Presidio Levee Specs 02.35.27 20100803.pdf

Urban Levee Remediation Rio Grande & Cibolo Creek Presidio, Texas

DIVISION 02

USIBWC Contract No. IBM09D0006 EXISTING CONDITIONS

US INTERNATIONAL BOUNDARY & WATER COMMISSION

GOVERNING TECHNICAL SPECIFICATIONS AND PROVISIONS

DIVISION 02 – EXISTING CONDITIONS

(SPECIFICATION 02.35.27,

“Soil-Bentonite (S-B) Slurry Trench” ONLY)

Presidio, Texas

DIVISION 02

USIBWC Contract No. IBM09D0006 EXISTING CONDITIONS

This Page Intentionally Blank

Presidio, Texas

SPECIFICATION 02 35 27

SOIL-BENTONITE (S-B) SLURRY TRENCH

This specification includes requirements for construction of soil-bentonite slurry trench within the work area, and includes the following:

1.0 General

2.0 Materials & Equipment

3.0 Construction Methods

4.0 Measurement and Payment

PART 1 – GENERAL

1.1 RELATED DOCUMENTS, CONTRACT CLAUSES, & SPECIFICATIONS

The following may not include all related documents, contract clauses, & technical specifications, and does not relieve the Contractor of the responsibility of performing work associated with this specification in accordance with all terms of the Contract herein.

A. Related documents: As described in paragraph 1.2 of SPECIFICATION 01 01 00.

B. Contract: Section I, 52.236-21“Specifications and Drawings for Construction”

C. Technical Specifications:

• Specification 01 39 00, “Safety”

• Specification 35 41 00, “Construction of Levee”

D. References:

• American Petroleum Institute (API) 13B-1 (2009) - Standard Procedure for Field Testing

Water-based Drilling Fluids

• API Specification 13A (2010) – Specification for Drilling-fluids Materials

• API Recommended Practice (RP) 13B-1 – Recommended Practice for Field Testing

Water-based Drilling Fluid (Third Edition)

• ASTM International (ASTM) C143 / C143M - Standard Test Method for Slump of

Hydraulic-Cement Concrete

• ASTM D1140 - (2000; R 2006) Amount of Material in Soils Finer than the No. 200

(75-micrometer) Sieve

• ASTM D2216 - (2005) Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass

• ASTM D2434 - (1968; R 2006) Permeability of Granular Soils (Constant Head)

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 1

Presidio, Texas

• ASTM D2487 - (1966; R 2006) Classification of Soils for Engineering Purposes

• ASTM D422 - (1963; R 2007) Particle-Size Analysis of Soils

• ASTM D4318 - (2005) Liquid Limit, Plastic Limit, and Plasticity Index of Soils

• ASTM D5084 - (2003) Measurement of Hydraulic Conductivity of Saturated Porous

Materials Using a Flexible Wall Permeameter

• ASTM D698 - (2007el) A Laboratory Compaction Characteristics of Soil Using Standard

Effort (12,400 ft-lbf/cu. ft. (600 kN-m/cu. m.))

• U.S. Environmental Protection Agency (EPA) 600/4-79/020 – (1983) Method for Chemical Analysis of Water and Wastes

1.2 GENERAL

The work covered by this Specification consists of furnishing all labor, equipment, materials, and all efforts necessary to construct slurry trench along the landside toe of levee in the areas defined on the plan sheets. The slurry trench is a three (3) foot minimum width trench excavated through the existing ground or prepared working surface using the slurry method of excavation and backfilled with S-B backfill material, to form a low permeability cutoff wall.

1.3 QUALIFICATIONS

The Contractor shall provide certification for the following:

A. Contractor. The Contractor shall have successfully installed a minimum area of 1,000,000 square feet of slurry trench. The qualifications and experience of personnel who shall be responsible for conducting the operations shall include references (name and telephone number) of the owners of the Contractor's previous slurry trench construction projects.

