A07.02-AMD_02-31_56_14.pdf

ARCF Natomas Reach H 2068

SECTION TABLE OF CONTENTS

DIVISION 31 - EARTHWORK

SECTION 31 56 14

SOIL-BENTONITE (SB) CUTOFF WALL - OPEN TRENCH

04/15

PART 1 GENERAL

1.1 SUMMARY

1.2 REFERENCES

1.3 GENERAL CONDITIONS

1.3.1 Lines and Grades

1.3.2 Conduct of Work

1.3.3 Access and Ramps

1.3.4 Protection of Existing Facilities

1.3.5 Permits

1.3.6 Construction Method

1.3.7 Sequencing of the Work

1.3.8 Water for Construction

1.4 DEFINITIONS

1.4.1 Cutoff Wall

1.4.2 Slurry Trench

1.4.3 Bentonite

1.4.4 Slurry Method of Excavation

1.4.5 Bentonite Slurry

1.4.6 SB Slurry Cutoff Wall Backfill

1.4.7 Ground Water Level

1.4.8 Starter Trench

1.4.9 Working Surface

1.4.10 Key-In Material

1.4.11 Slurry Cutoff Wall Specialist

1.4.12 Slurry Cutoff Wall Excavation Equipment Operator

1.4.13 Trench Quality Control Technician (TQCT)

1.4.14 Trench Logger

1.4.15 Quality Control Engineer

1.4.16 Quality Control Laboratory

1.4.17 Quality Control Report

1.4.18 Excavation Refusal

1.4.19 Obstructions

1.4.20 Remediation Plan

1.4.21 Elevation Datum

1.4.22 Material Safety Data Sheet(MSDS)

1.5 SUBMITTALS

1.6 QUALIFICATIONS

1.6.1 Contractor Qualifications

1.6.2 Qualifications of Slurry Cutoff Wall Specialist and Slurry

Cutoff Wall Excavation Equipment Operators

1.6.2.1 Slurry Cutoff Wall Specialist

1.6.2.2 Slurry Cutoff Wall Excavation Equipment Operator

1.6.3 TQCT

1.6.4 Trench Logger

1.6.5 Quality Control Engineer

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AMENDMENT

1.6.6 Quality Control Laboratory

1.7 DELIVERY, STORAGE, AND HANDLING

1.8 GEOTECHNICAL SITE CONDITIONS

1.8.1 Exploration

1.8.2 Subsurface Conditions

1.8.3 Ground Water

1.8.4 Knowledge of Subsurface Data

PART 2 PRODUCTS

2.1 GENERAL

2.2 BENTONITE

2.3 WATER

2.3.1 Source

2.3.2 Water Quality

2.4 BACKFILL MIX DESIGN

2.5 PROPERTIES OF BENTONITE SLURRY MIXING AREA

2.6 PROPERTIES OF BENTONITE SLURRY IN TRENCH

2.7 SB SLURRY CUTOFF WALL BACKFILL

2.7.1 Soil for Backfill

2.7.2 Soil-Bentonite Trench Backfill

2.8 MATERIAL STORAGE FACILITY

2.9 ENVIRONMENTAL PROTECTION

2.10 DISPOSAL SITE

2.11 TRENCH PLATES

2.12 EQUIPMENT

2.12.1 Trench Excavation Equipment

2.12.2 Bentonite Slurry Mixing Equipment

2.12.3 Field Laboratory Equipment

2.12.4 Slurry Transporting Equipment

2.12.5 Hauling Equipment

2.12.6 Equipment Weight, Speed, and Width

2.13 CONSTRUCTION STAKING

2.13.1 Initial and Final Elevation

2.14 PERMANENT METAL MARKER STAKES

PART 3 EXECUTION

3.1 GENERAL

3.1.1 SB Slurry Cutoff Wall Implementation Plan

3.2 SITE WORK

3.3 WORKING SURFACE

3.3.1 Construction Staking

3.3.2 Construction of Working Surface

3.4 SLURRY TRENCH EXCAVATION

3.4.1 General

3.4.2 Starter Trench

3.4.3 Vertical Tolerance

3.4.4 Bottom Depth

3.4.5 Trench Stability and Slurry Loss

3.4.6 Continuity of Cutoff Wall

3.4.7 Trench Excavation

3.4.8 Trench Bottom Cleaning

3.4.9 Top of Cutoff Wall

3.5 SB CUTOFF WALL CONSTRUCTION

3.5.1 Slurry Mixing and Placement

3.5.2 Mixing Areas

3.5.3 Mixing SB Backfill

3.5.4 Placement of SB Backfill

31 56 14 - 2

3.5.5 Temporary Cap

3.5.6 Settlement Plate Installation and Monitoring

3.5.7 Removal of Temporary Cap and Settlement Plates

3.5.8 High Water Event

3.5.9 Cutoff Wall Protection

3.5.10 Cleanup

3.6 AS-BUILT PROFILE

3.7 MIXING WATER AND WASH WATER

3.7.1 Mixing Water

3.7.2 Wash Water

3.8 QUALITY CONTROL

3.8.1 General

3.8.2 Access to Work Site

3.8.3 Cutoff Wall Mix Quantities

3.8.4 Mixing Area Sampling

3.8.4.1 Slurry Sampling in Mixing Area

3.8.5 Logging of Trench Excavation

3.8.6 Trench Soundings

3.8.7 Slurry Sampling

3.8.7.1 In Mixing Area

3.8.7.2 In Trench

3.8.8 Backfill Sampling

3.8.9 Protocol for Custody of Samples

3.8.10 Testing

3.8.10.1 Slurry in Mixing Areas

3.8.10.2 Slurry in Trench

3.8.10.3 Backfill Slump Testing

3.8.10.4 Laboratory Testing

3.8.10.5 Hydraulic Conductivity Testing

3.8.10.6 Coordination of Testing Laboratories

3.8.11 QUALITY CONTROL REPORTS

3.8.11.1 Daily Quality Control Report

3.8.11.2 Weekly Quality Control Report

3.8.12 Quality Control Records

3.8.13 Rejected Cutoff Wall Sections

3.9 QUALITY ASSURANCE TESTING

3.10 CUTOFF WALL CLOSE OUT AND ACCEPTANCE

3.10.1 Construction Records

3.10.2 Construction Documentation

3.10.3 Construction Quality Control Test Results

3.10.4 Construction Log

3.10.5 As-Built Drawing

3.10.6 Acceptance

3.10.7 Acceptance Criteria

-- End of Section Table of Contents --

31 56 14 - 3

SECTION 31 56 14

SOIL-BENTONITE (SB) CUTOFF WALL - OPEN TRENCH

04/15

PART 1 GENERAL

1.1 SUMMARY

The work covered by this section consists of furnishing all plant, labor, equipment, and materials and of performing all operations in connection with the construction of a seepage cutoff wall, in accordance with these Specifications and applicable Plans. The cutoff wall construction method addressed by this Specification is the open trench slurry soil-bentonite (SB) cutoff wall method. The intent of the cutoff wall is to provide permanent, continuous, homogeneous, low permeability barrier to embankment and foundation seepage within the vertical depth limits and horizontal station limits shown on the Plans. The cutoff wall shall be formed from a work platform by the slurry trench excavation method from the center of the degraded levee using bentonite slurry as the stabilizing agent and backfilled with an SB mixture.

