1.0042.9

75.097.4

1.12372.490.97

0.5000.510

4.4

0.00

3

30.4

72.064.1

1.20952.49

1.0044.2

76.8105.1

1.07252.490.94

1.0000.982

3.6

0.00

Tested By: AST

Client: GHD

Project: EID Pacific Tunnel Portal

Location: TP-2

Sample Number: TP-2 Depth: 0-1'

Proj. No.: 11136547 Date Sampled:

Sample Type: Remolded 1" by 2.49" ring.

Description:

Assumed Specific Gravity= 2.55Remarks: Strain raye in/min: .00125

Appendix

Sample No.

Water Content, %Dry Density, pcfSaturation, %Void RatioDiameter, in.Height, in.Water Content, %Dry Density, pcfSaturation, %Void RatioDiameter, in.Height, in.

Normal Stress, tsfFail. Stress, tsf Strain, %Ult. Stress, tsf Strain, %Strain rate, in./min.

Initi

alA

t Tes

t

She

ar S

tress

, tsf

0

0.25

0.5

0.75

1

1.25

1.5

Strain, %

0 5 10 15 20

1

2

3

Fail.

Stre

ss, t

sf

0

0.5

1

1.5

Normal Stress, tsf

0 0.5 1 1.5 2 2.5 3

C, tsf , deg Tan()

Results0.193

43.10.94

1

42.7

76.299.8

1.08982.49

1.0045.3

76.9108.0

1.06892.490.99

0.2500.417

3.6

0.00

2

42.7

71.087.5

1.24322.49

1.0044.8

72.094.2

1.21182.490.99

0.5000.676

4.4

0.00

3

42.7

71.087.5

1.24322.49

1.0045.4

72.997.8

1.18492.490.97

1.0001.124

5.6

0.00

GHD | Geotechnical Investigation | 11110191 | Appendix E

Appendix D Seismic Refraction Survey Results

Page 1 of 7

Seismic refraction is a geophysical method used to determine the depth and velocities of subsurface layers. This method utilizes a seismic wave generated on the surface. For this survey, seismic energy was emitted by a sledgehammer striking on a metal plate. The seismic waves propagate downward through the ground until they are reflected or refracted off subsurface layers. When the seismic wave returns to the surface its arrival is detected by a series of geophones and recorded on a seismograph. Two profiles where acquired and processed to produce detailed two-dimensional P-wave (Vp) models of the subsurface. Line 1 had 8 channels and traversed a distance of 12 ft. There were 5 hit locations along the line including two hits off either end. Line 2 was also 12 ft long and was acquired using 8 geophones with 4 hit locations along the array. Line 3 was processed as two segments – an east-west one that 6 channels and was 8 ft long and a north-south segment that had 3 channels and was 4 ft long The first step is to “stack” or sum the hits at each location. Stacking helps increase the signal to noise ratio and remove uncorrelated noise from the data. Sample gathers along each line are shown in Figures 1, 2 and 3. The very short lines allowed for very shallow velocity resolution – as shallow as 3ft for the Line 3 EW section and as deep as 10 ft for Line 2.

Figure 1: Sample shot gather showing the first-arrival picks (blue lines) along Line 1. These are then input into

SeisOpt® @2D™ to generate the velocity model.

Page 2 of 7

Figure 2: Sample shot gather showing the first-arrival picks (blue lines) along Line 2. These are then input into

SeisOpt® @2D™ to generate the velocity model.

Figure 3a: Sample shot gather showing the first-arrival picks (blue lines) along Line 3, north-south section. These

are then input into SeisOpt® @2D™ to generate the velocity model.

Page 3 of 7

Figure 3b: Sample shot gather showing the first-arrival picks (blue lines) along Line 3, east-west section. These are

then input into SeisOpt® @2D™ to generate the velocity model.

First-arrival picks were then input into Optim’s SeisOpt® @2D™ refraction tomography software to produce detailed 2D velocity models (Figure 3). SeisOpt @2D uses an optimization technique called simulated annealing to obtain velocity information from refraction picks and is specifically designed for mapping subsurface structure characterized by strong lateral velocity variations Simulated annealing is a Monte-Carlo estimation process that can match P-wave arrival times to a velocity model even where sophisticated non-linear inversion methods may fail (Pullammanappallil and Louie, 1993; Pullammanappallil and Louie, 1994). The algorithm works by randomly perturbing an arbitrary starting model until the synthetic seismic wave travel times computed through it match the travel times picked from the new data. New models producing less travel time error are accepted for further enhancements, and models having increased error can be accepted conditionally based on their total error. As annealing proceeds, conditional acceptance becomes less and less likely. Unlike linear, iterative inversions, simulated annealing optimization will find the global velocity solution while avoiding local error minimums. It is also completely insensitive to the starting velocity model, removing the interpreter bias that may be involved. It makes no assumption of the direction of the subsurface velocity gradient, unlike other more conventional seismic refraction methods.

