SPECIAL SPECIFICATION 3153 Geosynthetic Clay Liner

Transcription

1 2004 Specifications CSJ , etc. SPECIAL SPECIFICATION 3153 Geosynthetic Clay Liner 1. Description. Install a Geosynthetic Clay Liner (GCL) in accordance with this specification and as shown on the plans. 2. Definitions. For the purposes of this specification guideline, the following terms are defined below: A. Geosynthetic Clay Liner (GCL). A manufactured hydraulic barrier consisting of clay bonded to a layer or layers of geosynthetics. B. Geomembrane. An essentially impermeable geosynthetic composed of one or more geosynthetic sheets. C. Geotextile. Any permeable geosynthetic comprised solely of textiles. D. Minimum Average Roll Value. For geosynthetics, the value calculated as the typical value minus 2 standard deviations from documented quality control test results for a defined population from one specific test method associated with one specific property. E. Overlap. Where two adjacent GCL panels contact, the distance measuring perpendicular from the overlying edge of one panel to the underlying edge of the other. F. Typical Value. The mean value calculated from documented manufacturing quality control test results for a defined population obtained from one test method associated with one specific property. 3. Materials. Provide GCLs consisting of a layer of natural sodium bentonite clay encapsulated between two geotextiles and that comply with the criteria listed in this specification. Reinforce the GCL with the two geotextiles needle-punched together. Laminate one geotextile with a flexible 5 mil membrane liner. Imprint a 9-in. overlap guideline on both edges of the upper geotextile component of the GCL as a means for providing quality assurance of the overlap dimension. Imprint the lines using easily visible, non-toxic ink. Before installing the GCL, furnish test results demonstrating that the proposed material meets the requirements of this specification. Also before installing, obtain approval of the GCL by the Project Engineer

2 The minimum acceptable length dimension of full-size GCL panels is 100 ft. Supply short rolls (those manufactured to a length greater than 70 ft. but less than a full-length roll) at a rate no greater than 3 per truckload or 3 rolls every 36,000 sq. ft. of GCL, whichever is less. A. Accessory Bentonite. Make the granular bentonite sealing clay used for overlap seaming, penetration sealing, and repairs, from the same natural sodium bentonite as used in the GCL, or as approved. Conduct seaming of GCLs in accordance with the manufacturer's specifications and as shown on the plans. 4. Certified Properties. Use materials meeting the requirements listed on Table 1. Table 1 Material Properties and Testing Requirements Material Property Test Method Test Frequency Required Values Bentonite Swell Index ASTM D per 50 tons oz./lb. min. Bentonite Fluid Loss ASTM D per 50 tons oz. max. Bentonite Mass/Area 1 ASTM D ,000 ft lb./sq.ft. min GCL Grab Strength 2 ASTM D 4632 ASTM D 6768 GCL Peel Strength 2 ASTM D 4632 ASTM D ,000 ft lbs. 30 lbs./in. 40,000 ft 2 15 lbs. 2.5 lbs./in. GCL Index Flux 3 ASTM D 5887 Periodic 1 x 10-6 oz. 3 /ft. 2 /sec. max GCL Hydraulic Conductivity 3 ASTM D 5887 Periodic 1.97 x in./sec. max GCL Hydrated Internal ASTM D 5321 Shear Strength 4 ASTM D 6243 Periodic 500 psf typical 1 Bentonite mass/area reported at 0 percent moisture content. 2 Perform tensile strength and peel strength testing in the machine direction using 4 in. grips per modified ASTM D Report results as minimum average roll values unless otherwise indicated. Upon request, report tensile strength per ASTM D 6768 and peel strength per ASTM D Perform ASTM D5887 Index flux and hydraulic conductivity testing with deaired, distilled/deionized water at 80 psi cell pressure, 77 psi headwater pressure, and 75 psi tailwater pressure. Reported value is equivalent to 92 gal/acre/day. This flux value is equivalent to a permeability of 5x10-10 cm/sec for typical GCL thickness. ASTM D 5887 testing is performed only on a periodic basis because the membrane is essentially impermeable. 4 Peak value is measured at 200 psf (10 kpa) normal stress for a specimen hydrated for 48 hours. Use only site-specific materials, GCL products, and test conditions to verify internal and interface strength of the proposed design. 5. Product Quality Documentation. Ensure the GCL manufacturer provides the Contractor or other designated party with manufacturing QA/QC certifications for each shipment of GCL. The certifications are to include:

3 Certificates of analysis for the bentonite clay used in GCL production demonstrating compliance with the parameters swell index and fluid loss. Manufacturer s test data for finished GCL product(s) of bentonite mass/area, GCL tensile strength, and GCL peel strength demonstrating compliance with the index parameters shown. GCL lot and roll numbers supplied for the project (with corresponding shipping information). 6. Product Labeling. Before shipment, ensure the GCL manufacturer labels each roll, identifying: Product identification information (Manufacturer s name and address, brand product code). Lot number and roll number. Roll length, width, and weight. 7. Packaging. Ensure the GCL is wound around a rigid core whose diameter is sufficient to facilitate handling. The core is not necessarily intended to support the roll for lifting but should be sufficiently strong to prevent collapse during transit. Ensure all rolls are labeled and bagged in packaging that is resistant to photodegradation by ultraviolet (UV) light. 8. Storage. Select a dedicated storage area that is away from the high traffic areas, is level, dry, well drained, and approved by the Engineer. Store rolls in a manner that prevents sliding or rolling from the stacks. Chock blocks may be used for this. Stack rolls at a height no higher than that which can be safely handled by the lifting apparatus. Cover the stored GCL materials and the accessory bentonite with a plastic sheet or tarpaulin until their installation. Preserve the integrity and legibility of the labels during storage. 9. Earthwork. Prepare and compact any earthen surface upon which the GCL is installed, in accordance with the project specifications and plans. Provide a surface that is smooth, firm, and unyielding, and free of vegetation, construction debris, sticks, sharp rocks, void spaces, ice, abrupt elevation changes, standing water, cracks larger than 0.25 in. in width, and any other foreign matter that could contact the GLC

4 Subgrade surfaces consisting of granular soils or gravel are not be acceptable due to their large void fraction and puncture potential. Immediately before GLC deployment, final-grade the subgrade to fill in voids or cracks and then smooth-roll to provide the best practicable surface for the GCL. At completion of this activity, ensure no wheel ruts, footprints, or other irregularities exist in the subgrade. Remove, crush, or push into the surface, protrusions extending more than 0.5 in. from the surface, with a smooth drum compactor. The Engineer will inspect the subgrade before placing the GCL. After placing the GLC, it is the installer s responsibility to indicate to the Engineer any change in the condition of the subgrade that could cause the subgrade to be out of compliance with any of the requirements listed in this Section. At the top of sloped areas of the job site, excavate an anchor trench for the GCL or utilize an equivalent runout in accordance with the project plans and specifications and as approved by the Engineer. When utilizing an anchor trench design, excavate the trench and obtain approval by the Engineer before placing the GCL. Do not allow loose soil to remain at the bottom of the trench and ensure no sharp corners or protrusions exist anywhere within the trench. 10. Placing the GCL. Ensure the GCL rolls are delivered to the working area of the site in their original packaging. Immediately before deploying, carefully remove the packaging without damaging the GCL. Orient the GCL (i.e., which side faces up) as directed. Do not allow equipment, which could damage the GCL, to travel directly on it. If the installation equipment causes rutting of the subgrade, restore the subgrade to its originally accepted condition before continuing placement. Execise caution to minimize the extent to which the GCL is dragged across the subgrade in order to avoid damage to the bottom surface of the GCL. A temporary geosynthetic subgrade covering commonly known as a slip sheet or rub sheet may be used to reduce friction damage during placement. Place the GCL panels parallel to the direction of the slope. Ensure the GCL panels lie flat on the underlying surface, with no wrinkles or folds, especially at the exposed edges of the panels. Deploy only as much GCL as can be covered at the end of the working day with soil, a geomembrane, or a temporary waterproof tarpaulin. Do not leave the GCL uncovered overnight. If the GCL is hydrated when no confining stress is present, it is necessary to remove and replace the hydrated material. This work is subsidiary to this Item. Consult the Engineer and the GCL supplier for specific guidance if premature hydration occurs. 11. Anchorage. As directed by the project plans and specifications, place the end of the GCL roll in an anchor trench at the top of the slope or use an equivalent runout design. When utilizing an anchor trench design, round the front edge of the trench to eliminate any sharp