1.2 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only.

AMERICAN PETROLEUM INSTITUTE (API)

API RP 13B-1 (2009; Errata 2014) Recommended Practice for Field Testing Water-Based Drilling Fluids

API Spec 13A (2010; Errata 1 2014; Errata 2-3 2015) Specification for Drilling-Fluid Materials

ASTM INTERNATIONAL (ASTM)

ASTM C143/C143M (2015) Standard Test Method for Slump of Hydraulic-Cement Concrete

ASTM D2488 (2009a) Description and Identification of Soils (Visual-Manual Procedure)

ASTM D3740 (2012a) Minimum Requirements for Agencies Engaged in the Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction

ASTM D4380 (2012) Standard Test Method for Density of Bentonitic Slurries

ASTM D4832 (2010) Preparation and Testing of Controlled Low Strength Material (CLSM) Test Cylinders

31 56 14 - 4

ASTM D5084 (2010) Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter

ASTM D7263 (2009) Standard Test Methods for Laboratory Determination of Density (Unit Weight) of Soil Specimens

U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA)

EPA 600/4-90/027F (1993) Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms

STATE OF CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS)

Bridge Design Manual (2004) Bridge Design Specifications

CA MUTCD (2012) California Manual on Uniform Traffic Control Devices

URS CORPORATION (URS)

REACH H GDR (2016) Geotechnical Data Report, American River Common Features Project Natomas Basin - Reach H

1.3 GENERAL CONDITIONS

1.3.1 Lines and Grades

The Contracting Officer may at any time prior to or during construction require a change in the cutoff wall depth. The objective of the cutoff wall is to block potential seepage through the levee embankment and/or through the levee foundation materials. The cutoff wall may be optimized by increasing or decreasing the depth of the cutoff wall. The potential variation from the depth indicated in the Plans is estimated to be plus or minus five feet, but Contractor's excavating equipment shall be capable of excavating a maximum of 10 feet deeper than the maximum depth indicated on the Plans.

1.3.2 Conduct of Work

Maintain and protect the cutoff wall in a satisfactory condition at all times until final completion and acceptance of all work under the Contract.

1.3.3 Access and Ramps

See Section 01 50 02 TEMPORARY CONSTRUCTION FACILITIES and Section 31 00 00 EARTHWORK for details and requirements for access and ramps.

1.3.4 Protection of Existing Facilities

Construction shall be conducted in a manner that avoids damage to all existing facilities that are not designated for removal or reconstruction.

31 56 14 - 5

1.3.5 Permits

The Contractor and subcontractors shall obtain and pay all necessary fees for all local, state, and federal permits required of the Contractor and subcontractors to accomplish the Work.

1.3.6 Construction Method

The SB cutoff wall shall be constructed using a mixture of water and bentonite mixed in proper proportions to achieve stable trench excavation and then backfilled with an SB mixture to achieve the hydraulic conductivity properties conforming to the Specifications.

1.3.7 Sequencing of the Work

The Contractor may use multiple headings to achieve the required schedule completion dates. Consult section 00 73 05 SUPPLEMENTAL CONDITION REQUIREMENTS FOR REACH H for any information regarding using multiple work shifts per day to achieve the required schedule completion dates.

1.3.8 Water for Construction

Details regarding water supplies, and the pumping and conveyance of the water, are presented in Section 01 50 02, TEMPORARY CONSTRUCTION FACILITIES. This water source will be used for all trial mixes and production.

1.4 DEFINITIONS

1.4.1 Cutoff Wall

The cutoff wall is a minimum 36-inch-wide trench constructed from the working surface by the slurry trench excavation method using bentonite slurry as the stabilizing agent and subsequently backfilled with SB mixture to form a low permeability cutoff wall with specified maximum permeability.

1.4.2 Slurry Trench

The slurry trench is a 36-inch wide trench excavated through the existing ground or prepared working surface using the slurry method of excavation.

1.4.3 Bentonite

Bentonite is an ultrafine natural clay whose principal mineral constituent is sodium cation montmorillonite.

1.4.4 Slurry Method of Excavation

The slurry method of excavation consists of excavating a vertical walled trench and at the same time keeping the trench filled with bentonite slurry. The purpose of the slurry is to support the walls of the trench while excavating to the design depth until replaced with an SB mixture.

