clayton quarry, clayton, california · evaluation of east pitslope stability and fill slopes....

EVALUATION OF EAST PITSLOPE STABILITY AND FILL SLOPES

Clayton Quarry, Clayton, California

Submitted To: Mr. Pete Cotter & Mr. Ron Wilson Cemex 5180 Golden Foothill Parkway, Suite 200 El Dorado Hills, CA 95762 Submitted By: Golder Associates Inc. 425 Lakeside Drive Sunnyvale, CA 94085 Distribution: Mr. Ron Wilson, Cemex Mr. Pete Cotter, Cemex Ms. Karen Spinardi Golder Associates, Sunnyvale, CA May 2015 Project No. 1520962

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May 2015 i Project No. 1520962

Table of Contents

1.0 INTRODUCTION .............................................................................................................................. 1 1.1 Purpose ........................................................................................................................................ 1 1.2 Scope of Work .............................................................................................................................. 1 1.3 Method of Work ............................................................................................................................ 1 1.4 Available Data .............................................................................................................................. 2

2.0 SITE DESCRIPTION ........................................................................................................................ 3 2.1 Site Topography and Layout ........................................................................................................ 3 2.2 Climatic Conditions ...................................................................................................................... 3 2.3 Geologic Setting ........................................................................................................................... 3

2.3.1 Structural Conditions ................................................................................................................ 4 2.3.2 Groundwater Conditions .......................................................................................................... 4

2.4 Seismicity ..................................................................................................................................... 4 2.5 Quarry Development .................................................................................................................... 5

3.0 SITE RECONNAISSANCE AND SUBSURFACE EXPLORATIONS ............................................... 6 3.1 Site Reconnaissance ................................................................................................................... 6 3.2 Subsurface Explorations .............................................................................................................. 6

4.0 LABORATORY TESTING ................................................................................................................ 8 4.1 2015 Field Program ...................................................................................................................... 8

4.1.1 Point Load Tests ...................................................................................................................... 8 4.1.2 Soil Index Tests........................................................................................................................ 8

4.2 Previous Testing (Golder, 2015) .................................................................................................. 9 4.2.1 Point Load Tests ...................................................................................................................... 9 4.2.2 Soil Index Tests........................................................................................................................ 9 4.2.3 Compaction Test .................................................................................................................... 10 4.2.4 Consolidated Undrained Triaxial Shear Tests ....................................................................... 10

5.0 GEOTECHNICAL CHARACTERIZATION ..................................................................................... 12 5.1 Bedrock Units ............................................................................................................................. 12

5.1.1 Uniaxial Compressive Strength .............................................................................................. 12 5.1.2 Rock Structure ....................................................................................................................... 12

5.1.2.1 Major Structures ................................................................................................................. 13 5.1.2.2 Rock Fabric (Minor Structure) ............................................................................................ 13

5.1.3 Rock Mass Quality (GSI) ....................................................................................................... 14 5.1.4 Jar Slaking Test ..................................................................................................................... 15

5.2 Groundwater Conditions ............................................................................................................ 15 5.3 Controls on Quarry Slope Stability ............................................................................................. 16

5.3.1 Overall Slope .......................................................................................................................... 16 5.3.2 Benches ................................................................................................................................. 16

g:\projects\clayton quarry cemex\1520962 (cemex geotechnical investigation)\final report\clayton quarry report_ east pit slope_final_wlf-5-29-15_r4.docx

May 2015 ii Project No. 1520962

5.3.3 Groundwater .......................................................................................................................... 17 5.3.4 Seismic Slope Stability ........................................................................................................... 17

5.4 Overburden Fill ........................................................................................................................... 17 6.0 ENGINEERING ANALYSES .......................................................................................................... 19

6.1 Overall Bedrock Slope ............................................................................................................... 19 6.1.1 Kinematic Analyses ................................................................................................................ 19 6.1.2 Limit Equilibrium Analyses ..................................................................................................... 19

6.1.2.1 Rock Mass Properties ........................................................................................................ 20 6.1.2.2 Seismic Loading ................................................................................................................. 21 6.1.2.3 Results of Analyses ............................................................................................................ 22

6.2 Limit Equilibrium Analysis of Overburden Fill Slopes................................................................. 23 6.2.1 Overburden and Foundation Strength Parameters ................................................................ 23 6.2.2 Results of Analyses ............................................................................................................... 23

7.0 CONCLUSIONS AND RECOMMENDATIONS.............................................................................. 26 7.1 Conclusions ................................................................................................................................ 26

7.1.1 East Quarry Slopes: ............................................................................................................... 26 7.1.2 Overburden Fill Slopes .......................................................................................................... 26

7.2 Recommendations ..................................................................................................................... 27 7.2.1 East Quarry Slopes ................................................................................................................ 27 7.2.2 Overburden Fill....................................................................................................................... 27

8.0 USE OF THIS REPORT................................................................................................................. 28 9.0 CLOSING ....................................................................................................................................... 29 10.0 REFERENCES ............................................................................................................................... 30

List of Tables Table 1 Proposed Bench Configurations Table 2 Results of Point Load Tests on Core Samples (B-1) Table 3 Results of Soil Index Tests Table 4 Uniaxial Compressive Strength from Point Load Tests (Golder 2015) Table 5 Results of Soil Index Tests on Backfill (Golder 2015) Table 6 Results of Compaction Test (ASTM D-1557 Method B) (Golder 2015) Table 7 Characteristic UCS by Rock Type Table 8 Description of Rock Fabric by Rock Type Table 9 Geologic Strength Index (GSI) by Rock Type Table 10 Rock Mass Properties Table 11 Results of Limit-Equilibrium Slope Stability Analyses for Overall Slope Table 12 Overburden and Foundation Strength Parameters Table 13 Results of Infinite Slope Analyses for Overburden Fills

List of Figures Figure 1 Project Location Figure 2 Site Layout


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Figure 3 Site Geology Figure 4 East Wall (March 2014) Figure 5 Definition of Bench Face Angle, Catch Bench, and Inter-ramp Slope Angle Figure 6 Geologic Strength Index (GSI) Figure 7 Results of Stability Analysis – Case 1 Figure 8 Results of Stability Analysis – Case 2 Figure 9 Results of Stability Analysis – Case 3 Figure 10 Results of Stability Analysis – Case 4 Figure 11 Results of Stability Analysis – Case 5 Figure 12 Results of Stability Analysis – Case 6 Figure 13 Results of Stability Analysis – Case 7

List of Appendices Appendix A Boring Logs for B-1, B-2, and B-3 Appendix B Results of Laboratory Tests Appendix C Results of Previous Laboratory Tests (Golder 2015)


May 2015 1 Project No. 1520962

1.0 INTRODUCTION Golder Associates Inc. (Golder) is pleased to provide this evaluation of pitslope stability and overburden

fill stability for the Clayton Quarry operated by Cemex S.A.B. de C.V (Cemex) and located near Clayton,

California (Figure 1). This report presents the results of field and engineering studies and provides our

conclusions and recommendations regarding the stability of the proposed east quarry slope and the

placement of overburden fills outside the pit limits.

1.1 Purpose The purpose of this study was to assess the long-term overall pit slope stability for the east side of the

Clayton Quarry, and the stability of overburden fills placed outside the pit limits. The location of the

overburden fill has not been finalized, so the recommendations included in this report are general

recommendations to assist in the design of a repository for overburden. It is recommended that Golder

review final fill placement plans once a final location and configuration for the fill has been selected. It is

our understanding that our recommendations will be used by Cemex to develop a mine plan for the quarry

that will, in our opinion, meet Surface Mining and Reclamation Act of 1975 (SMARA) standards for pit

slope and overburden fill stability.

1.2 Scope of Work The Scope of Work for this study was defined in Golder’s proposal, “Proposal for Geotechnical Slope

Investigation, Clayton Quarry, Clayton, California,” Proposal Number P15-20962, dated January 27, 2015.

The scope of work included:

Pre-field Preparation and Records Review to obtain existing information about the site and select drilling locations

Exploratory Borings consisting of:

Two 30-foot deep Hollow Stem Auger (HSA) borings in the existing native slope below the ridge line on the east side of the quarry where overburden will likely be placed

One 100-foot deep corehole along the crest of the ridge defining the east wall of the quarry

Laboratory tests of soil and rock samples obtained from the borings and corehole

A slope stability analyses of overall pit slope of the east side of the quarry

Preparation of this report documenting the results of our investigation

1.3 Method of Work The work was initiated on February 17, 2015 with the start of the field drilling. The subsurface

explorations consisted of two HSA borings and one corehole were drilled by Gregg Drilling of Martinez,

CA under subcontract to Golder. Leah Feigelson, Staff Geologist, logged the soil and core samples



obtained from the borings, collected soil and rock samples, and transported the samples to Golder’s

Sunnyvale office.

Soil samples from the borings were delivered to Cooper Testing Laboratory, Inc. in Palo Alto, California

for soil index tests. Samples of rock core were shipped to Golder’s Reno, Nevada office for point load

tests. After obtaining the results of laboratory testing, we proceeded with our engineering analyses and

preparation of this report.

1.4 Available Data Cemex and their civil engineering and environmental consultant, Spinardi Associates of Piedmont,

California, provided the following data for use in our studies:

Aerial photograph of the quarry dated April 18, 2012 (Figure 2)

Site topography based on 2012 aerial photography (Figure 2)

A mining plan and sections showing preliminary quarry slope configurations

Golder performed a previous study at the Clayton quarry. That study included geologic mapping,

collection of samples for laboratory testing, and laboratory testing, slope stability analyses, and

preparation of the report “Evaluation of Pitslope Stability and Rockfall Hazard for the Clayton Quarry,

Golder Associates, January 2015” (hereafter Golder, 2015). Our previous report focused on the stability of

the west wall of the quarry comprised predominantly of diabase and included an analysis of potential rock

fall hazards. We used portions of the data and results obtained from that study in the engineering

analyses presented in this report.



2.0 SITE DESCRIPTION

2.1 Site Topography and Layout The Clayton Quarry is located approximately 3.5 miles north-northwest of Mount Diablo in central Contra

Costa County, California on the east side of Mount Zion (Figure 1). Mount Zion is approximately 1585 feet

high, with natural slope inclinations of approximately 20 to 35 degrees to the southeast in the area of the

quarry. The area in the vicinity of the quarry is drained by Mitchell Creek, an intermittent stream trending

to the north-northeast, and draining the northwest-slopes of Mount Diablo and the east side of Mount

Zion. The elevation of Mitchell Creek, located about 1800 to 2000 feet east of the quarry, ranges from

approximately 550 to 675 feet.

2.2 Climatic Conditions The climate in the area of the quarry can be characterized by mild, moist winters and hot dry summers.

Data from the Western Regional Climate Center (2014) indicates that mean daily temperatures range

from approximately 40 to 50 degrees Fahrenheit (F) during the winter to 70 to 80 degrees F during the

summer months. Frost can occur during winter months and temperatures as high as 100 to 110 degrees

F can occur during the summer. The mean annual precipitation is approximately 20 inches, and almost all

precipitation falls in the winter. Pampeyan (1963) reports that light snow can occur during the winter on

the mountains to an elevation of about 1000 feet.

2.3 Geologic Setting A detailed description of the geologic setting, lithology, geologic structure, groundwater conditions, and

seismicity of the site are provided by Golder (2015). This report contains a brief summary of these topics

to the extent necessary for the understanding of our engineering analyses and recommendations. A

geologic map showing the location of the quarry is shown in Figure 3.

