Physical_Data_-_Geotech_and_Pavement_Report.pdf

FINAL

GEOTECHNICAL AND PAVEMENT DESIGN REPORT

HAMMONTON SMARTVILLE ROAD

CA FLAP CR 36(1)

YUBA COUNTY, CALIFORNIA

Yeh Project No.: 214-113

March 31, 2015

Prepared for:

Jacobs Engineering Group 707 17th Street, Suite 2300

Denver, CO 80202

And

Federal Highway Administration Central Federal Lands Highway Division

12300 West Dakota Avenue Lakewood, Colorado 80228

Prepared by:

Yeh and Associates, Inc.

2000 Clay Street, Suite 200

Denver, Colorado 80211

Phone: 303-781-9590 Fax: 303-781-9583

TABLE OF CONTENTS

1. PURPOSE AND SCOPE OF STUDY

2. PROPOSED CONSTRUCTION

3. GEOLOGICAL SETTING AND SITE CONDITIONS

3.1 SEISMICITY

3.2 SITE CONDITIONS

3.2.1 TERRAIN

3.2.2 CLIMATE

3.2.3 CUTS AND FILLS

3.2.4 PAVEMENT CONDITION

4. SUBSURFACE INVESTIGATION

4.1 FIELD EXPLORATION

4.2 LABORATORY TESTING

5. SUBSURFACE CONDITIONS AND SEISMICITY

5.1 PAVEMENT BORINGS

5.2 STRUCTURE BORINGS

5.2.1 BOX CULVERT EXTENSION

5.2.2 RETAINING WALL STATION 132+49 TO 133+92

5.2.3 RETAINING WALL STATION 135+90 TO 138+40

5.3 CUT SLOPES

5.3.1 CUT SLOPE 92+00 TO 94+50

5.3.2 CUT SLOPE 114+75 TO 116+25

5.3.3 CUT SLOPE 124+00 TO 125+00

5.3.4 CUT SLOPE 110+25

5.3.5 CUT SLOPE 136+25

6. CUT AND FILL SLOPE RECOMMENDATIONS

6.1 FILL SLOPES

6.2 CUT SLOPES

7. FOUNDATION DESIGN RECOMMENDATIONS

7.1 RETAINING WALL STATIONS 132+49 TO 133+92

7.1.1 MSE WALL

7.1.2 GABION WALL

7.1.3 FILL SLOPE

7.2 SOIL NAIL RETAINING WALL 135+90 TO 138+40

7.2.1 SOIL NAIL WALL RECOMMENDATIONS

7.2.2 GLOBAL STABILITY

7.2.3 CONSTRUCTION

8. BOX CULVERT EXTENSION

9. PAVEMENT RECOMMENDATIONS

9.1 SUBGRADE STRENGTH

9.2 TRAFFIC LOADING

9.3 RECOMMENDED PAVEMENT THICKNESS

9.4 BINDER AND MIX RECOMMENDATIONS

10. CONSTRUCTION RECOMMENDATIONS

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10.1 SITE GRADING

10.2 CORROSION

11. LIMITATIONS

12. REFERENCES

List of Figures

FIGURE 1. PROJECT LOCATION MAP

FIGURE 2. GEOLOGIC MAP NO SCALE

FIGURE 3. GEOLOGIC MAP LEGEND

FIGURE 4. CUT SLOPE AT APPROXIMATE STATION 92+50; LOOKING WEST

FIGURE 5. CUT SLOPE AT APPROXIMATE STATION 93+00; LOOKING EAST, NOTE OUTCROPS

FIGURE 6. CUT SLOPE AT APPROXIMATE STATION 114+75; LOOKING EAST

FIGURE 7. CUT SLOPE AT APPROXIMATE STATION 124+50; SHOWING SOIL AND WEATHERED ROCK

FIGURE 8. CUT SLOPE AT APPROXIMATE STATION 124+50

FIGURE 9. CUT SLOPE AT APPROXIMATE STATION 124+50; SHOWING WEATHERED ROCK

FIGURE 10. CUT SLOPE AT APPROXIMATE STATION 110+25, LOOKING EAST

FIGURE 11. CUT SLOPE AT APPROXIMATE STATION 110+25; SHOWING FRESH AND WEATHERED ROCK FIGURE 12. CUT SLOPE AT APPROXIMATE STATION 136+25; SHOWING FRESH ROCK IN DITCH LINE

FIGURE 13. CUT SLOPE AT APPROXIMATE STATION 136+25, LOOKING EAST, NOTE BEDROCK

FIGURE 14. EXISTING GABION WALL AND BOX CULVERT

FIGURE 15. SHOWING BEDROCK OUTCROPPING ABOUT 20 LEFT (NORTH) OF GABION WALL

FIGURE 16. SHOWING RIP RAP RUNDOWN AND EROSION ALONG MARGIN

FIGURE 17. MSE WALL WITH GABION WALL LEFT IN PLACE

FIGURE 18. MSE WALL WITH COMPOUND SLOPE

FIGURE 19. TYPICAL GABION WALL

List of Tables

TABLE 1 - SUBGRADE SOIL CLASSIFICATIONS

TABLE 2 - PAVEMENT AND BASE THICKNESS

TABLE 3 - MSE WALL BEARING RESISTANCE

TABLE 4 - GABION WALL BEARING RESISTANCE

TABLE 5 - SOIL PROPERTIES

TABLE 6 - PAVEMENT DESIGN PARAMETERS

TABLE 7 - TREATMENTS AND ACP THICKNESS

List of Appendices

APPENDIX A BORING LOCATIONS

APPENDIX B BORING LOGS AND TEST PITS

APPENDIX C LABORATORY TEST RESULTS

APPENDIX D ANALYSIS AND SAMPLE RESULTS

APPENDIX E PAVEMENT CONDITION PHOTOGRAPHS

APPENDIX F TRAFFIC LOADING

APPENDIX G PAVEMENT DESIGN AND BINDER INFORMATION

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Hammonton Smartsville Road CA FLAP CR 36(1) Project No. 214-113 Final Geotechnical and Pavement Report

1. PURPOSE AND SCOPE OF STUDY

Yeh and Associates, Inc., as a subconsultant to Jacobs Engineering Group, Denver, Colorado, was retained by the Federal Highway Administration (FHWA), Central Federal Lands Highway

Division (CFLHD) to provide geotechnical, foundation and pavement recommendations for preliminary and final design of improvements to Hammonton Smartsville Road in Yuba County, California. Hammonton Smartsville Road extends easterly from Marysville, connecting with

State Highway 20 west of Grass Valley. The project limits extend from approximately 850 feet west of the intersection with South Golden Parkway easterly to approximately 350 feet east of the intersection of Chuck Yeager Road. The route is classified as a major collector with a posted operating speed of 55 MPH with speed advisory plaques of 35 MPH and lower in this section. The roadway is maintained by Yuba County. The project location is shown on Figure

1.

