Meeks_Bay_BikeBridge-Final_GeotechReport.pdf

Bridge Name: Meeks Bay Bicycle Bridge Geotechnical Design Report Bridge Number: 25-01512 Meeks Bay Bike Path Dist-County-Route-PM: 03-ED-25.55 CA FLAP SR89(2) Caltrans EA: 03-3F6201 El Dorado County, California Caltrans PIN: 03 1300 0083

April 28, 2017

Submitted To:

Mr. John Rohner

CH2M Hill, Inc.

9191 South Jamaica Street

Englewood, Colorado 80112

By:

Shannon & Wilson, Inc.

1321 Bannock Street, Suite 200 Denver, Colorado 80204

23-1-01373-209

23-1-01373-209_R1_rev1/wp/lmr 23-1-01373-209 i

TABLE OF CONTENTS

Page

1.0 INTRODUCTION

2.0 PROJECT AND SITE DESCRIPTION

3.0 PREVIOUS FIELD EXPLORATIONS AND LABORATORY TESTING

4.0 SUBSURFACE CONDITIONS

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 Bridge Foundation

5.2 Retaining Walls

5.3 Faulting and Seismicity

5.3.1 Fault Rupture

5.3.2 Tsunami

5.3.3 Ground Motion Design Parameters

5.3.4 Seismically Induced Settlement

5.4 Slope Discussion

5.4.1 General

5.4.2 Fill Slopes

5.4.1 Cut Slopes

5.4.2 Slope Protection

5.5 Pavement

5.5.1 Traffic Loading

5.5.2 Subgrade Conditions

5.5.3 Preliminary Asphalt Pavement Sections

5.6 Corrosive Soil

6.0 CONSTRUCTION CONSIDERATIONS

6.1 Site Preparation

6.2 Earthwork

6.2.1 General

6.2.2 Subgrade Preparation

6.2.3 Fill Slopes

6.2.4 Structural Fill

6.2.5 Fill Placement and Compaction

6.2.6 Excavation Potential

6.3 Aggregate Base (AB)

6.4 Paving Materials

7.0 CONSTRUCTION OBSERVATION

TABLE OF CONTENTS (cont.)

Page ii

8.0 CLOSURE

9.0 REFERENCES

TABLES

1 Bridge Abutment Foundations 2 Proposed Retaining Walls 3 Recommended Soil Parameters for Retaining Wall Design 4 Retaining Wall Foundations 5 Design Response Spectrum 6 Slope Stability Material Properties 7 Corrosion Test Results

FIGURES

1 Vicinity Map 2 Caltrans/AASHTO Design Response Spectrum

APPENDICES

A Previous Subsurface Exploration from Marvin E. Davis & Associates Inc., 2014 B Previous Laboratory Test Results from Marvin E. Davis & Associates, Inc., 2014 C Review Comment Sheet D Important Information About Your Geotechnical/Environmental Report

GEOTECHNICAL DESIGN REPORT

MEEKS BAY BIKE PATH

CA FLAP SR89(2)

EL DORADO COUNTY, CALIFORNIA

1.0 INTRODUCTION

This report presents our geotechnical engineering recommendations and construction considerations for the planned Meeks Bay Bike Path in El Dorado County, California, refer to Figure 1. Our work was completed in general accordance with CH2M Hill, Inc. (CH2M) award number 10006-7-107205 of Contract Number DTFH68-16-D-00007, signed February 15, 2017.

For our study, we reviewed the 100 percent design submittal plan set (CH2M, 2017) and a previous geotechnical report for the bike path prepared by Marvin E. Davis & Associates, Inc.

(MEDA, 2014). We did not perform additional surface mapping, subsurface exploration, or laboratory testing as a part of this study.

Our study also included responding to comments 3, 5, and 6 presented by the California Department of Transportation (Caltrans), in the Federal Lands Highway Division PS&E Review Comment Sheet. A copy of the sheet is included in Appendix C. Also included are the tabulated N60 values, calculated from the information reported in the MEDA boring logs.

This report is a revision of our March 31, 2017 report, to address two Caltrans comments. To address these comments, we have added the project identification information to our cover sheet and augmented our response to Comment 6 of the Federal Lands Highway Division PS&E Review Comment Sheet.

2.0 PROJECT AND SITE DESCRIPTION

The proposed bike path will extend approximately three-quarters of a mile from Meeks Bay Resort and Marina toward Sugar Pine Point state park (CH2M, 2017). The path will be located between Lake Tahoe and State Route 89 (SR89) and cross a road and three driveways that access single-family residences along the alignment. Topography through the area slopes eastward toward Lake Tahoe. The area contains a modest growth of shrubs and coniferous trees. There are overhead utility lines along the eastern side of SR89.

We understand that the project involves constructing the bike path at approximately the existing grades. Cut and fill slopes will be used to accommodate grade changes. Retaining walls are also planned in two locations, and they will consist of geosynthetic-reinforced soil (GRS) with a rockery or rock facing. There is one 65-foot-long, single span bridge proposed, which will be a GRS integrated bridge system. The abutments and wing walls will be founded on reinforced soil foundations (RSF), which consist of aggregate backfill encapsulated in geosynthetic reinforcement.

For this report, we relied on the construction material descriptions and properties provided on sheet G7 and S2 of the plans (CH2M, 2017). The materials specified include: backfill, geosynthetic reinforcement, retained backfill, aggregate backfill, and roadbed backfill.

3.0 PREVIOUS FIELD EXPLORATIONS AND LABORATORY TESTING

To characterize the subsurface conditions along the proposed bike path alignment we reviewed six previous exploratory borings and three refraction microtremor (ReMi) shear wave velocity measurements reported by MEDA. The borings were designated B1A, B1B, and B2 through B5 and the ReMi arrays ReMi1 through ReMi3. The approximate locations are shown in Figure A-1 in Appendix A. Appendix A also presents the individual boring logs, a key to the symbols used in the boring logs, and the ReMi shear wave velocity profiles.