Cemex excavates rock from diabase dikes from a sheeted dike complex (part of the Mt. Diablo Ophiolite

Complex) which it then crushes and screens to produce construction aggregate. The sheeted dike

complex is bounded to the west and east by the Jurassic Knoxville Formation (part of the Great Valley

Sequence). The Knoxville Formation consists of micaceous shale with intermittent lenses of limestone

and sandstone beds (Pampeyan, 1963). The Great Valley deposits were thought to on-lap the rocks of

the Mt. Diablo Ophiolite complex in this area as a depositional contact, however, the contact may also

have experienced uplift and faulting over geologic time, but the contact is not considered a Holocene-

active fault.

The contact between the Knoxville Formation and the diabase dikes is characterized by altered rock-like

materials derived from both the Knoxville Formation and the diabase. Based on our 2014 site



reconnaissance and mapping (Golder, 2015), it typically consists of a dense, highly fractured dark green

to black aphanitic rock containing slickensides on fracture surfaces.

Quaternary Alluvium occurs in the valley that contains Mitchell Creek east of the quarry (Dibblee, 2006).

In the immediate vicinity of Mitchell Creek this alluvium consists of alluvial gravel, sand and clay.

2.3.1 Structural Conditions The diabase sheeted dike complex mined at Clayton Quarry is within the Mt. Diablo antiform, in the upper

plate of the Coast Range Thrust. The orientations of the dikes have an average dip direction of 310° and

dip of 38°. These orientations are persistent over long distances because similar dike orientations are

reported for the Kaiser Quarry on the west side of Mt. Zion (Figure 3). Pampeyan (1963) writes that joints

in the diabase appear to be randomly oriented and this was confirmed by joint orientation measurements

in the quarry (Golder, 2015). Williams (1984) indicates the contact on the east side of the quarry between

the Knoxville Formation and the sheeted dike complex to be a fault that dips east at about 60 degrees.

Site specific drilling data evaluated by P. Cotter of Cemex (Pers. Comm. 2015) indicate that the contact

dips at approximately 61 degrees in the east wall of the Quarry. Geologic maps by Dibblee (1980) and

Williams (1984) indicate that the dip of the Knoxville Formation strata ranges from moderate (30 to 60

degrees) dips to the east to near vertical.

2.3.2 Groundwater Conditions The Clayton Quarry does not intersect a geologic unit that contains enough groundwater to be considered

a significant aquifer. Water that occurs in the Diabase exposed in the quarry appears likely consists of

surface infiltration that has percolated into discontinuities within the rock mass (i.e., seeps along fractures)

which then daylights in the quarry pitslopes. The current base of the quarry (~ el. 580 amsl) contains a

small pit lake formed from the seepage; however, the generally dry conditions and high rates of

evaporation minimize the accumulation of water in the pit lake.

2.4 Seismicity The Clayton Quarry is located in a seismically active area of California. The following seismic design

parameters were selected based on a probabilistic disaggregation of USGS seismicity data for the site

(Golder, 2015):

Peak Ground Acceleration (PGA) of 0.51g (475 year return period)

Modal design earthquake magnitude (M) of 6.57

Modal distance (r) to the causative fault is 10.2 kilometers

These values of PGA, M, and r were used to estimate the seismic coefficient for use in pseudo-static

slope stability analyses.



2.5 Quarry Development The quarry is approximately 2850 feet long in a north-south direction and 1800 feet wide (Figure 2). As of

April 2012 the elevation of the bottom of the quarry was at an elevation of about 580 feet. The east wall of

the quarry is still being developed, and the crest of the east quarry wall ranges in elevation from

approximately 900 feet to 750 feet. Large portions of the west wall of the quarry are final slopes. As of

April 2012, the overall slope of the east quarry wall was about 20 to 25 degrees (approximately 2.7H:1V

to 2.2H:1V). An aerial photograph of the quarry with an overlay of the topography is shown in Figure 2. A

photograph of the existing east quarry wall is shown in Figure 4.

The diabase is blasted in order to loosen it so it may be excavated with loaders and placed into trucks so

it can be hauled to the plant for processing into construction aggregate. Mined soil and rock that cannot

be processed into construction aggregate (overburden) has been placed along the ridge between the

quarry and Mitchell Creek. We understand that portions of this overburden will likely be removed as part

of mining of the east wall of the quarry and ultimately reclamation.

The Proposed Mining and Reclamation Plans (Spinardi Associates 2015) indicate the bottom of the

quarry will be excavated to an elevation of approximately. 300 amsl. The east quarry slope will be

designed so as to not significantly lower the existing ridgeline below the original ground surface between

the quarry and Mitchell Creek. Cemex proposes to develop the east side of the quarry using the bench

configurations listed in Table 1.

Table 1: Proposed Bench Configurations

Rock Type Bench Face Slope

Bench Height

Catch Bench Width

Design Inter-Ramp Slope

Knoxville Formation (sandstone,

siltstone, claystone)

1H:1V (45 degrees) 60 feet 30 feet 1.5H;1V

(33.7 degrees)

Knoxville/Diabase Contact

(Transition)

Vertical (90 degrees) 60 feet 60 feet 1H:1V

(45 degrees)

Diabase Vertical (90 degrees) 60 feet 30 feet 0.5H:1V

(63.4 degrees) Note: See Figure 5 for definitions of Bench Face Angle, Catch Bench and Inter-ramp Slope

After mining has been completed, the pit will be allowed to fill with water to an approximate elevation of

735 feet to form a pit lake.

An overburden fill (the Permanent Overburden Fill Area) will be constructed outside the limits of the

quarry. The final location has not been selected but areas south and east of the existing quarry are being

evaluated (i.e., the native slope between the quarry and Mitchell Creek).



3.0 SITE RECONNAISSANCE AND SUBSURFACE EXPLORATIONS Golder performed a site reconnaissance in March 2014 (Golder, 2015) and again in February 2015 during

the drilling program. We used site reconnaissance data to supplement that data collected from the three

borings performed as part of this study.

3.1 Site Reconnaissance During the site visit in March 2014 and the recent drilling campaign in February 2015, no tension cracks

or features indicating instability of overall slope on the east side of the pit were observed. Review of aerial

photographs (Figure 2) and visual observation of slopes (Figure 4) does not indicate the presence of

tension cracks or other features that would indicate that from a global perspective (i.e., crest to toe) the

existing east quarry slope is unstable.

3.2 Subsurface Explorations The subsurface explorations consisted of one corehole (B-1) and two hollow stem auger (HSA) borings

(B-2 and B-3) at the locations shown in Figure 2. Corehole B-1 was drilled to obtain information about the

rock conditions below the overburden located at the top ridgeline between Mitchell Creek and the quarry.

Boring B-2 and Boring B-3 were drilled approximately 700 feet southeast of the east ridge of the quarry in

native ground to obtain information about foundation conditions for the potential overburden fill.

Both the corehole and the HSA Borings were drilled using a truck mounted Mobile B-53 drill rig. Upon

completion of the drilling, each boring was grouted with a mixture consisting of water, cement, and

bentonite. Drilling operations were observed by Leah Feigelson of Golder, and she also logged the

borings and collected soil and rock samples from the corehole and each of the borings.

The corehole (B-1) was advanced by mud rotary methods equipped with a five-foot long, HQ core barrel.

The core barrels was advanced with a series of maximum 5-foot long runs and the core barrel was then

extracted from the corehole, unscrewed from the drill rods and emptied into cardboard core boxes.

Drillers marked the ends of the core run with the drill footage marked on wooden boxes

The corehole log for B-1 is presented in Appendix A along with a description of Golder’s rock core logging

procedure and Bieniawski’s Rock Mass Rating (RMR76) system. Information recorded for the core

included Total Core Recovery (TCR), Rock Quality Designation (RQD), fracture frequency (calculated as

the natural fracture count divided by the core run length), field estimate of the Uniaxial Compressive

Strength (UCS), and degree of weathering. Information collected on individual natural fractures in the core

consisted of the fracture type (bedding plane, joint, etc.) shape, roughness, infill type and thickness, angle

to core axis, joint roughness coefficient (JRC) and Joint Condition Rating (JCR). The JRC is a measure of

fracture roughness (Barton and Chouby, 1977), and the JCR is description of the mechanical properties



of the fracture and is used in making estimate of Bieniawski’s (Bieniawski, 1976) Rock Mass Rating

(RMR).

Borings B-2 and B-3 were drilled use HSA drilling methods. Both boring were advanced to 31.5 feet below

the existing ground surface (bgs). Driven samples were retrieved from the borings at 5-foot intervals using

a Modified California (MC) steel tube-lined split spoon sampler (3 inch O.D. and 2½ inch I.D.) at depths of

5, 15 and 25 feet below ground surface (bgs) in both holes; and a Standard Penetration Test (SPT) split

spoon sampler (2 inch O.D. and 1⅜ inch I.D.) was used to obtain samples at depths of 10, 20 and 30 feet

(bgs). The samplers were driven 18 inches (unless otherwise noted) into the bottom of the boring using a

140-pound automatic hammer with a 30-inch drop. Hammer blows were recorded in 6-inch intervals for

each sample and are presented on the borings logs. The penetration resistance (N-value) of the soil is

calculated as the sum of the number of hammer blows required to drive the sampler the final 12 inches.

The N-value is an indication of the apparent density of cohesionless soils and the consistency of cohesive

soils. Generally, if a total of 50 blows were recorded for a single 6-inch interval, the test was terminated

and the blow count was recorded as 50 blows for the inches of penetration observed. All blow counts

presented on the boring logs are uncorrected values and do not take into consideration the efficiency of

the automatic hammer, overburden, or other influences.

HSA Boring logs for B-2 and B-3 are presented in Appendix A. The soils were classified according to the

Unified Soil Classification System (USCS) (ASTM D2488). Soil samples collected from the borings were

stored in plastic bags and sealed to minimize moisture loss, then transported to Golder’s Sunnyvale,

California office upon completion of the field investigation.



4.0 LABORATORY TESTING Laboratory testing was performed on the samples of soil and rock obtained from the HSA borings and the

corehole. Results of these tests performed as part of this study area are included in Appendix B. The

testing performed as part of our previous studies (Golder, 2015) were also utilized in this study, and are

detailed in Section 4.2.

4.1 2015 Field Program

4.1.1 Point Load Tests The Point Load Strength Index was measured by performing point load tests (ASTM, 2006) on two

samples of siltstone (Knoxville Formation) from the corehole to verify UCS values assigned to rock units

in the field. The Point Load Strength Index is correlated to the uniaxial compressive strength (UCS) of

intact rock by multiplying the Point Load Strength Index by a factor, N. For this project, N was assumed to

equal 24. Test results are summarized in Table 2.

Table 2: Results of Point Load Tests on Core Samples (B-1)

Depth (feet) Rock Type Point Load Strength (psi)

Estimated Uniaxial Compressive Strength

(psi) 45.8 siltstone 61 1474

65.9 siltstone 326 7817

4.1.2 Soil Index Tests Soil index tests (particle size distribution and Atterberg Limits) were performed by Cooper Laboratories, of

Palo Alto, California on samples of soil obtained from the corehole (B-1) and the HSA borings (B-2 and B-

3). Results of these tests are summarized in Table 3.

Table 3: Results of Soil Index Tests

Boring Depth (feet)

Water Content (percent)

Dry Density3,4

(pcf)

Atterberg Limits2

USCS1 Material Description LL PL PI

B-1 91.4-92 10.6 NR 25 18 7 SC-SM Very Dark Gray Silty, Clayey SAND

B-2 5.5-6 13.0 119.9 36 18 18 SC Dark Yellowish Brown Lean Clayey SAND w/Gravel

B-2 10-11.5 15.9 NR 41 20 21 CL Dark Yellowish Brown Sandy Lean CLAY

B-3 5.5-6 31.4 106.0 51 22 29 CH Dark Yellowish Brown

Sandy Fat CLAY/Fat Clayey SAND w/Gravel



B-3 10.5-11.5 18.5 123.9 39 24 15 CL Lean Clayey Gravel with Sand

Notes: 1. USCS = Unified Soil Classification System, USCS of fines based on Atterberg Limits and Material Description 2. LL= Liquid Limit, PL=Plastic Limit, PI = Plasticity Index

3. NR = Not Reported 4. Assumed Gs = 2.7 for determination of Dry Density

4.2 Previous Testing (Golder, 2015) In March 2013, samples of rock and backfill were collected by Golder personnel during a site visit to

Clayton Quarry. Backfill samples were analyzed by Cooper Testing Laboratory, Inc. in Palo Alto,

California for soil index, compaction, and triaxial shear strength tests. Rock samples were subjected to

Point Load Index Testing by Golder personnel. Material properties were estimated from the test results

and used in the engineering analyses presented in this report.