B. Slurry Trench Specialist. The slurry trench specialist shall be an individual who has had experience with at least five projects in all aspects of slurry trench construction which includes, but is not limited to:

(1) The use, testing, and control of bentonite slurries,

(2) The mixing methods required to properly mix the slurry and backfill materials as required,

(3) Trench excavation and backfilling procedures,

(4) Experienced excavating in both sands and gravels, and

(5) A thorough knowledge of construction equipment and material testing required for slurry trench construction.

C. Slurry Trench Excavation Equipment Operator. The slurry trench excavation equipment operator shall have experience using similar slurry trench excavation equipment to be used for this

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 2

Presidio, Texas contract in a minimum of two projects of similar or greater magnitude (depth).

1.4 SUBMITTALS

A. Preconstruction Submittals.

(1) Preconstruction Testing Plan. The Contractor shall submit a plan providing a list of test equipment, procedures, and materials to be used to verify the mix design for the S-B backfill.

(2) Slurry Trench Implementation Plan. The Contractor shall submit a plan describing the general work sequence and layout of operations. The layout of operations shall include scale drawings, which depict slurry and S-B backfill preparation and storage areas. The plan shall describe Contractor qualifications, equipment, method of trench excavation, use or disposal of excavated material, bottom cleaning, slurry preparation and maintenance, S-B backfill preparation and placement, and site clean-up. The plan shall provide a description of quality control equipment and test procedures, sample test forms for reporting test results, and the offsite laboratory proposed for use.

The Contractor shall submit data on the equipment to be used in the construction of the slurry trench; equipment to be used to verify depth and width of slurry trench, equipment to be used to obtain record control samples of the completed slurry trench; and equipment to be used in the Contractors quality control testing.

B. Shop Drawings.

(1) As-built Profile. The Contractor shall submit a scaled-drawing providing a log of the subsurface materials excavated from the trench, and a profile of the completed slurry trench.

The limits of each batch of S-B backfill shall be delineated as placed.

C. Samples.

(1) Bentonite. The Contractor shall submit a minimum of 10 pounds of the proposed bentonite at least one month prior to use.

(2) Backfill Material. The Contractor shall submit a minimum of 50 pounds of each type of proposed borrow soil at least one month prior to use.

D. Test Reports.

(1) S-B Backfill Test Report. The Contractor shall submit a report summarizing the procedures and results of the Pre-construction S-B backfill mix tests. The report shall include a description of mix proportions, gradations, slumps, densities, permeabilities, and moisture contents of at least five samples of the final S-B backfill mix using the bentonite and backfill materials proposed for use.

(2) Quality Control Testing. The Contractor shall submit the results from quality control testing.

(3) Soundings. The Contractor shall submit a record of soundings and measurements taken during construction of the slurry trench.

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 3

(4) Water. The Contractor shall submit a record of the water source and associated chemical analysis.

(5) The Contractor shall submit Bentonite Slurry Mixes Slurry Properties and a record of bentonite slurry mix quantities, proportions of additives utilized, and adjustments for each batch.

E. Certificates.

(1) Bentonite. The Contractor shall submit a copy of the test results from the bentonite manufacturer for each lot shipped to the site and a certificate of compliance stating that the bentonite complies with applicable standards.

1.5 DELIVERY, STORAGE, AND HANDLING

Materials delivered and placed in storage shall be protected from the weather, flooding, dirt, dust or other contaminants.

1.6 GEOTECHNICAL SITE CONDITIONS

A. Exploratory Borings. Subsurface exploratory borings have been obtained by the Government to determine the character of materials to be excavated. Locations of the borings and the logs of those borings, which fall within the area of this contract, are shown on the drawings for the convenience of the Contractor. The Government assumes no responsibility for interpretation or deductions made by the Contractor from the logs and borings. Local minor variations may exist in the subsurface materials between boring locations and, if encountered, will not be considered as being materially different within the purview of this contract. Soils classifications shown on the logs are the result of field visual classifications and laboratory classifications in accordance with the Unified Soil Classifications System. The results of all laboratory testing performed during the subsurface investigation are available for review by the Contractor in the Geotechnical Report. Attention is invited to paragraph SUBSURFACE INVESTIGATIONS in the Special Clauses for availability of soil samples for inspection.