The station numbers provided on the MEDA Site Exploration Map are from an earlier alignment reference, not the same station numbers shown in the CH2M plans provided. In addition, the MEDA report includes a boring log labeled B1E, but does not include a log for boring B1A. We believe the log B1E is mislabeled and have relied upon it as B1A.

We reviewed the previous geotechnical laboratory test results by MEDA to estimate index and engineering properties of the subsurface materials. The laboratory testing performed includes:

tests for soil water content and unit weight, material passing the U.S. No. 200 sieve, grain size distribution, Atterberg limits, compaction characteristics, shear strength, and corrosion potential.

The laboratory test results are provided in Appendix B.

4.0 SUBSURFACE CONDITIONS

The MEDA boring logs indicate the site is underlain by fill and native materials. The borings encountered fill to depths of between 8.5 and 13 feet below the existing ground surface (bgs).

This fill makes up the embankment for SR89 and consists of interbedded layers of silty sand and layers of cobbles and boulders. Field Standard Penetration Test results in the fill ranges from 17 to greater than 50 blows per foot.

Each of the MEDA boring logs indicate the fill is underlain by native materials. The native material consists of fat clay, clayey silt, silty sand, clayey sand, poorly graded sand, clayey gravel, and layers of cobbles and boulders. The fine-grained materials were reported to be hard and in a moist to wet condition, while the coarse-grained units were dense to very dense and moist to wet.

MEDA boring logs B4 and B5 indicate groundwater was present at elevations of approximately 6,288 and 6,292 feet, respectively. Each of the other boring logs indicate wet or wet to saturated materials were encountered about 20 to 25 feet bgs.

5.0 CONCLUSIONS AND RECOMMENDATIONS

5.1 Bridge Foundation

Bridge Abutment 1 and Abutment 2 will be supported on GRS structures with heights of 12 feet and 15 feet, respectively, as shown on sheet S7 (CH2M, 2017). The GRS structures were designed in accordance with the Federal Highway Administration (FHWA) GRS Integrate Bridge System Interim Implementation Guide (2012). The superstructure was designed in accordance with American Association of State Highway and Transportation Officials (AASHTO, 2016) with Caltrans Amendments (2014a). The reinforced zone will consist of open-graded, clean, crushed, granular stone (OGS) with geosynthetics reinforcement layers that are 11 feet, 8 inches long, and spaced 8 inches vertically; there are also intermediate 6-foot-long reinforcement layers under the beam seat. Each abutment is supported by a RSF that consist of a 1.5-foot-thick layer of OGS, encapsulated in geosynthetic reinforcement. The bottom elevations of the RSFs are 6,296.87 and 6,297.17 feet. These elevations correspond to minimum embedment depths of approximately 4 feet and 3 feet, respectively. It is our understanding the proposed abutment backfill, behind the reinforced zone, will consist of the retaining wall reinforced zone and retained backfill.

Based on the MEDA borings, the subgrade beneath the proposed bridge abutments is anticipated to consist of native materials. For the GRS design, we recommend a nominal coefficient of sliding resistance of 0.52, for the interface between the RSF and the native soil. Resistance factors for the coefficient of sliding resistance should be applied per Caltrans (2014a) for the strength and extreme limit states.

We have summarized the nominal bearing resistance, factored bearing resistance, and bearing pressure for each abutment in Table 1. In accordance with Caltrans (2014a) recommendations, a resistance factor of 0.65 was used to determine the factored bearing resistance. Assuming a dense and unyielding bottom, the abutment should be designed using the bearing pressure in Table 1 to limit total settlement to approximately 1 inch with differential settlement on the order of ½ inch across 30 feet.

TABLE 1

BRIDGE ABUTMENT FOUNDATIONS

Abutment

Nominal/Extreme Event Bearing

Resistance (ksf)

Factored Bearing

Resistance (ksf)

Bearing Pressure for

1 inch of Settlement1

(ksf) 1 38.9 25.3 9.0 2 38.9 25.3 9.0

Note:

1 Settlement calculations based on N60 values determined from blow counts and hammer efficiency reported by MEDA.

We evaluated the global and external stability for the maximum abutment height and reinforcement length indicated in the plans. For the proposed abutments, our global stability analyses indicated factors of safety (FS) greater than 1.5 for static conditions and greater than 1.1 for pseudo-static seismic conditions, which satisfy Caltrans (2014a) requirements. Our external stability analyses indicated capacity-demand ratios (CDRs) greater than one for sliding and bearing resistance. Our analyses also indicated that eccentricity was within allowable limits.

The RSF embedment depth exceeds the frost depth of 1.5 feet, reported by the El Dorado County (2017). A minimum embedment for sloping conditions is not applicable as the bottom elevation of the RSF is below the existing toe of slope. The structural engineer should verify the embedment are below the anticipated scour depth. We recommend the lateral earth pressures and coefficients provided in Table 3 below be used for the abutment wall design.

5.2 Retaining Walls

The plans indicate there are four GRS retaining walls planned as summarized in Table 2.

TABLE 2

PROPOSED RETAINING WALLS

Retaining Wall

Station Maximum Retained

Height (feet)

Maximum Geosynthetic

Reinforcement Length (feet) Beginning End

Retaining Wall 1 26+50 31+75 10 7.5 Retaining Wall 2 34+82 39+70 16 12.0 Abutment 1 38+30.29 12 11.7 Abutment 2 38+95.29 15 11.7

The materials used for the GRS construction are specified on sheet G7 of the plans and include:

retained backfill, aggregate backfill, geosynthetic layers, and roadbed aggregate (CH2M, 2017).

We evaluated the GRS retaining walls considering reinforcement lengths of 6 and 12 feet. Based on the MEDA borings, we anticipate the foundation material for Retaining Walls 1 and 2 will consist of native materials and existing fill; for our analyses, we assumed fill foundation material. Based on the use of Structural Fill for the retained backfill, we recommend the parameters in Table 3 for the wall design.

