W912P722B0002 Geotechnical Report.pdf

Dry Creek Ecosystem Restoration Project, Phase I Final Design Documentation Report

Inter-Fluve JANUARY 2021

Appendix E: Geotech 2011 Investigation Results wwwww.w sandersgeo.comwww sandndersgeo como

4180 Douglas Blvd., Ste. 100

Granite Bay, CA 95746

P (916) 729-8050

F (916) 729-7706

Geotechnical Investigation Report

Dry Creek Habitat Enhancement

Demonstration Projects - Phase 3 Sonoma County, California

SAGE Project No. 07-082.02

Prepared for:

Inter-fl uve Inc.

1020 Wasco Street

Suite 1

Hood River, OR 97031

March 11, 2011

DRAFT

Sanders & Associates Geostructural Engineering, Inc.

4180 Douglas Blvd., Ste. 100, Granite Bay, CA 95746 P: (916) 729-8050 F: (916) 729-7706 www.sageengineers.com

Project No. 07-082.02 3.02

Mr. Michael Burke Inter-Fluve, Inc.

1020 Wasco St., Ste. 1 Hood River, OR 97031

RE: Revised Draft Geotechnical Investigation Report

Dry Creek Habitat Enhancement Demonstration Projects Station 325+00 to 383+00 Sonoma County, California

Dear Mr. Burke:

Sanders & Associates Geostructural Engineering, Inc. (SAGE) is pleased to submit this revised draft report presenting the results of our geotechnical investigation for the proposed habitat enhancements in Dry Creek, a major tributary to the Russian River in Sonoma County, California.

Specifically, this investigation was focused on the first phase of enhancements along an approximately 1.1 mile length of Dry Creek, referred to as the Demonstration Reach, which extends from the mouth of Grape Creek downstream to the mouth of Crane Creek (station 325+00 to 383+00). We are submitting one (1) copy of this draft report for your review.

We explored the subsurface conditions at selected off channel enhancement sites and a bank stabilization site by excavating eight (8) test pits and drilling two (2) small-diameter borings (Figure 2). In addition, NORCAL Geophysical Consultants performed a geophysical survey at an off channel enhancement site which could not be accessed by conventional mechanized equipment.

In general, we encountered alluvial soils consisting of mixtures of gravel and sand with interbedded layers of finer material. The material ranged from loose to dense, with the least dense materials generally near the ground surface. Saturated materials were very loose upon excavation and could not maintain excavation cuts or slopes.

Based on the results of the geophysical survey, the depth to bedrock at Off-Channel Enhancement Area D is estimated between 2 and 9 feet on the northwest and southeast ends of a seismic refraction line performed at this site, respectively. The recorded velocities suggest the rock is rippable to moderately rippable with a CAT 9L bulldozer. Bedrock was not encountered in any of the test pits excavated at the site.

Mr. Michael Burke Project No. 07-082.02 3.02

The report submitted herewith contains recommendations regarding site grading, temporary and permanent slopes, slope stability, and bearing capacity. These recommendations are based on limited subsurface exploration and laboratory testing. Consequently, variations between expected and actual soil conditions may be found during construction. SAGE should be retained to observe the earthwork to evaluate actual conditions encountered for conformance with the geotechnical aspects of the plans and specifications.

Please call us should you have questions.

Sincerely yours, Darren A. Mack Drew G. Kennedy Geotechnical Engineer Engineering Geologist

TABLE OF CONTENTS

1.0 INTRODUCTION

2.0 SCOPE OF SERVICES

3.0 SITE CONDITIONS

4.0 GEOLOGIC CONDITIONS

4.1 Regional Geologic Setting

4.2 Site Geology

5.0 SUBSURFACE CONDITIONS

6.0 SEISMICITY

6.1 Regional Seismicity

6.2 Seismic Hazards

6.3 Fault Rupture

7.0 RECOMMENDATIONS

7.1 Demolition & Clearing

7.2 Fill Material and Compaction Requirements

7.3 Aeration

7.4 Excavatability

7.5 Temporary Slopes

7.6 Permanent Slopes

7.7 Slope Stability and Bearing Capacity

8.0 SERVICES DURING CONSTRUCTION

9.0 LIMITATIONS

10.0 REFERENCES

FIGURES

Figure 1 Site Location Map Figure 2 Subsurface Exploration Map

APPENDICES

Appendix A – Field Exploration Program

Figure A-1 Soil Classification Chart

Figures A-2 Logs of Soil Borings B1 and B2 through A-3

Figure A-4 Logs of Test Pits TP1 through TP8

Appendix B – Laboratory Test Results

Appendix C – Geophysical Survey Report

4180 Douglas Blvd., Ste. 100, Granite Bay, CA 95746 P: (916) 729-8050 F: (916) 729-7706 www.sageengineers.com

REVISED DRAFTGEOTECHNICAL INVESTIGATION REPORT

Dry Creek Habitat Enhancement Demonstration Projects Station 325+00 to 385+00

Sonoma County, California

1.0 INTRODUCTION

Sanders & Associates Geostructural Engineering, Inc. (SAGE) is pleased to submit this revised draft report presenting the results of our geotechnical investigation for habitat enhancements in Dry Creek, a major tributary to the Russian River in Sonoma County, California. Specifically, this investigation was focused on the first phase of enhancements along an approximately 1.1 mile length of Dry Creek, referred to as the Demonstration Reach, which extends from the mouth of Grape Creek downstream to the mouth of Crane Creek (STA 325+00 to 383+00).1

The purpose of the proposed habitat enhancements is to develop summer rearing and winter refugia habitat for local fish species, specifically coho salmon and steelhead trout. Based on our review of the 30% Dry Creek Habitat Enhancement Demonstration Projects plans, we understand this will be achieved using a combination of enhancement approaches, including backwater ponds and channels for the fish to inhabit. The backwater ponds and channels will require excavation in stream terraces adjacent to the active stream channel. Slope inclinations for channel regarding are expected to be on the order of 2H:1V or flatter, with cuts up to 15 feet. In channel enhancement measures will include new riffle areas, deepening of existing pools, and construction of artificial log jams.