The purpose of the geotechnical investigation is to evaluate geologic and subsurface conditions in the project area and provide recommendations for the design of pavements, foundations and cut slopes. This report presents the results the geotechnical investigation along Hammonton

Smartsville Road. This report addresses potential geotechnical constraints for the proposed improvements, existing pavement conditions along Hammonton Smartsville Road, and includes recommendations for foundations at the retaining wall and box culvert extension locations, cut slopes, pavement section thickness design.

Figure 1. Project Location Map

Project Location

2. PROPOSED CONSTRUCTION

The proposed project will provide 4 foot shoulders on an approximate 1.07 mile section of the road that currently has little or no shoulders. In order to remain within the right of way the project will shift the widening from side to side requiring minor cutting and filling as well as retaining wall construction and culvert extensions. The project also includes drainage improvements, asphalt concrete pavement (ACP) in addition to signing, striping, guardrail and other safety-related features need to meet current design practice.

The improvements will be designed and implemented in accordance with CFLHD, and American

Association of State Highway and Transportation Officials (AASHTO) Highway Design

Standards, in cooperation with Yuba County and the United States Air Force (Beale Air Force

Base).

3. GEOLOGICAL SETTING AND SITE CONDITIONS

The project location is on the eastern edge of the San Joaquin Valley in the foothills of the

Sierra Nevada Mountains. The project lies within the Western Metamorphic Belt. This belt of metamorphic rocks lies to the west of the Sierra Nevada batholith and extends for approximately

200 miles through the central and northern Sierra Nevada foothills, varying from 30 miles in width at the southern end to 60 miles wide in the north. The Western Metamorphic Belt consists of rocks that were deposited in subduction zones during Paleozoic to Jurassic time. In the subduction process these rocks were subjected to extensive folding, faulting and metamorphism. In addition, numerous granitic and mafic plutons intrude through the metamorphic rocks. Longitudinally, three separate subduction zones are represented. These three resulting geologic terrains and complexes are divided by extensive fault zones. The project lies within the Foothill Terrane, the western most of the terrains, which is bounded on its eastern border by the Bear Mountain Fault Zone.

The project area is underlain by rocks of the Smartsville Complex within the Foothill Terrain.

The Smartsville Complex is a piece of oceanic crust that was thrust upon to existing material in the subduction zone. The rocks of the Smartsville Complex include a lower volcanic unit, consisting mainly of basaltic flows, and an upper volcanic unit of andesitic volcanoclastic rocks.

Both of these units have been intruded by dykes and irregular bodies of diabase. Rocks of volcanic origin as well as diabase were encountered during the geotechnical investigation.

According to the map entitled “Reported Historic Asbestos Mines, Historic Asbestos Prospects, and Other Natural Occurrences of Asbestos in California” by Bradley S. Van Gosen, U.S.

Geological Survey, Denver, CO and John P. Clickenbeard, California Geological Survey, Sacramento, CA 2011, no occurrence of asbestos has been observed at the project location.

Typically asbestos occurrence in California is associated with the presence of ultramafic rocks.

No ultramafic rocks are mapped or were encountered during the field investigation at the project location. There are six known locations in Yuba County where asbestos has been observed, all greater than 20 miles from the project location.

3.1 Seismicity

The project is located in the Bear Mountains Fault Zone and is within the area of influence of both the Swain Ravine Fault Zone Section and the Spenceville Fault Section. According to the

2007 Caltrans Deterministic PGA Map both of these faults could produce an earthquake with a maximum magnitude of 6.5. Peak Ground Accelerations at the project location associated with an event of maximum magnitude could be as high as 0.4g.

Figure 2. Geologic Map No Scale

Figure 3. Geologic Map Legend

3.2 Site Conditions

3.2.1 Terrain

The site is located in rolling terrain of the High Sierra Foothills with vegetation consisting of both deciduous and coniferous trees, grasses and shrubs. At the project location, Hammonton

Smartsville Road is winding and has a nearly continuous moderate downward grade, west to east. The roadway drops from an elevation of approximately 900 feet at South Golden Parkway to an elevation of 740 feet at Chuck Yeager Road.

3.2.2 Climate

At the project location the majority of rainfall occurs between October and April, followed by hot dry summers. The following climate data collected from nearby Beale AFB is representative of the project location. The average annual rainfall at the Beale weather station is 22.07 inches.

The annual average low temperature which occurs in January is 37 degrees Fahrenheit. The annual average high temperature which occurs in July is 96 degrees Fahrenheit. The frost line depth at the project location is less than 6 inches.

3.2.3 Cuts and Fills

The majority of the cut slopes at the project location are less than 10 feet high and are performing well. The cuts are composed of silty and clayey sand soil, weathered bedrock with some fresh bedrock outcrops. Slope angles vary from approximately 30 to 55 degrees, depending on material type. Minimal sloughing and no rock fall was observed on the slopes which are vegetated mainly with grasses.

The fill slopes also appear to be performing well. Throughout the length of the project no pavement distress associated with fill settlement was observed. A slope angle of approximately

40 degrees was recorded for the fill at approximate station 113+00.

3.2.4 Pavement Condition

The majority of the pavement in the project is in poor condition. There are numerous areas where the pavement has high severity fatigue cracking in the wheel paths in addition to extensive patching. In the area near Boring TH -8, even the patch contains high severity fatigue cracking and pop-outs. The remaining sections of pavement have low to moderate severity thermal transverse cracks as well as some block cracking. A photographic survey of the pavement conditions is presented in Appendix D.