1.4.5 Bentonite Slurry

Bentonite slurry is a colloidal mixture of bentonite (adequately hydrated) and water and other suitable material prepared in accordance with API Spec 13A.

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1.4.6 SB Slurry Cutoff Wall Backfill

A homogeneous mixture of material produced by mixing soil, bentonite, and water approved by the Contracting Officer, which is used to construct the SB slurry cutoff wall.

1.4.7 Ground Water Level

The ground water level is the piezometric level of the ground water as shown on the exploration logs in the REACH H GDR. Groundwater levels indicated on the exploration logs were levels found at the time of exploration. The groundwater table can vary significantly depending on time of year, variation from normal precipitation, and the water levels in NEMDC Channel.

1.4.8 Starter Trench

A sloped excavation used to initiate the construction of a cutoff wall trench.

1.4.9 Working Surface

The working surface is the top of the degraded levee crown, prepared as shown on the Plans and described in the Specifications from which the cutoff wall shall be constructed.

1.4.10 Key-In Material

The key-in material is the soil stratum into which the bottom of the cutoff wall is embedded.

1.4.11 Slurry Cutoff Wall Specialist

The slurry cutoff wall specialist is an individual working for the Contractor who will have responsibility for the construction of the SB cutoff wall.

1.4.12 Slurry Cutoff Wall Excavation Equipment Operator

The slurry excavation equipment operator is an individual who will operate the excavation equipment used to excavate the SB cutoff wall.

1.4.13 Trench Quality Control Technician (TQCT)

The TQCT working under the direction of the Contractor's slurry cutoff wall specialist will take required measurements of trench geometry, perform trench slurry and backfill sampling, and perform trench soundings.

1.4.14 Trench Logger

The trench logger is an individual working for the Contractor who will have responsibility for logging the description and classification of the material excavated from the slurry trench.

1.4.15 Quality Control Engineer

The Quality Control Engineer is a Registered Professional Engineer who is an individual working for the Contractor and is responsible for verifying Contractor's Quality Control Program is being properly implemented and the

31 56 14 - 7 specified cutoff wall properties are being achieved.

1.4.16 Quality Control Laboratory

Contractor's Quality Control Laboratory shall perform quality control testing on material samples to verify compliance with the Specifications.

1.4.17 Quality Control Report

A report prepared by the Contractor for each shift and for each rig (if multiple headings of the cutoff wall are advanced) that documents the progress on the SB cutoff wall construction and present the results of the quality control inspection and testing.

1.4.18 Excavation Refusal

The Contracting Officer will determine when excavation refusal is reached.

Excavation refusal will be defined as the inability of the Contractor's approved production excavator to excavate more than one foot of depth over a bottom trench length of 30 feet in a period of 60 minutes with excavator equipment in proper and effective operating condition utilizing the equipment discussed in paragraph TRENCH EXCAVATION EQUIPMENT.

1.4.19 Obstructions

The Contracting Officer shall be the sole judge of whether an obstruction has been encountered. Culverts, standpipes, and other buried features (e.g. existing cutoff walls, etc.) that are shown on the Plans and that are either to be preserved and protected or removed and replaced as part of the Work shall not be considered obstructions. Existing utilities shown on the Plans or marked by Underground Service Alert (USA) shall not be considered obstructions. Naturally-occurring materials such as cobbles and boulders shall not be considered obstructions.

1.4.20 Remediation Plan

A plan that describes the steps to be taken by the Contractor to bring any section of wall back into compliance with the specifications.

1.4.21 Elevation Datum

All elevations are referenced to the North American Vertical Datum of 1988 (NAVD-88) in feet.

1.4.22 Material Safety Data Sheet(MSDS)

A detailed informational document prepared by the manufacturer or importer of a hazardous chemical that describes the physical and chemical properties of the product.

1.5 SUBMITTALS

The following shall be submitted in accordance with Section 01 33 00

SUBMITTAL PROCEDURES.

SD-01 Preconstruction Submittals

All Preconstruction Submittals, except the Preconstruction SB Slurry Trial Mix Design Plan and Preconstruction SB Slurry Trial

31 56 14 - 8

Mix Design Report, shall be submitted no later than 30 calendar days after Notice-to-Proceed. The Preconstruction SB Slurry Trial Mix Design Plan shall be submitted no later than 7 calendar days after Notice-to-Proceed and the Preconstruction SB Slurry Trial Mix Design Report shall be submitted no later than 75 days after Notice-to-Proceed.

SB Slurry Cutoff Wall Implementation Plan; G, DO

Preconstruction SB Slurry Trial Mix Design Plan; G, DO

Preconstruction SB Slurry Trial Mix Design Report; G, DO

SB Cutoff Wall Quality Control Program; G, DO

Water Quality Test Results; G, DO

Contractor Qualifications; G, DO

Quality Control Laboratory Qualifications; G, DO

Remediation Plan; G, DO

SD-04 Samples

Bentonite;

Cutoff Wall Key-in Material;

SD-06 Test Reports

Daily Quality Control Report; G, DO

Weekly Quality Control Report; G, DO

Laboratory Testing Report; G, DO

Construction Quality Control Test Results ; G, DO

SD-07 Certificates

Bentonite Powder Manufacturer Test Results; G, RO

Calibration of Scales and Flow Meters; G, RO

SD-11 Closeout Submittals

Construction Records; G, DO

Construction Documentation; G, DO

Construction Log; G, DO

As-built Drawing; G, DO

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1.6 QUALIFICATIONS

1.6.1 Contractor Qualifications

This paragraph is reserved.The Contractor, his subcontractor, joint venture partner, or merged company shall have successfully constructed a minimum three SB cutoff wall projects in the last 5 years of similar size and complexity as this project with similar access constraints, and similar depth and length. Consider multiple cutoff wall segments under one contract to be one project. The qualifications and experience of personnel who shall be responsible for conducting the operations shall include references of the previously completed project owners with owner name;

telephone number; address; and project description including depth, length, and construction method of the Contractor's previous successful SB cutoff wall construction projects. An individual's experience from former companies shall not qualify as the present company's experience. However this experience can be used as individual experience such as for the slurry cutoff wall specialists. Submit Contractor Qualifications for approval.