The samples were obtained from the existing fill placed on the ridge on the east side of the quarry and in

the general vicinity of corehole B-1. Results of this previous laboratory testing are in Appendix C.

4.2.1 Point Load Tests The Point Load Strength Index was measured by performing point load tests (ASTM, 2006) on samples of

diabase, siltstone (Knoxville Formation) and rock-like material from the contact between these two units.

The Point Load Strength Index is correlated to the uniaxial compressive strength (UCS) of intact rock. The

UCS was estimated for each rock type tested by multiplying the Point Load Strength Index by a factor, N.

For this project, N was assumed to equal 24, a value that is appropriate for many rock types. Test results

are summarized in Table 4.

Table 4: Uniaxial Compressive Strength from Point Load Tests (Golder 2015)

Rock Type Number of Tests

Estimated Unconfined Compressive Strength (psi)

Minimum Average1,2 Maximum Standard Deviation

Weathered Diabase 3 2300 5230 5580 N/A

Slightly Weathered to Fresh Diabase 25 1661 18270 39400 10330

Siltstone (Knoxville Fm.) 8 3310 5330 7340 1540

Diabase / Knoxville Contact 23 3165 7400 11870 2720

Notes: 1. The two highest and lowest test results are deleted from the data set for sample sizes greater than 10. 2. The highest and lowest test results are deleted from data set for sample sizes less than 10.

4.2.2 Soil Index Tests Soil index tests (particle size distribution and Atterberg Limits) were performed on two samples of backfill

material obtained during the site visit. One sample was obtained from the base of the overburden pile


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located near the southern rim of the quarry pit (Golder 2015) and may contain a larger portion of near

surface weathered rocks from the Knoxville Formation than typical backfill. The second sample consisted

of material obtained approximately 200 feet east near the crest ridgeline (Golder 2015). These samples

are considered more representative of typical overburden material and were combined for testing. The

results of these tests are summarized in Table 5.

Table 5: Results of Soil Index Tests on Backfill (Golder 2015)

Sample Type Depth Atterberg Limits USCS

Symbol Soil Description LL PL PI

x19 Bucket Surface 38 26 12 SC Lean Clayey Sand with Gravel

x20 and x21 Bucket Surface 26 17 9 GC Lean Clayey Gravel with Sand Notes: USCS = Unified Soil Classification System LL= Liquid Limit, PL=Plastic Limit, PI = Plasticity Index These test results indicate that the backfill consists of Lean Clayey Sand with Gravel (SC) and Lean

Clayey Gravel with Sand (GC). The fines fraction classify as clay of low plasticity.

4.2.3 Compaction Test The relationship between moisture content and the dry unit weight of compacted backfill was obtained by

performing a Modified Proctor Compaction Test (ASTM D-1557 Standard Method for Laboratory

Compaction of Soil Using Modified Effort) on the sample collected from locations x20 and x21. Since the

purpose of this test was to provide information for selecting unit weights for the triaxial shear test

specimens, only the material passing the ½-inch sieve was utilized in the compaction test. The results of

the compaction tests are shown in Table 6:

Table 6: Results of Compaction Test (ASTM D-1557 Method B) (Golder 2015)

Test Results Maximum Dry Density

(pcf) Optimum Water Content

(percent)

Uncorrected 140.7 8.5 Corrected for Oversize 142.2 8.1 Notes: pcf = pounds per cubic foot

4.2.4 Consolidated Undrained Triaxial Shear Tests Consolidated, undrained triaxial tests with pore pressure measurements (CU/pp) were performed on

samples of backfill to provide shear strength properties. Similar to the compaction test, only material

passing the ½-inch sieve was used to prepare test specimens. The three triaxial shear test specimens

each had an approximate dry density of 121 pounds per cubic foot (pcf) and moisture content of

approximately six percent. This density is approximately 85 percent of the maximum dry density of the soil

obtained in the compaction test, and approximates the density of the backfill when placed with little or no


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compaction. The results of the tests indicate that the effective friction angle of the backfill is approximately

39 degrees with zero cohesion.


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5.0 GEOTECHNICAL CHARACTERIZATION For this study, we defined soil and rock mass units, termed geotechnical units, based on their physical

and structural characteristics. Geotechnical units can be comprised of individual geologic units, or

combinations of geologic units that can be grouped together because they have similar engineering

properties. Alternatively, geotechnical units may be subdivisions of geologic units if mechanical and

structural characteristics within the units are different. The available published data, data we collected

during our site reconnaissance, and the laboratory testing results were used to define geotechnical units.

5.1 Bedrock Units The quarry rock mass on the east side of the quarry was divided into three geotechnical units, Knoxville

Formation (siltstone, sandstone, and claystone), Knoxville/Diabase contact material (Transition), and

Diabase.

5.1.1 Uniaxial Compressive Strength The UCS of the intact rock is required to estimate the rock mass shear strength properties. We estimate

the UCS for the Knoxville/Diabase contact material and Diabase from point load tests on hand specimens

performed as part of our previous study (Table 4).

The point load tests performed on core and hand specimens of Knoxville Formation may overestimate the

intact rock strength of this unit since suitable samples for point load testing can be difficult to obtain in

highly altered and weathered rock units; therefore, we assigned the UCS of the Knoxville Formation

based on weighted average of the field estimate of the UCS of intact rock made during core logging

(approximately 3000 psi) and shown in the log for the corehole (B-1) in Appendix B. We assigned

characteristic UCS values to the various rock types for use in our engineering analyses as shown in Table

7.

Table 7: Characteristic UCS by Rock Type

Rock Type Average Uniaxial Compressive Strength (psi)

Slightly Weathered to Fresh Diabase 18300

Knoxville/Diabase Contact 7400

Siltstone (Knoxville Fm.) 3000

5.1.2 Rock Structure Geologic structures pertinent to quarry wall slope stability studies are divided into major and minor

structures (rock fabric).


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Major structures consist of persistent individual geologic structures such as contacts between rock types,

faults, and other structures that extend over many benches or the entire quarry wall. Typically, these

structures can be mapped and shown as individual structures on large-scale geologic maps or quarry

geology maps. For slope stability studies, the effect of each major structure is assessed individually by

considering its location and orientation in the pit slope and evaluating if the major structures individually or

in combination intersect the pit slopes in a manner that may result in slope instability.

Rock fabric consists of those small-scale geologic structures such as joints, bedding planes, and small-

scale faults that form discontinuities that pervade the rock mass and are so numerous and with such

limited persistence that they cannot be shown on maps as individual structures. Their effect on slope

stability is assessed by considering their average orientation, persistence (trace length of the structure in

rock exposures), and spacing, and assuming that similarly oriented structures will be found throughout the

geotechnical unit.

5.1.2.1 Major Structures There are no other major structures of note in the quarry other than the east-dipping contact (shown as a

fault contact on Williams’ map [1984]) between the Knoxville Formation and the Diabase.

5.1.2.2 Rock Fabric (Minor Structure) During our site visit in 2014 (Golder, 2015) we observed and collected rock discontinuity data on the east

quarry slope from benches excavated in the Diabase and Knoxville/Diabase contact. A description of the

rock fabric of the Knoxville Formation was based on the discontinuity descriptions contained in the core

log provided in Appendix A. The descriptions of rock fabric are provided in Table 8.

Table 8: Description of Rock Fabric by Rock Type

Rock Type Discontinuity Set Description

Knoxville Formation

Primary

Type: Bedding Planes Orientation: Dip is vertical to 40 degrees east Persistence: High (> 30 feet) to Continuous Spacing: Very Close (< 6 inches) Surface Condition: Planar, Smooth

Secondary

Type: Joints Orientation: Orthogonal to Bedding Planes Persistence: Very Low (< 3 feet) Spacing: Close (< 6 inches) Surface Condition: Planar, Smooth


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Knoxville/Diabase Contact

Primary

Type: Joints and Shears Orientation: Random Persistence: Very Low to Low (< 3 feet to 10 feet) Spacing: Very Close (< 6 inches) Surface Condition: very irregular to undulating, smooth to slickensided surfaces with non-softening infillings. Note: Contact material consists of a sheared irregular mass of moderately strong angular rock blocks.

Secondary None

Diabase

Primary

Type: Dike Contacts Orientation: Dip is 40 to 60 degrees to northwest Persistence: High to Very High (10 to > 60 feet) Spacing: Wide to Very Wide (6 inches to < 6 feet) Surface Condition: Planar to Undulating, tight, rough, no to non-softening clay and silt infilling

Secondary

Type: Joints/Shears Orientation: Random Persistence: Low to Medium (< 3 to 10 feet) Spacing: Close to Wide (few inches to 3 feet) Surface Condition: smooth to rough, undulating to planar

5.1.3 Rock Mass Quality (GSI) Rock mass quality is an indication of the condition of the rock that accounts for the intact strength of the

rock, and the persistence, spacing, and condition of the natural fractures in the rock mass. It is used to

estimate rock mass shear strength properties used in slope stability analyses. For this project and the

previous study (Golder, 2015), we estimated the rock mass quality by estimating the Geologic Strength

Index (GSI) according to the guidelines provided by Hoek et al. (1992) and shown in Figure 6.

The Diabase consists of a Very Blocky to Blocky rock mass. The individual rock blocks are interlocked

and formed by three or more intersecting discontinuities that are pervasive throughout the rock mass.

The rock mass is typically fresh to slightly weathered with rough discontinuities, so the discontinuity

surface condition is classified as Very Good to Good.

The Knoxville/Diabase contact material consists of a highly fractured rock mass with angular individual

rock blocks formed by sheared contacts and numerous randomly oriented joints. Based on Figure 6, it

would be classified as a Blocky/Disturbed/Seamy rock mass with Poor to Very Poor conditions for

discontinuities.

Since there are no fresh outcrops of the Knoxville Formation in the Clayton Quarry, we estimated the rock

mass quality based on the Rock Mass Rating (RMR76) for the corehole (boring B-1). The weighted

average of the RMR76 assigned to each core run is 30 based on the log for B-1 provided in Appendix A.

Hoek, et al. (1993), indicates that GSI = RMR76 when RMR76 > 18. Since the value of RMR76 might be


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influenced by core intervals with high RMR, and we only had a short (50 foot interval of core) in the

Knoxville Formation, we conservatively estimated that the GSI = RMR76 = 20 for estimating rock mass

shear strength properties.

We assigned values of GSI to the rock mass as shown in Table 9.

Table 9: Geologic Strength Index (GSI) by Rock Type

Rock Type Structure Discontinuity

Surface Conditions

Geologic Strength Index (GSI)

Diabase Very Blocky Very Good to Good 55

Diabase/Knoxville Contact Blocky/Disturbed/Seamy Poor to Very Poor 20

Knoxville Formation Blocky/Disturbed/Seamy Poor to Very Poor 20

5.1.4 Jar Slaking Test Golder performed two jar slake index tests on samples of Knoxville siltstone. The test was performed in

general accordance with the Jar Slake Test method by Caltrans (2007). The two samples were placed in

a water filled jar and observed continuously for the first 10 minutes, at 30 minutes, and then a final

observation after 24 hours. There were no signs of slaking observed during the duration of the test. The

samples stayed intact and did not appear to develop any fractures or break. Both Knoxville samples were

given a jar slake index value (Ij) of 6; the highest value possible, describing, “no change to condition of the

rock fragment” (Caltrans, 2007).