TABLE 3

RECOMMENDED SOIL PARAMETERS FOR RETAINING WALL DESIGN

Design Parameter Recommended Value

Retained Backfill Unit Weight (pcf) 132 Friction Angle (degrees) 34 Cohesion (psf) 0 Equivalent Fluid Density for Active Retaining Conditions and Horizontal Backfill (pcf)1 37 Equivalent Fluid Density for At-Rest Retaining Conditions and Horizontal Backfill (pcf)2 58 Coefficient of Sliding Resistance 0.45 Active Earth Pressure Coefficient with Earthquake Effect (Kae) for Horizontal Backfill1 0.43 At-Rest Earth Pressure Coefficient with Earthquake Effect (Koe) for Horizontal Backfill2 0.60

Notes:

1 The active retaining conditions should be used where the walls are free to deflect 0.001 times the height of the wall.

2 The at-rest retaining condition should be used where the wall is not free to deflect.

pcf = pounds per cubic foot psf = pounds per square foot

The parameters provided for the retaining walls assume a free-draining backfill condition. As such, it will be important to control surface water and reduce its potential to infiltrate into the ground around the retaining walls. Surface water behind the wall should not discharge directly into the wall backfill. In addition, water should not discharge or pond around walls. Weep holes should be incorporated into the retaining walls to provide for drainage of backfill. A geotextile should be placed behind weep holes to reduce the potential for soil loss.

We have calculated the nominal bearing capacity for the proposed retaining walls considering the minimum and maximum reinforcement lengths indicated in the plans of 6 and 12 feet. We have also taken into consideration sloping conditions in front of the wall. We have summarized the nominal bearing resistance, factored bearing resistance, and bearing pressure for Retaining Walls 1 and 2 in Table 4. In accordance with Caltrans (2014a) recommendations, a resistance factor of 0.65 was used to determine the factored bearing resistance. Assuming a dense and unyielding bottom, Retaining Walls 1 and 2 should be designed using the bearing pressure to limit total settlement to approximately 1 inch with differential settlement on the order of ½ inch per 30 feet.

TABLE 4

RETAINING WALL FOUNDATIONS

Foreslope Angle

(degrees) Reinforcement

Length (ft)

Nominal Bearing

Resistance (ksf)

Factored Bearing

Resistance (ksf)

Bearing Pressure for 1" Settlement1

(ksf)

0 6 22.1 14.4 6.0 12 32.5 21.1 6.0

6 3.9 2.5 2.5

12 6.9 4.5 4.5 Note:

1 Settlement calculations based on N60 values determined from blow counts and hammer efficiency reported by MEDA.

We evaluated the global and external stability of the proposed GRS Retaining Walls 1 and 2, at the maximum proposed wall height for each, and with the reinforcement lengths shown in the plans. Our analyses resulted in an FS for static conditions of 2.0 to 2.2 and 1.4 to 1.5 for pseudo-static conditions, which satisfies Caltrans (2014a) requirements for global stability. Our analyses also indicated that eccentricity was within allowable limits. Our external stability analyses resulted in CDRs greater than one for sliding and static bearing resistance. However, our analysis of seismic bearing resistance resulted in a CDR of less than 1.0. This analysis, at approximately station 37+90, considered Wall Type B with a 12 foot geosynthetic length, fill foundation material, 30 degree foreslope, and 0.9 resistance factor.

The retaining wall foundation depth of embedment should consider the frost depth and sloping conditions. The RSF embedment depth should exceed the frost depth of 1.5 feet, reported by the El Dorado County (2017). In order to comply with this specification, we recommend the OGS material specifications limit the percent passing the #4 sieve to less than 50 percent. In this case, the Type A and Type B wall details achieve the frost depth since the OGS material would be considered non-frost susceptible.

In order to comply with Caltrans (2014a) and AASHTO (2016) recommendations for retaining walls in slopes, they should be embedded a minimum of 2 feet as measured vertically from the proposed grade in front of the wall to the top of the leveling pad (for rock facings) or bottom of the base rock (for rockery facings). In addition, a 4-foot horizontal bench should be provided from the front of the wall facing to the slope face. The details provided for both Wall Type A and Wall Type B do not meet these criteria. We understand the details will be reviewed by the design team to determine if they should be modified to satisfy the criteria.

5.3 Faulting and Seismicity

5.3.1 Fault Rupture

Lake Tahoe formed as a result of extensional faulting along faults paralleling the east and west shores. Active faults in the area are considered significant seismic sources and include the West Tahoe Fault, Stateline Fault, and Incline Village Fault (Kent and others, 2016). Mapped faults within the vicinity of the bike path include:

West Tahoe Fault: This fault is mapped along the western boundary of the Tahoe Basin and generally parallels the west shore of Lake Tahoe. The closest offshore trace of the fault is approximately 1.35 miles east of the site (U.S. Geological Survey [USGS], 2006). The closest mapped onshore strands of the West Tahoe Fault are located around Emerald Bay (Seitz, 2016).

These strands are considered active and are included within Alquist-Priolo Earthquake Fault Zones (California Geological Survey, 2016).

There is no evidence of onshore, active faulting associated with the West Tahoe Fault north of Emerald Bay (Kent and others, 2016). Considering the nearest offshore trace and onshore zone, the potential for fault rupture of the West Tahoe Fault to impact the proposed bike path improvements is low.

Unnamed Fault: Several unnamed fault traces are mapped south and west of the site (USGS, 2006; Saucedo, 2005). The closest of these traces is approximately 1.5 to 2 miles toward the southwest, and trends northwest. Approximately 3 miles south of the site, the USGS mapped another unnamed fault trace, which trends toward the site. The USGS identified these fault trace as potentially active faults associated with the Tahoe-Sierra frontal fault zone.

However, the relationship of these fault traces and age of most recent activity is unclear (Earth Consultants International, 2011). Considering the distance to the nearest mapped trace of these faults, the potential for fault rupture of these unnamed faults to impact the proposed bike path improvements is low.