1.6.2 Qualifications of Slurry Cutoff Wall Specialist and Slurry Cutoff Wall Excavation Equipment Operators

Maintain a slurry cutoff wall specialist and equipment operator at the site on a full-time basis while the cutoff wall is being constructed. The primary or alternate employee shall be committed to the Contractor for the duration of the project, unless a written release is obtained from the Contracting Officer's Representative.

Provide slurry cutoff wall specialist qualifications as part of the Contractor Qualifications submittal for approval. Qualifications must meet the requirements of paragraph SLURRY CUTOFF WALL SPECIALIST.

Provide slurry cutoff wall excavation equipment operator qualifications as part of the Contractor Qualifications submittal for approval.

Qualifications must meet the requirements of paragraph SLURRY CUTOFF WALL EXCAVATION EQUIPMENT OPERATOR. If the Contractor utilizes multiple headings, submit qualifications for slurry cutoff wall excavation equipment operators for each heading.

The following information shall be submitted to the Government for both the slurry cutoff wall specialist and slurry cutoff wall excavation equipment operators:

a. Name, address, and telephone number of owner/company and point of contact for projects forming the experience record.

b. Contract number, contract amount, date of award, and date of completion of the project forming the experience.

c. SB cutoff wall length and depth.

d. A copy of the portion of the specification requirement from the reference project indicating the required wall acceptance criteria (e.g., permeability) or a letter of reference from the owner for each project submitted the briefly describes the specification requirements.

e. Description of the method of construction and excavation equipment used.

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1.6.2.1 Slurry Cutoff Wall Specialist

The slurry cutoff wall specialist shall be onsite at all times during the trenching and slurry placement operations and provides supervision and control of the composition, mixing, placing, and maintenance of the SB slurry.

The slurry cutoff wall specialist shall be an individual who has had experience with at least 32 projects, or 2 projects and five construction seasons of experience and 5 years of experience in all aspects of slurry cutoff wall construction which includes, but is not limited to:

a. Controlling composition, mixing, placing, testing, and maintaining the bentonite slurry.

b. Supervision of alignment, verticality, and depth of cutoff walls.

c. Trench excavation, bentonite slurry trench filling, and SB backfilling procedures.

d. The mixing methods required to properly control composition, mixing, testing, and placement of SB backfill as required.

e. A thorough knowledge of cutoff wall construction equipment and material testing required for slurry cutoff wall construction.

f. Show successful construction of at least three SB cutoff walls having similar access constraints and at a minimum as deep. Project experience not in North America may be cited, however subject to approval based on verification.

1.6.2.2 Slurry Cutoff Wall Excavation Equipment Operator

Each slurry cutoff wall excavation equipment operator shall have a minimum of 5 construction seasonsyears of previous successful experience using similar cutoff wall excavation equipment to be used for this Contract and shall have performed a minimum of two successfully completed projects of similar complexity with similar or greater length and depth.

1.6.3 TQCT

The TQCT shall have a minimum of 2 construction seasonsyears experience including cutoff wall construction and the taking of required measurements of trench geometry, performing trench slurry sampling, and performing trench soundings.

1.6.4 Trench Logger

The trench logger shall have experience in the description and classification of the excavated material, have a minimum of 2 successfully completed projects, and have a minimum of 5 years experience using ASTM D2488. The trench logger shall be working under the responsible charge of a geologist, civil engineer practicing in geotechnical engineering, or geotechnical engineer registered in the State of California. Submit the trench logger qualifications as part of the Contractor Qualifications.

1.6.5 Quality Control Engineer

The Quality Control Engineer shall have a minimum of 5 years of

31 56 14 - 11 construction experience including: cutoff wall construction; a minimum of two SB seepage cutoff wall projects; and experience working as a Cutoff Wall Quality Control Engineer on projects of similar scope, project type, physical size and complexity. The Quality Control Engineer shall provide supervision and control of all quality control aspects related to the SB seepage cutoff wall. Submit the Quality Control Engineer qualifications as part of the Contractor Qualifications submittal. Maintain a Quality Control Engineer at the site on a full-time basis while the cutoff wall is being constructed. The primary or alternate employee shall be committed by the Contractor for the duration of the project, unless a written release is obtained from the Contracting Officer's Representative.

1.6.6 Quality Control Laboratory

The Contractor's quality control laboratory shall be an independent commercial laboratory and shall comply with the requirements of Section 01 45 00.15 RESIDENT MANAGEMENT SYSTEM CONTRACTOR MODE (RMS CM) and be a USACE accredited laboratory. Submit Quality Control Laboratory Qualifications for approval.

1.7 DELIVERY, STORAGE, AND HANDLING

Protect materials delivered and placed in storage from weather, soil, dust, or other contaminants.

1.8 GEOTECHNICAL SITE CONDITIONS

1.8.1 Exploration

Subsurface exploratory borings and cone penetrometer test have been performed by the Government to evaluate the subsurface conditions.

Approximate locations of the explorations, boring logs, and CPT logs are included in the REACH H GDR for the convenience of the Contractor. The Government assumes no responsibility for interpretations made by the Contractor from the explorations. Local variations in the subsurface materials are to be expected and, if encountered, will not be considered as being materially different within the purview of this Contract.

1.8.2 Subsurface Conditions

The levee embankment and subsurface materials encountered during explorations are described in the REACH H GDR.