5.2 Groundwater Conditions The Clayton Quarry does not appear to intersect a geologic unit that is likely to be a significant aquifer.

Water that occurs in the Diabase exposed in the quarry appears to consist of water that is contained in

discontinuities within the rock mass (i.e., seeps along fractures).

The quarry is unlikely to encounter significant groundwater or intersect a regional aquifer during mining. In

our opinion, it is unlikely that Mitchell Creek will contribute to groundwater flows into the quarry because:

The relative elevations and distance between the quarry and the creek are significant

The quarry is in a different geologic unit than that under Mitchell Creek

No known faults and structures appear to form a hydraulic connection between the creek and the quarry

Based on information provided by Cemex, and for the purposes of our slope stability analyses presented

in this report, it was assumed the gradient and position of the future water table in the pit walls (post


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reclamation) would be defined by the elevation of the pit lake (735 feet) which will be controlled by the

elevation of the outlet from the quarry at its north end.

5.3 Controls on Quarry Slope Stability

5.3.1 Overall Slope The stability of the overall slope (quarry slope crest to toe) in rock masses can be controlled by the

persistence and orientation of large-scale geologic structures (geologic contacts and faults), and also

persistent bedding planes in sedimentary rocks. Structurally-controlled failures are evaluated by

performing a kinematic analysis that takes into consideration the orientations of the slope and controlling

structures. Overall slope stability is also controlled by the shear strength of the rock mass. While shear

through the rock mass is unlikely in strong, brittle rocks such as the Diabase, slopes composed of highly

fractured rock like the Knoxville are more liable to become unstable due to shear through the rock mass.

The level of stability of a rock slope can be quantified by performing a limiting equilibrium slope stability

analyses.

5.3.2 Benches Benches are left in quarry slopes as a rockfall control measure. Catch benches (Figure 5) will be left in

the slope to retain rockfall and small bench-scale failures. Leaving benches in the slope does not improve

or decrease overall global slope stability.

The steepness of bench faces excavated in rock is controlled by both the mining method and the

persistence and orientation of geologic structures that might form plane shear and wedge type bench-

scale failures. In strong, brittle rock such as the Diabase, near vertical bench faces have been formed in

the quarry by pre-splitting, a controlled blasting method. Where dike contacts dip out of the bench face,

bench-scale plane shear failures may form and a few of these have formed in the existing east wall of the

quarry. The size of these plane shear failures is limited by the persistence of the dike contacts, typically

less than 30 feet in length. Where they have occurred, they have been removed during mining and bench

scaling operations.

There are few benches in the Diabase/Knoxville contact material in the existing quarry, but as indicated in

Table 8, discontinuity orientations vulnerable to bench-scale plane shear and/or wedge failures do not

appear to be present. Bedding planes in the Knoxville Formation dip either near vertical or to the east –

orientations favorable for bench slope stability in the east wall of the quarry.

The steepness of bench faces in the highly fractured Knoxville Formation and the Diabase/Knoxville

contact is likely to depend on mining method, and may vary locally depending on the degree of fracturing

of the rock mass. The bench faces in the Knoxville Formation may be formed by mechanical excavation

such as ripping and trimming with a dozer or digging with an excavator.


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5.3.3 Groundwater Groundwater would not appear to be a control on overall slope stability of the ridge on the east side of the

quarry as the ground surface is sloped to promote runoff and the recharge area is small, so infiltration of

surface water into fractures in the rock mass is not likely to be a source of significant groundwater in final

quarry slopes. Therefore, the rock mass can be assumed to be “dry” for the purposes of the slope stability

analyses. As previously discussed, we have conservatively assumed that the future position of the water

table would be defined by the elevation of a pit lake in the quarry at a final elevation of 735 feet.

5.3.4 Seismic Slope Stability Clayton quarry is located in a seismically active area of California. Keefer (1984) summarized the

geologic environments likely to produce earthquake-induced landslides and his findings were included in

California Geological Survey, Special Publication 117 (2008). Keefer’s study was based on analysis of 40

earthquakes and found that different types of landslides occur with different frequencies.

Keefer (1984) indicates large, deep-seated rock slumps, rock block slides, and rock avalanches are less

common. Large rock block slides require a conspicuous, persistent plane of weakness such as a bedding

plane, fault, or geologic contact dipping out of the slope. Such large-scale structures do not appear to be

present in the east slope of the Clayton Quarry. Rock slides triggered by earthquakes occur most

frequently in slopes composed of weakly cemented, intensely fractured, or weathered rock containing

conspicuous planes of weakness when the slopes are steeper than 35 degrees. Rock avalanches

typically occur in high (typically greater than 500 feet) slopes steeper than 25 degrees composed of

intensely fractured rock with either planes of weakness dipping out of the slope or weak cementation or

signs of previous sliding.

While portions of the east quarry slope will be composed of highly fractured rock, the quarry slope is not

particularly steep or high nor will it contain planes of weakness dipping out of the slope and so do not

correspond to the conditions Keefer indicates are likely to produce large-scale, earthquake-induced

landslides. As part of our engineering analyses we performed limiting equilibrium analyses using the

pseudo-static method to assess the level of stability under seismic loading conditions.

Keefer (1984) noted that small rock falls (falls of boulders or small disrupted masses of rock) and rock

slides (masses of rock fragments that slide on discontinuities dipping out of the rock) are relatively

common. At the Clayton Quarry, small rock falls from bench faces and slides of rock blocks, if they occur

during an earthquake would likely be retained on catch benches left in the slope.

5.4 Overburden Fill Based on laboratory testing performed as part of previous studies (Golder, 2015), the overburden material

consists of clayey gravel to clayey sand that the triaxial shear tests indicate will behave as a cohesionless


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material when it is not compacted (Appendix B). While this material contains about 15 percent fines,

based on our experience it will likely drain and not build up high pore pressures when placed in the

permanent overburden fill area with minimal compaction.


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6.0 ENGINEERING ANALYSES We performed a screening level kinematic analyses to evaluate the potential for overall slope instability to

develop due to a large geologic structure intersecting the east quarry slope. Limiting equilibrium analyses

were used to evaluate the stability of the proposed west facing quarry slope and the overburden fill

slopes.

6.1 Overall Bedrock Slope

6.1.1 Kinematic Analyses The stability of slopes in competent rock can be controlled by structures, or combinations of structures

that define kinematically admissible failure modes. A failure formed by discontinuities in the rock mass

results when the shear strength of the discontinuities is sufficiently low to allow sliding of an intact rock

block along one or more discontinuities, typically in planar, wedge, or a combination of these modes.

Each of these modes is described as follows:

Planar failure can occur where individual discontinuities dip towards the slope face and daylight such that the overlying rock block can displace.

Wedge failures can occur where two planar structures intersect to form a rock wedge and the line of intersection between the two structures dips toward and daylights in the slope.

Toppling failures can occur where there are persistent, closely spaced discontinuities that dip at a high angle into the slope so as to form slabs and blocks of rock that can overturn or topple from the slope. Toppling may occur from steep bench faces, but typically does not form a failure mechanism for an overall slope.

The only major structure on the east side of the quarry with sufficient persistence to impact overall quarry

slope stability is the contact between the diabase and the Knoxville Formation. This contact dips to the

east into the overall slope of the quarry at about 60 degrees, and thus does not form a kinematically

admissible failure. That is, the contact is not in an orientation that would allow sliding to occur. Similarly

the existing geologic data appears to indicate that the bedding planes in the Knoxville Formation are

either near vertical or dip into the quarry slope and are likewise not in an orientation upon which sliding

can occur.

6.1.2 Limit Equilibrium Analyses The weight of the soil and rock in pit slopes creates shear stresses within slopes. Pore pressures in the

slope from groundwater (if present) reduce the available effective shear strength of the rock mass. If the

shear stresses are greater than the available effective shear strength over large zones within the slope,

the pit slope will become unstable. Such failure mechanisms are evaluated by performing limiting

equilibrium analyses along surfaces that pass through the rock mass and mobilize the rock mass shear

strength.


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For this study, the level of stability of the high bedrock slopes was quantified by performing limiting

equilibrium slope stability analyses using Spencer’s Method of Slices (Spencer, 1967) as implemented in

the computer program Slide 6.0 (Rocscience, 2010). Spencer’s method is an “accurate” method that

satisfies both horizontal and vertical force and moment equilibrium. It provides calculated factors-of-

safety (FOS) that are comparable to values calculated by other “accurate” methods. Algorithms

programmed within Slide generate trial slope surfaces and identify the surface with the lowest FOS

(critical surface). This minimum FOS of all of the trial surfaces provides an indication of the level of

stability of the slope. For static loading, the minimum acceptable factor of safety is typically between 1.2

and 1.3 for slopes with a low consequence of failure (Duncan and Wright, 2004; Read and Stacey, 2009).

6.1.2.1 Rock Mass Properties The practical limitations for shear strength testing of the rock mass in the laboratory (samples are too

small to be representative) requires that empirical methods be used to estimate rock mass shear strength

such as occurs on the east side of the Clayton Quarry. For this study, as in the previous study (Golder,

2015), we estimated the rock mass shear strength based on an empirical method initially developed by

Hoek and Brown (1980) and subsequently modified (Hoek. et al., 2002). This is the most widely used

method of estimating rock mass shear strength for rock slope stability.

The Hoek-Brown failure criteria defines the strength of a rock mass as a function of the parameters: mb,

s, and a. These are in turn defined by the following properties:

Uniaxial Compressive Strength (UCS) of the intact rock (Table 7)

Geologic Strength Index (GSI) of the rock mass (Table 9)

A material constant, mi, of the intact rock

A disturbance factor, D, that accounts for loosening of the rock mass due to blast damage or stress relief

Values of mi were selected based on typical values (Hoek and Karzulovic, 2000). For the Knoxville

Formation, we assumed a, an average value for sedimentary rocks consisting of sandstone, siltstone and

claystone. We also used a mi of 7 for the Knoxville/Diabase contact as it appears to consist of fine-

grained material likely derived from the Knoxville Formation.

The disturbance factor, D, was selected based on guidelines developed by Hoek (2012). D can range

from 0 to 1.0 with lower values indicating lesser degrees of disturbance due to stress relief and blast

damage. A disturbance factor, D, of 0 was selected for use in our analysis for the portion of the rock mass

located deep in the slope as Hoek indicates blast damage typically does not occur more than a bench

height into the slope and may be less where controlled blasting methods and mechanical excavation are

used to form bench faces.


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A summary of the values of UCS, RMR76, mi, and D used in the Hoek-Brown Failure Criterion formulas to

obtain the Hoek-Brown rock mass shear strength parameters, mb, s, and a, used in our analyses is

provided in Table 10.

Table 10: Rock Mass Properties

Geotechnical Unit Unit

Weight (pcf)

Hoek-Brown Failure Criterion

UCS (psi) GSI mi D mb s a

Knoxville Formation 140 3000 20 7 0 0.40203 0.000138 0.5437

Knoxville/Diabase Contact 150 7400 20 7 0 0.40203 0.000138 0.5437

Diabase 175 18300 55 15 0 3.007 0.006738 0.5040

Analyses were performed assuming the slope is not saturated, and therefore there are negligible pore

pressure effects. We also evaluated the overall slope stability assuming a pit lake forms with a surface

water elevation of 735 feet as part of the revised reclamation plan currently under consideration.