4. SUBSURFACE INVESTIGATION

Yeh and Associates, Inc. contracted with Taber Drilling of West Sacramento, CA. to drill exploratory borings for both the pavement and structure foundation investigations. Traffic control during drilling was provided by Road Safety, Inc. of Rocklin, California. The borings were drilled between September 2nd and 5th of 2014.

After the September 2014 field work was completed, the alignment was shifted into the existing cutslope from about Station 135+90 to 138+40 resulting in an oversteepened cutslope requiring stabilization. An additional five test pits were hand sampled for this area on March 11, 2015.

4.1 Field Exploration

A total of 11 borings were drilled at the project location. The presence of overhead utilities along the entire alignment greatly influenced and in some cases controlled the placement of the borings. Please see Appendix A for the boring locations.

Borings TH-3, TH-7, TH-8 and TH-10 were drilled to a maximum depth of 11.5 feet, to collect information for pavement design and to evaluate subgrade conditions. These borings were drilled with a truck mounted CME 55 drilling rig using 4 and 6 inch flight augers. Bulk samples and split spoon samples using a 1.5 inch split soon sampler were obtained at selected intervals.

The remaining borings were drilled at cut slope locations, for the proposed box culvert widening, and at the proposed retaining wall replacement location. These borings were drilled with the same truck mounted CME 55 drilling rig using 6 and 4 inch flight augers as well as HQ coring equipment. Augers were drilled to refusal, drilling was then switched to HQ for rock coring.

Prior to auger refusal, split spoon samples using a 1.5 inch split soon sampler were obtained at selected intervals.

The split-spoon sampler was driven into the subsoils with a 140-pound hammer falling 30 inches. The number of blows needed to drive the sampler 12 inches constitutes the blow count, N, reported on the Boring Logs (Appendix D). The blow count can be used as a relative measure of the material stiffness or density. Bulk samples of auger cuttings were also obtained from the borings at selected intervals. Upon completion, the borings were backfilled with auger cuttings. The pavement was patched with cold asphalt patch mix.

4.2 Laboratory Testing

Samples retrieved during the field exploration were returned to our laboratory for observation by the project geotechnical engineer. An applicable program of laboratory testing was developed to determine engineering properties of the subsurface materials. Following the completion of the laboratory testing, the field descriptions were confirmed or modified as necessary and boring logs were prepared.

Laboratory tests performed included gradation (ASTM D 421, C 136 and AASHTO T 27), Atterberg limits (AASHTO T 89/T 90), moisture content (AASHTO T 265), R-value (ASTM D

2844), sulfate content (AASHTO T290), pH (ASTM D 4972/AASHTO T 289), chloride ion content (ASTM D 4327), Unconfined Compression Test (ASTM 7012),and soil resistivity

(AASHTO T 288).

Gradation and Atterberg limits test results were used to classify the soils in accordance with the

AASHTO classification system and the Unified Soil Classification System (USCS). Moisture content provides an estimate of the moisture conditions of the subgrade and underlying materials. Soil R-value is a measure of soil subgrade strength used for pavement design.

Tests for soluble sulfate content, pH, chloride content and resistivity are used to evaluate the potential of the soil to be aggressive to concrete and to corrode buried metal. The laboratory test results are presented in Appendix C and on the boring logs in Appendix B. Photos of the pavement conditions and boring locations along the project are presented in Appendix E.

5. SUBSURFACE CONDITIONS AND SEISMICITY

5.1 Pavement Borings

The pavement thickness ranged from 4 inches to 7 inches with an average thickness of 5.7 inches.

Aggregate base course (ABC) thickness ranged from 6 inches to 11 inches with an average thickness of 7 inches. The asphalt surface course and aggregate base thicknesses are summarized in Table 2. Laboratory tests performed on samples of the subgrade soils and bedrock are presented in Appendix D.

Samples were taken between the depths of 1 foot to 5 foot on each of the borings through the pavement. At some locations samples were taken at 1 to 2.5 feet and also from 2.5 to 5 feet.

The AASHTO soil classifications of the soil samples immediately below the aggregate base are presented in Table 1.

Table 1 - Subgrade Soil Classifications

AASHTO Soil Classification

Number of Samples

USCS Soil Classification

A-2-4(0) 1 SC

A-2-6(0) 2 SC

A-6 4 CL

A-6 1 SC

A-7-6 2 CL

A-7-6(42) 1 CH

The A-6 and A-7-6 soils had group indices ranging from 4 to 11, except for the sample at Boring

TH-8 which is a subexcavation area. The index of the soil in this area was 42 and is highly plastic clay.

Table 2 - Pavement and Base Thickness

Boring Number Station Location Pavement Thickness (inches)

Base Thickness (inches)

TH-1 146+ 65 6' rt 7 11 TH-2 146+45 6' lt

7 11 TH-3 137+30 7' lt 4 8 TH-4 132+80 7.5' lt 7 5 TH-5 125+10 6.5' rt 6.5 5 TH-6 115+50 6' rt 6 5 TH-7 107+35 7.5' lt 4.5 6 TH-8 96+75 7' rt 6 6 TH-9 92+40 10' lt 4.5 6 TH-10 91+50 7' lt 4 8 TH-11 33+25 8' rt 6 6

Average 5.7 7.0

5.2 Structure Borings

5.2.1 Box Culvert Extension

Boring TH-1 located at 6 feet right of approximate station 146+65 encountered 7 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of

1.5 feet. Below 1.5 feet, medium to very dense clayey sand was found to an approximate depth of 12 feet. Below 12 feet weathered and fractured diabase bedrock was encountered. HQ coring began at 16.8 feet and continued to the bottom of the boring at 30.5 feet. The recovered diabase core was fresh and hard to very hard. RQD’s ranged from 28 percent between 16.8 and 20.2 feet to 97 percent between 25.5 and 30.5 feet, consistently improving with depth.

Boring TH-2, located at 6 feet left of approximate station 146+45 encountered 7 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of

1.5 feet. Below 1.5 feet, medium to very dense clayey sand was found from 1.5 feet to a depth of 8 feet. Below 8 feet very dense gravelly, clayey sand was found to approximately 11 feet.

Between approximately 10.9 feet and 12.1 feet the boring encountered fractured and weathered bedrock. Below 12.1 feet the recovered diabase core was fresh and hard to very hard. RQD’s ranged from 13 percent between 12.9 and 17.6 feet to 100 percent between 21.9 and 26.9 feet, consistently improving with depth.