1.8.3 Ground Water

A description of the regional ground water condition is presented in the

REACH H GDR.

1.8.4 Knowledge of Subsurface Data

It is the Contractor's responsibility to become acquainted and satisfied as to the character, quality, and quantity of surface and subsurface materials by inspecting the site, performing additional explorations as necessary for soil classification and mix design formulation and by evaluating information derived from the exploration work performed for this Project and included in these Plans and Specifications. Any failure by the Contractor to become acquainted with all the available information and any other site specific conditions such as utilities will not relieve the Contractor from responsibility for properly estimating the difficulty or

31 56 14 - 12 cost of successfully performing the work.

PART 2 PRODUCTS

2.1 GENERAL

Maintain at the job site a sufficient quantity of raw materials and other supplies such that the work can proceed uninterrupted by material shortages. The bentonite slurry and SB slurry cutoff wall backfill to be used shall be suitable for the Project. If necessary, modify the cutoff wall backfill design mixes to meet the requirements for permeability, continuity, and homogeneity specified in this Specification section.

Undertake any additional tests necessary to assist in material selection, to verify compliance with the Specifications, and to demonstrate the characteristics of the cutoff wall.

2.2 BENTONITE

Bentonite shall be sodium cation base montmorillonite powder that conforms to API Spec 13A, Section 9. Bentonite shall be new, pulverized, high-swelling natural sodium cation montmorillonite (Premium Grade Wyoming-type bentonite or equivalent). Chemically treated bentonite will not be allowed. No bentonite from the bentonite manufacturer shall be used prior to acceptance by the Contracting Officer. All bentonite shall be subject to inspection, sampling, and verification of quality by Contractor quality control (QC) testing and Government quality assurance (QA) testing. Bentonite not meeting Specifications shall be promptly removed from the site and replaced with bentonite conforming to specification requirements at the Contractors expense. Bentonite shall be protected from moisture loss during transit and storage.

Provide a sample of the bentonite material used within the mix upon request from the Contracting Officer's representative. The sample shall consist of a minimum of 10 pounds of the proposed bentonite at least 5 days prior to use with certification that it meets API Spec 13A.

Submit a copy of the Bentonite Powder Manufacturer Test Results for each lot shipped to the site and a certificate of compliance stating that the bentonite complies with all applicable standards.

2.3 WATER

2.3.1 Source

Refer to Section 01 50 02, TEMPORARY CONSTRUCTION FACILITIES for information on potential water supplies and the requirements that apply to providing the water supply for construction of the Project. Provide the water sources used for production and associated pH, hardness, total dissolved solids analysis (water sources used for production shall be same as trial mix). City hydrants if used by Contractor shall be identified in the implementation plan: (1) note the locations of hydrants for use, and

(2) procure appropriate permits. Abide by any and all regulations and other requirements governing such use. Include the cost of all related fees in the bid items pertinent to the Work.

2.3.2 Water Quality

The water shall comply with the standards specified below. Furnish Water Quality Test Results for water used for mixing with the slurry to assure

31 56 14 - 13 conformance with these standards.

Property Property Requirement Test Method pH Value 7.0 +/- 1.0 API RP 13B-1

Total Dissolved Solids <500 ppm EPA 600/4-90/027F

Oil, organics, acids, or other deleterious

<50 ppm each API RP 13B-1

Hardness <50 ppm API RP 13B-1

Water with hardness in excess of 50 ppm will be acceptable to the Government for use to construct the SB cutoff walls based on performance in the trial and backfill mix as long as the required permeability standards specified herein for the backfill mix are achieved throughout the project.

2.4 BACKFILL MIX DESIGN

Backfill mix design for the SB slurry backfill shall be the responsibility of the Contractor and shall take into account the subsurface conditions along the project alignment. prepare and submit a Preconstruction SB Slurry Trial Mix Design Plan. The plan shall summarize the procedures of the preconstruction SB slurry backfill trial mix design. The plan shall include a description of materials, mix proportions (bentonite, soil, and water), and test procedures in the proposed SB trial mixes. The Preconstruction SB Slurry Trial Mix Design Plan shall be approved by the Contracting Officer prior beginning SB Slurry trial mix designs and associated testing.

Trial mixes shall be made using soils which will represent the range of materials expected to be encountered or used along the entire extent of the project. perform subsurface explorations in sufficient number to obtain soil samples representative of the material that will be encountered during the excavation for the cutoff wall trench.

Perform a series of trial backfill mix designs based on the approved Preconstruction SB Slurry Trial Mix Design Plan to evaluate a range of bentonite mix proportions. Prepare a sufficient number of samples to support the Contractor's proposed mix design. The minimum number of trial backfill mix designs shall be three covering a range of bentonite mix constituent. All mixes shall be a minimum of 3 percent bentonite of the total mix weight.

The testing for the trial backfill mix shall include but be not limited to bleed, temperature, density, and hydraulic conductivity of samples at ages of 7, 14, and 28-day.

The initial design mix for the slurry cutoff wall SB backfill shall be selected by the Contractor and approved by the Contracting Officer based upon the approved Preconstruction SB Slurry Trial Mix Design Report. The report shall summarize the procedures and results of preconstruction SB slurry trial mix designs along with the Contractor's selected mix design for the SB slurry backfill. Modifications to the initial design mix shall be made only with the approval of the Contracting Officer.

The Contractor may sample existing monitoring wells to verify chemical compatibility of the groundwater with the proposed backfill mix design. See

31 56 14 - 14 paragraph GROUND WATER for identification of exiting monitoring wells.

See subpart paragraph SOIL-BENTONITE TRENCH BACKFILL for hydraulic conductivity test requirements for SB backfill. Only mixes meeting or exceeding the test requirements shall be approved for use.

2.5 PROPERTIES OF BENTONITE SLURRY MIXING AREA

Testing of slurry properties shall be in accordance with API RP 13B-1.