Page 4 of 7

Figure 4: Flow chart showing SeisOpt® @2D™ optimization process

Figures 5, 6, 7 and 8 show the P-wave models along Lines 1, 2, 3NS and 3EW.

Page 5 of 7

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Distance, ft

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

3826

3827

3828

3829

3830

3831

3832

Ele

vatio

n,

ft

3826

3827

3828

3829

3830

3831

3832

200

400

600

800

100

0

120

0

140

0

160

0

180

0

200

0

220

0

240

0

260

0

280

0

300

0

320

0

340

0

360

0

380

0

400

0

420

0

440

0

460

0

480

0

500

0

P-wave Velocity, ft/s

Figure 5: P-wave velocity model along Line 1.

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

Distance, ft

-1 0 1 2 3 4 5 6 7 8 9 10 11 12

3824

3825

3826

3827

3828

3829

3830

3831

3832

3833

3834

3835

Ele

va

tio

n,

ft

3824

3825

3826

3827

3828

3829

3830

3831

3832

3833

3834

38352

00

40

0

60

0

80

0

10

00

12

00

14

00

16

00

18

00

20

00

22

00

24

00

26

00

28

00

30

00

32

00

34

00

36

00

38

00

40

00

42

00

44

00

46

00

48

00

50

00


Figure 5: P-wave velocity model along Line 2.

vrfiedler

Text Box

6:

Page 6 of 7

0 1 2 3 4 5 6 7 8

Distance, ft

0 1 2 3 4 5 6 7 8

3830

3831

3832

3833

3834

3835

3836

3837

Ele

va

tio

n,

ft

3830

3831

3832

3833

3834

3835

3836

3837

20

0

40

0

60

0

80

0

10

00

12

00

14

00

16

00

18

00

20

00

22

00

24

00

26

00

28

00

30

00

32

00

34

00

36

00

38

00

40

00

42

00

44

00

46

00

48

00

50

00


Figure 7: P-wave velocity model along Line 3 east-west section.

0 1 2 3 4

Distance, ft

0 1 2 3 4

3834

3835

3836

3837

Ele

va

tio

n,

ft

3834

3835

3836

3837

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000


Figure 8: P-wave velocity model along Line 3 north-south section.

Page 7 of 7

References:

Pullammanappallil, S.K., and Louie, J.N., 1993, Inversion of seismic reflection traveltimes using a nonlinear optimization scheme: Geophysics, v. 58, p. 1607-1620.

Pullammanappallil, S.K., and Louie, J.N., 1994, A generalized simulated-annealing optimization for inversion of first arrival times: Bulletin of the Seismological Society of America, v. 84, p. 1397-1409.

GHD | Geotechnical Investigation | 11110191 | Appendix E

Appendix E Tunnel Condition Assessment

Tunnel Condition Assessment (revised) Pacific Tunnel El Dorado County, California


GHD | 4080 Plaza Goldorado Circle Suite B Cameron Park CA 95682 USA

11136547 | September 2018

Executive Summary

The Pacific Tunnel is an approximately 190-foot-long untreated water tunnel in El Dorado Irrigation District’s water delivery system. The Pacific Tunnel conveys flow along the El Dorado Canal (FERC Project 184) below access road R82.

The approximate 180-foot horseshoe-shaped tunnel (nominal) is unlined rock over much of its length with timber-lined sections at the inlet and outlet portals.

El Dorado Irrigation District (District) scheduled an annual maintenance outage in October 2016 to inspect the Pacific Tunnel and to construct improvements. The tunnel inspection occurred on December 22, 2016. Overall, the condition of the portals and tunnel is good.

Tunnel inspection photographs are provided in Attachment A.

If you have any questions regarding the information contained in this report, or if we may be of further assistance, please do not hesitate to contact us.

Sincerely,

GHD

David B. Jermstad, P.G., C.E.G.