5.2.2 Retaining Wall Station 132+49 to 133+92

Boring TH-4 located at 7.5 feet left of approximate station 132+80 encountered 7 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of

1.0 feet. Below 1.0 feet, medium dense clayey sand was found to an approximate depth of 6 feet. From 6 feet to the bottom of the boring at 21 feet, the recovered diabase core was fresh and hard to very hard. RQD’s ranged from 28 percent between 5.5 and 7 feet to 100 percent between 12 and 15 feet. The final core run from 16 to 21 feet had an RQD of 88%. Drill fluid circulation was 100% lost at 8 feet and did not return for the remainder of the boring.

Boring TH-11 located at 8 feet right of approximate station 133+25 encountered 6 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of

1.0 feet. From 1.0 feet to 6 feet, medium dense clayey sand was found. From 6 feet to the bottom of the boring at 21.9 feet, the recovered diabase core was fresh and hard to very hard.

RQD’s ranged from 31 percent between 5.5 and 11.2 feet to 68 percent for the final core run between 16.9 and 21.9 feet. The very rapid advance of the drill rod between approximately 7.8 to 9.0 feet, coupled with 100 percent loss of drill fluid circulation at this elevation are indicators of a possible void.

In addition to the borings, observations were made at the existing retaining wall footing elevation and to left of station beyond the wall face. The existing wall appears to be stable and no settling or pavement distress was noted at the wall location. Bedrock sloping from approximately 5 to

20 degrees is exposed approximately 40 feet to the left of the wall face. Between the exposed rock and the wall face, the rock is covered by a thin soil veneer approximately less than 2 feet thick. The exposed bedrock appears to have similar characteristics to the rock found in Borings

TH-4 and TH-11.

5.2.3 Retaining Wall Station 135+90 to 138+40

After the September 2014 field work was completed, the alignment was shifted into the existing cutslope from about station 135+90 to 138+40 resulting in an oversteepen cutslope requiring stabilization. An additional five test pits were hand sampled in this area on March 11, 2015.

Five bulk soil samples were collected from the soils exposed in the cut locations. Samples were tested to determine soil classification of the geological materials including results for natural moisture content, gradation, and Atterberg limits. In addition, two samples were tested by

Colorado Analytical Laboratories, Inc. for water soluble sulfate and chloride concentrations, pH and resistivity. The test results indicate the soils vary from silty sand and gravels (AASHTO A-

4) to A-7-6 (CH). The laboratory test results are included in Appendix C. The test pits log is included in Appendix B.

5.3 Cut Slopes

Borings were conducted in the roadway at three proposed cut slope locations. In all three cases existing cut slopes will be re-sloped to accommodate roadway realignment. At all three cut slopes, boring locations were influenced by the presence of overhead power lines and/or an underground fiber optic cable.

Above ground observations and hand tool excavations were conducted at two other minor cut slope locations. These are included at the end of this section.

5.3.1 Cut Slope 92+00 to 94+50

Boring TH-9 located in the roadway at 10 feet left of approximate station 92+40 encountered 4.5 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of 0.9 feet. Below 0.9 feet, dense fine to coarse sand with few clay fines was found to an approximate depth of 4 feet. Below 4 feet to approximately 8.3 feet the boring encountered very dense fine to coarse angular sand with few clay fines. This material appeared to be decomposed bedrock. Below approximately 8.3 feet to the bottom of the boring at 15.7 feet, fresh, hard to very hard metavolcanic bedrock was found. RQD’s ranged from 13% between 8.3 and 10.8 feet to 56 percent for the final core run between 12.7 and 15.7 feet.

Visual observations and hand tool excavations into the cut slope face revealed weathered rock and soil. Fresh bedrock outcrops are visible throughout the length of this cut slope. The existing cut slope angle varies from approximately 42 to 55 degrees and has a maximum height of approximately 7 feet. The existing cut is partially vegetated with grasses and appears to be performing well. The terrain above the cut is nearly flat, to sloping less than 10 degrees.

Figure 4. Cut Slope at Approximate Station 92+50; looking west

Figure 5. Cut Slope at Approximate Station 93+00; looking east, note outcrops

5.3.2 Cut Slope 114+75 to 116+25

Boring TH-6 located in the roadway at 6 feet right of approximate station 115+50 encountered 6 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of 0.9 feet. Below 0.9 feet, very dense clayey sand with trace to few gravels was found to an approximate depth of 5.5 feet. Below 5.5 feet to the bottom of the boring at 18 feet the boring encountered moderately weathered to decomposed volcanic bedrock. An RQD of 13% was measured for the core run from 5.5 to 8 feet. Subsequent runs from 8 feet to 18 feet yielded 0 RQD. Below 8 feet the rock was extremely weathered and fractured, recovered as gravel in the core barrel.

Visual observations and hand tool excavations into the cut slope face revealed weathered rock with a minimum soil cover. A fresh bedrock outcrop was observed at approximate station

114+50. The existing cut slope angle varies from approximately 39 to 50 degrees and has a maximum height of approximately 6 feet. The existing cut is partially vegetated with grasses and appears to be performing well. The terrain above the cut is nearly flat, to sloping less than

10 degrees.

Figure 6. Cut Slope at Approximate Station 114+75; looking east

Figure 7. Cut Slope at Approximate Station 124+50; Showing soil and weathered rock

5.3.3 Cut Slope 124+00 to 125+00

Boring TH-5, located in the roadway at 6.5 feet right of approximate station 125+10 encountered

6.5 inches of asphalt concrete underlain by gravelly, silty sand road base material to an approximate depth of 0.9 feet. Below 0.9 feet, medium dense clayey mostly fine sand was found to an approximate depth of 4 feet. Below 4 feet to the bottom of the boring at 21.5 feet the boring encountered very dense clayey fine to medium sand. This material is decomposed volcanic bedrock.

Visual observations and hand tool excavations into the cut slope face revealed both weathered rock and soil. No bedrock outcrops were observed at this location, but could be presenting deeper in the hillside. The existing cut slope angle varies from approximately 42 to 47 degrees.