B. Subsurface Conditions. In general, non-cohesive sands (SP) and gravels (GP) were observed below the ground surface to depths of about 48 to 80 feet. Thin layers of sandy clays (CL) and/or clayey sands (SC) should be anticipated within the upper 20 feet.

C. Ground Water. The depth-to-water level readings obtained during the geotechnical investigations ranged from about 5 to 16 feet below the original ground surface. In general, the depth-to-water levels did not rise from their initial readings after a 15-minute observation period.

Given the close proximity of the borings to the Rio Grande and the presence of significant deposits of clean, coarse gravels within the floodplain, it is expected that the areal groundwater is generally dominated by the water levels within the Rio Grande. It is likely for groundwater to exist beneath this site at shallower depths on a transient basis following periods of precipitation and/or flooding. Fluctuations in groundwater levels occur due to variations in rainfall and surface water run-off. The construction process itself may also cause variations in the groundwater level.

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 4

Presidio, Texas

D. Embankment Conditions. Levee fill material consisting of locally available soils were observed at the levee crest extending to the natural ground elevations. Lean clays (CL) were the predominate fill material observed in the borings performed for this study. Areas of clayey sands (SC) and sandy clays (CL) were also observed.

1.7 QUALITY CONTROL TESTING

The Contractor shall provide Quality Control Inspectors as necessary for bentonite slurry preparation and maintenance, trench excavation, and S-B backfill preparation and placement.

A. Bentonite Tests. A minimum of one test for each specified requirement shall be performed for each truck or rail car shipment delivered to the site.

B. Water Tests. A minimum of one test for each specified requirement shall be performed for each water source used. Testing shall be performed as specified in Table 1.

C. Backfill Material Tests. One set of backfill material tests, as specified in Table 1, shall be performed for every 500 cubic yards used.

D. Slurry Properties. Slurry shall be required to hydrate a minimum of eight hours prior to use.

The initial bentonite slurry shall be tested prior to placing in the trench and a minimum of 2 times each eight hour shift per mixing plant.

E. S-B Backfill Tests. Sampling and testing shall be performed, in accordance with the approved

Preconstruction Testing Plan, just prior to placing S-B backfill in the trench as shown in Table 1.

The density of the S-B backfill shall be calculated using a 4 inch cylindrical mold as described in Paragraph 6 of ASTM D 698. S-B backfill shall be placed in the mold and rodded 10 times.

Additional S-B backfill shall then be added to fill the mold. The weight and volume of the molded S-B backfill shall then be used to determine the density. The density of the S-B backfill shall be determined using a mud balance. Density shall be determined at a rate of 1 test for every 1000 cubic yards. A sample of S-B backfill for permeability testing shall be taken just prior to placement in the trench for every 1000 cubic yards. The Contractor shall submit an S-B Backfill Test Report containing the results of the tests performed.

PART 2 – MATERIALS & EQUIPMENT

2.1 MATERIALS

A. Bentonite. The bentonite shall be sodium cation base montmorillonite powder that conforms to

API Spec 13A, Section [10], and Table 1, located at the end of this section. Chemically treated bentonite will not be allowed. No bentonite from the bentonite manufacturer shall be used prior to acceptance by the Contracting Officer. Bentonite not meeting specifications shall be promptly removed from the site at the Contractors expense. Bentonite shall be protected from moisture during transit and storage.

B. Water. The Contractor shall supply water required for mixing with bentonite to produce slurry.

The water shall be clean, fresh, and comply with the standards specified in Table 1. The Contractor shall furnish water quality test results for water used for mixing the bentonite slurry to

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 5

Presidio, Texas assure conformance to these standards.

C. Backfill Material. The backfill material shall be in accordance with SPECIFICATION 35 41 00.

Backfill shall be free of contamination, roots, debris, brush, sod, organic or frozen material.

Material passing the No. 200 sieve shall have a liquid limit greater than 30 and a plasticity index greater than 10. Materials shall be thoroughly blended prior to mixing with bentonite slurry and shall conform to the following gradation requirements:

Screen Size or Number Percent Passing

(U.S. Standard) by Dry Weight

3 inch 75-100 No. 4 40-80 No. 40 25-60 No. 200 20-40

The Contractor should assume that the minimum of thirty (30) percent of the total trench volume will be comprised of imported clay fill for cost estimate purpose. However, it is the Contractor’s responsibility to provide appropriate volume of backfill material to the trench construction to meet the construction requirements specified in this Specification.