5.3.2 Tsunami

A tsunami is a wave produced by a submarine earthquake. The University of Nevada Seismological Laboratory indicates that a tsunami wave of up to approximately 17 feet may be experienced along the shoreline of Lake Tahoe at Meeks Bay as a result of seismic activity from faults present beneath the lake (Ichinose and others, 1999). Tsunamis can also be generated by a landslide, static or dynamically induced (Seitz and Mareschal, 2014).

The southern end of the bike path is at an elevation of approximately 6239 feet, about 8 feet above the Take Tahoe water level. The bottom of the retaining walls are at elevations of 6,300 feet or higher, while the bridge abutment foundations are at elevations of approximately 6,297 feet, or 66 feet above the water level. Considering a 17-foot-tall tsunami, those parts of the project at and below an elevation of 6,248 would be impacted, which includes the approximately 400 feet of southern portion of the path. The potential impact to those parts of the path below elevation 6,248, due to tsunami, is considered moderate, while those areas at elevations above 6,248 the potential is considered low.

5.3.3 Ground Motion Design Parameters

Our seismic analysis is based on ground motion levels, performance criteria, and methods as described in AASHTO (7th Edition, 2016) and the Caltrans Amendments to AASHTO (2014a). We determined the site class using shear wave velocities reported by MEDA (2014), for the upper 100 feet of the soil profile in the vicinity of the proposed bridge and retaining walls. The average shear wave velocities of 1,100 feet per second indicate Site Class D should be used in design, in accordance with AASHTO and Caltrans site class criteria.

The design response spectrum corresponds to a 975-year return period ground motion and was determined for the project site using the Caltrans ARS Online application (Version 2.3.08).

The design response spectrum is based on the larger of the deterministic and probabilistic spectral accelerations. The design response spectrum is presented in Figure 2 and numerical values provided in Table 5.

TABLE 5

DESIGN RESPONSE SPECTRUM

Period (seconds) Spectral Acceleration1 (g)

0.01 0.44

0.05 0.68

0.10 0.83

0.15 0.94

0.20 1.02

0.25 0.99

0.30 0.97

0.40 0.94

0.50 0.90

0.60 0.87

0.70 0.83

0.85 0.78

1.00 0.73

1.20 0.63

1.50 0.51

2.00 0.37

3.00 0.23

4.00 0.16

5.00 0.12

Note:

1 Spectral values include near fault factors as incorporated by Caltrans ARS Online.

5.3.4 Seismically Induced Settlement

Seismically induced settlement is divided into two parts, soil above and below the groundwater table. Settlement below the water table is associated with liquefaction of loose, saturated, granular soil due to seismic loading. Settlement above the water table is associated with the densification of loose, granular soil due to seismic loading.

Our scope of services did not include analyses of the potential seismically induced settlement that may impact the proposed retaining walls and bridge. Based on the subsurface conditions and material properties reported by MEDA, it is our opinion that the risk of liquefaction is low.

5.4 Slope Discussion

5.4.1 General

We used the plans provided to determine the location of the critical fill and cut slopes proposed and the cross sections provided in the plans to model them (CH2M, 2017). We characterized the distribution and engineering properties of artificial fill and native materials based on the previous MEDA borings and laboratory test results (MEDA, 2014). The material properties used in our analyses are summarized in Table 6.

TABLE 6

SLOPE STABILITY MATERIAL PROPERTIES

Unit

Unit Weight

(pcf) Φ

(degrees) c (psf) Structural Fill1 132 34 0 Native2 125 37 0

Notes:

1 Structural Fill strengths are assumed values based on correlations for compacted granular fills and our judgment.

2 The native soil angle of internal friction is based on correlations using Standard Penetration Test N60 values and the Unified Soil Classification System.

c = cohesion pcf = pounds per cubic foot psf = pounds per square foot Φ = angle of internal friction

We performed slope stability calculations using the software Slope/W Version 8.16 by

Geo-Studio. Our analyses used the Morgenstern-Price method of analysis, assuming a rotational mode of failure. The Caltrans Geotechnical Manual indicates embankments potentially impacting structures should have a minimum FS of 1.3 for static conditions (Caltrans, 2014b).

These guidelines do not recommend seismic stability analyses for conditions not associated with structures.

5.4.2 Fill Slopes

The design plans indicate new fill slopes will be constructed to heights of 28 feet or less and no steeper than 1 vertical to 2 horizontal (1V:2H) (CH2M, 2017). We evaluated the 28-foot-tall fill slope, which occurs at approximately Station 19+00 (as shown in Sheet X10 of the plans). Boring B1A is the closest subsurface exploration to this slope, approximately 250 feet north and 35 feet higher in elevation. We have assumed the native material that makes up the existing natural slope consists of the dense, sand with silt and gravel (SP) described at the bottom of B1A. Our analysis indicates this fill slopes has a FS greater than 1.3 for static conditions, which satisfies the requirements of Caltrans (2014b).

5.4.1 Cut Slopes

The design plans indicate proposed cut slopes will be constructed to heights of 15 feet or less and at inclinations no steeper than 1V:2H (CH2M, 2017). We evaluated the 15-foot-tall cut slope, which occurs at approximately Station 20+50 (as shown in Sheet X11 of the plans).

Boring B1A is the closest subsurface exploration to this slope, approximately 150 feet north.

The boring was drilled from an elevation of approximately 6,312 feet to approximately 6,285 feet, which coincides with the toe of slope in this area. For the purposes of our calculations, we have assumed the native material that will be exposed in the cut slope consists of the sand with silt and gravel (SP) encountered at the bottom of B1A. However, we expect the slope will also expose some layers with cobble and boulders, which should be considered for construction and revegetation planning. Our analysis indicates this cut slopes has a FS greater than 1.3 for static conditions, which satisfies the requirements of Caltrans (2014b).

5.4.2 Slope Protection

We anticipate the proposed 1V:2H slopes will be erodible due to the granular nature of the exposed materials. We recommend implementing a revegetation plan for new slopes to reduce the potential for erosion to occur.