In addition, stabilization of the creek banks will be locally required to retain property and to enhance the habitat characteristics along the edge of Dry Creek. Anticipated bank stabilization measures will include: (1) flattening the existing slopes and covering with biodegradable fabrics; (2) bank reconstruction using log cribs with live willow cuttings; and (3) bank reconstruction using fabric encapsulated soil with live willow cuttings. The log cribs will have nominal widths (perpendicular to slope) of 20 to 25 feet, and will be underlain at the toe by 3- to 4-foot-wide by 5- to 8-foot-deep pads of 18-inch-minus rock. Backcuts for taller stabilization efforts are expected to consist of temporary slopes, although shoring may be required locally where layback space is limited by the presence of existing vineyards.

The approximate project location is shown on the Site Location Map (Figure 1). The important project features are shown on the Subsurface Exploration Map (Figure 2).

1 Project stations (STA) are based on the 30% Dry Creek Habitat Enhancement Demonstration Projects plans prepared by Inter-Fluve, dated October 1, 2010.

Geotechnical Investigation Report

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2.0 SCOPE OF SERVICES

We performed a subsurface investigation in support of the proposed habitat enhancements for the Demonstration Reach. We have summarized the observations and results of our investigation in this geotechnical report, which provides recommendations and conclusions for developing the habitat enhancement design. Specifically, our investigation consisted of:

Conducting a site reconnaissance to review selected locations for subsurface exploration;

Obtaining the necessary drilling permits and coordinating our subsurface exploration program;

Retaining the services of a private utility locator to clear investigation locations for possible underground utilities and/or buried objects;

Performing a subsurface exploration program including eight (8) test pits and two (2) soil borings;

Performing a geophysical survey at an off channel enhancement site which could not be accessed by conventional mechanized equipment;

Collecting representative samples of the soil encountered in the test pits and soil borings;

Performing laboratory testing on selected soil samples; and Preparing this geotechnical report.

3.0 SITE CONDITIONS

Dry Creek is an incised stream with flows regulated by the upstream Warm Springs Dam. Flow regulation has reduced the frequency and severity of major floods while providing a continuous baseflow during the summer months. This has resulted in the rapid growth of dense riparian vegetation and shrubs along the channel banks and formerly active bar surfaces since the dam was put into service in 1984. Where visible through the dense vegetation, the channel banks are generally steep to very steep and locally subject to erosion. Alluvial terraces are locally preserved along the Demonstration Reach, and are positioned above the active stream channel. These terrace surfaces, including a prominent terrace at Off Channel Enhancement Area C (Figure 2), are relatively flat benches with areas of dense vegetation to open grassy meadows.

4.0 GEOLOGIC CONDITIONS

4.1 Regional Geologic Setting

The Demonstration Reach is located in the Dry Creek drainage valley within the Coast Ranges geomorphic province of California. The Coast Ranges province is generally characterized by northwest-trending mountain ranges and intervening valleys that are controlled by right-lateral strike-slip faulting along the San Andreas fault system.

Review of available geologic mapping and literature sources indicate that the Dry Creek drainage valley is a structurally-controlled valley that generally lies on the boundary between sedimentary units

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p. 3 of the Great Valley Complex to the east and various fault bounded lenses of the Coast Range ophiolite and metamorphic rock units of the Franciscan Complex to the west (Blake, Graymer, and Stamski, 2002). However, sandstone, siltstone, and shale units belonging to the Great Valley Complex are also mapped along the western margin of the valley adjacent to the Demonstration Reach. The valley is filled with stream channel and floodplain deposits associated with Dry Creek and include up to three terrace deposits, the oldest of which appears to be approximately 1,000 years old (Harvey and Schumm, 1985).

4.2 Site Geology

Geologic conditions at the site are generally similar to those depicted by Huffman and Armstrong (1980) and Blake, Graymer, and Stamski (2002). In general, the Demonstration Reach is underlain by alluvial deposits of varying age. The deposits are comprised of clay, silt, sand, gravel, and cobble mixtures of varying rock types derived from tributaries extending into the adjacent Coast Range ophiolite, Great Valley Complex, and Franciscan Complex. The youngest alluvium is found within the active stream channel and low-lying gravel bars that are seasonally inundated.

Alluvial terraces are preserved along the length of the Demonstration Reach, and are comprised of older alluvial deposits. The position of these terraces relative to the active stream channel varies along the reach. In general, terraces positioned higher than the active stream channel are well vegetated, particularly the prominent terrace at Off Channel Enhancement Area C (Figure 2).

Shallow slope failures are locally present along the active channel and terraces banks in areas where the banks are actively being undercut.

Bedrock outcrops observed along the active stream channel are generally limited to Grape and Crane Creeks near the confluence with Dry Creek, and within the Dry Creek channel below and immediately downstream of Lambert Bridge. The exposures are comprised of interbedded layers of weak siltstone and somewhat stronger, thicker beds of sandstone that appear to be consistent with descriptions of the siltstone, sandstone, and shale units of the Great Valley Complex. In general, the siltstone and sandstone exposures can easily be broken with a rock hammer, and are expected to be excavatable using conventional grading equipment. At Grape Creek, the bedrock is locally folded along a west-southwest plunging axis approximately parallel to the apparent syncline evident in the mapped Great Valley Complex units exposed on the western flank of the valley.

5.0 SUBSURFACE CONDITIONS

We explored the subsurface conditions at selected off channel enhancement sites and bank stabilization site by excavating eight (8) test pits and drilling two (2) small-diameter borings (Figure 2). In addition, NORCAL Geophysical Consultants (NORCAL) performed a geophysical survey at an off channel enhancement site which could not be accessed by conventional mechanized equipment. Table 1 summarizes the subsurface exploration performed. A description of our field exploration program, as well as the test pit and borings logs, is presented in Appendix A. The results of laboratory testing are presented in Appendix B.