Before mixing bentonite slurry, the bentonite slurry mixture in the mixing area shall be required to be adequately hydrated and have the following properties.

Property Property Requirement Test Method

Viscosity > 40 marsh-seconds API RP 13B-1

Density > 64 pcf ASTM D4380

Filtrate Loss < 20 cubic cm API RP 13B-1 pH 6.5 to 10 API RP 13B-1

2.6 PROPERTIES OF BENTONITE SLURRY IN TRENCH

Testing of slurry properties shall be in accordance with API RP 13B-1. The bentonite slurry in the trench shall have the following properties:

Property Property Requirement Test Method

Density > 64 pcf and < 85 pcf ASTM D4380 pH 6.5 to 10 API RP 13B-1

Filtrate Loss < 30 cubic cm API RP 13B-1

Viscosity > 40 marsh-seconds API RP 13B-1

If required for trench stability, thicken the slurry mixture to a more viscous condition than the limits specified above. Use additional hydrated bentonite, and the amount added shall be the amount required to make the trench stable.

2.7 SB SLURRY CUTOFF WALL BACKFILL

2.7.1 Soil for Backfill

Gradation for the soil used as backfill shall meet the following requirements:

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Sieve Size or Number Percent (%) Passing by Dry Weight

2-inch 100

No. 4 > 40

No. 200 > 20

In addition, the soil shall be free of roots, debris, concentrations of organic materials, and all other deleterious material that may adversely affect the properties of the backfill. Sources for soil for use in the SB mix shall include:

a. Suitable soil selected from the slurry trench excavation spoils that conforms to the Specifications.

b. Soils selected from mandatory project excavations. These soils shall be blended by the Contractor, as necessary, to produce suitable material that conforms to the Specifications.

c. Soils selected from mandatory project excavations blended by the Contractor with soils imported from borrow areas to produce suitable material that conforms to the Specifications.

Make every effort to maximize the reuse of on-site soils from mandatory excavations. This includes blending different excavated soils to produce material for the SB mix that meets the Specification requirements. If suitable SB mix soils cannot be obtained or manufactured from mandatory excavations, suitable soils shall then be imported from off-site borrow site(s) as backfill or for blending with on-site excavated soils to make a suitable soil backfill that conforms to the Specifications.

2.7.2 Soil-Bentonite Trench Backfill

Initial SB mixture shall contain a minimum of five percent bentonite by dry weight of soil. Bentonite slurry and dry bentonite (as needed) shall be added and mixed uniformly and homogeneously with the soil backfill so the soil-bentonite backfill has the following properties:

a. Uniformity: The soil-bentonite backfill shall be thoroughly mixed prior to placement in the cutoff wall such that the bentonite is uniformly mixed through the backfill and the mixture is homogeneous with no unmixed soil clods larger than 2 inches in size.

b. Maximum Particle-Size: The soil-bentonite backfill shall not contain unmixed soil clods or rock larger than 2 inches in size.

c. Slump: The soil-bentonite backfill shall have a saturated paste placement consistency and water content corresponding to a slump cone value of 5 inches to 7 inches determined in general accordance with ASTM C143/C143M. No test result shall be less than 4 inches.

d. Density: The soil-bentonite backfill must have a placement saturated unit weight at least 15 pounds per cubic foot greater than the density of the bentonite slurry in the trench based on

31 56 14 - 16 the maximum in-place trench slurry density measurement (ASTM D7263

e. Hydraulic Conductivity: The SB backfill shall have 80 percent of a 10-test running average equal to 5x10-7 centimeters per second (cm/sec) or less when measured at 28 days and tested in accordance with ASTM D5084. No test shall be greater than 1x10-6 cm/sec. Any test greater than 1x10-6 cm/sec and may be retested once before rejection of work.

The initial design mix may be adjusted by the contractor if necessary and if approved by the Contracting Officer's Representative to adapt to changes in field conditions at no additional cost to the Government.

2.8 MATERIAL STORAGE FACILITY

Provide all necessary materials, equipment, and personnel to store bentonite and other additives to prevent moisture or other contaminants from mixing with the materials prior to use.

2.9 ENVIRONMENTAL PROTECTION

The raw materials and other supplies used in the construction of the SB slurry cutoff wall and any spoil disposed of shall be non-hazardous and shall comply with the SECTION 01 57 20 ENVIRONMENTAL PROTECTION to prevent, and provide for abatement and control of, any environmental pollution arising as a part of the work.

2.10 DISPOSAL SITE

Cutoff wall trench excavated material and/or excess bentonite slurry that are not suitable for use per Section 31 00 00 EARTHWORK shall be disposed of off-site at the Contractor's own expense.

2.11 TRENCH PLATES

The minimum plate thickness shall be 1-1/4 inches for the specified trench width. Steel plates also known as steel plate bridging shall consist of steel designed for HS20-44 truck loading per Caltrans Bridge Design Manual.

Maintain on the steel plates a non-skid surface having a minimum coefficient of friction of 0.35 as determined by California Test Method

342. The trench plates shall extend a sufficient distance beyond the edge of the trench walls so that load transfer from the plates does not impact trench stability during curing and strength development of the wall.

2.12 EQUIPMENT

Furnish all necessary plant and equipment for use on this Project. Obtain and maintain at the jobsite a supply of spare critical replacement parts or backup equipment sufficient to allow the cutoff wall construction to proceed with minimum loss of time due to mechanical breakdown or equipment failure. Calibration of Scales and Flow Meters shall be provided by the Contractor.

Maintain a properly functioning desander at the site during cutoff wall construction.