Senior Engineer

GHD | Tunnel Condition Assessment | 11136547 | Page iii

Table of Contents

1. Introduction 5

2. Tunnel Inspection Overview 5

3. Tunnel Inspection Safety 5

3.1 Identified Hazards and Mitigation Measures 5

3.1.1 Tunnel Instability 5 3.1.2 Atmospheric Hazards 5 3.1.3 Operational Hazards 5 3.1.4 Biologic Hazards 6

3.2 Applicable Safety Regulations 6

3.3 Safety Preparations 6

3.3.1 Communication 6 3.3.2 Personal Protective Equipment 6 3.3.3 Safety Instruction 7 3.3.3.1 Overview 7 3.3.3.2 Safety Instruction 7 3.3.3.3 Biologic 7 3.3.3.4 Confined Space 7 3.3.4 Pre-entry Activities and Monitoring During Inspection 8

4. Inspection Methodology 8

5. Observations and Recommendations 8

5.1 Observations 8

5.2 Recommendations 11

6. Summary 11

7. Limitations 11

Table Index

Table 4.1 Summary of Observations 8

Table 5.1 Summary of Recommendations 11

Attachment Index Attachment A Photographs

GHD | Tunnel Condition Assessment | 11136547 | Page iv

Distribution

To: El Dorado Irrigation District

Brian Mueller, P.E.

2890 Mosquito Road

Placerville, CA 95667

cc: Dan Gibson

From: GHD

David Jermstad, PG, CEG

4080 Plaza Goldorado Circle, Suite B

Cameron Park, CA 95682

GHD | Tunnel Condition Assessment | 11136547 | Page 5

1. Introduction

This report presents the findings, conclusions, and recommendations developed from our geotechnical engineering investigation. The investigation was conducted in accordance with the Professional Service Agreement *On-Call Contract – Geotechnical Notice to Proceed N1216-291 dated 12/05/16. This report supersedes our previous geotechnical investigation report dated February 6, 2017.

2. Tunnel Inspection Overview

The Pacific Tunnel was inspected on December 22, 2016. The inspection team entered the tunnel at the upstream gate access, inspected the intake portal, walked downstream to approximately Station 1+78 and exited at the downstream portal access.

3. Tunnel Inspection Safety

3.1 Identified Hazards and Mitigation Measures

Safety was a high priority for the tunnel inspection. Three primary hazards, which are common to all tunnel inspections, were identified: tunnel instability, atmospheric hazards immediately dangerous to life or health (IDLH), and operational hazards. Steps were taken to mitigate the risks associated with each of these hazards.

3.1.1 Tunnel Instability

GHD’s trained inspectors watched for localized tunnel instability throughout the inspection. The absence of hydraulic anomalies in the tunnel suggested that the tunnel cross section was stable and that no immediate need for scaling was observed.

3.1.2 Atmospheric Hazards

Recent work in the Pacific Tunnel did not identify atmospheric hazards, but unsafe oxygen and hydrogen sulfide levels were the most likely atmospheric hazards. Throughout the inspection, the atmosphere was monitored for unsafe levels of oxygen and hydrogen sulfide. At no point during the inspection did air monitors indicate a potentially hazardous atmosphere.

3.1.3 Operational Hazards

The most significant operational hazard on the Pacific Tunnel inspection was the potential for flooding. Flooding was prevented through a lock-out-tag-out (LOTO) protocol that isolated the Pacific Tunnel from the rest of the system. Two forms of LOTO exist in most agencies: physical and administrative. Administrative LOTO places a clearance tag or man-on-line tag (typically paper) on equipment control surfaces. Operators are trained not to place equipment in service if a tag is present. Physical LOTO requires that equipment be temporarily disabled or prevented from


operating. A combination of administrative and physical LOTO methods was used during the Pacific Tunnel outage.

The LOTO actions were effective and provided a safe work environment for the inspection.

3.1.4 Biologic Hazards

The tunnel back above normal flow line was colonized by spiders.

3.2 Applicable Safety Regulations

There are no specific tunnel safety regulations covering the inspection of in-service water tunnels in California. A combination of the General Industry Safety Orders and Tunnel Safety Orders was applied to the inspection.

3.3 Safety Preparations

3.3.1 Communication

Communication between the surface support team and tunnel entrants is difficult in tunnel inspections. The team checked in and out with District personnel during the inspection. The team included two attendants at the tunnel adit that could be sent for help if needed. Fortunately, emergency communication was not necessary.