We selected Section A-A’ (shown in Figure 2) to analyze the highest and steepest slope in the quarry

where the contact between the Knoxville and the Diabase will be exposed. The location of geotechnical

units corresponding with Table 10 are shown in Figures 7 through 13.

We searched for the most critical shear surfaces in the overall slope configuration from the uppermost

bench in the Knoxville and passing through both the contact zone and the Diabase. We limited our

search to failures that would pass below individual benches, as bench failures would most likely consist of

sliding of rock blocks as discussed in Section 5.3.2 and would be either be removed during mining as part

of normal operations or retained on catch benches left in the slope.

6.1.2.2 Seismic Loading For this study, we evaluated the effect of seismic loading on the rock slopes by performing a pseudo-

static analysis. A pseudo-static analysis is a type of limit-equilibrium analysis used to assess the level of

stability of a slope subjected to ground accelerations likely to be experienced at the site during an

earthquake. In a pseudo-static analysis, the effect of the earthquake on the stability of the slope is

represented by a constant horizontal acceleration that, when multiplied by the weight of the failure mass,

produces a lateral de-stabilizing force that acts through the centroid of the slide mass. The horizontal

acceleration (expressed as a percentage of gravity, 32.2 ft/s2) that produces this lateral force is

represented by a parameter called the seismic coefficient (k). For limit-equilibrium SLIDE analyses, this


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additional force is incorporated into the equilibrium equations of the slice method and the FOS is

calculated.

The value of the seismic coefficient (k) used in this analysis is selected to reflect the anticipated level of

earthquake shaking at the site, or more specifically the accelerations acting on the potential failure mass.

The seismic coefficient used in slope stability analyses is assumed to be less than the PGA predicted for

the site because, during earthquake shaking, a time-variant spatial distribution of accelerations exists

within the slope and not all points in the slope move simultaneously with the same intensity. The seismic

coefficient, k, is selected based on expected soil behavior and seismicity of the site as represented by the

values of PGA, M and r as determined during our previous study (Golder, 2015) and consistent with

recommendations for performing pseudo-static analyses by Blake et al. (2002). Because the diabase rock

mass is considered a strain-softening material (i.e., because the post-peak strength is low relative to the

peak strength), a value of k equal to 0.21 was used in our pseudo-static analyses. A pseudo-static FOS

greater than 1.0 assuming k = 0.21 indicates the performance of the slope will be acceptable under

seismic loading.

6.1.2.3 Results of Analyses We performed the analyses over a range of pit depths and also restricted the search for the critical shear

surface (shear surface with the lowest FOS) to selected geotechnical units. For the overall slope

including at the end of mining and after reclamation is completed, the results of the slope stability

analyses are shown in Table 11.

Table 11: Results of Limit-Equilibrium Slope Stability Analyses for Overall Slope

Critical Failure Surface Case No. Figure No. Water Condition

Factor-of-Safety (FOS)

Static k= 0

Pseudostatic k=0.21

Overall Slope (toe to crest) (pit bottom at 300 feet)

1 7 No Pit Lake 2.51 1.88 2 8 Pit Lake 2.70 1.74

Toe of surface in Diabase 3 9 No Pit Lake 2.34 1.69 4 10 Pit Lake 2.38 1.60

Toe of surface in Knoxville/ Diabase Contact

5 11 No Pit Lake 2.02 1.41 6 12 Pit Lake 2.00 1.31

Toe of surface in Knoxville Formation 7 13 No Pit Lake 2.36 1.65

The critical shear surfaces for each of the analyses listed in Table 11 are provided in Figures 7 through

13. The critical shear surface is not the shear surface over the full height of the slope due to the high

strength diabase unit in the toe of the slope. The lowest factor of safety of 1.31 was obtained from the

shear surface shown in Figure 11 that passes through the Knoxville/Diabase contact.


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The results of these analyses indicate acceptable factors-of-safety are achieved for both static and

seismic loading for the overall slope and therefore the proposed slopes meet the requirements of

SMARA.

6.2 Limit Equilibrium Analysis of Overburden Fill Slopes

6.2.1 Overburden and Foundation Strength Parameters Table 12 summarizes the estimated strength parameters for the geotechnical materials of the overburden

fill and the soil-like foundation materials below the fill.

Table 12: Overburden and Foundation Strength Parameters

Strength Parameters

Overburden Fill Area Mohr-Coulomb

Geotechnical Unit Unit

Weight (pcf)

Effective Friction

Angle (φ') (˚)

Cohesion (c) (psi)

Overburden 130 39 0

Overburden/Kk (weathered) Contact 125 25 0

Kk (highly weathered) 125 25 3.5

Kk (moderately weathered) 140 25 20.8

6.2.2 Results of Analyses As part of our slope stability evaluation, we performed an infinite slope analyses to assist us in selecting

an appropriate slope for design of the overburden fill. In an infinite slope analysis, the potential sliding

mass is assumed to be a long, thin slab of material sliding on top of a continuous shear surface that is

parallel to the sloping ground surface. This will be the critical shear surface (surface with the lowest factor

of safety) for long straight continuous slopes composed of a cohesionless Mohr-Coulomb material.

The pseudo-static FOS for an infinite slope in a dry, Mohr-Coulomb material is calculated as follows

(Duncan and Wright, 2004):

FOS = c’+(γz cos2 (β) – kγz cos(β) sin(β))tan (∅’) γz sin (β) cos (β)+kγz cos2(β) Where:

c’ = effective cohesion z = depth of failure surface


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γ =the saturated unit weight of the soil β = the slope of ground surface ∅’ = effective friction angle of the soil k = seismic coefficient (k=0 for static analyses)

We selected a seismic coefficient, k, for use in the analyses following guidelines by Blake et al. (2002).

The results of the laboratory testing (Golder, 2015) indicate that the coarse, granular material comprising

the waste fill is not strain-softening. The pseudo-static analyses procedure described by Blake indicates

that the slope will have acceptable performance under seismic loading when k = 0.18 and the computed

FOS equal or greater than 1.0.

The results of these analyses are shown in Table 13. Table 13: Results of Infinite Slope Analyses for Overburden Fills

Type of Analysis

Slope Angle (degrees) k FOS

Static

34 0 1.20 33.7 (1.5H:1V) 0 1.21

33 0 1.25 32 0 1.30

26.6 (2H:1V) 0 1.62

Pseudo-static

33.7 (1.5H:1V) 0.18 0.84 29 0.18 0.99 28 0.18 1.03

26.6 (2H:1V) 0.18 1.08

The results of these analyses indicate adequate factors of safety for a 1.5H:1V slope (approximately 34

degrees) under static loading; however, this slope would not have an adequate factor of safety under

seismic loading. The pseudo-static analyses indicate the slope would have to be flatter than 1.8H:1V

(approximately 29 degrees) to achieve a FOS of 1.0 under seismic loading; therefore we recommend that

future overburden fill slopes be designed at a maximum slope of 2H:1V (approximately 26.6 degrees).

The results of infinite slope analyses for use in design of overburden fills are typically conservative

because they assume a very thin layer of soil slides along an infinitely long slope. The actual overburden

fill will have some finite dimension and the thickness of the shear surface of interest is likely to be greater

than just a few feet deep. Slope stability analyses that include a search for a critical shear surface will

yield somewhat higher factors of safety than indicated in Table 13 depending on the length and depth of

the fill slope; however, the slope angles from the infinite slope analyses provide constraints on the


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maximum achievable slope angles for overburden fill that will satisfy SMARA requirements for seismic

stability.

Limit equilibrium analyses for a block failure along the base of the fill, and for circular failure modes

intersecting the foundation yielded static FOS of 1.7 and 1.92, respectively, indicating that the foundation

is of adequate strength for the proposed fill. Seismic FOS exceeded 1.0 for foundation-related failures

modes.


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7.0 CONCLUSIONS AND RECOMMENDATIONS Our conclusions and recommendations are based on:

Our knowledge of geology of the site as observed in the field and literature review

The data we collected during both the drilling program in February 2015 and our site visit in March 2014

Our experience with similar high, steep slopes excavated in similar rock masses

Our understanding of geologic environments which are vulnerable to large-scale slope instability under static conditions and seismic loading

The results of the subsurface explorations, laboratory testing, and our engineering analyses

7.1 Conclusions

7.1.1 East Quarry Slopes: The major structures (i.e., discontinuities) that could result in large structurally-controlled

instability of east quarry slope are not present at the site

The formation of large deep-seated slope instability due to shear through the rock mass in the east slope of the quarry is not indicated by either the geologic conditions or our slope stability analyses for either seismic or static loading. The computed minimum factors of safety under static conditions and pseudo-static conditions meet the requirements of the Surface Mining and Reclamation Act (SMARA).

Rockfalls from bench slopes and small bench-scale failures due either to static or seismic load will likely either be mined out or retained on catch benches left in the overall pit slope during mining.

Differences between the geotechnical characterization and geologic models described in this report and the actual geotechnical and geologic conditions should be anticipated. Geologic risks related to the slope stability of the east side of the pit include:

Extensive weathering of the Knoxville Formation over time resulting in reduced strengths more like a soil than a rock mass.

Unidentified faults, geologic contacts, or changes in the orientation of bedding planes in the Knoxville Formation or orientation of dike contacts in the Diabase

Distribution of more highly fractured zones that could affect the ability to develop steep bench and stable bench faces and the ability to implement effective controlled blasting methods (pre-split and trim blasting)

7.1.2 Overburden Fill Slopes Overburden fill slopes of 2H:1V meet the current requirements for static and seismic

stability of the Surface Mining and Reclamation Act (SMARA) (FOS > 1.0).

Foundation conditions in the proposed overburden fill area (native slopes east-southeast of the quarry) appear suitable for the proposed fills provided that design of the fills provide proper stripping of surface soils and organics.


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7.2 Recommendations

7.2.1 East Quarry Slopes The east quarry slope can be designed using the slope configurations shown in Table 1

and illustrated in Figures 7 through 13.

The height and character of the various rock units exposed in the pit slope may change the factor of safety from that indicated in Figures 7 through 13. We recommend that the geologic model be verified as the slopes are excavated to confirm the assumptions used in this report.

Occasional bench-scale failures due to either rock blocks sliding along discontinuities or raveling may occur locally. Catch benches with appropriate berms (if required) should be left in the slope to retain material from such small-scale failures

We recommend that quarry personnel conduct regular visual inspections to identify conditions (e.g., tension cracks, excessive raveling, rockfall, etc.) that might indicate the development of an unstable overall slope. If potential signs of slope instability are observed, we recommend that you contact us so we may evaluate the conditions and the recommendations in this report and revise them, if appropriate.

7.2.2 Overburden Fill The purpose of these recommendations is to assist Cemex in design of a overburden fill. A final location

and configuration of a overburden fill has yet to be selected. The following recommendations will assist in

developing a preliminary design:

The slope of the overburden fill should be no greater than 2H:1V for overburden placed in lifts with little compactive effort (i.e., assumes wheel and track rolling only).

For preliminary design assume that a keyway at the base of the fill will be constructed to enhance stability. For preliminary designs, assume that the key way will be 30 foot to 50 foot wide by 5 foot depth. The keyway should be inspected to verify that all unsuitable soft and organic soils have been removed.

Keyways should be evaluated for the presence of seepage. If seepage is present, a geotechnical engineer should provide recommendations for a subdrain.

If the existing subsurface explorations do not adequately represent ground conditions, additional subsurface explorations consisting of test pits and borings may be required once a final location of the fill has been selected. We recommend that a slope stability analysis of the final overburden fill design be completed once a final location and configuration for the fill has been selected.


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8.0 USE OF THIS REPORT This report has been prepared for the exclusive use of Cemex and their consultants for specific

application to the Clayton Quarry mine design.