31 56 14 - 17

2.12.1 Trench Excavation Equipment

Equipment for excavating the slurry trench shall be any type or combination of excavating equipment capable of performing the Work as specified and shown on the Plans. The equipment shall be one that reduces live-load surcharge to a level that will maintain stability of the trench. The equipment shall be capable of excavating the required minimum width of trench in a single pass of the excavating equipment. The buckets utilized with such equipment may be perforated, tapered, and equipped with bottom-side cutter teeth protruding no more than 6 inches. The excavator bucket teeth shall be replaceable with rock excavating teeth and capable of being fitted with a ripper tooth. The bucket shall be designed to maintain the width of the trench and to minimize raveling of the trench sides during use. The equipment shall be able to excavate a maximum of 10 feet deeper than the depth shown on the Plans. However, between Station 44+50 and Station 50+00, the equipment is not required to be able to excavate below the depth shown on the Plans.

In addition to the excavating equipment, have available on the job site a chopping bit, ripping block, or other suitable devices as required to accomplish the trench excavation to the full required depth. All equipment and any equipment modifications shall be reviewed and certified by the equipment manufacturer.

If there is instability due to equipment, repair the wall at no expense to the Government.

2.12.2 Bentonite Slurry Mixing Equipment

The equipment used for mixing the bentonite water slurry shall be capable of mixing the materials into a homogeneous mixture conforming to the Contract specification requirements. The slurry mixing plant shall be equipped with a high-speed/high-shear, colloidal mixer or a high-velocity/high pressure venturi jet mixer used in conjunction with a high-speed/high-shear centrifugal pump. The plant shall be equipped with a mechanically or hydraulically agitated sump and shall include pumps, valves, hoses, supply lines, tools, and other equipment and materials required to prepare the slurry and deliver it in a continuous supply from the hydration tanks to the slurry trench. Mixers shall be capable of achieving complete dispersion of bentonite and additives, and shall be capable of continually mixing the hydrated SB slurry to provide and maintain a uniform blended slurry. Tanks or other storage facilities for storage of hydrated slurry shall be in accordance with the approved Contractor's implementation plan.

The Contractor is required to record and report the daily weight of dry bentonite and water used in the slurry preparation.

2.12.3 Field Laboratory Equipment

The field laboratory equipment for Contractor's quality control testing shall be made available for Government testing at any time and shall contain, at a minimum, the following equipment:

1. Two Marsh funnel sets.

2. One standard filter press.

3. Two mud balances (direct reading of density).

4. One slurry sampler.

5. Two No. 200 sieves.

31 56 14 - 18

6. One set of standard sieves and sieve shaker.

7. One oven for moisture content.

8. One scale.

9. One pH meter.

10. Two slump cones.

11. Adequate number of 3-inch by 6-inch cylindrical sample molds.

2.12.4 Slurry Transporting Equipment

Equipment used for delivering bentonite slurry to the trench shall be pumps that are capable of delivering bentonite slurry quantities without spillage, delays in placement or inducing discontinuities in the wall. All non-complying material shall be removed and replaced at the expense of the contractor.

2.12.5 Hauling Equipment

Earthwork-related hauling and SB mixing equipment shall be pneumatic-tired and track equipment suitable for hauling excavated material and mixing soil with bentonite slurry and meeting the requirements of paragraph EQUIPMENT WEIGHT, SPEED, AND WIDTH. To ensure trench stability, Establish and maintain a minimum setback distance from the open trench side wall to the hauling equipment path.

2.12.6 Equipment Weight, Speed, and Width

Weight of equipment to be used on the levee crown shall be limited to a maximum gross loaded axle weight of 34,000 pounds for trucks. For tracked vehicles, the maximum ground pressure allowed is 2,500 pounds per square foot. The maximum weight of the long-stick excavator shall not exceed 300,000 pounds without prior approval of the Contracting Officer and after evaluation by the Contractor of the effect on levee stability by use of stability analyses. The maximum operating speed of all equipment used on the levee crown or levee toe roads shall be 15 mph. The maximum overall width of equipment used on the levee shall be 18 feet.

2.13 CONSTRUCTION STAKING

Provide, install, and maintain all layout and necessary construction staking to locate the cutoff wall centerline within the alignment of the cutoff wall and the cutoff wall length as shown on the Plans. Surveyor's caps, appropriately identified to include survey control number and name of survey company and mounted on a 2-inch diameter, 2-foot-long steel pipe, driven into the ground, shall be provided at each end of the cutoff wall.

Wooden stakes shall be placed along the cutoff wall centerline at 100-foot maximum intervals between the ends. Coordinates and elevations shall have units consistent with the Plans. A tabulated list containing survey control numbers, grid coordinates, station number, and elevations shall be submitted to the Government within five working days of completing each heading and a summary list at the completion of all survey controls. The beginning and ending of the cutoff wall and utility crossings shall be identified on this list. Survey construction control staking shall be performed by a California licensed surveyor and all survey data shall be stamped by the licensed surveyor.

2.13.1 Initial and Final Elevation

The survey caps at ends of the cutoff wall shall be surveyed to establish initial elevation and final elevation to an accuracy of plus or minus 0.1

31 56 14 - 19 foot and these stakes shall be maintained and protected from damage or movement throughout the work. Submit a report to the Government for the cutoff wall installation showing any settlements that occurred and also indicating the final restored levee crown elevation in comparison to the pre-construction elevation. The cutoff wall stations shall have the theoretical maximum elevations of the bottom of the cutoff wall established, and furnished as part of the submittal. A system for locating stations along the cutoff wall alignment and relating them to the Plans shall be established by the Contractor and submitted to the Government for approval.

2.14 PERMANENT METAL MARKER STAKES

Upon completion of the cutoff wall installation, permanent metal markers stakes meeting the requirement of Type L-1 Object Markers of CA MUTCD shall be placed. In-lieu of the yellow reflective sheeting referenced in the Type L-1 Object Markers, the station location and levee mile of the cutoff wall ends shall placed on the marker. The markers shall be surveyed in at the corresponding projected station location and installable at the landside toe of the levee at the cutoff wall ends.