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TABLE 1

SUMMARY OF EXPLORATION LOCATIONS

Enhancement Site* Property

Owner(s) Subsurface Exploration

Off Channel Enhancement Area A Bank Stabilization (STA 334+00 – 337+70)

Wallace & Farrow

Test pits (TP5 to TP8)

Off Channel Enhancement Area C Van Alyea Test pits (TP1 thru TP4) Bank Stabilization (STA 360+00 – 363+55, STA 365+10 – 365+80)

Mascherini Soil borings (B1, B2)

Off Channel Enhancement Area D Seghesio Geophysical survey

TP1 through TP4 were excavated at Off Channel Enhancement Area C. The upper 6 to 12 inches of TP1 through TP3 were composed of loose to medium dense gravelly silt and silty gravel with organic material. TP4 exposed four feet of medium stiff gravelly clay at the surface of the excavation. Below the surficial layer, we encountered easily excavatable loose to medium dense sand and gravel mixtures. Groundwater was encountered around Elevation 122 feet in each test pit.

Soils encountered in TP5 through TP9 generally comprised sandy gravel with trace fines and cobbles up to 10 inches. Localized layers of sand and clayey sand were also encountered. The subsurface material was loose to medium dense and could be easily excavated. Groundwater was encountered between Elevation 115 and 118 feet.

The soils encountered in B1 and B2 indicate that the upper 13 to 15 feet of the creek bank is variable. In B1, we encountered loose to medium dense silty sand and sand. In B2, we encountered medium stiff to stiff clay with some silty sand. Below 15 feet, we encountered sand and gravel with varying silt and clay content. Groundwater was between 21 and 23 feet below existing grade, which corresponds to between Elevation 121 and 122 feet.

The water level in Dry Creek was measured adjacent to TP-1 and TP-5. At these two locations, the measured groundwater elevations in the test pits were approximately the same as the adjacent water surface elevation in Dry Creek. Although not measured in the field, we would expect similar results for the remaining test pits.

The test pit side slopes were marginally stable in dry to moist conditions. However, rapid caving or sloughing generally occurred below the water table, particularly where active seepage was encountered, which limited the depth of the test pits.

Although bedrock of the Great Valley Complex is visible in Grape and Crane Creeks near the confluence with Dry Creek, and within Dry Creek below and immediately downstream of Lambert Bridge, bedrock was not encountered in the test pits and borings. At Off Channel Enhancement Area D, the results of the NORCAL survey suggest the depth to sedimentary bedrock is between 2 and 9 feet below existing grades on the northwest and southeast ends of the seismic refraction line, Project No. 07-082.02 3.02

p. 5 respectively. The recorded velocities suggest the rock is rippable to moderately rippable with a CAT 9L bulldozer. The approximate location of the seismic line is shown on Figure 2, and the full geophysical report is presented in Appendix C.

6.0 SEISMICITY

6.1 Regional Seismicity

Seismicity is defined as the geographical and historical distribution of earthquakes, or more simply, earthquake activity. The potential for ground shaking at the site is related to earthquake activity that might occur along nearby or distant faults. Based on historical earthquake activity and fault hazard mapping, the Sonoma County region is considered to have a relatively high potential for seismic activity related to the San Andreas fault system.

The 2002 Working Group on California Earthquake Probabilities (WGCEP) suggests the overall probability of one or more MW≥6.7 earthquakes occurring in the San Francisco Bay region during the period from 2002 to 2032 is 62 percent (WGCEP, 2003). The highest probability of 27 percent was assigned to the Hayward/Rodgers Creek fault zone.

The closest active faults in this system are the Maacama and Rodgers Creek faults, which are mapped approximately 6 miles northeast and 8 miles southeast of the site, respectively. The San Andreas fault is mapped approximately 20 miles southwest of the site.

Regional fault maps and databases (Jennings et al., 2010; USGS, 2010) and a fault evaluation report (Bryant, 1982) show several strands of the Healdsburg fault within and adjacent to the Dry Creek drainage valley. No strands are mapped as crossing or projecting towards the Demonstration Reach.

Seismically, the Healdsburg fault comprises an approximately one mile wide system of northwest trending, right-lateral strike-slip fault strands. These strands appear to be a northwest extension of the Rodgers Creek fault and define part of a complex seismic stepover with the Maacama fault to the north (McLaughlin and Sarna-Wojcicki, 2003). Both the Rodgers Creek and Maacama fault systems are zoned as active2 under the State of California Alquist-Priolo (AP) Earthquake Fault Zoning Act (Bryant and Hart, 2007).

Although not currently zoned as active under the AP Act, workers mapping in the surrounding region considered some traces of the Healdsburg fault to be “recently active” (Huffman and Armstrong, 1980) or “Quaternary active” (Blake, Graymer, and Stamski, 2002). Based on available paleoseismic studies for the region and the structural relationship of the Healdsburg fault with the active Rodgers Creek and Maacama fault systems, the Healdsburg fault should be considered potentially active3.

2 Active faults are defined as those exhibiting either surface ruptures, topographic features created by faulting, surface displacements of Holocene (younger than about 11,000 years old) deposits, tectonic creep along fault lines, and/or close proximity to linear concentrations or trends of earthquake epicenters.

3 Potentially active faults displace geologic deposits of Pleistocene age (about 2 million to 11,000 years old).

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6.2 Seismic Hazards

Based on the close proximity of the site to the Maacama, Rodgers Creek, and other major active faults in the area, there is a high potential for the site to experience moderate to very strong ground shaking during a major earthquake on one of these faults. The intensity of earthquake ground motion at the site will depend on the characteristics of the generating fault, the distance to the earthquake epicenter, the magnitude and duration of the earthquake, and specific site geologic conditions.

In addition, given the sandy nature of the materials and high elevation of the groundwater table encountered during the subsurface excavation, liquefaction may occur. It is possible that liquefaction or ground shaking may damage the bank stabilization structures due to lateral spreading. However, damage caused by lateral spreading should not cause a safety hazard for the local population since the improvements are for the remediation of an existing habitat and are not infrastructure related.

Therefore, recommendations regarding liquefaction and liquefaction mitigation were not included in our scope of work.

6.3 Fault Rupture

Given the structural relationship of the Healdsburg fault with the active Rodgers Creek and Maacama faults, there is a reasonable chance of ground surface rupture along traces of the Healdsburg fault during a major earthquake on either of the active faults. Stereoscopic analysis of aerial photos and digital imagery suggests that one or more low sinuosity reaches of Dry Creek upstream/downstream of the Demonstration Reach may be structurally controlled along unmapped traces of the Healdsburg fault or other lineaments that may be associated with the fault. However, the Demonstration Reach is a higher sinuosity reach that does appear to be structural controlled. In addition, given the nature of the proposed habitat enhancements, any potential fault offset would be unlikely to have any significant impacts to the long term performance.