D. Bentonite Slurry Mixes.

(1) Initial Bentonite Slurry Mixture. The initial bentonite slurry mixture shall conform to the standards specified in Table 1.

(2) Trench Bentonite Slurry Mixture. The trench bentonite slurry mixture shall conform to the standards specified in Table 1.

(3) Bentonite. If directed by the Contracting Officer, the Contractor shall thicken the slurry to a more viscous condition than the limits specified above. The Contractor shall use additional bentonite, as directed.

(4) Additives. Peptizing agents and bulking agents shall not be mixed with the slurry.

Approved thinners or dispersants and flocculants of the types used in the control of oil field drilling muds, may be used to control standard properties of the slurry such as apparent viscosity, pH and filtration characteristics.

(5) S-B Backfill. The S-B backfill, consisting of backfill material, bentonite slurry, and a minimum of two percent dry bentonite shall be thoroughly mixed and shall conform to the standards specified in Table 1 just prior to placement in the trench.

2.2 EQUIPMENT

A. 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 drawings. 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

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 6

Presidio, Texas inches. The bucket shall be designed to maintain the width of the trench and to minimize ravelling of the trench sides during use. The equipment shall be able to reach at least five feet deeper than the maximum depth shown on the drawings.

B. Slurry Mixing and Cleaning Equipment. 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 pond [or 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 slurry to provide and maintain a uniform blended slurry. The Contractor shall have sufficient ponds [or tanks] for storage of hydrated bentonite slurry. Slurry cleaning equipment shall be available to reduce sand, sediment, or other solids as necessary to maintain the sand content or density requirements of the slurry in the trench. Slurry cleaning equipment may include but not be limited to vibratory shaker screens, centrifugal sand separators, or stilling ponds.

C. Field Laboratory Equipment. The field laboratory shall contain as a minimum the following equipment:

• One (1) Mold and rod for slump test.

• One (2) Marsh funnel sets.

• One (1) Standard filter press.

• One (2) Mud balances (direct reading of density).

• One (1) Slurry sampler.

• One (2) Number 200 sieves.

• One (1) Set of standard sieves and sieve shaker.

• One (1) Oven for moisture content.

• One (1) Balance.

• One (1) pH meter.

• One (2) Sand content sets.

• One (1) 4-inch Cylindrical mold.

PART 3 – CONSTRUCTION METHODS

3.1 GENERAL

The slurry trench shall be constructed to the elevations, lines, grades, and cross-sections shown and in accordance with these specifications, unless otherwise directed. The Government may modify the dimensions and quantities of the work as determined necessary. The Contractor shall submit a Slurry Trench Implementation Plan for approval, a minimum of four weeks prior to the start of construction.

The Contractor shall conduct its operation in a safe manner. Any damage to the existing levee shall be repaired to the original condition at no additional costs to USIBWC.

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 7

3.2 WORKING SURFACE

Slurry trench construction shall be accomplished from the working surface, as shown on the drawings.

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 material and compaction requirements are described in SPECIFICATION 35 41 00. In the event that the static ground water table is encountered at a depth of 3.0 foot or less below the designated working surface, the Contractor shall, at the direction of the Contracting Officer, raise the working surface to a height of 3.0 feet above the measured static ground water level with approved fill material. The working surface thus constructed shall be utilized as a basis for measurement for payment.

3.3 SLURRY TRENCH EXCAVATION

The excavation shall begin from the working surface and shall provide a vertical (within 2 percent) continuous three foot minimum width trench to the required depth along the centerline of the excavation.

The Contracting Officer may direct the Contractor to modify the trench depth based on examination of bucket cuttings or drive samples. The toe of the slope of the trench excavation shall not precede the toe of the S-B backfill slope by less than 30 feet or more than 100 feet. At the intersection of 2 straight line segments, the trench excavation shall extend a minimum of five feet beyond the outside of the intersection at all depths. If trench excavation overlaps into previously completed slurry trench, the excavation shall extend a minimum of ten feet into the previously placed S-B backfill at all depths. Any removed section of completed slurry trench shall be refilled with S-B backfill at no additional expense to the Government.