The existing cut is partially vegetated with grasses and appears to be performing well. The terrain above the cut is nearly flat, to sloping less than 10 degrees.

Figure 8. Cut Slope at Approximate Station 124+50

Figure 9. Cut Slope at Approximate Station 124+50; Showing weathered rock

5.3.4 Cut Slope 110+25

Visual observations and hand tool excavations into the cut slope face revealed both weathered rock and soil. One fresh bedrock outcrop was observed at this location. The existing cut slope angle is approximately 42 degrees and is less than 6 feet in height. The existing cut is partially vegetated with grasses and appears to be performing well. The terrain above the cut is nearly flat to sloping less than 10 degrees.

Figure 10. Cut Slope at approximate Station 110+25, looking east

Figure 11. Cut Slope at Approximate Station 110+25; Showing fresh and weathered rock

5.3.5 Cut Slope 136+25

Visual observations and hand tool excavations into the cut slope face revealed fresh bedrock outcrops, weathered rock, and soil. Pockets of bedrock are exposed in the ditch line and in the cut slope. Boulders and cobbles were observed in the cut slope. The existing cut slope angle varies from approximately 27 to 38 degrees and is approximately 15 feet high. The existing cut is partially vegetated with grasses and appears to be performing well.

Figure 12. Cut Slope at Approximate Station 136+25; Showing fresh rock in ditch line.

Figure 13. Cut Slope at Approximate Station 136+25, looking east, note bedrock.

6. CUT AND FILL SLOPE RECOMMENDATIONS

6.1 Fill Slopes

For ease of revegetation, 1H:2H fill slopes are preferred. However, unreinforced fill slopes as steep as 1H:1.5V have previously performed well on other CFLHD projects and are may be used for fill slopes up to 15 feet high.

Because of construction difficulties, we recommend shifting the alignment to eliminate sliver fills

(fills less than equipment width) such as those from Station 91+50 to 92+50. If they are not eliminated, we recommend including a benching detail in the plans requiring the fill slopes to be benched a minimum of equipment width (8 to 10 feet) into existing fill slopes.

6.2 Cut Slopes

Bedrock outcroppings with unconfined compressive strengths ranging from approximately

11,010 to 33,390 psf are present in many of the cut slope locations. The remainder of the material in the cuts is weathered to decomposed rock, and soil. The bedrock outcrops are not rippable and blasting will be required for excavation.

Due to the presence of the bedrock, slopes with compound angles are recommended. The bedrock outcrops can stand vertically and it is recommended that the soil and weathered/decomposed rock be excavated at a minimum of 1.5H:1V. Slope rounding at the top of the newly excavated cut slopes will help to prevent an overhanging brow condition as the cut slopes age.

In areas were compound slopes are not attainable, Stations 136 to 138 for example, we recommend stabilizing the slope by installing a cut retaining wall. Because a soil nailed wall can be installed in lifts from the top down, so that the toe of the slope is not fully unsupported during wall construction, it is the recommended wall type for this application. The soil nailed wall shotcrete face could be hand trowelled and stained to match rock outcropping in the area or covered with a stacked rock façade (rockery).

7. FOUNDATION DESIGN RECOMMENDATIONS

7.1 Retaining Wall Stations 132+49 to 133+92

To mitigate a sharp curve and accommodate roadway widening, the existing gabion retaining wall from about Station 132+49 to 133+92 on the left (north) side of the roadway will be impacted and the box culvert extended (Figure 14)

Figure 14. Existing Gabion wall and Box Culvert.

As noted in Section 5.2.2 bedrock was encountered in both borings TH-04 and TH-11 at 6 feet.

In addition bedrock visibly outcrops about 20 feet below the wall (Figure 15).

Figure 15. Showing Bedrock Outcropping about 20 left (north) of Gabion Wall.

As shown in Figure 16, some erosion is occurring at the margin of the existing box culvert rip rap rundown.

Figure 16. Showing Rip Rap Rundown and Erosion along Margin

The most viable retaining wall options for this site are a new gabion wall or a wire face mechanically stabilized earth wall (MSE). Depending on the width of the roadway widening, the existing gabion wall could be left in place to retain the existing embankment. For example, for a

MSE wall, the base width of the wall should be a minimum of 0.7H. From the cross sections provided by Jacobs Engineering Group in August 2014, the maximum wall height is about 18 feet, resulting in a minimum base width requirement of 12.6 feet. This would require moving the wall about 12 additional feet to the left to accommodate leaving the gabion wall in place.

However, if the retaining wall is founded on rock, the bottom reinforcement could be reduced to

0.4H (AASHTO C11.10.2.1), shortening the distance the bottom of the wall would have to be shifted, resulting in a truncated base. If the MSE wall is constructed on a steeper slope ratio then the gabion wall as shown on the cross sections, a base width of 0.7H would be achieved before the wall reaches full height, (reference Figures 17 and 18).

Erosion

Figure 17. MSE Wall with Gabion Wall Left in Place

Figure 18. MSE Wall with Compound Slope

Widening the roadway with a new gabion wall would require placing the new wall the width of

The roadway widening (about 10 feet) in front of the existing wall. The void between the new gabion baskets and the existing wall should be filled with coarse granular material. The top two to three courses of the existing wall should be removed, a woven Class 1 separation geotextile fabric meeting the requirements of Table 714-1 of the FP-14 placed across the top of both walls.

Then reinforce the top two baskets with at least two layers of geogrid reinforcement that extends about 6 feet behind the existing wall to tie the walls together. Backfill the geogrid layers with

Select Granular Backfill meeting the requirement of FP-14 Section 704.08. Reference Figure 19.

Figure 19. Typical Gabion Wall

The two (2) wall borings placed 7.5 feet left and right of the existing roadway centerline, encountered rock at a depth of 6 feet. Therefore, the existing embankment could be excavated on a compound slope ratio with the soil on a 1:1 slope and the rock excavated on a steeper slope ratio, possibly negating the advantage of leaving the gabion wall in place.