7.0 RECOMMENDATIONS

We believe the proposed construction is feasible from a geotechnical standpoint provided our geotechnical recommendations are incorporated into project design and construction. The primary geotechnical considerations for the site are the excavatability of the native subsurface material and stability of temporary and permanent slopes. In accordance with our scope of services, the following subsections present our recommendations for site grading, temporary and permanent slopes, and excavations.

7.1 Demolition & Clearing

Site demolition is expected to be minimal, but could include the removal of existing below-grade improvements, if any, that will interfere with the proposed construction. These could include utilities, culverts, and abandoned auto bodies.

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Where utilities are to be abandoned and removed, they should be capped or plugged with grout at the Right-of-Way (ROW). Where it is feasible to abandon utilities in-place, utilities greater than three inches in diameter should be completely filled with flowable cement grout over their entire length. Where abandoned utilities are perpendicular to an excavation, they should be filled with grout to the nearest manhole or valve. It may be necessary to pothole utilities in several locations to facilitate and/or verify grouting. Utilities less than or equal to three inches in diameter can be plugged with concrete at the sides of the excavation. Existing utility lines, where encountered, should be addressed on a case-by-case basis.

Any demolition requiring excavation should be properly backfilled with engineered fill according to the recommendations provided later in this section.

7.2 Fill Material and Compaction Requirements

On-site soil will be acceptable for use as general site fill provided it is free of organic material and contains no rocks or lumps larger than four inches in greatest dimension. Rock fragments larger than four inches can be reused in the fill provided they are broken down to less than four inches in diameter.

If imported fill is required, it should be free of organic matter or other deleterious material, contain no rocks or lumps larger than four inches in greatest dimension, and have a relatively low expansion potential (defined by liquid limit less than 40 and a plasticity index lower than 15).

All fill material, including on-site fill, should be submitted to the Geotechnical Engineer for approval at least 72 hours before it is to be used on site. Where imported fill is required, the grading subcontractor should provide analytical test results or other suitable environmental documentation at least three days before use at the site indicating the proposed fill material is free of hazardous materials.

Where fill is required, the exposed subgrade should be scarified to a depth of eight inches, moisture-conditioned to at least two percent above optimum moisture content, and compacted to at least 90 percent relative compaction.4 However, 85 percent relative compaction is acceptable where vegetation or replanting is planned. Where the thickness of the fill layer will be five feet or greater, the soil should be placed in eight-inch loose lifts and compacted to above optimum moisture content.

7.3 Aeration

If wet subgrade conditions are encountered at the site, or the base of excavations or backfill areas become soft, unstable and/or disturbed by construction equipment, it may be necessary to stabilize the base of the excavation prior to fill placement. For granular soils, particularly gravels, installation

4 Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same material, as determined by ASTM D1557-00 laboratory compaction procedure.

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p. 8 of sumps to locally lower the water level will likely be sufficient to stabilize the material provided the pumps are large enough to keep up with infiltration. For clayey soils, the least costly stabilization measure typically consists of aeration (drying) of the wet soil to reduce its moisture content to a compactable level. However, depending on climatic conditions, several days to several weeks of relatively warm, dry weather may be required to dry the soil to an acceptable level. In addition, it is often necessary to turn the material several times a day to promote uniform drying. The soil will be deemed sufficiently aerated when the required degree of compaction can be achieved and/or the resulting subgrade surface is firm and unyielding.

7.4 Excavatability

Based on the results of our borings and test pits, we believe standard construction equipment, such as a hydraulic excavator, should be able to complete the excavations required for the proposed habitat improvements. The encountered materials were generally loose to medium dense and were easily excavated. No cemented soils or bedrock was encountered in our borings or test pits.

Based on the preliminary results of the seismic refraction line performed at Area D, bedrock appears to be about 2 to 9 feet below existing grade. The reported seismic velocities range from about 1,000 feet per second in overburden materials to over 6,800 feet per second in bedrock, which suggests the bedrock is rippable to marginally rippable using a CAT D9L bulldozer. We expect bedrock encountered at Crane Creek, Grape Creek, and Lambert Bridge will be similar.

7.5 Temporary Slopes

Temporary slopes are expected to be cut for bank stability construction in areas B and C. All temporary slopes should be excavated in accordance with the latest edition of the CAL-OSHA excavation and trench safety standards as a minimum (CCR, 2005). We understand some top-of-cut setback limitations may exist in these areas due to the proximity of an existing vineyard.

Test borings B1 and B2 were drilled through the proposed backslope materials for Area C. In boring B1, the upper 20 feet of the materials encountered consist of loose to medium dense sand, silty sand, and silty sandy gravel. Because this is a layered system, the maximum slope inclination is controlled by the least stable layer, in this case, the sand. At this location, it is our opinion that the soil should be preliminarily classified as Type C according to the CAL-OSHA classification system. The maximum allowable slope for Type C soil is 1.5H:1V. Vertical benches should not be cut into the base of temporary excavations.Type C should also be assumed for Areas B, where access limitations did not allow for site specific exploration to be performed.

At the location of boring B2, however, the upper 11 feet of the embankment consists of medium stiff to stiff sandy clay, which in our opinion can be preliminarily classified as a Type B soil. The maximum allowable slope for Type B soil is 1H:1V. Below this depth, the soil is classified as silty sand and gravel, and a direct shear test in the silty gravel indicates the material has some apparent cohesion. The silty sand and gravel is transitional between Type B and C soil and will require on-site classification during excavation to determine the CAL-OSHA soil type. Because OSHA does not

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p. 9 allow layered systems with upper slopes steeper than lower slopes, we recommend cuts taller than 11 feet in the vicinity of boring B2 have an assumed inclination of 1.5H:1V for preliminary planning purposes.

The contractor should be responsible for all temporary slopes excavated at the site, and should designate one of their on-site employees as a “competent person” who is responsible for trench and excavation safety. The competent person should be responsible for determination of the correct CAL-OSHA soil type and should direct the excavation crews to use shallower slopes than presented above if appropriate. The competent person should also be prepared to flatten slopes if seepage is observed within the excavation.