Termination of excavation will be approved by the Contracting Officer.

3.4 SLURRY PLACEMENT AND TESTING

A. Slurry Placement. Slurry shall be introduced into the trench at the time excavation begins. The level of the slurry in open trenches shall be maintained a minimum of 3 feet above ground water level and no more than 2 feet below the top of the working surface until the placement of S-B backfill is complete. If the density or sand content of the slurry in the trench does not conform to the standards specified in Table 1, the excess solids shall be removed from the slurry using approved methods or the slurry shall be replaced with fresh slurry. Slurry shall not be diluted by surface water. Conditioning of the slurry may require recirculation through a shaker screen or the addition of approved additives. The Contractor shall have sufficient personnel, equipment, slurry storage areas, and prepared slurry materials shall be ready to raise the slurry level at any time in the excavated trench, weekends and holidays included.

B. Slurry Testing. The bentonite slurry in the trench shall be sampled a minimum of 2 times each eight hour shift (near the beginning and end of each shift), at two depths; approximately 2 feet below the slurry surface and approximately 2 feet above the bottom of the trench. These samples shall be taken within 5 feet of the toe of the S-B backfill slope. Additional samples shall be obtained at the request of the Contracting Officer.

3.5 EXCAVATION INTO LEVEE EMBANKMENT

For construction of slurry trench, the existing levee embankment needs to be excavated along the

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 8

Presidio, Texas riverside of the levee as shown on the plans. A series of keys and benches shall be constructed for excavation operations in accordance with SPECIFICATION 35 41 00.

3.6 EXCAVATED MATERIAL

Material excavated from the trench which meets the material requirements specified in Paragraph 2.1 herein shall be used as backfill. Excavated material to be used as backfill shall be stockpiled for subsequent processing in approved areas. Excavated trench material not used as backfill shall be disposed of at the off-site disposal areas, provided by the Contractor.

3.7 STABILITY

The Contractor shall be responsible for insuring and maintaining the stability of the excavated trench at all times for its full length and depth and shall be responsible for maintaining slurry densities and levels within specified limits. The Contractor shall control surcharges from all excavation and backfilling equipment, waste, berm construction, backfill stockpiles, and any other loading situations that may affect trench stability. It is the Contractor's sole responsibility to ensure that the mixing of S-B backfill and any stockpiles do not affect the open trench stability. In the event of failure of the trench walls prior to completion of backfilling, the Contractor shall at his expense re-excavate the trench and remove all material displaced into the trench and take corrective action to prevent further deterioration.

3.8 TRENCH CLEANING

At a minimum, unless otherwise approved, the trench bottom shall be cleaned at the start of each day. If S-B backfill placement operations have ceased for longer than 24 hours, the face of the S-B backfill slope shall be cleaned prior to the placement of additional S-B backfill. The trench bottom shall be probed for any deposits or sloughed materials prior to cleaning. The trench bottom shall be cleaned by using an excavator bucket or other approved equipment to ensure removal of sand, gravel, sediment, and other material left in the trench during excavation or which has settled out of the slurry. Cleaning equipment shall not remove material from the walls of the trench. The Contracting Officer may require more frequent cleaning. After the trench bottom has been cleaned, the Contractor shall sample the trench bottom with a sampler approved by the Contracting Officer. After examining the samples, the Contracting Officer will either approve the excavation at the points checked or require additional cleaning.

If additional cleaning is required, then additional samples shall be furnished by the Contractor as specified above.

At the end of the work week or when backfill operations are expected to cease for more than 24 hours, the bentonite slurry within the trench shall be cleaned to reduce the need for trench cleaning prior to placement of new S-B backfill. The Contractor shall reduce the sand content of the trench slurry to two (2) percent or less as determined by API RP 13B-1, or directed by the Contracting Officer.

