1. SCOPE The work shall consist of furnishing, transporting, and placing a buried flexible membrane liner to the elevations, grades and cross sections as shown on the drawings or as staked in the field.
2. MATERIALS The buried membrane liner shall have a nominal thickness as shown on the drawings or as specified in Section 10. The liner shall conform to the material properties shown in Table 1.
3. SHIPPING AND STORAGE The buried membrane liner shall be shipped to the job site in a manner so as not to damage the material. The liner shall be stored so that it is protected from puncture, dirt, grease, water, moisture, mechanical abrasion, excessive heat or other damage, The material shall be stored on a smooth surface and not stacked. The material shall be protected from direct sunlight.
All buried membrane liner shall be free of damage or defect. Each package delivered to the job site shall bear the name of the material, the manufacturer’s name or symbol, the quantity therein, and the thickness of the material.
4. SUBGRADE PREPARATION The area to be lined shall be drained and allowed to dry until the surface is smooth. All cut and fill slopes to be lined shall be constructed in accordance with the drawings. The area on which the flexible membrane will be placed shall be raked to remove all large clods, roots, brush, sod or rocks that might endanger the membrane. The subgrade shall be rolled to provide an extra measure of safety against punctures. In rocky areas, a layer of fine soil shall be provided as a protection against irregularities that cannot be removed by rolling.
5. PLACEMENT The placement of the flexible membrane line shall be performed in accordance with the manufacturer’s recommendations or under the supervision of an authorized representative of the manufacturer.
Liner installation shall not begin until the subgrade has been inspected and approved by the Engineer.
The liner shall not be deployed during fog, precipitation, in the presence of excessive winds or in temperatures less than 40o F. The liner shall be loosely spread over the foundation with sufficient slack to accommodate thermal expansion and contraction expected during construction. Each panel shall be laid out and positioned to keep the number and length of the liner field joints to a minimum and consistent with proper methods of installation. The method used to place the panels shall minimize wrinkles (especially differential wrinkles between adjacent panels). Seams shall be oriented down, not across the slope. Sharp corners shall be avoided. Up slope panels shall overlap down slope panels. Horizontal and T-shaped seams shall not be placed on slopes. No base T-shaped seam shall be closer than 5 feet to the toe of the slope. Seams shall be aligned with the least possible number of wrinkles or “fishmouths.” Adequate anchorage (that will not damage the liner) shall be placed to prevent relocation of the panels or uplift by wind.
Anchor trenches for the liner shall be excavated in accordance with the drawings or as specified in Section 10. The membrane shall conform to the trench shape and shall extend a minimum of 8 inches up the opposite side of the trench. The trenched shall be carefully backfilled and compacted after the membrane is in place.
Motorized equipment contact and/or traffic shall not be allowed on the liner. No equipment or tools shall damage the liner by handling, traffic, or by other means. Personnel working on the liner shall not smoke, wear damaging shoes, or engage in other activities that could damage the liner. Use of metal tools shall be kept to a minimum.
6. SEAMING Seaming shall be in accordance with manufacturer's recommendations. The seams shall be a minimum 4-inch wide fully bonded seam without wrinkles or voids. Wrinkles or fishmouths shall be cut and patched with a minimum 4 inches of material beyond the cut in all directions. A sample seam shall be made on a daily basis or in the event that weather conditions change drastically during field seaming operations.
7. SEAM TESTING All field seams will be air lance tested in accordance with Section 7.1.1 of ASTM Designation D 4545. The air lance test consists of direction a flow of pressurized air through a 3/16-inch nozzle using as minimum of 50 psi. The air lance wand nozzle shall be held not more than 2 inches from the seam. Where visual or audible signs occur, which indicate unbonded seam area; they shall be repaired. Air lance test shall not be conducted until a minimum of 4 hours after the seam is complete.
8 FINAL TESTING AND INSPECTION Upon completion of the work, installation shall be subjected to a final inspection. All work in the system therein being tested shall be complete, cleaned and ready for use. The work shall meet the requirements as to line, grade, cleanliness and workmanship. Any discrepancies shall be repaired.
9. METHOD OF PAYMENT Payment for Flexible Membrane Impervious Liner shall be made at the contract lump sum price and will constitute full compensation for all labor, materials, equipment, and all other items necessary and incidental to the delivery and placement of the liner
Table 1. Requirements of polyvinyl chloride plastic sheeting
10. ITEMS OF WORK AND CONSTRUCTION DETAILS Items of work to be performed in conformance with this specification and the construction details are:
a. Bid Item 2, Impervious Membrane 1. This item shall consist of furnishing, transporting, and installing an impervious membrane as shown on the drawings or as staked in the field.
2. A single, continuous sheet of material may be used in lieu of construction of field seams.
3. Material used for the impervious membrane shall be approved by the Engineer prior to delivery to job site. The material shall have a minimum nominal thickness of 20 mils.
4. In Section 4, Subgrade Preparation, the sub grade shall be rolled with a smooth drum roller weighing not less than 8 tons.
5. Backfilling and compaction of materials in Anchor trenches shall be in accordance with Construction Specification 23, Earthfill. Backfill material and bedding material for riprap shall not be dropped from heights greater than 18 inches to avoid damage to impervious material.
NRCS – NV 400- 1/00
TWIN LAKES MODIFICATION ROBINSON CREEK, MONO, CO., CA