If there is insufficient space to construct temporary slopes, temporary shoring may be required.

Given the medium dense nature of the sands and gravels encountered at the site, we anticipate steel sheet piles, installed using a vibratory hammer mounted to a hydraulic excavator, are the most likely method of shoring to be used at the site. For design of temporary shoring, and assuming granular slope deposits, we recommend using active pressures of 35 and 65 pounds per cubic foot (pcf) for level backslope conditions and a maximum backslope of 1.5H:1V, respectively. Passive resistance should be computed using allowable passive pressures of 300 and 145 pcf above and below the groundwater table, respectively. These passive pressures include a factor of safety of 1.5 to limit sheet pile deflections.

7.6 Permanent Slopes

Permanent slopes are expected to be cut for channel regarding. They will generally be excavated in gravelly sands and sandy gravels with no appreciable cohesion. All permanent slopes should have a maximum finished slope of 2H:1V. Permanent slopes should be revegetated and/or be covered in biodegradable fabrics as shown in the final construction plan set.

7.7 Slope Stability and Bearing Capacity

We understand bank stabilization will be performed at Off Channel Enhancement Area B and C.

For evaluation of slope stability at these locations, a cohesion of 250 psf and a friction angle of 24 degrees can be used for native soils to remain or recompacted native soil. If imported soil meeting the requirements presented in section 7.2 is used, a friction angle of 32 degrees (no cohesion) can be used.

The proposed log crib structures may bear on underlying soils at two points. An average bearing pressure may be imposed over the width of the overall crib structure, which is estimated to be on the order of 20 to 25 feet. However, pressures may be imposed locally on the 18-inch-minus rock streambed substrate (toe rock) buried beneath the toe of the wall. If it is necessary to evaluate the bearing capacity at these two points, we recommend using the allowable dead load bearing capacities presented in Table 2.

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TABLE 2

ALLOWABLE DEAD LOAD BEARING CAPACITY

Structure Min. Width, ft Min. Embedment*, ft

Allowable Dead Load Bearing Pressure, psf

Log crib (overall structure)

20 None required 4,000

Toe Rock 3 5 3,000 *Measured vertically from creek bed to bottom of improvement

These values assume fully saturated (submerged) soil conditions and a factor of safety of at least 3 for dead load conditions. The toe pressures are provided as a check to ensure that excessive toe pressures at not imposed, which could cause the bank stabilization system to settle and/or rotate toward the channel.

8.0 SERVICES DURING CONSTRUCTION

The recommendations provided in this report are based on the assumption that SAGE will be retained to provide plan review and observation and testing services during construction in order to evaluate compliance with our recommendations. Prior to construction, we should review the excavation and/or shoring plans prepared by the contractor. During construction, we should periodically check the materials exposed due to excavation of temporary and permanent slopes.

These observations will allow us compare the subsurface conditions observed during construction with those encountered during our investigation and allow us to assess the contractor’s work with respect to the project plans and specifications and the recommendations presented herein. If SAGE is not retained for these services, we cannot assume responsibility for any and all potential claims that may arise during or after construction as a result of misuse or misinterpretation of SAGE’s report by others.

9.0 LIMITATIONS

This report has been prepared for the sole use of Sonoma County Water Agency and their agents specifically for the design of the Dry Creek Habitat Enhancement Demonstration Projects described herein. The opinions, conclusions, and recommendations contained in this report are based upon the information obtained from our site subsurface exploration, our engineering studies, experience, and engineering judgment, and have been formulated in accordance with generally accepted geotechnical engineering practices that exist at the time this report was prepared. No other warranty, expressed or implied, is made or should be inferred. In addition, the recommendations presented in this report are based on the subsurface conditions encountered in a limited number of test pits and borings. Actual conditions may vary. If subsurface conditions encountered in the field differ from those described in this report, we should be consulted to determine if changes to our conclusions or supplemental recommendations are required.

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The opinions presented in this report are valid as of the date of this report for the property being evaluated. Changes in the condition of a property can occur with the passage of time, whether due to natural processes or the works of man. If site conditions vary from those described herein, we should be consulted to evaluate the impact of the changes, if any. In addition, changes in applicable standard of practice can occur, whether from legislation or the broadening of knowledge.

Accordingly, the opinions presented in this report may be invalidated, wholly or partially, by changes outside of SAGE’s control. In any case, this report should not be relied upon after a period of three years without prior review and approval by SAGE.

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10.0 REFERENCES

Blake, M.C., Graymer, R.W., and Stamski, R.E., 2002, Geologic Map and Map Database of Western Sonoma, Northwestern Marin, and Southernmost Mendocino Counties, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-2402, Version 1, 1 sheet, scale 1:100,000.

Bryant, W.A., 1982, Chianti, Healdsburg, Alexander, Maacama and related faults, Sonoma County: California Division of Mines and Geology Fault Evaluation Report 135, 18 p., scale 1:24,000, parts of 5 quadrangles, scale 1:24,000.

Bryant, W.A., and Hart, E.W., 2007, Fault-Rupture Hazard Zones in California, Alquist-Priolo Earthquake Fault Zoning Act with Index to Earthquake Fault Zones Maps: California Geological Survey, Special Publication 42, Interim Revision 2007.

California Code of Regulations (CCR), 2005, Register 2005, No. 17, Title 8, Division 1 – Department of Industrial Relations, Chapter 4 – Division of Industrial Safety, Subchapter 4 – Construction Safety Orders, Article 6 – Excavations, Sections 1539 through 1547, April 29.

Harvey, H.D., and Schumm, S.A., 1985, Geomorphic Analysis of Dry Creek, Sonoma County, California from Warm Springs Dam to Russian River Confluence: Department of the Army Sacramento District Corps of Engineers, Contract No. DACW05-85-P-0064

Huffman, M.E., and Armstrong, C.F., 1980, Geology for planning in Sonoma County: California Division of Mines and Geology Special Report 120, 31 p., 5 pls., scale 1:62,500.

Inter-Fluve, Inc., 2010a, 30% Complete Design Report, Dry Creek Habitat Enhancement Demonstration Projects: River Miles 6.2 to 7.3, October 1, 2010.

