TABLE OF CONTENTS

1.0 SCOPE AND APPLICABILITY ............................................................................ 1

2.0 PROCEDURES ................................................................................................ 2

2.1 Borehole and Test Locations ................................. 22.2 Cone Penetration Testing ...................................................................... 22.3 Hollow Stem Auger Drilling ................................................................... 32 .4 S o il S a m p ling ........................................................................................ . . 3

2.4.1 Continuous Core Samples .......................................................... 32.4.2 Split-spoon Samples .................................................................. 42.4.3 California Split-barrel Samples .................................................... 42.4.4 Shelby Tube Samples ................................................................. 42.4.5 Bulk Samples .............................................................................. 52.4.6 Sample Descriptions ................................................................... 52.4.7 Field QA/QC Samples ............................................................... 5

2.5 Decontamination ..................................................................................... 52.5.1 Borehole and CPTAbandonment ............................................... 5

3.0 DOCUMENTATION AND RECORDS MANAGEMENT ..................................... 7

4.0 REFERENCES ................................................................................................. 8

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1.0 SCOPE AND APPLICABILITY

This Standard Operating Procedure (SOP) describes the procedure for hollow stemauger (HSA) drilling and collecting geotechnical soil samples, as well as conepenetration testing (CPT). The borings and test locations will be conducted at locationsspecified in the Work Plans. The sample intervals and test parameters are specified inthe Work Plans. The procedures presented here are intended to be general in nature toallow various methods to be used based on variable site specific conditions.

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2.0 PROCEDURES

2.1 BOREHOLE AND TEST LOCATIONS

Borehole locations will be initially located by a surveyor or by field staff using hand-heldGPS coordinates provided in the Work Plans. Locations may be adjusted as needed inany direction from the preliminary location to facilitate drill rig access or to obstacles.Actual (adjusted) locations based on GPS coordinates will be noted on the field logs attime of drilling.

On completion of backfilling of each borehole, the location will be marked with a surveystake, noting the borehole number as provided in the Work Plans. On completion ofbackfilling and marking by survey stakes of all boreholes, ground surveys will becompleted to locate the boreholes according to the marked locations.

2.2 CONE PENETRATION TESTING

A CPT(u) rig capable of measuring pore pressures in-situ and performing seismic CPTswill be used to advance the cone penetrometer through the tailings and native site soils(as applicable) according to the procedures outlined in ASTM D5778 (ASTM, 2012). Ifnecessary, waste rock or other stiff surficial soils that cannot be penetrated withoutdamaging CPT equipment will be penetrated using hydro-punch or auger drillingmethod to provide a pilot hole through such layers prior to CPT sounding.

The cone penetrometer will be advanced into the tailings at a target constant rate ofabout 2 cm/sec to provide a continuous profile of the material. The cone penetrometerwill be advanced until refusal. Should refusal occur at a significantly shallower depththan expected, the rig will be moved five feet and the penetrometer will again beadvanced until the anticipated depth at that location is reached.

2.2.1 Porewater Pressure Dissipation Tests

If perched water is encountered, pore pressure dissipation tests will be performed, onceper sounding location, where positive pore pressure conditions exist, or as directed bythe supervising field engineer or geologist. In order to properly measure pore pressures,the operator will saturate-de-air the porous stones to be used within the probe beforeeach test-sounding is started.

The field engineer or geologist will monitor pore pressures, in real-time, while the probeis being pushed. The dissipation tests will be performed at locations identified duringsoundings by the field personnel. If the pressures indicate a zone of saturation, within amaterial of interest: advancement of the probe will be stopped. A test will be initiatedand the changes in porewater pressure will be recorded over time.

Dissipation tests performed for Ch and Kh estimates will be run until at least 50%dynamic pore pressure dissipation has occurred. Dissipation tests performed to provideestimates of equilibrium pore pressures will generally target higher permeability sand

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zones (as determined by generalized CPT-based soil behavior type or site-specificCPT-soil type correlations) and will be run until stabilized pore pressure measurementsare obtained (per ASTM D5778 Section 12.3.7). Regardless of test objective, CPTdissipation tests will not be run for a duration greater than one hour.