7.1.1 MSE Wall

The MSE wall should be designed with a minimum base width B=0.7H unless it is founded on rock as noted in Section 6.1 then it can be reduced to 0.4H. However, additional geotechnical information (hand auger or geophysical) would have to be obtained at the location of the toe of the wall to verify that the wall will be founded on rock. In addition, if the gabion wall is to remain in place, the top two layers of the wall would have to be removed and the remaining wall would have to be covered with a separation geotextile to prevent the retained soil mass from migrating into the gabion wall. The top two layers of reinforcement would also have to be extended to about 6 feet behind the existing gabion wall, to tie them together. If the gabion wall is removed, the existing roadway embankment can be excavated on a compound slope as noted in Section

6.1.

The following soil parameters are applicable for the MSE wall:

Foundation Soils

• Unit weight ϒ= 125 pcf

• Phi Angle Φ= 34 degrees

Reinforced Soil Mass

Retained Fill

From the cross sections an average slope angle below the wall of 22 degrees was determined, resulting in the bearing resistance shown in Table 3. A resistance factor of 0.65 per AASHTO

Table 11.5.7.1 for MSE walls was used.

Table 3 - MSE Wall Bearing Resistance

Width of Footing

B (ft)

Length of Footing

L (ft)

Depth of Embedment df

Nominal Bearing

Resistance (psf)

Factored Bearing

(psf) 6 100 2 5,337 3,469 8 100 2 7,058 4,588 10 100 2 8,749 5,687 12 100 2 10,412 6,768

Provide a minimum horizontal bench width of 4 feet in front of the wall as required in AASHTO

Section 11.10.7.2. Figure 17 depicts a MSE wall with the existing gabion wall removed. Figure

18 shows a MSE wall constructed in front of the gabion wall. Note the top 2 gabion baskets are removed and the upper 2 layers of reinforcement is extended 6 feet beyond the gabion wall to tie the walls together.

7.1.2 Gabion Wall

From the cross sections an average slope angle below the wall of 22 degrees was determined, resulting in the bearing resistance shown in Table 4. A resistance factor of 0.55 per AASHTO

Table 11.5.7.1 for gabion wall (gravity and semi-gravity walls) was used.

Table 4 - Gabion Wall Bearing Resistance

Width of Footing

B

Length of Footing

L (ft)

Depth of Embedment df

Nominal Bearing

(psf)

Factored Bearing

(psf) 6 100 2 5,337 2,935 9 100 2 6,358 4,349 12 100 2 10,412 5,726

Provide a minimum horizontal bench width of 4 feet in front of the wall as required in AASHTO

Section 11.10.7.2. Figure 19 depicts a gabion wall constructed in front of the existing wall.

7.1.3 Fill Slope

Considering the existing gabion wall if left in place, and the exposed bedrock below the wall, a maximum 1V:1.5H fill slope would be a viable, alternative. This alternative would require removing the upper 2 gabion baskets and two layers of geogrid be placed as shown in Figure

19 to tie the fill into the slope. Positive drainage would have to be provided to outlet any water collected in the gabion baskets. In addition a separator geosynthetic meeting the requirements of FP-14 Table 714-1, Class 1, Type A should be placed between the face of the gabion baskets and the fill material.

7.2 Soil Nail Retaining Wall 135+90 to 138+40

Soil and rock strength properties used in the design of the soil nail walls were estimated from the laboratory classification tests. Table 5, below shows the soil types encountered and parameters used for design.

Table 5 - Soil Properties Material Type Unit Weight

(pcf) ϕ Angle

(degrees) Cohesion

(psf) Bond Stress

(psi) Silty Sand/Sandy Clay and Gravel

125 34 100 8

Bedrock 135 0 5000

The estimated soil properties shown, and the software SNAP (FHWA 2011) were used to develop the soil nail wall design.

7.2.1 Soil Nail Wall Recommendations

The following ASD values are recommended for design of soil nail walls on this project:

• The nominal, minimum long-term bond strength between the native earthen materials and the grout is estimated to be 8 psi. This value assumes gravity or low pressure grouting methods and should be evaluated by the designer and verified in the field by the contractor.

• A factor of safety of 2.0 shall be applied to the nominal bond strength.

• The length and spacing of the soil nails was determined partly from global stability analyses. The lengths of the soil nails are recommended to be 8 feet long for soil slopes 9 feet or less in height. Recommended spacing is 5 foot vertical and 5 foot horizontal. Verification tests shall be performed in the field to confirm the design bond factor of safety.

• Nails should be durable and manufactured with corrosion protection consisting of an epoxy coating, in accordance with AASHTO M-284 or ASTM A-775. Extra corrosion protection is generally applied near the front of the nail with a manufacturer’s grouted polymer sleeve (multiple corrosion protection). The ground nails should be centered in the grouted hole. Grout should fill the drill hole through a tremie tube that extends to the bottom of the hole.

This analysis assumed an 8 inch shotcrete facing, wire mesh, and number 4 bar walers.

7.2.2 Global Stability

Global stability analyses were completed using the software Slide v6.015 by Rocscience for critical cross-sections at locations determined by maximum height of the cut slope, and steepness of back slopes. The factor of safety was estimated using a Simplified Bishop method of slices for the following conditions:

• The existing condition for the slope configuration

• The proposed wall configuration with a pseudo-static seismic force.

The results of the analyses indicate that the proposed wall configurations will provide a global factor of safety of at least 1.3 for the design static case and a minimum factor of safety of 1.1 for the extreme seismic event for slip surfaces extending through and around the retaining walls.

Results of the analyses are provided in Appendix E.

7.2.3 Construction

Excavation of the slopes for the soil nail walls exposed varied materials, including silty and clayey gravels and sands, as wells as cobbles, large boulders and bedrock. Excavation of these materials may create an uneven surface that will require additional work and materials to restore the wall layout to plan.

Some of the soils are granular and may collapse during drilling. Therefore, caving ground conditions should be anticipated and when encountered the ground nail drill holes will need to be inserted into a cased hole

8. BOX CULVERT EXTENSION

Using Load Resistance Factor Design (LRFD) criteria, a nominal bearing capacity can be determined for shallow spread footing foundations placed on existing natural sands, weathered bedrock, flow fill, or properly placed and compacted Select Borrow Backfill using Equation 1.1 based on a minimum footing width of 3 feet:

qn = 6.2 + 1.3(B-2e)………………………………………………………Equation 1.1 where: qn – nominal bearing capacity in ksf

B – footing width in feet e – eccentricity in feet

Bearing capacity resistance factor equal to 0.45 may be used for shallow foundations per

AASHTO Table 10.5.5.2.2-1. The resistance factor shall be applied to the nominal bearing capacity to determine the factored bearing capacity.