Inter-Fluve, Inc., 2010b, 30% Dry Creek Habitat Enhacement Demonstration Projects Plan Set, October 1, 2010.

Jennings, C.W., Bryant, W.A., and Saucedo, G.J., 2010, Fault Activity Map of California: California Geological Survey, California Geologic Data Map Series, Map No. 6, scale 1:750,000.

McLaughlin, R.J., and Sarna-Wojcicki, A., 2003, Geology of the Right Stepover Region between the Rodgers Creek, Healdsburg, and Maacama Faults, Northern San Francisco Bay Region – A Contribution to Northern California Geological Society Field Trip Guide, June 6-8, 2003: U.S. Geological Survey Open-File Report 03-502.

U.S. Geological Survey (USGS) and California Geological Survey, 2010, Quaternary fault and fold database for the United States, accessed October 2010, from USGS web site:

http//earthquakes.usgs.gov/regional/qfaults/

Project No. 07-082.02 3.02

p. 13

Working Group on California Earthquake Probabilities, 2003, Earthquake Probabilities in the San Francisco Bay Region: 2002 to 2031: U.S. Geological Survey Open-File Report 03-214.

FIGURES

DRAFT

dmack Draft

APPENDIX A

Field Exploration Program

A.1 Field Exploration Program

Our field exploration program consisted of excavating eight (8) test pits and drilling two (2) small-diameter soil borings. The approximate test pit and boring locations, designated TP1 through TP8 and B1 through B2, respectively, are presented on Figure 2.

Prior to the start of drilling, SAGE obtained a drilling permit from the Sonoma County Permit and Resource Management Department (PRMD) and notified Underground Service Alert (USA) at least 48 hours prior to the start of work. Furthermore, all borings and test pits were cleared by a private utility locator.

The test pits were excavated by Luce Backhoe Excavation of Santa Rosa, California. Test pits TP1 through TP4 were excavated on August 18, 2010 using a CAT 416C rubber-tire backhoe equipped with a 24-inch bucket. Test pits TP5 through TP8 were excavated on August 19, 2010 using a CAT 315L track-mounted excavator equipped with a 42-inch bucket. The test pit depths were limited to

13.5 feet or less due to caving conditions below groundwater.

Borings B1 and B2 were drilled on August 20, 2010 by Clear Heart Drilling of Santa Rosa, California. The borings were drilled using a truck-mounted DR5K1 drill rig equipped with seven-inch-diameter hollow stem augers. B1 and B2 were advanced to a depth of 41.5 feet below the existing ground surface, which corresponds to 21.3 and 23.2 feet below the existing channel bed invert, respectively.

During excavation of the test pits and drilling of the borings, our geologist logged the materials encountered and obtained representative samples for visual classification and laboratory testing. The materials encountered were classified in general accordance with the Unified Soil Classification System (USCS) as summarized on Figure A-1. Logs of the borings and test pits are presented as Figures A-2 through A-3 and Figure A-4, respectively.

Representative soil samples were recovered during drilling using the following sampler types:

Modified California (MCA) split-barrel sampler with a 3.0-inch-outside diameter fitted with 2.43-inch-inside-diameter, six-inch-long brass or stainless steel liners;

Standard Penetration Test (SPT) split-barrel sampler with a 2.0-inch-outside diameter, without liners; and

Both split-barrel samplers were driven with a 140-pound, safety (rope and cathead) hammer falling 30 inches. The blow counts required to drive the samplers over a standard 18-inch-drive were recorded in six-inch increments in the field. Where refusal was encountered, defined as greater than 50 blows over any six-inch increment, drive lengths less than 12 inches were also recorded. The final 12-inches of the drive (less in the case of refusal) were added to develop the reported blow count. The blow counts for the MCA sampler were corrected for the effects of sampler size and converted to SPT N-values using a conversion factor of 0.6. The final, corrected values for each drive are presented on the boring logs and represent N60 values.

Due to the proximity of the borings to Dry Creek, grout migration through the coarse grained alluvial deposits and into the creek was a concern. To mitigate this, our geologist obtained verbal approval from the on-site Sonoma County PRMD inspector to backfill the borings with soil cuttings to 15 feet, and top off with neat cement grout. The remaining cuttings were spread out on the ground surface adjacent to the boring.

SAMPLERS: MCA, SPT

HAMMER DROP (IN): 30HAMMER WT (LBS): 140

HAMMER TYPE: Rope and cathead (safety)

DRILL RIG: DR5KI Truck Mounted

GW DEPTH (FT): 22.7

BACKFILL MATERIAL: Soil cuttings & neat cement

CASING NOTES: N/A

GW DATE: 8/20/2010

DRILLING SUBCONTRACTOR: Clear Heart Drilling

DATUM: NAVD 88ELEVATION (FT): 144.2

LOGGED BY: D. Kennedy

BORING LOCATION: See Figure 2

MCA

DRILLING METHOD:

7-inch hollow stem auger

DATE FINISHED: 8/20/2010DATE STARTED: 8/20/2010

brown, medium dense, moist, fine grained sand, trace silt, locally grades to medium grained sand

SAND (SP)

yellow brown, loose, moist, fine grained sand

SILTY SAND (SM)

brown, medium dense, moist, fine grained sand, approximately 25% fines

SPT

MCA

MCA

MCA

loose, with SILTY SAND (SM) interbeds

SILTY SAND (SM)

GRAVEL WITH SILT AND SAND (GW-GM)

brown, medium dense, moist, fine gravel with some coarse gravel, medium to coarse sand, trace fines

SILTY SANDY GRAVEL (GM)

gravel at 13.5 based on change in drilling

E L

E V

(F

T

F

IN

E S

S P

T N

V A

L U

E

LOG OF BORING B1

L

O G

O F

B O

R

IN

G

-0

G

IN

T

B O

R

IN

G L

O G

S .G

P J

S A

G E

.G D

T

/1

/1

S A

M P

L E

PI

D R

Y D

E N

S

IT

Y (p c f)

MCA and SPT blow counts converted to SPT N60 values using conversion factors of 0.6 and 1.0, respectively.