2.3 HOLLOW STEM AUGER DRILLING

The boreholes will be drilled with hollow stem augers (HSA) of various sizes. Soilsampling may include continuous core, California barrel samples, standard split spoonsamples, and Shelby tube samples. In borrow areas, Ddrill cuttings will be placed on theground adjacent to the boreholes. In areas of concern, the cuttings will be placed onplastic sheeting or plywood, until they can be returned to the boreholeare drummed.

2.4 SOIL SAMPLING

The types and frequencies of soil samples will be provided in the Work Plans.Descriptions of the proposed sample types are included in the following sections.

2.4.1 Continuous Core Samples

Continuous core samples will be collected with a five-foot long continuous sampler barreladvanced inside the HSA as the HSA are advanced. Acrylic sample sleeves (30 or 60-inches long) may be used within the continuous core sampler to collect samples ofsensitive materials. The continuous sampler barrel will be retrieved, opened, and therecovery measured/recorded. Out of place soils (slough) at the top of the sampler will bediscarded. The soil core will be transferred intact to a core-logging table or truck bed,and core depth intervals marked with legible labels. Samples may be either removedfrom the core barrels prior to logging, or may be retained in transparent liners.

Photos of the labeled soil core will be taken. The samples will be logged and classifiedas specified in under Sample Descriptions and in SOP-17 Soil Logging. After loggingand photographing the core, samples may be retained by one of two procedures at thediscretion of the field geologist or geotechnical engineer, as follows:

1. Bulk samples: zones of similarly classified materials greater than 1-foot thick maybe placed in bulk sample containers and handled as specified in Section 2.4.5.Adjacent core materials from the subsequent run or runs having similarclassifications may be combined (composited) with the previously collected bulksamples. Subsamples of minor strata (less than 1 foot thick) having distinctlydifferent field classifications than adjacent major strata, and samples for moisturetesting will be placed in 1 gallon resealable bags and placed inside the samplebuckets on top of the associated bulk composite samples.

2. Liner samples: Samples collected in transparent plastic liners may be retained inthe liners. Liner caps will be sealed with plastic tape. Sample orientation will beindicated by an arrow pointing up or a "T" on the top cap.

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Sample buckets, bags, and retained liners will be marked with the boring number anddepth interval in accordance with SOP-14.

2.4.2 Split-spoon Samples

Split-spoon samples will be collected by driving the split spoon ahead of the HSA with a140-lb hammer falling 30 inches. The sampler will be driven 18 inches and blow countswill be recorded for 6-inch intervals. Various diameters of split-spoon samplers may beused. The HSA will be advanced into the soils as necessary to provide discrete sampleintervals. When retrieved, the split-spoon sampler will be opened, the recovery will bemeasured/recorded, and the soil described as specified in Section 2.4.6.

Split-spoon samples will be collected on a maximum of five feet vertical intervals. Thesampled interval will be placed in gallon resealable bags. Out of place soils (slough) atthe top of the sampler will not be sampled. Samples will be labeled and handled asspecified in SOPs-06, 14, and 17. Sample depth will be the starting depth of the sample.

2.4.3 California Split-barrel Samples

California split-barrel samples will be collected by driving the California split barrel aheadof the HSA with a 140-lb hammer falling 30 inches. The California split-barrel samplerwill be driven 18 inches and blow counts will be recorded for 6-inch intervals. Californiasplit-barrel samples will be collected utilizing a 2.5-inch outside diameter (OD) Californiasplit barrel sampler lined with three 2-inch diameter by 4-inch long brass liners, plusadditional brass liners as necessary to fill the California split barrel sampler. Alternatesampler diameters may be considered for use, depending on the application.

The sample recovery will be measured/recorded and the soil described as specified inSection 2.4.6. The bottom two, 4-inch long, brass liners will be retained and capped;other recovered soils will be discarded. The brass liners will be labeled with the projectnumber, borehole, sample depth, liner identification, sample date, and orientation.Sample depth is defined as the starting depth of the sample drive. Brass lineridentification is "A" for the bottom brass liner and "B" for the brass liner above the "A"brass liner. Sample orientation is an arrow pointing up, a "T" on the top cap, or theorientation of the sample labeling.