3.9 S-B BACKFILL MIXING AND PLACEMENT

A. Mixing. The S-B backfill shall be thoroughly mixed via disking, harrowing, bulldozing, blading, or other approved methods into a homogeneous mass, free from large lumps or clods of soil or pockets of fines, sand, or gravel. Occasional lumps of up to three inches in their largest dimension will be permitted. All particles shall be coated with slurry. The S-B backfill may be sluiced with slurry during the mixing operations. Sluicing with water is not permitted. The

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 9

Presidio, Texas

S-B backfill shall be mixed along the side of the trench. When mixing the S-B backfill along the side of the trench, heavy equipment such as bulldozers shall not operate in a back and forth fashion, paralleling the open trench, closer than 60 feet from the lip of the trench. Excess slurry may be allowed to flow back into the trench.

B. Placement. Initial S-B backfill placement shall be by one of the following methods: (1)

Placement by lowering S-B slurry to the bottom of the trench with crane and clamshell bucket, or tremie methods until the surface of the S-B backfill rises above the surface of the slurry trench at the end of the trench; (2) Construct a lead-in trench [1-1/2H:1V] or flatter at a point outside of the limits of work to allow a S-B backfill face to form prior to reaching the full depth of the required slurry trench. No payments will be made for the portions of trenches which lie outside of the limits of work. Placement operations shall proceed in such a manner that the slope of the initially placed S-B backfill is maintained. Free dropping of S-B backfill through the slurry is not permitted. The S-B backfill shall be placed so that it will slide down the forward face of the S-B backfill slope. The S-B backfill shall be placed in the excavated trench so that no pockets of slurry are trapped and that a constant slope is maintained. Placement shall be continuous from the beginning of the trench in the direction of the excavation to the end of the trench.

C. Mixing and Placing During Cold Weather. No mixing or placing of the S-B backfill shall be performed when the air temperature is below 20 degrees F. Frozen S-B backfill shall not be placed in the trench and backfill material containing frozen lumps shall not be used to mix S-B backfill.

D. Testing. When required, additional samples for permeability testing shall be taken at 500 ft intervals for the full depth of the completed slurry trench using a sampler approved by the Contracting Officer. If test results do not meet the requirements listed in Table 1, corrective action, as determined by the Contracting Officer, shall be taken.

3.10 SOUNDINGS

Excavation and S-B backfill soundings shall be taken every 20 feet along the trench centerline using a weighted tape, cable, or other approved device. Soundings shall be measured to the nearest 0.1 ft. The soundings shall measure the following:

A. Elevation of Trench Bottom Prior to Backfilling. The Contractor shall determine the elevation of the trench bottom after the trench has been cleaned and approved as described under paragraph Trench Cleaning. This sounding shall not precede the toe of the S-B backfill slope more than 50 feet. This elevation is subject to approval by the Contracting Officer.

B. Profile of S-B Backfill Slope and Trench Bottom. The S-B backfill slope and trench bottom shall be sounded at the beginning and end of each shift, and at additional times as directed, at intervals of 20 feet.

3.11 AS-BUILT PROFILE

An as-built profile of the trench bottom and S-B backfill slopes, including descriptions of materials encountered in the trench bottom, shall be continuously maintained. This profile shall indicate extent of excavation and the S-B backfill profile at the end of each work day. The S-B backfill batch numbers shall appear on the profile with the limits of each batch of material delineated as placed.

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 10

3.12 TREATMENT OF TOP OF SLURRY TRENCH

Prior to placement of the compacted trench cover, a temporary plastic sheeting cover shall be placed over the trench to prevent desiccation. The temporary cover material shall be placed within 6 hours after S-B backfill placement is completed over each 100 foot reach. If any depression develops within the completed slurry trench area, it shall be repaired by placing and compacting additional trench cover soil.

After a minimum two weeks, the temporary trench cover shall be removed and replaced by a final compacted trench cover. A final compacted trench cover five feet wide and two feet deep shall be placed to a dry density of at least 95 percent of maximum density at optimum moisture to plus 3 percent in accordance with ASTM D 698. Heavy construction equipment and machinery shall only be driven over the slurry trench at approved heavy equipment crossing points.