LL

S H

E A

R S

T R

E N

G T

H (k s f)

U N

C O

N F

IN

E

D S

T R

E N

G T

H (t s f)

M O

IS

T

U R

E C

O N

T E

N T

Dry Creek Demonstration Reach Sonoma County, CA

T Y

P E o f

T E

S T

LABORATORY TEST DATA

Project No:

PLASTICITY

07-082.02

S A

M P

L E

T Y

P E

PROJECT:

A-2

Figure:

Sheet 1 of 2

D E

P T

H

F T

L

IT

H O

L O

G Y

DESCRIPTION

SM

SP

SM

GM

A-2

Figure:

MCA

S A

M P

L E

T Y

P E

07-082.02

Project No:

LABORATORY TEST DATA

T Y

P E o f

T E

S T

Sheet 2 of 2

Approximate elevation of channel bed invert

MCA

MCA

MCA

SPT

6.6GRAVEL WITH SILT AND SAND (GW-GM)

(Con't) softer drilling below 22.7', groundwater encountered gravel size increases, fine to coarse gravel, decreased sand content locally, wet

GRAVELLY SILTY SAND (SW)

brown gray, medium dense, wet, medium to coarse grained sand, fine to coarse gravel (1/4" to 1"), some silt dense, coarse grained sand, gravels up to 2.5" medium to coarse grained sand, reduced gravel content, with some clay locally brown, medium dense, moist, primarily fine gravel with coarse sand, medium grained sand lenses locally

M O

IS

T

U R

E C

O N

T E

N T

Dry Creek Demonstration Reach Sonoma County, CAPROJECT:

F

IN

E S

U N

C O

N F

IN

E

D S

T R

E N

G T

H (t s f)

S H

E A

R S

T R

E N

G T

H (k s f)

LL

Boring terminated at a depth of 41.5 feet below existing ground surface.

MCA and SPT blow counts converted to SPT N60 values using conversion factors of 0.6 and 1.0, respectively.

PI

S A

M P

L E

L O

G O

F B

O R

-0

G

IN

T B

O R

IN

G

L O

G S

.G

G E

.G

/1

D R

Y D

E N

S

IT

Y (p c f)

D E

P T

H

F T

DESCRIPTION

L

IT

H O

L O

G Y

PLASTICITY

S P

T N

V A

L U

E

LOG OF BORING B1

E L

E V

(F

T

/2

/2

GW-

GM

SW

HAMMER WT (LBS): 140

Figure:

DATE STARTED: 8/20/2010

GW DEPTH (FT): 20.0

BORING LOCATION: See Figure 2

DRILLING METHOD:

7-inch hollow stem auger

HAMMER DROP (IN): 30

HAMMER TYPE: Rope and cathead (safety)

DRILL RIG: DR5KI Truck Mounted

DRILLING SUBCONTRACTOR: Clear Heart Drilling

SAMPLERS: MCA, SPT

MCA

Sheet 1 of 2

DATE FINISHED: 8/20/2010

ELEVATION (FT): 142.3

GW DATE: 8/20/2010

brown, loose, moist, fine grained sand DSDC: Ø=24°, c=250psf; See Appendix B

SILTY SAND (SM)

silty sand lense brown, medium stiff to stiff, moist, fine grained sand

SANDY CLAY (CL)

BACKFILL MATERIAL: Soil cuttings and neat cement

Approximate elevation of channel bed invert

MCA

MCA

MCA

DATUM: NAVD 88

20.8

GRAVELLY SILTY SAND (SM)

brown, medium dense to dense, moist, medium to coarse sand, fine gravel, trace fines, weakly cemented locally

CASING NOTES: N/A

64.6

A-3

D R

Y D

E N

S

IT

Y (p c f)

LOG OF BORING B2

L

O G

O F

B O

R

-0

G

IN

T

B O

R

IN

G L

O G

S .G

G E

.G

/1

U N

C O

N F

IN

E

D S

T R

E N

G T

H (t s f)

LOGGED BY: D. Kennedy

MCA and SPT blow counts converted to SPT N60 values using conversion factors of 0.6 and 1.0, respectively.

S A

M P

L E

PI

F

IN

E S

M O

IS

T

U R

E C

O N

T E

N T

LL

S H

E A

R S

T R

E N

G T

H (k s f)

E L

E V

(F

T

PLASTICITY

Dry Creek Demonstration Reach Sonoma County, CA

L

IT

H O

L O

G

Y LABORATORY TEST DATA

Project No:

07-082.02

S A

M P

L E

T Y

P E

PROJECT:

T Y

P E o f

T E

S T

S P

T N

V A

L U

E

D E

P T

H

F T

DESCRIPTION

CL

SM

/2

/2

MCA

Project No:

SPT

MCA

MCA

SPT

SPT

Sheet 2 of 2

Figure:

A-3

S A

M P

L E

T Y

P E

07-082.02 brown, medium dense, wet, medium to coarse grained sand, fine gravel with some coarse gravel

GRAVELLY SILTY SAND (SM) (Con't) some clay

CLAYEY SAND (SC)

gray, loose, wet, fine grained sand, marsh or overbank deposit

GRAVELLY SILTY SAND (SM)

brown, medium dense to dense, wet, medium to coarse sand, fine gravel with some coarse gravel, with thin clay lenses

SAND (SP)

GRAVELLY SILTY SAND (SM)

SILTY SANDY GRAVEL (GM)

brown to yellow brown, dense, wet, with locally clean gravel lenses little to no coarse gravel gray, loose to medium dense, wet, medium grained sand, trace fines

M O

IS

T

U R

E C

O N

T E

N T

PROJECT:

D R

Y D

E N

S

IT

Y (p c f)

F

IN

E S

U N

C O

N F

IN

E

D S

T R

E N

G T

H (t s f)

S H

E A

R S

T R

E N

G T

H (k s f)

LL

E

L E

V (F

T

L O

G O

F B

O R

-0

G

IN

T B

O R

IN

G

L O

G S

.G

G E

.G

/1

Boring terminated at a depth of 41.5 feet below existing ground surface.

MCA and SPT blow counts converted to SPT N60 values using conversion factors of 0.6 and 1.0, respectively.