The conclusions and recommendations contained in this report are based on data obtained by others as

well as the site reconnaissance and subsurface explorations conducted by Golder. The methods used

generally indicate geologic conditions at the time and locations explored and sampled. Our assessment of

geologic conditions based on conditions exposed in the existing quarry (ground surface) and samples

obtained from widely spaced borings may not disclose geologic features either hidden from view or not

sampled in the borings; and such undisclosed geologic features may result in slope instability under

certain conditions. In addition, groundwater conditions can vary with time.

The contacts between geologic units indicated on the subsurface exploration logs and cross represent the

approximate boundaries between soil and/or bedrock units, and actual transitions may be more gradual.

Subsurface descriptions are based on conditions encountered at the time of exploration and conditions

outside of the exploration locations may vary from those encountered during this investigation.

The findings, conclusions, and recommendations presented in this report were prepared in accordance

with generally accepted geotechnical engineering practice that exists within the area at the time of the

work. No other warranty, expressed or implied, is made.


May 2015 30 Project No. 15-20962

c:\users\blara\appdata\local\microsoft\windows\temporary internet files\content.outlook\cvlw1gpq\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx

9.0 CLOSING We appreciate the opportunity to work with Cemex on this project. Please call us if you have any

questions or require clarification of our findings and recommendations.

GOLDER ASSOCIATES INC. George Lightwood William Fowler, PG, CEG Senior Engineer Principal Engineering Geologist GL/WF/rk

May 2015 31 Project No. 15-20962

10.0 REFERENCES Barton, N. and V. Chouby, 1977, The shear strength of rock joints in theory and practice. Rock

Mechanics, vol. 10, pp 1 – 54.

Bieniawski, Z.T., 1976, Rock mass classification in rock engineering. Proceedings, Symposium on Exploration for Rock Engineering, Johannesburg, Vol. 1, 1976, p. 97-106.

Blake, T.F., R.A. Hollingsworth, J.P. Stewart, 2002, Recommended Procedures for Implementation of DMG Special Publication 117 Guidelines for Analyzing and Mitigating Landslide Hazards in California, published by the Southern California Earthquake Center, June 2002.

California Geological Society, Special Publication 117, Guidelines for Evaluation and Mitigating Seismic Hazards in California, Revised September 2008.

Caltrans. 2010. Rock Logging, Classification, and Presentation Manual. State of California, Department of Transportation, Division of Engineering Services, Geotechnical Services.

Dibblee, T.W., 2006, Geologic Map of the Clayton quadrangle, Contra Costa County, California, Dibblee Geology Center Map #DF-192, Santa Barbara Museum of Natural History, Santa Barbara, California.

Dibblee, T.W., 1980, Preliminary geologic map of the Clayton quadrangle, Contra Costa County, California: U.S. Geological Survey, Open File Report no. 80-547.

Duncan, J.M. and S. G. Wright, 2005, Soil Strength and Slope Stability, Wiley, New York.

Golder, 2015, Evaluation of Pitslope Stability and Rockfall Hazard, Clayton Quarry, Clayton, California, Project No. 113-01127, report prepared for Mr. Ron Wilson, Cemex, Eldorado Hills, CA, Project Number 113-01127.

Hoek, E., 2012, Blast Damage Factor D, Technical note in RocNews, winter, 2012, dated February 2, 2012.

Hoek, E., and Brown, E.T., 1980. Underground Excavations in Rock, Institute of Mining and Metallurgy, London.

Hoek, E., Carranza-Torres, C., and Corkum, B., 2002. Hoek-Brown Failure Criterion, 2002 Edition. Proceedings, 5th North American Rock Mechanics Symposium, Toronto, p. 267-273.

Hoek, E., P.K. Kaiser, and W.F. Bawden, 1993, Support of Underground Excavations in Hard Rock, Taylor and Francis, New York.

Hoek, E., and Karzulovic, A., 2000. Rock-Mass Properties for Surface Mines, in Slope Stability in Surface Mining. Society for Mining, Metallurgy, and Exploration, Inc., p. 59-69.

Keefer, D.K. 1984. Landslides caused by earthquakes, Geological Society of America Bulletin, vol. 98, pp. 406-421.

Pampeyan, E.H., 1963, Geology and mineral deposits of Mt. Diablo, Contra Costa County, California Division of Mines and Geology Special Report 80.

Read, J., and Stacey, P., 2009. Guidelines for Open Pit Slope Design. Published by CRC Press/Balkema.

g:\projects\clayton quarry cemex\1520962 (cemex geotechnical investigation)\final report\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx

May 2015 32 Project No. 15-20962

Rocscience, 2012, Slide: 2D Limit Equilibrium Slope Stability Analysis, Rocscience, Inc., Toronto, Ontario,

Canada.

Spencer, E., 1967, A method of analysis of the stability of embankments assuming parallel interslice forces, Geotechnique, Vol. 17, p. 11-26.

Williams, K. M., 1984, Geologic map and cross sections of the Coast Range Ophiolite at Mount Diablo, Contra Costa, County, California, U.S. Geological Survey, Open File Report no. 84-557.

g:\projects\clayton quarry cemex\1520962 (cemex geotechnical investigation)\final report\clayton quarry report_ east pit slope_final_wlf-5-11-15.docx

FIGURES

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF

113-01127 003 0 PHASE No. FIGURE

CLIENT

PROJECT

CEMEX

GEOTECHNICAL SLOPE EVALUATION, CLAYTON QUARRY

1

PROJECT LOCATION TITLE

CONSULTANT

Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF

003 0 PHASE No. FIGURE

CLIENT

PROJECT

CEMEX


Cemex Clayton Quarry

Source: U.S. Geological Survey. Clayton quadrangle, California [map]. Photorevised 1980. 1:24,000. 7.5 Minute Series. Reston, Va: United States Department of the Interior, USGS, 1953.

Source: OpenStreetMap http://www.openstreetmap.org/copyright

15-20962 PROJECT No.

!(

!(

!(

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!(

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!(!(!(

!(

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!( !(

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x1

x2

x3

x4

x6x7

x9

x11

x12x13

x14

x15

x18 x19

x20

x21

x8

x10

x5

x16

x17

1500

1400

1300 1200

11001000

900800

600

700

600

700

600

700600

6143200.00 6144000.00 6144800.00 6145600.00

2160

000.00

2160

800.00

2161

600.00

2162

400.00

2163

200.00

CLIENTCEMEX

LEGEND!( Station!( Station on Db/Kk contact

Surface Contour (100ft. Intervals)Approximate Diabase/Knoxville ContactCross Section

NOTES

REFERENCECOORDINATE SYSTEM: NAD 1983 STATEPLANECALIFORNIA III FIPS 0403 FEETSERVICE LAYER CREDITS: SOURCE: ESRI,DIGITALGLOBE, GEOEYE, I-CUBED, USDA, USGS, AEX,GETMAPPING, AEROGRID, IGN, IGP, SWISSTOPO, ANDTHE GIS USER COMMUNITY

PROJECT

TITLESITE LAYOUT

113-01127 #### #### 2

07-05-2014DZFDZFLF####

Path: G:\GIS\Sites\ClaytonQuarry\Maps\SiteMap.mxd


CONSULTANT

PROJECT No. CONTROL REVIEW FIGURE

YYYY-MM-DDPREPAREDDESIGNREVIEWAPPROVED1 inch = 300 feet

300 0 300150Feet

C C'

B

B'

A'

A

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF


CLIENT

PROJECT

CEMEX


4

EAST WALL (March 2014) TITLE

CONSULTANT

Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF


CLIENT

PROJECT

CEMEX


15-20962 PROJECT No.

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF


CLIENT

PROJECT

CEMEX


5

DEFINITION OF BENCH FACE ANGLE, CATCH BENCH, AND INTER-RAMP SLOPE ANGLE

TITLE

CONSULTANT

Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED

2014-04-30

RLK

GTL

GTL

WLF


CLIENT

PROJECT

CEMEX

PROJECT No.

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX


6

GEOLOGIC STRENGTH INDEX (GSI)

2014-05-05

RLK

GTL

GTL

WLF

FIGURE

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX


Pseudostatic Analysis (k=0.21)

2015-04-09

7

SAM

GTL

GTL

WLF

FIGURE

RESULTS OF STABILITY ANALYSIS – CASE 1

Static Analysis

NOTE: See Table 9 for loading conditions.

FS = 2.505

FS = 1.88

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX



2015-04-09

8

SAM

GTL

GTL

WLF

FIGURE


Static Analysis


FS = 1.74

FS = 2.70

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX



2015-04-09

9

SAM

GTL

GTL

WLF

FIGURE


Static Analysis


FS = 1.69

FS = 2.34

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX




Static Analysis

10

2015-04-09

SAM

GTL

GTL

WLF

FIGURE NOTE: See Table 9 for loading conditions.

FS = 1.60

FS = 2.38

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX


2015-04-09

11

SAM

GTL

GTL

WLF

FIGURE



Static Analysis


FS = 1.41

FS = 2.02

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX


12

2015-04-09

SAM

GTL

GTL

WLF

FIGURE



Static Analysis


FS = 1.31

FS = 2.00

TITLE

CONSULTANT

PROJECT No. Rev.

YYYY-MM-DD

PREPARED

DESIGN

REVIEW

APPROVED


CLIENT

PROJECT

CEMEX


13

2015-04-09

SAM

GTL

GTL

WLF

FIGURE



Static Analysis


FS = 1.65

FS = 2.36

APPENDIX A

Clayton Quarry Geotechnical DrillingDate:

Project No. 1520962.002 Azimuth Elevation 879 Sheet 1 of 1Borehole # B1 Inclination Ref. Point Logged by Leah FeigelsonDrilling Method HQ N 37° 55 25 W 121° 56 49 Drill Rig mud rotary

Rubble Gouge

ROCK TYPE

RUN

From

(ft.)

To (f

t.)

Rec

over

y

Bed

ding

Dom

inan

t

RQ

D, f

t

Nat

ural

Fra

ctur

e C

ount

(N

/A fo

r "ic

e cu

be"

bx)

Ave

rage

Min

imum

Stre

ngth

Inde

x

Wea

ther

ing

Inde

x

Dep

th

TYPE

Cou

nt

Shap

e

Rou

ghne

ss

Infil

l

Thic

knes

s (m

m)

JRC

JCR

From

TO Type

From

TO

ADDITIONAL TESTING OR COMMENTS, SAMPLES COLLECTED

0.0 14.0 CASING set to 14 feet.