3.3.2 Personal Protective Equipment

Personal protective equipment for the tunnel entrants was selected to protect against the identified hazards, including:


Hard hat

Helmet mounted light

Flashlight and spare batteries

Back-up flashlights

Safety glasses

Atmospheric monitoring meters – one per inspection team

Gloves

Thermal shirt

Water repellant jacket

Walking sticks

Waders and sturdy boots

Emergency whistle

First aid kit—one per inspection team (safety rep)

Water and snacks

3.3.3 Safety Instruction

On the morning of December 22, 2016 the tunnel entrants and support team participated in an extended safety tailboard. The agenda included the topics discussed below.

3.3.3.1 Overview

Purpose of inspection, access, anticipated conditions, safety procedures, and emergency procedures.

3.3.3.2 Safety Instruction

Recognition and avoidance of hazards, awareness of other work going on at/near the Pacific Tunnel, air monitoring, illumination, communication, flooding, LOTO, use of personal protective equipment, fire prevention and control, emergency procedures, evacuation, and personal accountability requirements.

3.3.3.3 Biologic

Recognition and avoidance of spiders.

3.3.3.4 Confined Space

Recognition and protective measures for confined space entry.


3.3.4 Pre-entry Activities and Monitoring During Inspection

Prior to entry, the entry permit was updated with information from the hazards assessment, incident action plan, communication plan, LOTO procedures, personnel accountability plan, personal protective equipment list, and atmospheric monitoring equipment list.

On the surface, the standby rescue team monitored surface conditions.

4. Inspection Methodology

The objective of the inspection was to visually inspect and evaluate the current condition of Pacific Tunnel. To achieve this objective, the inspection party performed the condition assessment, including geologic interpretation of the tunnel condition, identification of anomalies, measurement of cross-sectional dimensions, measurement of seeps and water inflow, and photography of conditions.

5. Observations and Recommendations

5.1 Observations

From Station 0+05 to 0+15 the right back bottom line boards and the left rib boards are bowing. At Station 0+21 the bottom and right rib line boards terminate. At Station 0+32 the left rib line board terminates. From Station 0+32 to 1+62 scouring is present in unlined Mehrten Formation volcanics. At Station 1+78 to the exit portal, new lining timber is present, no bottom line boards installed. Photographs are presented in Attachment A, the location of the photographs is detailed below in Table 4.1.

Table 4.1 Summary of Observations

Photo # Station Location

Schmidt Rebound Hammer

(PSI)

Average Schmidt Rebound Hammer

(PSI)

Notes

Normal Water Line

Height (Ft.)

Invert Probe Depth (In.)

001, 064

0+10

Left Rib 1,000

2,840 distressed

timber cribbing

3

Tunnel Back Left 2,900

063 Tunnel Back Center 1,700

Tunnel Back Right 8,000

065, 066 Right Rib 600

0+20

Left Rib 600

2,910

3 6 Tunnel Back Left 5,650



Tunnel Back Right 3,600 002 Right Rib 2,600

004, 005

0+30

Left Rib 600

2,650

3 12


Tunnel Back Center 2,900

Tunnel Back Right 3,200 Right Rib 2,950

006, 009

0+40

Left Rib 3,250

2,730

scour

3 12



Tunnel Back Right 2,100 007, 010 Right Rib 3,700

0+50

Left Rib 2,200

4,150

3 18



Tunnel Back Right 4,000 011 Right Rib 3,700 scour

0+60

Left Rib 1,000

2,640

3 18



Tunnel Back Right 2,100 014, 015 Right Rib 600 scour

0+70

Left Rib 1,000

2,840

3 24



Tunnel Back Right 8,000 018, 019,

020 Right Rib 600 scour 025

0+80

Left Rib 600

1,340

3 24

Tunnel Back Left 900

027, 028 Tunnel Back Center 2,900

Tunnel Back Right 1,300 026 Right Rib 1,000 rockfall 029

0+90

Left Rib 0

1,140

scour

3 8 Tunnel Back Left 1,700



Tunnel Back Right 900 030 Right Rib 1,400 scour 034

1+00

Left Rib 0

1,340

scour

3 18



Tunnel Back Right 1,700 035 Right Rib 0

1+10

Left Rib 1,000

1,380

6



Tunnel Back Right 2,500 Right Rib 0

1+20

Left Rib 0

2,480

2



Tunnel Back Right 3,600 Right Rib 0 scour

1+30

Left Rib 600

1,600

scour

2



Tunnel Back Right 2,500 Right Rib 0 scour

1+40

Left Rib 600

1,180

0



Tunnel Back Right 1,300 Right Rib 1,400 scour

1+50

Left Rib 0

2,060

0



Tunnel Back Right 3,200 Right Rib 600

055

1+59

Left Rib 2,200

1,820

0



Tunnel Back Right 1,700 056 Right Rib 1,000


057, 062 1+63

Left Rib 200 200 timber

cribbing 059, 060, 061 Right Rib 200

5.2 Recommendations

It is recommended that the cribbing and lining at the tunnel portals be replaced either in-kind or with reinforced concrete. Due to the probe depths measured at the tunnel invert, it is recommended that an invert slab be poured to improve flow characteristics and prevent future invert erosion.