S A

M P

L E

PI

PLASTICITY

Dry Creek Demonstration Reach Sonoma County, CA

T Y

P E o f

T E

S T

LABORATORY TEST DATA

L

IT

H O

L O

G Y

LOG OF BORING B2

DESCRIPTION

S P

T N

V A

L U

E

D E

P T

H

F T

SM

SM

GM

SP

SM

SC

FIGURE A-4 – LOGS OF TEST PITS TP1 THROUGH TP8

Test Pit Number

Depth (feet)

Soil Classification

Soil Description

TP1

(El. 126.0)

0’ – 1’

SILTY

GRAVEL

(GM)

brown, loose to medium dense, dry with some sand, fine to coarse gravel, with organics

1’ – 6’

SANDY

GRAVEL

(GW)

brown, loose, moist to 3.5’, wet below 3.5’, primarily fine gravel with some coarse gravel, medium to coarse sand, with fines; Laboratory Gradation: 64.3% gravel, 35.4% sand, 0.3% fines Groundwater encountered at El. 122.8’

TP2

(El. 128.3)

0’ – 0.5’

SILTY

GRAVEL

(GM)

brown, loose to medium dense, dry, with some sand, fine to coarse gravel, with organics

0.5’ – 3.5’

SANDY

GRAVEL

(GW – GM)

brown, loose, dry to moist, primarily fine gravel with some coarse gravel, medium to coarse sand, trace fines, clean gravel interbeds locally, estimate 50% gravel (40% fine, 10% coarse), 45% sand, 5% fines

3.5’ – 10’

GRAVELLY

SAND

(SW)

brown gray, medium dense, moist to 6.5’, wet below 6.5’, medium to coarse grained sand, gravel primarily fine with some coarse, trace fines; Laboratory Gradation: 37.7% gravels, 61.7% sand, 0.6% fines

Groundwater encountered at El. 121.8’

TP3

(El. 131.1)

0’ – 0.5’

GRAVELLY

SILT (ML)

brown, soft to medium stiff, dry, with some sand, fine to coarse gravel, with organics

0’ – 3.0’

SANDY

GRAVEL

(GW – GM)

brown, loose to medium dense, dry, primarily fine gravel with some coarse gravel, medium to coarse sand, trace fines, clean gravel interbeds locally ,estimate 60% gravel (50% fine, 10% coarse), 35% sand, 5% fines

3.0’ – 4.5’

SAND WITH

GRAVEL (SP)

brown, loose, dry to moist, medium grained sand, with fine to coarse gravel, some organics/roots, estimate

70% sand, 30% gravel

4.5’ – 12’

GRAVELLY

SAND (SW)

brown gray, medium dense, moist to 8.5’, wet below 8.5’, medium to coarse grained sand, fine to coarse gravel, trace fines, estimate 60% sand, 35% gravel (25% fine, 10% coarse), 5% fines

Groundwater encountered at El. 122.6’

TP4

(El. 126.6)

0’ – 4’

GRAVELLY

CLAY (CL)

brown, medium stiff, dry to moist, with some sand, fine to coarse gravel, with organics

4’ – 11’

SANDY

GRAVEL

(GW – GM)

brown gray, medium dense, moist to 4.4’, wet below 4.4’, primarily coarse grained sand with medium grained sand, fine to coarse gravel, trace fines, estimate 35% sand, 55% gravel (35% fine, 20% coarse), 10% fines, trace cobble Groundwater encountered at El. 122.2’

TP5

(El. 119.2) 0’ – 10’

SANDY

GRAVEL

(GW –GM)

brown gray, loose to medium dense, moist, wet below 2.5’, fine to coarse gravel, medium to coarse sand, trace cobbles (up to 6”), traces fines, estimate 60% gravel (40% fine, 20% coarse), 30% sand, 5% cobbles, 5% fines Groundwater encountered at El. 117.6’

TP6

(El. 118.5) 0’ – 10.5’

SANDY

GRAVEL

(GW – GM)

brown gray, loose to medium dense, moist, wet below 2.4’, fine to coarse gravel, medium to coarse sand, trace cobbles (up to 10”), trace fines; Laboratory Gradation:

64.4% gravel, 35.1% sand, 0.5% fines CLAYEY SAND (SC) interbed at ~10’, medium grained, increased clay content locally, estimate interbed is less than 0.5’ thick Groundwater encountered at El. 115.9’

TP7

(El. 121.4)

0’ – 3.8’

SANDY

GRAVEL

(GW)

brown gray, loose to medium dense, moist, fine to coarse gravel, medium to coarse sand, trace fines, estimate 60% gravel (40% fine, 20% coarse), 35% sand, 5% fines

3.8’ – 5.5’ SAND (SP) olive brown, loose to medium dense, moist, medium grained sand, trace coarse grained sand and fine gravel

5.5’ – 13.5’

SANDY

GRAVEL

(GW – GM)

brown gray, loose to medium dense, moist, wet below 6’, fine to coarse gravel, medium to coarse sand, trace fines, trace cobbles, cobbles up to 6”, estimate: 50% gravel (30% fine, 20%), 40% sand, 5% cobbles, 5% fines Groundwater encountered at El. 115.5’

TP8

(El. 118.0)

0’ – 9’

SANDY

GRAVEL

(GW)

brown gray, loose to medium dense, dry in upper 1.5’, moist 1.5’ – 3.1’, wet below 3.1’, fine to coarse gravel, medium to coarse sand, trace fines (<5%), no cobbles observed, thin (~3”) clean gravel (fine) lenses visible in upper 3’ where pit can be safely accessed, increased sand content locally, estimate 50% gravel (30% fine, 20% coarse), 45+% sand, <5% fines Groundwater encountered at El. 114.9’

APPENDIX B

Laboratory Test Results

B.1 Laboratory Testing

Representative soil samples obtained from the borings were reviewed in our office to confirm field classifications. Representative samples were selected and submitted for laboratory testing. Samples were selected based on how representative they were of surrounding materials. Laboratory testing was performed to determine the following properties:

Percent Passing the No. 200 sieve (Fines Content) per ASTM D1140;

Consolidated-Drained Direct Shear (DSCD) per ASTM D3080;

Particle Size Analysis per ASTM D422;

LABORATORY TESTING SUMMARY

Boring/Test…