1 14.0 15.0 0.7 Drilling through waste dump; loosing2 15.0 20.0 0.8 circulation, therefore low recovery. Fines3 20.0 25.0 0.9 washed away, gravel/cobbles stay.4 25.0 26.0 0.35 26.0 31.0 0.76 31.0 36.0 0.6 checked depth with tape, confirmed at 36 feet.7 36.0 39.0 0.78 39.0 41.0 0.2 checked depth with tape, confirmed at 41 feet.9 41.0 42.5 0.2

10 42.5 44.0 0.511 44.0 45.0 0.411 45.0 46.0 0.7 N 0.0 7 10 8 R3 W3 46.0 B2 1 64 PL K ml C 8 8 45.4 45.7 Broken shale pieces are angular and have12 46.0 51.0 2.0 N 0.0 20 12 10 R3 W3 46.0 51.0 slicks, some pyrite on quartz vein13 51.0 54.0 1.5 N 0.0 15 12 10 R3 W3 52.9 J2 1 47 PL SR ml C 8 10

52.9 J2 1 32 PL SM ml C 2 8 rods stuck at 54 feet (took 1 day to un‐plug)53.5 J3 1 47 I SR ml C 10 14

14 54.0 56.0 2.0 N 0.4 16 12 10 R3 W2 54.2 B2 1 41 I K ml C 10 8 at 55.3'‐ a 0.3' section of sheared shale55.3 B2 1 41 PL K ml C 8 6 (fine bedding with some slicks)55.5 B2 1 67 PL SR ml C 12 10

15 56.0 57.8 0.5 N 0.0 5 10 8 R3 W3 at 57.8'‐ finely sheared at contactclayey SILTSTONE, heavily fractured 15 57.8 61.0 3.2 N 0.0 32 6 4 S4 W4 57.8 61.0 cl, ml *sample collected 59.5‐60.0 clayey siltstoneCLAYSTONE, dark gray, fractured 16 61.0 66.0 1.5 N 0.0 15 12 10 R3 W3 65.7 V1 1 62 PL R ml, cl <1 10 12 64.5 66.0 blocky fractures, angular

CLAYSTONE, light gray, abundant quartz veining 17 66.0 69.4 0.7 N 0.5 2 14 12 R3 W2 69.4 C2 1 62 I VR ml, cl C 16 14clayey SILTSTONE, dark gray 17 69.4 70.0 0.6 N 0.0 6 6 4 S3 W4 70.0 C1 1 36 I SR ml, cl <1 12 16 69.4 70.0 cl, ml at 70'‐ quartz veins and pyrite

CLAYSTONE, light gray, abundant quartz veining 17 70.0 70.6 0.6 N 0.0 4 12 10 R4 W2 70.4 V1 1 36 PL SR ml, cl C 8 12clayey SILTSTONE, dark gray 17 70.6 71.0 0.4 N 0.0 4 6 4 S1 W6 70.6 V2 1 85 I R ml, cl <1 18 20 70.6 71.0 cl, ml material from the shoe, therefore broken

clayey SILTSTONE, dark gray, heavily fractured 18 71.0 75.0 1.5 N 0.0 15 6 4 S4 W4 71.0 75.0 cl, ml heavily fractured, blocky

19 75.0 77.0 2.0 N 0.0 20 12 10 R3 W3 75.0 77.020 77.0 81.0 1.1 N 0.0 11 10 8 S5 W421 81.0 84.0 0.4 N 0.0 4 12 10 R3 W3 84.0 C2 1 44 I VR ml, cl C 18 1621 84.0 86.0 2.0 N 0.0 20 8 6 S4 W4 85.5 J2 1 44 C VR ml, cl <2 16 14 84.0 89.0 cl, ml some slicks at contact at 84.7'22 86.0 89.0 3.0 N 0.0 30 8 6 S4 W4 87.1 J2 1 64 I VR ml, cl <2 16 14

87.8 J2 1 48 PL R ml, cl <1 14 14 *sample collected 86.8‐87.6' clayey siltstone23 89.0 91.0 0.8 N 0.0 8 8 6 S4 W4 (direct shear/triax)24 91.0 91.5 0.2 N 0.0 2 4 2 S2 W6 91.0 94.0 cl, ml24 91.5 92.0 0.5 N 0.0 5 8 6 S4 W4 *sample collected 91.4‐92.0' silty claystone24 92.0 92.4 0.4 N 0.0 4 6 4 S3 W524 92.4 93.6 1.2 N 0.0 12 8 6 S5 W4 92.8 J1 1 50 PL SR ml, cl C 10 824 93.6 94.0 0.4 N 0.0 4 6 4 S3 W5

silty CLAYSTONE 25 94.0 96.0 1.1 N 0.0 11 12 10 R3 W3 95.4 J2 1 53 2 C ml, cl C 8 1026 96.0 96.8 0.8 N 0.4 4 12 10 R3 W326 96.8 98.0 1.2 N 0.0 12 8 6 S5 W4 *sample collected 96.9‐97.5' silty claystone26 98.0 99.0 1.0 N 0.0 10 6 4 S4 W4 98.0 99.0 cl, ml

silty CLAYSTONE 27 99.0 100.0 1.0 N 0.0 10 8 6 S5 W4 *sample collected 99.2‐99.7' silty claystone

TD=100'

Broken Core (smaller than core diameter)

Vertical

2/17/15‐2/19/15

Run Data

Recovery & Other Basic InformationJCR Strength Index

Detailed Discontinuity Data Gouge

clayey SILTSTONE

WASTE DUMP

CLAYSTONE, dark brownish‐gray

clayey SILTSTONE to silty CLAYSTONE, dark gray, fractured

CASING set to 14 feet.

01 in

152-0952

FIGURE

1

2015-03-16

JGE

GL

GL

CLAYTON QUARRY

2015 GEOTECHNICAL INVESTIGATION

CEMEX

CONTRA COSTA COUNTY

CLAYTON, CALIFORNIA

B1 DOWNHOLE PLOT

TITLE

PROJECT NO. REV.

PROJECTCLIENT

IF

T

HIS

M

EA

SU

RE

ME

NT

D

OE

S N

OT

M

AT

CH

W

HA

T IS

S

HO

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, T

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S

HE

ET

S

IZ

E H

AS

B

EE

N M

OD

IF

IE

D F

RO

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NS

I B

CONSULTANT

PREPARED

DESIGNED

REVIEWED

APPROVED

YYYY-MM-DD

Path: \\reno\data\Cemex - Clayton Quarry\Downhole Plot\ | File Name: Downhole Plot11x17.dwg

ISRM

STRENGTH

DESCRIPTION

UCS RANGE (PSI)

S1 VERY SOFT CLAY <4

S2 SOFT CLAY 4-7

S3 FIRM CLAY 7-15

S4 STIFF CLAY 15-35

S5 VERY STIFF CLAY 35-70

S6 HARD CLAY >70

R0 EXTREMELY WEAK ROCK 35-150

R1 VERY WEAK ROCK 150-725

R2 WEAK ROCK725-3,500

R3 MEDIUM STRONG ROCK3,500-7,500

R4 STRONG ROCK7,500-15,000

R5 VERY STRONG ROCK15,000-35,000

R6 EXTREMELY STRONG ROCK<35,000

LEGEND

WASTE DUMP

CLAYSTONE

SILTSTONE

CASING

RMR CLASSIFICATION

0 - 20

21 - 40

41 - 60

61 - 80

81 - 100

VERY POOR

POOR

FAIR

GOOD

VERY GOOD

CLAYEY SILT, low to medium plastic fines, some fine sand, trace medium to coarsesand, sub-angular to angluar; reddish-brown; moist; very soft.

gravelly CLAYEY SILT, low to medium plastic fines, some fine to coarse sand;reddish-brown, mottled; moist; soft.

gravelly CLAYEY SILT, low to medium plastic fines, some fine to coarse sand;reddish-brown, mottled; moist; very stiff.

SILTY CLAY, medium plastic fines, some medium to coarse sand, sub-angular;yellowish-brown; moist; firm.

SILTY CLAY to CLAY, medium to high plastic fines, trace fine to coarse sand,yellowish-brown; moist; very stiff.

gravelly SILTY CLAY, medium plastic fines, some sand, sub-angular to angular;yellowish-brown, mottled tan, green, red; moist; firm.

gravelly SILTY CLAY, medium plastic fines, some sand, sub-angular to angular;yellowish-brown, mottled tan, green, red; moist; very stiff.

Bottom of borehole at 31.5 feet.

ML

ML

ML

CL

CL-CH

CL

CL

18/18

18/18

18/18

18/18

18/18

12/18

MCB2-5

SPTB2-10

MCB2-15

SPTB2-20

MCB2-25

SPTB2-30

356

N=11

5811

N=19

6811

N=19

71112

N=23

4812

N=20

4811

N=19

2.0

10.0

15.0

20.0

25.0

30.0

31.5

LOGGED BY LF

GRAVEL PACK TYPE ----

CONTINUED

LOCATION Clayton, CA

SCREEN TYPE/SLOT ----

CASING TYPE/DIAMETER ----

GROUND ELEVATION

TOP OF CASING ----

REMARKS

GROUT TYPE/QUANTITY Neat cement grout.

DRILLING METHOD

LITHOLOGIC DESCRIPTION

BORING NUMBER B2PAGE 1 OF 1

GR

AP

HIC

LOG

PROJECT NAME Clayton Quarry

U.S

.C.S

.

5

10

15

20

25

30

DE

PT

H(f

t. B

GL)

PROJECT NUMBER 152-0962 DATE STARTED 2/20/15

DATE COMPLETED 2/20/15

L o g o

Golder AssociatesTelephone: 408-220-9223Fax: 408-220-9224

INC

HE

S

BLO

WC

OU

NT

SA

MP

LIN

GM

ET

HO

DA

ND

SA

MP

LE ID

CLA

YT

ON

QU

AR

RY

BO

RIN

G G

INT

ST

D U

S L

AB

_CLA

YT

ON

.GP

J L

OG

A E

WN

N01

.GD

T 3

/13/

15

CO

NT

AC

TD

EP

TH

L o g o

CLAY, medium to high plastic fines, trace coarse sand, trace roots; brown; moist; verysoft.

CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; hard.

CLAYSTONE/SILTSTONE, weathered; yellowish-brown; moist; very stiff.





Bottom of borehole at 31.5 feet.

CH

12/18

12/18

9/11

15/18

12/18

12/18

MCB3-5

SPTB3-10

MCB3-15

SPTB3-20

MCB3-25

SPTB3-30

82126

N=47

91115

N=26

1350 for 5"

5917

N=26

92735

N=62

81013

N=23

5.0

10.0

15.0

20.0

25.0

30.0

31.5

LOGGED BY LF

GRAVEL PACK TYPE ----

CONTINUED

LOCATION Clayton, CA

SCREEN TYPE/SLOT ----

CASING TYPE/DIAMETER ----

GROUND ELEVATION

TOP OF CASING ----

REMARKS

GROUT TYPE/QUANTITY Neat cement grout.

DRILLING METHOD

LITHOLOGIC DESCRIPTION

BORING NUMBER B3PAGE 1 OF 1

GR

AP

HIC

LOG

PROJECT NAME Clayton Quarry

U.S

.C.S

.

5

10

15

20

25

30

DE

PT

H(f

t. B

GL)

PROJECT NUMBER 152-0962 DATE STARTED 2/20/15

DATE COMPLETED 2/20/15

L o g o

Golder AssociatesTelephone: 408-220-9223Fax: 408-220-9224

INC

HE

S

BLO

WC

OU

NT

SA

MP

LIN

GM

ET

HO

DA

ND

SA

MP

LE ID

CLA

YT

ON

QU

AR

RY

BO

RIN

G G

INT

ST

D U

S L

AB

_CLA

YT

ON

.GP

J L

OG

A E

WN

N01

.GD

T 3

/13/

15

CO

NT

AC

TD

EP

TH

L o g o

TABLE 1

ABBREVIATIONS FOR GEOTECHNICAL ROCK CORE LOGGING Type Code Description Planarity Code Description

J1 Natural joint PL Planar J2 Joint, origin uncertain C Curved J3 Joint caused by drilling or handling U Undulating B1 Natural fracture along bedding plane ST Stepped B2 Fracture along bedding plane, origin uncertain I Irregular

B3 Fracture along bedding plane caused by drilling or handling

BT Trace of intact bedding plane Roughness Code Description

FO1 Natural fracture along foliation plane P Polished FO2 Fracture along foliation plane, origin uncertain K Slickensided

FO3 Fracture along foliation plane caused by drilling or handling SM Smooth

FOT Trace of intact foliation R Rough V1 Natural fracture along vein VR Very Rough V2 Fracture along vein, origin uncertian

V3 Fracture along vein caused by drilling or handling Infill Type Code Description

VT Trace of intact vein Ca Calcite FB1 Natural fracture along flow banding Cl Clay FB2 Fracture along flow banding, origin uncertain Si Silica

FB3 Fracture along flow banding caused by drilling or handling Qtz Quartz

FBT Trace of intact flow banding Chl Chlorite C1 Natural fracture along contact G Gouge C2 Fracture along contact, origin uncertain Bx Breccia

C3 Fracture along contact caused by drilling or handling Hm Hematite

CT Trace of intact contact Lm Limonite F Fault FeOx Iron Oxide S Shear

��

FIGURE

TP-1.2-2

5

PHYSICAL DESCRIPTIVE TERMS

��

FIGURE

TP-1.2-2

6

DISCONTINUITY ROUGHNESS PROFILE

APPENDIX B

(X=NO)PERCENTFINERSIZE

PASS?SPEC.*PERCENTSIEVE

Project No:

Project:Client:

Elev./Depth:Location:Date:Source of Sample:Sample No.:

Remarks

Classification

Coefficients

Atterberg Limits

Soil Description

*

AASHTO=USCS=

Cc=Cu=D10=D15=D30=D50=D60=D85=

PI=LL=PL=

Particle Size Distribution Report

10

20

30

40

50

60

70

80

90

0

100

PE

RC

EN

T F

INE

R

100 10 1 0.1 0.01 0.001500GRAIN SIZE - mm

% COBBLES % GRAVEL % SAND % SILT % CLAY

6 in

.