Foundations should be constructed on undisturbed natural sand soils or properly compacted granular fill or flow fill. Loose, disturbed soils encountered at foundation level should be removed and replaced with compacted fill or flow fill.

A coefficient of friction of 0.50 may be used for the calculation of sliding resistance when performing an external stability check.

Passive pressure against the sides of the CBC can be used for sliding resistance and can be calculated using an equivalent fluid unit weight of 350 pcf, if granular backfill is used.

All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures resulting from adjacent roadways, traffic, construction materials and equipment.

Select Borrow Backfill meeting the requirements of FP-14 specification 704.07 or flow fill is recommended for backfilling the CBC.

Foundations should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. Foundation excavations should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, supplemental recommendations will be required.

9. PAVEMENT RECOMMENDATIONS

9.1 Subgrade Strength

Two R-values were tested from soils sampled on the project. The samples were from Borings

TH-7 and TH -8. The R-value from TH-7 with an AAASHTO classification of A-7-6(11) was 19 and we believe is representative of the majority of the subgrade soils on the project. The R-value of the soil from Boring TH-8 was 7 and because of the very poor pavement condition and the area's designation as needing subexcavation and deep patching was not considered to be representative of the majority of the project area.

The following equations are from NCHRP Study 128, which was used in the AASHTO 1993

Pavement Design Guide.

S1 = [(R-5)/11.29] + 3 (Eq. 2.1)

MR = 10[S

+ 18.72)/6.24] (Eq. 2.2)

Where: MR = resilient modulus (psi) S1 = the soil support value R = the R-value obtained from the Hveem Stabilometer (AASHTO T190)

Using these equations, an R-value of 19 was used to calculate a resilient modulus of 4,781 psi.

This resilient modulus value was used as one of the inputs for the DARWin Pavement Design computer program to determine recommended pavement thickness. The DARWin pavement design computer program generally follows the AASHTO 1993 Pavement Design Manual.

Other structural layer coefficients used in design were found in the “FHWA CFL Project

Development and Design Manual (PDDM)”, March 2011.

9.2 Traffic Loading

Traffic information for this project was obtained from the Scoping Report and a breakdown by vehicle class provided by the Yuba County. The current and 20-Year Projected Average Daily

Traffic and vehicle classification breakdown was used to calculate the number of 18-kip

Equivalent Daily Loads (ESALs) that the roadway will receive The resulting traffic loading used for pavement thickness design is 1,932,343 ESALs. The calculation of ESALs and the Yuba

County vehicle classification study is presented in Appendix E.

9.3 Recommended Pavement Thickness

Using the strength information based on the soils testing and the strength coefficients from the

PDDM for various treatments, three treatments were evaluated for the widening and reconstruction.

The pavement thicknesses listed in Table 2 show that there is adequate thickness of ACP for this treatment. Table 5 contains the input parameters used for the pavement thickness design.

The parameters were taken from the FHWA Project Development and Design Manual based on the traffic loading and treatments for this pavement.

Table 6 - Pavement Design Parameters

Design Parameter Parameter Value Design Parameter Parameter Value

18-kip ESALs 1,932,343 Initial Serviceability 4.2

Reliability 75% Terminal

Serviceability 2.5

R-value 19 Resilient Modulus MR 4,781

Structural Number 4.17

The outputs from the DARWin Pavement Design Program is presented in Appendix G.

The options presented in Table 7.3.2 are:

1 - Pulverization of the existing pavement followed by a new ACP overlay

2 - Cold Recycling of the existing pavement

3 - Widening with ABC and new ACP overlay

Table 6 presents a summary of the treatments and proposed thicknesses for the pavement treatment options.

Table 7 - Treatments and ACP Thickness

Option No. Treatment ABC Thickness (inches)

ACP Thickness (inches)

Pulverized

Materials and/or

ABC

11 6

2 Cold Recycle (4 in.) Existing (7 in.) 3.5 3 Overlay Existing 3.5

Option 1 - Because this project contains widening of the pavement as well as realignment of the roadway in numerous locations for rock cuts, box culvert extensions and one retaining wall, we believe that the pulverization option is the best choice. Contractor will need to stockpile and move the existing pulverized pavement and existing ABC to address the new alignments.

In addition to pulverization and overlay, we recommend that the entire existing pavement and base be processed to passing the 2 inch sieve and that both the processed pavement and the existing ABC below the old pavement be reused on the project. For the widening, the processed pavement and ABC will need to be supplemented by new aggregate base course to provide sufficient thickness to address the anticipated 20-Year traffic loading.

Option 2 - Cold recycling of the existing pavement to a depth of 4 inches followed by a new 3.5 inch ACP overlay of the existing pavement addresses the thickness requirements for the existing pavement but does not address the widening and realignment sections. The widened sections would need to be constructed with 11 inches of ABC and 6 inches of new ACP and numerous areas would require patching prior to placing new ACP.

Option 3 - Overlay of the existing pavement with a new 3.5 inch ACP overlay will address the thickness requirements for the existing pavement but also does not address the widening, patching and realignment sections. We believe the existing cracks would soon reflect through the new pavement and a longitudinal crack would soon form at the joints between the old pavement and the new widening often develops using this treatment. This option would also require a large amount of patching.

9.4 Binder and Mix Recommendations

Using the Long Term Pavement Performance Binder Selection Program, LTPPBind, the 98% reliability binder for this project location based on the five closest weather stations is PG 64-10.

The Caltrans specification would recommend PG 64-16.

We recommend following the Low Mountain Caltrans recommendations and use PG 64-16 binder for this project because it meets the high temperature properties and exceeds the low temperature properties from the LTPP Program. The Caltrans Binder Selection Guidelines are presented in Appendix G following the pavement design program outputs.

The new ACP overlay should be a nominal l/2-inch or 3/4-inch mix conforming to the requirements in Section 703.7 of FP-14 with the above recommended binder. A mix meeting the requirements of Section 401 is recommended. The quantity of binder can be estimated at

6% by weight of the mix and the unit weight can be estimated at 145 lbs./ft3.