2.4.4 Shelby Tube Samples

Shelby tube samples will be collected at locations and intervals specified in the WorkPlans. Shelby tube samples will be collected by hydraulically advancing a 3-inchdiameter (or other approved diameter), 30-inch long, Shelby tube sampler two feet or torefusal. The recovery will be measured and the soils described as specified in Section2.4.6 by inspecting the soils at the top and bottom of the Shelby tube.

The Shelby tubes will be sealed before transport. The bottom cap will be secured withplastic tape. Melted wax (paraffin or paraffin with beeswax) will be poured into the top ofthe Shelby tube to stabilize and seal the top of the sample and be used to seal the end

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tape and caps. Spacers may also be used to stabilize the samples within the tubes.The top cap will then'be secured with plastic tape (see SOP-06).

Both the Shelby tube and the top cap will be labeled with the job number, borehole,sample interval, orientation, and sample date. Shelby tubes must be handled,transported, and stored vertically and cushioned against shock and vibration.

2.4.5 Bulk Samples

Bulk samples will be collected at intervals specified in the Work Plans. Bulk samplesmay be collected from continuous core samples (Section 2.4.1), or auger cuttings asindicated in the Work Plans and placed in plastic buckets (3.5 or 5 gallon) forgeotechnical testing and classification.

The sealed buckets will be labeled and handled as specified in the SOP-14.

2.4.6 Sample Descriptions

Soils will be described and classified in general accordance with SOP-17 (Soil Logging)and ASTM D2488 - Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) (ASTM, 2009). Sample descriptions will include soil type, moisturecontent, color (Munsell Color), density or consistency, plasticity, grain-size and shape,and other descriptors, as applicable.

Boreholes will be logged on MWH Borehole Log forms. An example MWH Borehole Logform for recording field information is attached to this SOP as Appendix A. Sampleintervals, recovery, blow counts (if performed), soil descriptions, and sample time will berecorded.

2.4.7 Field QAIQC Samples

Field duplicate and equipment blank samples for geotechnical samples will not becollected. Equipment blanks of geotechnical sampling equipment will not be collected.

2.5 DECONTAMINATION

HSA and CPT equipment will be decontaminated by removing visible material with ascraper or brush between test holes. Geotechnical sampling equipment will bedecontaminated by removing visible material with a scraper or brush between samples.Equipment will be decontaminated at the drill sites. See also SOP-31 for additionaldetails.

2.5.1 Borehole and CPT Abandonment

Abandonment specifics will be described in the Work Plans and may vary depending onthe sampling location at the site. HSA boreholes and CPT holes will be abandoned withbentonite grout anplor soil cuttings. Holes located within the impoundment will be

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abandoned with grout. Bentonite grout, when used, will be placed to within about 1 to 2feet from the ground surface, or to the top of the radon barrier, then the top of theborehole will be backfilled with dIGll lUthtin , or cover material.

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3.0 DOCUMENTATION AND RECORDS MANAGEMENT

Field data will be recorded in bound field books or on MWH Borehole Log forms(Appendix A). Documentation and records procedures are specified in SOP-14. Fielddata collected during CPT will be recorded in bound field books and by the instrumentsassociated with the cone penetrometer. Data recorded by the cone penetrometerinstrumentation will be provided, by the operator, to MWH within seven days ofcompletion of CPT activities.

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4.0 REFERENCES

ASTM. 2012. Standard Test Method for Electronic Friction Cone and PiezoconePenetration Testing of Soils. ASTM D5778-12. American Society for Testing andMaterials, West Conshohocken, PA.

ASTM. 2009. Standard Practice for Description and Identification of Soils (Visual- ManualProcedure). D2488-09a. American Society for Testing and Materials, WestConshohocken, PA.

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APPENDIX A

SAMPLE BOREHOLE LOG

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