3 in

.

2 in

.

1-1/

2 in

.

1 in

.

3/4

in.

1/2

in.

3/8

in.

#4 #10

#20

#30

#40

#60

#100

#140

#200

0.0 2.6 68.6 22.2 6.6

Figure287-201

Clayton Quarry - 1520962

Golder Associates

91.4-92'3/13/15B-1

SC-SM

2.9984.170.00520.01400.08290.2790.4401.19

72518

Very Dark Gray Silty, Clayey SAND

(no specification provided)

COOPER TESTING LABORATORY

100.099.597.494.167.759.251.538.728.825.019.916.814.612.811.09.37.16.75.5

3/4 in.3/8 in.

#4#10#30#40#50

#100#200#270

0.0345 mm.0.0220 mm.0.0128 mm.0.0091 mm.0.0065 mm.0.0046 mm.0.0033 mm.0.0023 mm.0.0013 mm.

(X=NO)PERCENTFINERSIZE

PASS?SPEC.*PERCENTSIEVE

Project No:

Project:Client:

Elev./Depth:Location:Date:Source of Sample:Sample No.:

Remarks

Classification

Coefficients

Atterberg Limits

Soil Description

*

AASHTO=USCS=

Cc=Cu=D10=D15=D30=D50=D60=D85=

PI=LL=PL=


10

20

30

40

50

60

70

80

90

0

100

PE

RC

EN

T F

INE

R

100 10 1 0.1 0.01 0.001500GRAIN SIZE - mm

% COBBLES % GRAVEL % SAND % SILT % CLAY

6 in

.

3 in

.

2 in

.

1-1/

2 in

.

1 in

.

3/4

in.

1/2

in.

3/8

in.

#4 #10

#20

#30

#40

#60

#100

#140

#200

0.0 26.0 35.7 22.7 15.6

Figure287-201


Golder Associates

5.5-6'3/13/15B-2

Due to the small sample size, relative to the largestparticle size, this data should be considered to beapproximate.

SC

0.00180.03100.2840.85812.0

183618

Dark Yellowish Brown Lean Clayey SAND w/ Gravel

(no specification provided)


100.094.581.074.068.456.553.650.544.338.335.830.026.724.322.419.618.017.015.913.0

1 in.3/4 in.3/8 in.

#4#10#30#40#50

#100#200#270

0.0310 mm.0.0200 mm.0.0118 mm.0.0084 mm.0.0060 mm.0.0043 mm.0.0030 mm.0.0022 mm.0.0013 mm.

Project:

Remarks:Client:Project No.

%<#200%<#40PIPLLLMATERIAL DESCRIPTION

LIQUID AND PLASTIC LIMITS TEST REPORT

Source: B-1 Elev./Depth: 91.4-92'

Figure



USCS

Golder Associates287-201

SC-SM28.859.271825Very Dark Gray Silty, Clayey SAND



SC38.353.6181836Dark Yellowish Brown Lean Clayey SAND w/ Gravel

Source: B-2 Elev./Depth: 10-11.5'

212041Dark Yellowish Brown Sandy Lean CLAY


292251Dark Yellowish Brown Sandy Fat CLAY/ Fat Clayey

SAND w/ Gravel

Source: B-3 Elev./Depth: 10.5-11.5'

152439Yellowish Brown Lean Clayey SAND

5 10 20 25 30 4020

28

36

44

52

60

NUMBER OF BLOWS

WA

TE

R C

ON

TE

NT

10 30 50 70 90 110LIQUID LIMIT

10

20

30

40

50

60P

LAS

TIC

ITY

IND

EX

47

CL-ML

CL or OL

CH or OH

ML or OL MH or OH

Dashed line indicates the approximateupper limit boundary for natural soils

APPENDIX C

Project No.:

Project:

Client:

Cu

Cc

COEFFICIENTS

D10

D30

D60

REMARKS:GRAIN SIZE

SOIL DESCRIPTIONPERCENT FINERSIEVEPERCENT FINERSIEVE

LLPLAASHTOUSCS% CLAY% SILT% SAND% GRAVEL

sizesizenumber


10

20

30

40

50

60

70

80

90

0

100

PE

RC

EN

T FI

NE

R

100 10 1 0.1 0.01 0.001200GRAIN SIZE - mm

6 in

.

3 in

.

2 in

.

1-1/

2 in

.

1 in

.

3/4

in.

1/2

in.

3/8

in.

#4 #10

#20

#30

#40

#60

#100

#140

#200

Figure

% COBBLES

287-147

Clayton Quarry Slope Evaluation - 113-01127Golder Associates, Inc.

Source: X19 Elev./Depth: Surface

1.47

37.718.3SC31.648.819.6

inches Dark Yellowish Brown Lean Clayey SAND w/Gravel


Source: X20+21 Sample No.: Composite Elev./Depth: Surface

0.9496.22

25.517.0GC14.938.047.1

Yellowish Brown Lean Clayey GRAVEL w/Sand

80.465.148.245.142.137.031.6

#4#10#30#40#50

#100#200

100.0

98.597.095.792.690.0

3"2.5

21.5"

1"3/4"1/2

3/8"

52.938.326.224.021.918.414.9

100.099.498.493.388.778.671.7

Project:Remarks:Client:Project No.

%<#200%<#40PIPLLLMATERIAL DESCRIPTION


Source: X19 Elev./Depth: Surface

Figure



USCS

Golder Associates, Inc.287-147

SC31.645.119.418.337.7Dark Yellowish Brown Lean Clayey SAND w/ Gravel

Clayton Quarry Slope Evaluation - 113-01127


GC14.924.08.517.025.5Yellowish Brown Lean Clayey GRAVEL w/ Sand

5 10 20 25 30 4023

27

31

35

39

43

NUMBER OF BLOWS

WA

TER

CO

NTE

NT

10 30 50 70 90 110LIQUID LIMIT

10

20

30

40

50

60P

LAS

TIC

ITY

IND

EX

47 CL-ML

CL or OL

CH or OH

ML or OL MH or OH

Dashed line indicates the approximateupper limit boundary for natural soils

654321

Curve No.

Project:Remarks:Client:Project No.

Material Description

TESTING DATA

AASHTOUSCS%<#200PILLSp.G.NM

Soil Data

SievePassingTest Performed on Material

Mold Size:Blows per Layer:Number of Layers:Hammer Drop:Hammer Wt.:

Test Specification:

DRY DENSITY

MOISTURE

TARE #2

WD + T #2

WW + T #2

TARE #1

WD + T #1

WW + T #1

WM

WM + WS

COMPACTION TEST REPORTD

ry d

ensi

ty, p

cf

Water content, %

131.5

134.0

136.5

139.0

141.5

144.0

2 4 6 8 10 12 14

ZAV SpG2.9

Figure

COMPACTION TEST REPORT



ROCK CORRECTED TEST RESULTS UNCORRECTED

%>3/8 in.

Material scalped on the 1/2" sieve.Golder Associates, Inc.287-147

Yellowish Brown Lean Clayey GRAVEL w/Sand

6.9

2.7

3/8 in.

.03333 cu.ft.25five

18 in.10 lb.

Oversize correction applied to each pointASTM D 1557-00 Method B Modified

Clayton Quarry Slope Evaluation - 113-01127

137.6135.9141.8140.74.910.38.66.8

318.10326.60324.80293.80817.30914.30968.70798.60842.80978.701027.20834.704.424.424.424.429.189.389.529.39

8.5 % Optimum moisture = 8.1 %

140.7 pcf Maximum dry density = 142.2 pcf

Triaxial Consolidated Undrained with Pore PressureASTM D4767

Sample: 1 2 3 4

MC, % 6.3 6.0 6.4

DD, pcf 120.7 121.0 120.5

Sat. % 42.8 41.4 43.7

Void Ratio 0.396 0.393 0.399

Diameter in 2.86 2.86 2.86

Height, in 6.00 6.00 6.00

MC, % 13.1 11.1 12.0

DD, pcf 124.4 129.7 127.1

Sat. % 100.0 100.0 100.0

Void Ratio 0.354 0.299 0.325

Diameter, in 2.84 2.79 2.82

Height, in 5.92 5.87 5.85

Cell, psi 104.9 120.1 149.9

BP, psi 90.0 89.0 89.6

Job No.: 287-147 Date: ####### Strain, % 5.0 5.0 5.0

Client: BY:DC Deviator ksf 1.706 3.340 6.501

Project: Excess PP 1.695 3.339 6.856

Sample 1) X20+X21;Composite @ Surface Sigma 1 2.161 4.479 8.326

Sample 2) X20+X21;Composite @ Surface Sigma 3 0.455 1.139 1.825

Sample 3) X20+X21;Composite @ Surface P, ksf 1.308 2.809 5.075

Sample 4) Q, ksf 0.853 1.670 3.250

Stress Ratio 4.753 3.931 4.562

Rate in/min 0.0005 0.0005 0.0005

Total C 0.0 ksfTotal phi 15.9 degrees

Eff. C 0.0 ksfEff. Phi 38.8 degrees

Remolded to 85% of 142.2 @ 5.7 (OPT-2.5%).

Yellowish Brown Lean Clayey GRAVEL w/ Sand

Final

Effective Stresses At:

Clayton Quarry Slope Evaluation - 113-01127Golder Associates



0

4

8

0 4 8 12 16

Shea

r Str

ess,

ksf

Normal Stress, ksf

Total Stress

Effective Stress

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 5 10 15 20 25

Dev

iato

r Str

ess,

psf

Strain, %

Stress-Strain Response

Sample 1Sample 2Sample 3Sample 4

-70

-60

-50

-40

-30

-20

-10

00.01 0.10 1.00 10.00 100.00 1000.00 10000.00

Pore

Vol

, ml

Elapsed Time, min.

Consolidation Phase

Sample-1

Sample-2

Sample-3

Sample-4

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

Q, K

SF

.

P, ksf

P vs. Q


(σ1 + σ3) / 2

(σ1 -

σ3)

/ 2

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 2 4 6 8 10 12 14 16 18 20

Dev

iato

r Str

ess,

psf

Strain, %

Stress-Strain Curves


0

1000

2000

3000

4000

5000

6000

7000

8000

0 5 10 15 20 25

Exce

ss P

ore

Pres

sure

, psf

Strain, %

Pore Pressure Response


1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

0 5 10 15 20 25

Stre

ss R

atio

Strain, %

Stress Ratio Sigma1/Sigma3


Golder Associates Inc. 425 Lakeside Drive

Sunnyvale, CA 94085 Tel: (408) 220-9223 Fax: (408) 220-9224

Golder, Golder Associates and the GA globe design are trademarks of Golder Associates Corporation

clayton quarry, clayton, california · evaluation of east pitslope stability and fill slopes....

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