5.5 Pavement

In general, the performance of a pavement system depends on the type of paving materials and thicknesses, design life, traffic loads and repetitions, subgrade strength, and subgrade drainage characteristics. Our pavement designs are based on the design procedures presented in the Caltrans Highway Design Manual (HDM, 2016). The following sections discuss each of these aspects as they relate to the bike path pavement.

5.5.1 Traffic Loading

The Caltrans HDM indicates the pavement design for bike paths should consider the anticipated loading conditions. Specific vehicle information (vehicle type, axle loading, and repetitions) for the bike path was not available. For our analyses, we have assumed typical loading conditions will consist of pedestrians and bicyclists. In consultation with CH2M and Central Federal Lands (CFL), we have also assumed maintenance vehicles may use the bike path. For our analyses, we have assumed a 20-year design life with 50 repetitions per year of an AASHTO H-10 truck (AASHTO, 2016). These assumptions correspond to approximately 600 equivalent single axle loads, which converts to a traffic index (TI) of 3.7. The Caltrans HDM indicates that for TIs less than 5, use a TI of 5.

5.5.2 Subgrade Conditions

The MEDA report did not include California Bearing Ratio or R-value test results. To estimate the strength of the subgrade materials, we reviewed the boring logs and laboratory test results. Based on this data we assumed an R-value of 40 in our analyses.

5.5.3 Preliminary Asphalt Pavement Sections

Using the Caltrans HDM procedures and the assumptions described above, we recommend a pavement section of 3 inches of hot asphalt concrete pavement (HACP) overlaying 6 inches of aggregate base (AB). The preliminary section specified in the plans is 3 inches HACP overlaying 8 inches AB, which exceeds the calculated section.

5.6 Corrosive Soil

Some soils can be corrosive to substructure elements. To assist in estimating the corrosion potential at the site, we reviewed the reported laboratory test results for pH, resistivity, water soluble sulfates, and chlorides from boring B4 between 7.5 and 9 feet below ground surface (MEDA, 2014). The results are summarized in Table 7.

TABLE 7

CORROSION TEST RESULTS

Parameter Result pH 5.77 Resistivity 1,900 ohm–cm Water Soluble Sulfates None detected Chlorides 150 mg/kg

Notes:

ohm-cm = ohm centimeters mg/kg = milligrams per kilogram

Caltrans considers site soils to be corrosive if chloride concentration is ≥ 500 parts per million (ppm), sulfate concentration is ≥ 2,000 ppm, or the pH is ≤ 5.5 (Caltrans, 2012). The MEDA test results do not meet any of these criteria.

6.0 CONSTRUCTION CONSIDERATIONS

The applicability of the design parameters is contingent on good construction practice. Poor construction techniques may alter conditions from those upon which our recommendations are based, and therefore result in poor performance. Our analyses assume that this project will be constructed according to FP-14 U.S. Customary Units (U.S. Department of Transportation [USDOT] and FHWA, 2014) standards. The following sections provide additional construction considerations for this project.

6.1 Site Preparation

We recommend that brush and other vegetation be cleared, and roots and stumps be removed from areas to be graded. Any existing surficial topsoil and soil containing organics should be stripped and removed from areas proposed for new fill. Topsoil and organic-rich soils are not considered suitable for reuse as fill and should be removed from the site or stockpiled for reuse in re-vegetation.

6.2 Earthwork

6.2.1 General

Earthwork, including placement of fill and subgrade preparation, should conform to the requirements provided in the FP-14 U.S. Customary Units (USDOT and FHWA, 2014) and the recommendations provided in the following sections.

6.2.2 Subgrade Preparation

Proper subgrade preparation is required for adequate performance of the proposed improvements. We recommend the contractor perform subgrade preparation in areas to receive fill or pavement. The subgrade should be scarified to a depth of at least 6 inches (if possible), moisture conditioned, and compacted to a dense and unyielding condition and to the requirements described in FP-14 (2014). Areas that are identified as being loose, soft, or yielding should be compacted in place or removed until dense and unyielding subgrade is exposed, then reconditioned or replaced with clean, coarse granular fill material. Care should be taken during proof-rolling and subgrade preparation to avoid disturbing subgrade soils and supporting soils that will remain in place, as they can rut and pump under repeated construction traffic. The final subgrade surface should be sloped to promote positive drainage and kept free of ponded water.

6.2.3 Fill Slopes

Fill slopes should be extended through loose surficial soil and be keyed and benched into existing native soils following FP-14.

Because groundwater and wet to saturated materials were reported during drilling, consideration should be given to installing backdrains where groundwater, wet, or saturated materials are encountered. They should be installed in a 1-foot-deep trench excavated at the heel of the fill slope key. The backdrain should consist of a 4-inch perforated pipe, surrounded by gravel, and wrapped in filter fabric (Mirafi 140 or equivalent). For slope heights in excess of 20 feet, we suggest installing an additional backdrain, in a bench, at approximately mid-height of the backcut. Backdrains should be provided with solid pipe outlets at approximately 250-foot intervals.

6.2.4 Structural Fill

We recommend that Structural Fill material used to backfill the retaining walls consist of free-draining sand and gravel Structural Backfill conforming to Section 704.04 of FP-14. Based on the MEDA report, we anticipate most of the granular onsite soils will meet the specifications in Section 704.04 and achieve the design values for retained backfill specified in the plans (i.e.

unit weight of 132 pounds per cubic foot and angle of internal friction of 34 degrees). We recommend laboratory testing to verify the material achieves the specifications.

6.2.5 Fill Placement and Compaction

We recommend that fill material be placed and compacted in accordance with Section 204 of FP-14.

6.2.6 Excavation Potential

Based on the ReMi profiles, bedrock will not be encountered during construction. We anticipate the onsite soil can be excavated using conventional excavating equipment, such as a rubber-tired backhoe or tracked hydraulic excavator.

Four of the six MEDA boring logs indicate boulders were encountered. Depending on the size, the boulders may be difficult to maneuver and reduce to sizes appropriate for use in Structural Fill.