5 corners. Remove loose soil from the floor of the trench. Ensure the GCL covers the entire trench floor but does not extend up the rear trench wall. 12. Seaming. Construct the GCL seams by overlapping their adjacent edges. Exercise caution to ensure that the overlap zone is not contaminated with loose soil or other debris. The minimum dimension of the longitudinal overlap is 9 in. Construct end-of-roll overlapped seams similarly, except that the minimum overlap is 24 in. Construct seams at the ends of the panels such that they are shingled in the direction of the grade to prevent the potential for runoff flow to enter the overlap zone. Construct Bentonite-enhanced seams between the overlapping adjacent panels described above. Expose the underlying edge of the longitudinal overlap and then apply continuous uniform application of granular sodium bentonite along the zone defined by the edge of the underlying panel and a line 6-in. from the edge. Make a similar application of granular sodium bentonite at the end-of-roll overlap. Apply the granular bentonite at a minimum application rate of 0.25 lb. per lineal foot. 13. Detail Work. Seal the GCL around penetrations and embedded structures, which are embedded in accordance with the design plans and the GCL Manufacturer. Cut the GCL using a sharp utility knife. Change the blade frequently to avoid damage to the geotextile components of the GCL during the cutting process. 14. Damage Repair. If the GCL is damaged (torn, punctured, perforated, etc.) during installation, it may be possible to repair it by cutting a patch to fit over the damaged area. Obtain the patch from the same lot number as the material being patched and cut it to size to achieve a minimum overlap of 12 in. around the entire damaged area. Apply granular bentonite as described in Section 12, Seaming, around the damaged area before placing the patch. 15. Cover Placement. Provide cover soils that are free of angular stones or other foreign matter that could damage the GCL. Cover material for use in placing on top of GCLs is to consist of hard, durable, clean sand, gravel, crushed stone, or other material specified on the plans, and that is free from organic matter, clay balls, or other deleterious matter. Unless otherwise shown on the plans, crushed limestone will not be permitted. Cover soils with high concentrations of calcium (e.g., limestone, dolomite) are not acceptable

6 Meet the gradation shown in Table 2 for the percent composition by weight of the cover soil material, unless approved otherwise: Table 2 Gradation for Cover Material COVER MATERIAL COMPOSITION SIEVE SIZE PERCENT RETAINED ON SIEVE 3/4 in. 0 3/8 in No No No No Less than 5 Smaller than No. 200 Place the soil cover over the GCL using construction equipment that minimizes stresses on the GCL. Maintain a minimum thickness of 1 ft. of cover between the equipment tires/tracks and the GCL at all times and locations during the covering process. Place the soil cover in a manner that prevents the soil from entering the GCL overlap zones. Push the cover soil up slopes, not down slopes, to minimize tensile forces on the GCL. Although direct vehicular contact with the GCL is to be avoided, lightweight, low ground pressure vehicles (such as 4-wheel all-terrain vehicles) may be used to facilitate the installation of any geosynthetic material placed over the GCL. Contact thr GCL supplier and the Engineer with specific recommendations on the appropriate procedures in this situation. 16. Measurement. This Item will be measured as the total surface area in square feet covered by the GCL as shown on the plans. This is a plans quantity measurement Item. The quantity to be paid for is the quantity shown in the proposal, modified by Article 9.2, Plans Quantity Measurement. Additional measurements or calculations will be made if adjustments of quantities are required. 17. Payment. The work performed and materials furnished in accordance with this Item and measured as provided under Measurement will be paid for at the unit price bid for Geosynthetic Clay Liner. This price is full compensation for furnishing, handling, storing, and placing the GCL s, bentonite sealed joints, cover material, and for any dewatering of ground water as directed, and for labor, tools, hardware, equipment, and incidentals. Payment for revised quantities due to a change in design will be paid for at the unit price bid per square foot measured