3.13 CLEAN-UP

Excavation spoil, unused S-B backfill, and excess slurry shall be removed following completion of S-B backfill placement. These materials shall be disposed of at the direction of the Contracting Officer.

3.14 EMERGENCY RESPONSE PLAN

The Contract shall submit the Emergency Response Plan (ERP) to USIBWC prior to the excavation for S-B slurry trench, detailing the emergency actions to be taken in case of existing levee failure due to the trench excavation, temporarily and partially removing existing levee on the riverside slope, and backfilling activities near the riverside toe of the levee. The ERP shall also detail the emergency actions to be taken, should a flood in the Rio Grande become imminent that could impact the work and the integrity of the levee system.

PART 4 – MEASUREMENT AND PAYMENT

4.1 MEASUREMENT

Measurement for S-B Slurry Trench shall be based on the area in linear foot of completed in place along the centerline of the slurry trench. Measurement shall be based on surveys and soundings taken at the site as directed and approved.

4.2 PAYMENT

The work performed and materials furnished in accordance with this Specification and measured as provided under "Measurement" will be paid for at the unit price bid for "Slurry Trench”. Such price will include costs incurred for the construction and completion of the slurry trench. No separate payment will be made for material, equipment, handling and cleaning the slurry, quality control testing, record keeping, excavation into existing levee embankment and repairing the levee to the original condition, and site preparation including construction of the working surface.

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 11

Table 1

Soil-Bentonite Slurry Trench Quality Control Testing

Property Requirement Test Method

Bentonite Powder

a. YP/PV Ratio 1.5 maximum API Spec 13A

b. Plastic Viscosity > 10 API Spec 13A

c. Filtrate Loss < 12.5 cubic cm API Spec 13A

d. Moisture Content < 10% ASTM D 2216

Chemical Analysis of Water

a. pH 6 to 8 API RP 13B-1

b. Hardness < 50 ppm API RP 13B-1

c. Total Dissolved < 500 ppm EPA 600/4-79/020 Solids Method 160.1

d. VOCs MCL SW-846 Method 5030B/8260B

e. SVOCs MCL SW-846 Method 3510C/8270C

f. TPH MCL SW-846 Modified 8015

g. Metals MCL SW-846 3005A/6010C

h. Pesticides MCL SW-846 3510C/8081A/8141A

MCL = Maximum Contaminant Level

Initial Bentonite Slurry

a. Viscosity > 40 sec API RP 13B-1

b. Density > 64 pcf API RP 13B-1

c. Filtrate Loss < 20 cubic cm API RP 13B-1

d. pH 6.5 to 10 API RP 13B-1

In-Trench Bentonite Slurry

a. Density 64-85 pcf and at least API RP 13B-1 15 pcf less than S-B backfill density

b. Viscosity > 40 sec API RP 13B-1

c. pH 6.5 to 10 API RP 13B-1

d. Sand Content * 10% max API RP 13B-1

* Sand Content limit can be waived, provided that the slurry has good flow characteristics and achieves the other requirements specified in this Specification herein.

Backfill Material

a. Grain Size Para. 2.1.3 ASTM D 422

b. Moisture content For record ASTM D 2216

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 12

Presidio, Texas

c. Fines Content Para. 2.1.3 ASTM D 1140

d. Atterberg limits Para. 2.1.3 ASTM D 4318

S-B Backfill

a. Slump Cone 4-6 inches ASTM C 143/C 143M

b. Density For Record ASTM D 698 and Para.2.4.5

c. Permeability < 1 x 10-7 cm/sec ASTM D 5084

NOTES:

(1) If more than one (1) batching plant is being used, these frequencies shall apply to each batching plant separately.

(2) Permeability tests may be performed using an approved fixed wall permeameter except that for every 5 such tests, there shall be 1 test using a flexible wall permeameter. Fixed wall test methods and procedures shall be submitted and approved prior to use.

(3) Flexible wall permeability tests shall be performed at a maximum effective confining pressure of

30 psi and a maximum hydraulic gradient of 60.

- END OF SPECIFICATION -

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 13

Presidio, Texas

USIBWC Contract No. IBM09D0006 Page 02.35.27 - 14

This Page Intentionally Blank