6.3 Aggregate Base (AB)

The AB should conform to FP-14 Section 703.05, Gradation D. AB material should be placed in maximum 6-inch-thick lifts, moisture conditioned to ±2 percent of the optimum moisture content, and compacted to at least 95 percent of the maximum dry density as determined by

AASHTO T-99.

6.4 Paving Materials

Binder selection is based on the anticipated pavement temperatures, traffic patterns, and local availability. Using a binder within an appropriate temperature and traffic loading range allows for a higher strength and better durability, and improved cohesion will translate into improved long term performance.

The Meeks Bay Bike Path is located in the High Mountains climate region (Caltrans, 2016). For this region, Caltrans recommends using performance grade (PG) binder 64-28. We also checked this recommendation using the FHWA Research and Technology online tool LTPPBind (v3.1).

Using 95-percent reliability, the minimum required binder for the site is a PG 58-22 (a binder that preforms in a temperature range of 58 degrees Celsius to negative 22 degrees Celsius).

Based on our research, the PG binder 64-28 is available in the Lake Tahoe area.

7.0 CONSTRUCTION OBSERVATION

Our geotechnical design recommendations are based on a review of the data reported from MEDA (2014) that was developed from a limited number of explorations and tests.

9.0 REFERENCES

American Association of State Highway and Transportation Officials (AASHTO), 2016, AASHTO LRFD bridge design specifications: U.S. customary units (7th ed. with 2015 and 2016 interim revisions): Washington, D.C., AASHTO, 2 v.

CH2M Hill, Inc. (CH2M), 2017, Meeks Bay bike path: Plans prepared by CH2M, Sacramento, Calif., for U.S. Department of Transportation, Federal Highway Administration, Central Federal Lands Highway Division, Denver, Colo., 119 sheets.

California Department of Transportation (Caltrans), 2012, Corrosion guidelines (ver. 2.0):

Sacramento, Calif., Caltrans, 44 p.

California Department of Transportation (Caltrans), 2014a, Caltrans Amendments to the AASHTO LRFD Bridge Design Specifications (2012 Sixth Edition), January, available:

http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/ca-to-aashto-lrfd-bds/caalbds_v6.html

California Department of Transportation (Caltrans), 2014b, Geotechnical manual, embankments:

Sacramento, Calif., Caltrans, December, 22 p.

California Department of Transportation (Caltrans), 2016, Highway design manual: Sacramento, Calif., Caltrans, available: http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm.

California Geological Survey, 2016, Earthquake fault zones map, Emerald Bay quadrangle:

scale 1:24,000, available:

http://gmw.consrv.ca.gov/shmp/download/quad/EMERALD_BAY/maps/EMERALD_BAY _EZRIM.pdf

Earth Consultants International, 2011, Geologic review of potential faulting and tsunami inundation hazards for the Homewood Resort project: Prepared by ECI, Santa Ana, Calif., project no. 3104, for Lozeau Drury LLP, Oakland, Calif., April, 11 p.

El Dorado County, 2017, Building design criteria: available:

http://edcapps.edcgov.us/building/DesignCriteria.asp.

Federal Highway Association (FHWA), 2012, Geosynthetic reinforced soil integrated bridge system interim implementation guide, June, publication no. FHWA-HRT-11-026, 176 p.

available:

https://www.fhwa.dot.gov/publications/research/infrastructure/structures/11026/11026.pdf

Ichinose, G.A.; Satake, K.; Anderson, J.G.; and others, 1999, The potential hazard from tsunami and seiche waves generated by future large earthquakes within the Lake Tahoe basin, California-Nevada: Geophysical Research Letters, v. 27, p. 1203-1206.

http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/ca-to-aashto-lrfd-bds/caalbds_v6.html http://www.dot.ca.gov/hq/esc/techpubs/manual/bridgemanuals/ca-to-aashto-lrfd-bds/caalbds_v6.html http://www.dot.ca.gov/hq/oppd/hdm/hdmtoc.htm http://gmw.consrv.ca.gov/shmp/download/quad/EMERALD_BAY/maps/EMERALD_BAY_EZRIM.pdf http://gmw.consrv.ca.gov/shmp/download/quad/EMERALD_BAY/maps/EMERALD_BAY_EZRIM.pdf http://edcapps.edcgov.us/building/DesignCriteria.asp

Kent, G.; Schmauder, G.; Maloney, J.; and others, 2016, Reevaluating late-Pleistocene and Holocene active faults in the Tahoe Basin, California-Nevada, in Applied Geology in California, Association of Environmental and Engineering Geologists, special publication.

no. 26, p. 833-858.

Marvin E. Davis & Associates, Inc. (MEDA), 2014, Geotechnical investigation report, Meeks Bay to Sugar Pine Point state park, Class 1 bike path project, El Dorado County, California:

Report prepared by MEDA, Reno, Nev., job no. 1244.001, for Nichols Consulting Engineers, Reno, Nev., April, 46 p.

Saucedo, 2005, Geologic map of the Lake Tahoe Basin, California and Nevada: California Geological Survey, 27 p., 1 sheet, scale 1:100,000.

Seitz, G., and Mareschal, M., 2014, Multiple-Event Deformation on the West Tahoe Fault from Lidar and Trenching: Reconciling On and Offshore Paleoseismology, American Geophysical Union, Fall Meeting 2014, abstract #T41C-4666.

Seitz, G., 2016, Fault evaluation report, West Tahoe Fault: California Geological Society FER 261, 3 plates, 28 p.

U.S. Department of Transportation (USDOT) and Federal Highway Administration (FHWA), 2008, Federal Lands Highway Project Development and Design Manual (PDDM): U.S.

Department of Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/manuals/pddm/.

U.S. Department of Transportation (USDOT) and Federal Highway Administration (FHWA), 2014, Federal Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects, FP-14: U.S. Department of Transportation and Federal Highway Administration, available from http://flh.fhwa.dot.gov/resources/pse/specs/.