This project is in a relatively remote location and we understand the asphalt plant may be several miles from the construction site. Loss of temperature and segregation of the hot asphalt mix can occur during long distance transport. We recommend the project specifications require the use of a material transfer device at the point of placement to insure uniform temperatures and prevent segregation of the mix during placement. Use of a material transfer device is especially important if the mix is placed in cool weather.

The application of tack coat (at 0.10 gallons/ yd2) is required on the pulverized base material prior to paving. The tack coat material should be CSS-1, CSS-1h, SS-1, or SS-1h. A tack coat at the above rate should be included between each lift of ACP.

Aggregate base course should receive a prime coat of an emulsion blended as a penetrating prime at a rate of 0.33 gallons/yd2.

12. REFERENCES

AASHTO 2012 6th ed. LRFD Bridge Design Specifications, American Association of State Highway and Transportation Officials, Washington, DC.

US Department of Transportation, Federal Highway Administration. Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects (FP-14).

Geologic Map of the Chico Quadrangle, California, Compilation by G.J. Saucedo and D.L.

Wagner, 1992, California Division of Mines and Geology

Appendix A

BORING LOCATIONS

Wade Polygonal Line

Wade Text Box Location 1

Wade Polygonal Line

Wade Text Box Location 2

Wade Text Box Location 3

Wade Polygonal Line

Wade

Location 4

Wade Text Box Location 5

Wade Polygonal Line

Wade

Location 6

Wade Text Box Location 7

Wade Polygonal Line

Wade

Location 8

Appendix B

BORING LOGS

9/9/6

9/28/32

12/50:4"

50:2"

0.0 - 0.5 ft. ASPHALT 7 inches.

0.5 - 1.0 ft. silty SAND BASECOURSE, gray -brown, dry.

1.0 - 5.0 ft. clayey SAND STRUCTURE BACKFILL, reddish brown to gray, dry, medium dense.

5.0 - 16.8 ft. sandy SILT STRUCTURE BACKFILL, reddish brown to gray, auger slowed and rockier at 9.5 ft, increasing gravel with depth.

16.8 - 25.5 ft. DIABASE, gray, fresh, very hard, joint, moderately close to wide, moderate angle, healed fractures, slightly rough surfaces.

25.5 - 30.5 ft. DIABASE, gray, fresh, very hard, joint, moderately close to wide, vertical, healed fractures, slightly rough surfaces.

Bottom of Hole at 30.5 ft.

MC= 9.7 %

#200= 31 %

LL= 34

PL= 18

PI= 16

AASHTO: A-2-6 (0)

USCS: SC

MC= 5.8 %

#200= 40 %

LL= NV

PL= NP

PI= NP

AASHTO: A-4 (0) SM

50:4"

50:2"

Depth Date Time

Total Depth: 30.5 ft Ground Elevation:

Location: EB lane, E. side of box culvert Coordinates: N: E:

Boring Began: 9/2/2014

Drilling Method: Solid-Stem Auger/Wireline Coring

Drill: CME 55, Automatic Hammer

Driller: Taber

Logged By: W. Hoon

Final By: M. Boyd

Inclination: Vertical

Completed: 9/2/2014 Drill Bit:

Casing:

Weather: sunny, hot

Ground Water Notes:

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

R Q

D

R ec ov er y

Blows per 6 in

YEH AND ASSOCIATES, INC.

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

Boring: TH-01 Project Number: 214-113 Date:

Field Notes and

Lab Tests

Sheet 1 of 1

Soil Samples

N

Project: Hammonton-Smartsville

Material Description

Li th ol o gy

B O

R

IN

G L

O G

-1

G

IN

T

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

D T

0/

/1

10/9/9

8/21/12

26/50:4"

0.0 - 0.6 ft. ASPHALT 7 inches.

0.6 - 1.0 ft. silty SAND BASECOURSE, gray -brown.

1.0 - 12.1 ft. sandy CLAY STRUCTURE BACKFILL, reddish brown to gray, medium dense to very dense, increasing gravel with depth.

12.1 - 17.6 ft. DIABASE, gray, fresh to slightly weathered, very hard, joint, close to very close, iron oxide stains, slightly rough surfaces, horizontal to vertical joints, some light clay glazing.

17.6 - 26.9 ft. DIABASE, gray, fresh, very hard, joint, moderately close to wide, minimal veining.

Bottom of Hole at 26.9 ft.

MC= 11.7 %

#200= 60 %

LL= 31

PL= 17

PI= 14

AASHTO: A-6 (6)

USCS: CL

50:4"

Depth Date Time

Total Depth: 26.9 ft Ground Elevation:

Location:

Coordinates: N: E:

Boring Began: 9/2/2014

Drilling Method: Solid-Stem Auger/Wireline Coring

Drill: CME 55, Automatic Hammer

Driller: Taber

Logged By: W. Hoon

Final By: M. Boyd

Inclination: Vertical

Completed: 9/2/2014 Drill Bit:

Casing:

Weather: sunny, hot

Ground Water Notes:

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

R Q

D

R ec ov er y

Blows per 6 in

YEH AND ASSOCIATES, INC.

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

Boring: TH-02 Project Number: 214-113 Date:

Field Notes and

Lab Tests

Sheet 1 of 2

Soil Samples

N

Project: Hammonton-Smartsville

Material Description

Li th ol o gy

B O

R

IN

G L

O G

-1

G

IN

T

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

D T

0/

Rock

GEOTECHNICAL ENGINEERING CONSULTANTS

R Q

D

R ec ov er y

Blows per 6 in

YEH AND ASSOCIATES, INC.

R un

S am pl e T yp e

D ep th (f ee t)

E le va tio n (f ee t)

Boring: TH-02 Project Number: 214-113 Date:

Field Notes and

Lab Tests

Sheet 2 of 2

Soil Samples

N

Project: Hammonton-Smartsville

Material Description

Li th ol o gy

B O

R

IN

G L

O G

-1

G

IN

T

.G P

J Y

E H

A S

S O

C

IA

T E

S .G

D T

0/

6/2/1

4/4/8

11/14/17

0.0 - 0.3 ft. ASPHALT 4 inches.

0.3 - 1.0 ft. silty SAND BASECOURSE, gray, dry.

1.0 - 6.5 ft. clayey SAND to course SAND, reddish…