From station 0+40 to 1+40, scour was observed at the bottom of the tunnel ribs. It is recommended that the tunnel be lined with either timbers or reinforced air-placed concrete. We recommend an alternatives repair analysis be performed to evaluate the net present value and long term costs and benefits of timber re-lining the tunnel vs. shotcrete lining the tunnel.

On the basis of the existing information, GHD recommends that the tunnel be inspected annually by District personnel to compare conditions to those described in this report. Additionally, an inspection of the tunnel by a licensed professional is recommended every 5 years.

6. Summary

Table 6.1 Summary of Recommendations

Priority Reach Description Impact Moderate Sta. 0+00 to 1+90 Distressed and

dilapidated timber Continued erosion and scouring of unprotected volcanic bedrock over years could result in collapse if nothing is done

Moderate Sta. 0+00 to 1+90 Invert erosion and sedimentation

Poor flow characteristics

Low Sta. 0+40 to 1+40 Scour on ribs Poor flow characteristics. Continued scour could eventually result in tunnel instability if not addressed

Very Low Monitor rockfall annually for changes

Increased rockfalls from those observed could be significant

7. Limitations

This Tunnel Condition Assessment Report (“Report”):


Has been prepared by GHD for the El Dorado Irrigation District (EID) under the professional supervision of those senior partners and/or senior staff whose seals and signatures appear herein

May only be used and relied on by EID, which is responsible to ensure that all relevant parties to the project, including designers, contractors, subcontractors, etc., are made aware of this report in its entirety

Must not be copied to, used by, or relied on by any person other than EID without the prior written consent of GHD

May only be used for the purpose of engineering design of the proposed structures at the project site described in this report (and must not be used for any other purpose)

GHD and its servants, employees and officers otherwise expressly disclaim responsibility to any person other than EID arising from or in connection with this Report.

To the maximum extent permitted by law, all implied warranties and conditions in relation to the services provided by GHD and the Report are excluded unless they are expressly stated to apply in this Report.

The services undertaken by GHD in connection with preparing this Report:

Were limited to those specifically detailed in sections 1-5;

Did not include GHD undertaking testing at some parts of the site.

The opinions, conclusions and any recommendations in this Report are based on assumptions made by GHD when undertaking services and preparing the Report (“Assumptions”), including (but not limited to):

The condition has remained essentially unchanged since our site visit.

GHD expressly disclaims responsibility for any error in, or omission from, this Report arising from or in connection with any of the Assumptions being incorrect.

Subject to the paragraphs in this section of the Report, the opinions, conclusions and any recommendations in this Report are based on conditions encountered and information reviewed at the time of preparation and may be relied on until 1-year from the date of the report after which time, GHD expressly disclaims responsibility for any error in, or omission from, this Report arising from or in connection with those opinions, conclusions and any recommendations.

GHD | Tunnel Condition Assessment | 11136547 | Attachment A

Attachment A Photographs

Pacific House Tunnel 001 Pacific House Tunnel 002

Pacific HouseTunnel 003 Pacific HouseTunnel 004





Pac

ific

Hou

se T

unne

l 013

Pacific House Tunnel 014


Pac

ific

Hou

se T

unne

l 017



Pac

ific

Hou

se T

unne

l 020

Pac

ific

Hou

se T

unne

l 021


Pac

ific

Hou

se T

unne

l 023

Pac

ific

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GHD

4080 Plaza Goldorado Circle Suite B Cameron Park, CA 95682 USA T: 1 530 677 5515

© GHD Inc 2018

This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorized use of this document in any form whatsoever is prohibited.

GHD

4080 Plaza Goldorado Circle Suite B Cameron Park, CA 95682 USA T: 1 530 677 5515

© GHD Inc 2018

This document is and shall remain the property of GHD. The document may only be used for the purpose for which it was commissioned and in accordance with the Terms of Engagement for the commission. Unauthorized use of this document in any form whatsoever is prohibited.

Documents

Geotechnical Investigation (revised)