U.S. Geological Survey (USGS), 2006, Quaternary fault and fold database of the United States, accessed March 1, 2017, from USGS web site:

http://earthquake.usgs.gov/hazards/qfaults/map/ http://flh.fhwa.dot.gov/resources/manuals/pddm/ http://flh.fhwa.dot.gov/resources/pse/specs/ http://earthquake.usgs.gov/hazards/qfaults/map/

CALIFORNIA

F i l e n a m e

I P

R O

J E

C T

S D e n v e r

P r o j e c t s

C

L

M e e k s

B a y D r a f t i n g F

I G

V

I C

I N

I T

Y

M

A P d w g

D a t e o g i n

L o u i s

L a r i o s

Sacramento

Los Angeles

23-1-01373-209

FIG. 1

VICINITY MAP

March 2017

Map adapted from aerial imagery provided by

Google Earth Pro, reproduced by permission granted by Google Earth ™ Mapping Service.

NOTE

Project

Location

TM

SCALE: 1"=2000'

2000 40001000

Meeks Bay Bike Path

CA FLAP SR89(2)

El Dorado County, California

PROJECT

LOCATION

Lake Tahoe

Meeks Bay maw

Meeks Bay Bike Path

CA FLAP SR89(2)

El Dorado County, California

NOTES

1. The design response spectrum corresponds to a 975-year ground motion return interval.

2. The design spectrum incorporates soil effects by incorporating a Vs30 equal to 335 meters per second.

3.

CALTRANS/AASHTO

DESIGN RESPONSE SPECTRUM

March 2017 23-1-01373-209

FIG. 2

ARS design response spectrum includes near fault factors as recommended by the Caltrans seismic design criteria (SDC).

As recommended by the Caltrans SDC, the design response spectrum is based on the larger of the deterministic and probabilistic spectra values.

4.

0.00

0.50

1.00

1.50

0.00 1.00 2.00 3.00 4.00 5.00

Sp ec tr al A cc el er at io n g)

Period (s)

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

APPENDIX A

PREVIOUS SUBSURFACE EXPLORATION FROM

MARVIN E. DAVIS & ASSOCIATES, INC., 2014

23-1-01373-209_R1_AA/wp/lmr 23-1-01373-209 A-i

APPENDIX A

PREVIOUS SUBSURFACE EXPLORATION FROM

A-1 Site Exploration Map A-2 Log of Boring B1E [sic] A-3 Log of Boring B1B A-4 Log of Boring B2 A-5 Log of Boring B3 A-6 Log of Boring B4 A-7 Log of Boring B5 A-8 Unified Soil Classification Chart A-9 Soil Shear Wave Velocity Vs. Depth, ReMi 1 A-10 Soil Shear Wave Velocity Vs. Depth, ReMi 2 A-11 Soil Shear Wave Velocity Vs. Depth, ReMi 3

FIG. A-1

SITE EXPLORATION MAP

F i l e n a m e

L a x f s v o l P

R O

J E

C T

S D e n v e r

P r o j e c t s

C

F L

M e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i s l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-2

LOG OF BORING B1E

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-3

LOG OF BORING B1B

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-4

LOG OF BORING B2

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-5

LOG OF BORING B3

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-6

LOG OF BORING B4

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-7

LOG OF BORING B5

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-8

UNIFIED SOIL CLASSIFICATION CHART

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-9

SOIL SHEAR WAVE VELOCITY VS

DEPTH, REMI 1

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-10

DEPTH, REMI 2

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. A-11

DEPTH, REMI 3

APPENDIX B

PREVIOUS LABORATORY TEST RESULTS FROM

23-1-01373-209_R1_AB/wp/lmr 23-1-01373-209 B-i

APPENDIX B

PREVIOUS LABORATORY TEST RESULTS FROM

B-1 Grain Size Analysis (2 sheets) B-2 Atterberg Limits B-3 Compaction Curve B-4 Direct Shear Test Report, B1B & B1A Composite 0-15 Feet B-5 Direct Shear Test Report, B3 at 15.5 Feet B-6 Direct Shear Test Report, B5 at 16 Feet B-7 Direct Shear Test Report, B5 at 20.5 Feet l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-1

GRAIN SIZE ANALYSIS

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-1

GRAIN SIZE ANALYSIS

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-2

ATTERBERG LIMITS

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-3

COMPACTION CURVE

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-4

DIRECT SHEAR TEST REPORT, B1B

& B1A COMPOSITE 0-15 FEET

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-5

DIRECT SHEAR TEST REPORT,

B3 AT 15.5 FEET

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-6

B5 AT 16 FEET

l e n a m e

L a x f s v o l

P

R O

J E

C T

S D e n v e r

P r o j e c t s e e k s

B a y D e l i v e r a b l e s R e p o r t A

P P

P S d t e g i n

L o u i s

L a r i o s

FIG. B-7

B5 AT 20.5 FEET

APPENDIX C

REVIEW COMMENT SHEET

23-1-01373-209_R1_AC/wp/lmr 23-1-01373-209 C-i

APPENDIX C

REVIEW COMMENT SHEET

TABLES

C-1 Federal Lands Highway Division PS&E Review Comment Sheet (2 sheets) C-2 N60 Values

TABLE C-1 SHANNON & WILSON, INC.

01373-209_Caltrans_96% Comments Meeks Bay Geotech_170424/wp/lmr Page 1 of 2 23-1-01373-209

Project Name: Truckee River Bridge (Meeks Bay Bicycle Bridge) Project Number: CA FLAP SR 89(1)

DISPOSITION ACTION CODES:

12/22/2015 Initial Disposition

AC - Accept Comment DC - Dismiss Comment

Response/Disposition of Comments ED - Evaluate by Designer Lead Designer: IO - Input from Others Project Manager: Final Disposition Other: C - Completed

Date: D - Dismissed R - Revised Comment Accepted

Regular Font = Comment of Minor Significance Bold Font = Comment of Major Significance

Initial Final Resp.