PART 3 EXECUTION

3.1 GENERAL

The cutoff wall shall be constructed to the elevations, lines, grades, and cross sections shown in the Plans and in accordance with these Specifications, unless otherwise directed. The Contracting Officer may modify the dimensions and quantities of the work as determined necessary.

3.1.1 SB Slurry Cutoff Wall Implementation Plan

Submit a SB Slurry Cutoff Wall Implementation Plan that includes a construction schedule, sequence of operations, equipment data, and quality control program details.

Describe the general work sequence and layout of operations, work hours, and number of headings. Include scale drawings that depict SB slurry preparation and storage areas in the layout of operations. Describe Contractor equipment, delivery and mixing equipment, slurry storage equipment, depth measurement equipment, method of trench excavation, disposal of excavated material, bottom cleaning, SB slurry preparation and placement, and site clean-up. Detail procedures for locating the cutoff wall in the field and confirming that the cutoff wall is plumb. Provide data and operations manuals on the trench depth measuring equipment.

Include a detail plan and procedure for monitoring and addressing slurry loss through the levee.

Describe the quality control program including quality control equipment;

testing and sampling equipment; procedures to obtain backfill bulk samples of SB backfill material; complete details, drawings, and operation of the bulk sampler to be used for sampling slurry at depth in the trench; all required test procedures; the laboratory proposed for use; sample preparation; sample storage; sample documentation; and the method of transporting samples to the laboratory. Include a reporting schedule for completed SB slurry density tests, and permeability tests. Include samples of test data sheets and sample data reduction to obtain hydraulic conductivity. Include a sample of the chain of custody form for quality control and quality assurance samples as documented in paragraph PROTOCOL

31 56 14 - 20

FOR CUSTODY OF SAMPLES.

3.2 SITE WORK

Furnish all plant, equipment, labor, and materials required to construct the SB cutoff wall as shown on the Plans and specified herein, except that the Contracting Officer may at any time direct changes to the wall depth and length to accommodate conditions encountered in the field.

3.3 WORKING SURFACE

Accomplish slurry trench construction from the working surface as shown on the Plans and defined in paragraph DEFINITIONS. The working surface as shown on the Plans shall constitute the top of the cutoff wall for the purpose of measurement and payment.

3.3.1 Construction Staking

Provide, install, and maintain all temporary benchmarks, layout staking, and necessary construction staking to locate the centerline of the wall.

Flagging shall be used to show the stationing every 10 feet. Survey construction control staking shall be performed by a Licensed Surveyor or Registered Professional Civil Engineer authorized to perform surveying in California. All survey data shall be stamped by the surveyor/engineer.

3.3.2 Construction of Working Surface

Construct a working surface as needed to achieve the limits shown on the Plans. If the Contractor's operations require a wider working surface the reason for the change shall be submitted. If approved, a wider working surface may be constructed at no additional cost to the Government.

Working surface subgrade and compaction requirements are described in Section 31 00 00 EARTHWORK. Upon completion of the cutoff wall installation, the levee shall be restored to final alignment lines and grade in accordance with Section 31 00 00 EARTHWORK.

3.4 SLURRY TRENCH EXCAVATION

3.4.1 General

The excavation shall begin from the working surface and shall provide a vertical (within two percent) continuous 36 inch minimum width trench to the required depth along the centerline of the excavation. The equipment shall have a configuration and orientation that reduces live load and dead load surcharge to an amount that will maintain stability of the trench.

Steel plates shall be used to bridge and distribute loads over the SB slurry cutoff wall. Construct the slurry trench using continuous excavation or other methods approved by the Contracting Officer. When trench excavation overlaps into previously placed backfill, the excavation shall extend a minimum of 20 feet into the previously placed backfill at all depths. During excavation, allow time for the excavator bucket to drain slurry from each bucket of excavated material to minimize slurry loss before loading excavated material into haul trucks. When rotating in a waterside direction minimize the bucket swing radius and employ additional environmental protection measures as outlined in the Contractor's Environmental Protection Plan to prevent slurry drainage into any water course. Suitable grading and earth-moving equipment shall be available for preparing and maintaining the work area for SB slurry cutoff wall installation including equipment for the construction of slurry spill

31 56 14 - 21 retainment berms or ditches.

3.4.2 Starter Trench

After grading of the working surface and prior to cutoff wall construction, a starter trench shall be excavated to the lines and dimensions shown on the Plans and backfilled with levee fill material in accordance with Section 31 00 00 EARTHWORK.

3.4.3 Vertical Tolerance

The cutoff wall shall not deviate from vertical more than two percent of the wall depth. Deviations from vertical of more than two percent shall be cause for rejection for that portion of the cutoff wall. Reconstruction of an SB cutoff wall segment because of excess deviation from vertical shall not be the cause for additional compensation. Provide written description on the method used for verifying vertical tolerance to the Government as part of the submittal package.

3.4.4 Bottom Depth

The cutoff wall shall be to the depth and grade shown on the Plans. The Contracting Officer may direct the Contractor to modify the depth based on refusal criteria, examination of trench cuttings, and key-in material information. The bottom elevation of the cutoff wall may vary from 5 feet above to 10 feet below the elevation shown on the Plans without a contractual change order. However, between Station 44+50 and Station 50+00, the cutoff wall will not extend below the depth shown on the Plans.

3.4.5 Trench Stability and Slurry Loss

EnsurE and maintain the stability of the excavated trench at all times for its full open length and depth and shall be responsible for maintaining slurry properties and levels within specified limits. Sample and test the SB slurry according to paragraph TESTING to verify the criteria are met in paragraph PROPERTIES OF BENTONITE SLURRY IN MIXING AREA.