Party

Wardak 1 Bridge Design Calculations Cover Sheet Please include Bridge, EA and Project numbers, on the cover sheet. AC AP/JGR Will add these items to the cover sheet on the addendum calculations.

Wardak 2 Bridge Design Calculations

Ped Br.

Design

Please define the abbreviations (CFL, GRF, RSF, CMU and etc.) first and then it can be used in the report.

Third paragraph. This sentence is confusing "This gives an overall abutment height of approximately 13 to 152 feet from the bottom of the RSF to the finished grade of the bike path above.

AC AP/JGR

The abbreviatsion were not addressed in the calculations.

CFL - Central Federal Lands; GRF is actually GRS = Geosythetic Reinforced Soil; RSF = Reinforced Soil Foundation; CMU = concrete masonry unit.

The sentence being referred to should say "13 to 15 feet" and both the orginal and addendum calculations used the correct height.

Wardak 3 Bridge Design Calculations

Br Design Criteria

Please specify the methodology (determistic or probabilistic) used to develop controlling design response spectra.

Caltrans Seismic Design Criteria, Version 1.7 may be used for the design of the proposed structure. Please exclude all the California Building Code (CBC) requirements.

Please provide only one controlling upper limit of an Acceleration Response Spectrum (ARS).

Please provide Vs30 calculations. Please note that N60 values (blow counts corrected for Hammer Energy) should be used in the Vs30 calculations.

Per Caltrans Memo To Designer 20-10, Fault Rupture studies should include both Alquist-Priolo Fault Zones and analysis of unzoned fault(s) that is Holocene or younger in age. Also, Caltrans online map is not an accurate source to obtain fault distances for fault rupture study.

SD/JGR

-We used the Caltrans ARS Online application (version 2.3.08) to determine the deterministic and probabilistic response spectrum. The design response spectrum is based on the larger of the deterministic and probabilistic spectral accelerations.

-We used the average shear wave velocity from the ReMi measurements to determine the site class.

-We evaluated the potential for fault rupture hazard using the California Geologic Survey Earthquake Fault Zones maps, U.S. Geological Survey interactive fault map, and geologic literature from our library and online sources (see S&W report reference list)

Wardak 4 Retaining Wall

Design Calculations

All required loads and geotechnical data should be provided according to LRFD Memo To Designer 5-19, July 2015. AC AP/JGR Will add summary table to the addendum calculations.

Wardak 5 Foundation Report (FR)

A revised foundation report was not included with the submittal dated November 12, 2015.

It is our recommendations to provide a complete separate foundation report for Meeks Bay Multi Used Path Bridge and retaining structure(s).

Is there any other foundation alternative to support the proposed structures? If yes, please include foundation alternatives.

JGR

Shannon & Wilson prepared an updated report dated April 28, 2017.

At the Type Selection meeting it was determined that GRS abutments would be used and so The investigation of other types of foundations was not necessary.

Federal Lands Highway Division PS&E Review Comment Sheet

Reviewer:

Date Reviewed:

15%/30% Review 50% Review 70% Review 95% Review

Asef Wardak

DISPOSITION

Reviewer Item Number

Various

SectionDocument RESPONSE/COMMENTReviewer COMMENT

TABLE C-1 SHANNON & WILSON, INC.

01373-209_Caltrans_96% Comments Meeks Bay Geotech_170424/wp/lmr Page 2 of 2 23-1-01373-209

Federal Lands Highway Division PS&E Review Comment Sheet

Wardak 6 LOTB

In Log of Test Borings (LOTB), the soil consistence should be described based on N60 not based on field below counts measurement.

The LOTB sheets should conform to Caltrans’ Soil & Rock Logging, Classification, and Presentation Manual (SRLCPM), currently dated 2010.

SD/JGR

-We did not perform additional subsurface exploration as a part of our study. We included the boring logs from the previous consultant in an appendix to our report.

-We have calculated and tabulated the N60 values for each of the blow counts reported on the MEDA logs. The table is included in an appendix to our report.

-The LOTBs in the plans were done to CFL standards per project agreement with District 03. However, notes, tables, and soil descriptions are now included on the LOTBs to resolve any ambiguity.

-S&W transfered the information and descriptions from the previous consultant's boring logs into the Caltran LOTB format. The previous consultant did not follow the Caltrans SRLCPM, so they do not conform.

TABLE C-2

N60 VALUES

SHANNON & WILSON, INC.

01373-209_N60 Values/wp/lmr Page 1 of 1 23-1-01373-209

Boring SPT Depth1

(feet) Field Blow Count2 (N) N603

B1A 15 120 160 10 100 133

14.5 120 160 20 120 160 25 100 133

3.5 26 35

7.5 27 36 15 200 267 25 300 400

2.5 300 400 5 69 92

20.5 200 267

22.5 150 200

2.5 49 65

7.5 51 68 15 75 100

2.5 20 27 5 17 23 9 16 21

17.5 37 49 25 120 160

Notes:

1 N60 values calculated for SPTs reported by MEDA (2014).

2 Blow counts for SPTs driven less than 12 inches were extrapolated to 12 inches.

3 Hammer efficiency reported by MEDA (2014) is 80 percent.

B1B

APPENDIX D

IMPORTANT INFORMATION ABOUT YOUR

GEOTECHNICAL/ENVIRONMENTAL REPORT

Page 1 of 2 1/2017

SHANNON & WILSON, INC.

Geotechnical and Environmental Consultants

Dated:

Attachment to and part of Report 23-1-01373-209

Date: April 28, 2017 To: Mr. John Rohner CH2M Hill, Inc.

IMPORTANT INFORMATION ABOUT YOUR GEOTECHNICAL/ENVIRONMENTAL

REPORT

CONSULTING SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND FOR SPECIFIC CLIENTS.

Consultants prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer. Unless indicated otherwise, your consultant prepared your report expressly for you and expressly for the purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the consultant. No party should apply this report for any purpose other than that originally contemplated without first conferring with the consultant.

THE…