The leachate collection system shall be equipped with a piping network.
- (1) Pipe material. Pipes shall be capable of withstanding the maximum overburden anticipated, and shall be constructed of at least six-inch diameter, schedule 80 PVC, HDPE-SDR of 11, or an equivalent approved by the DEQ. Piping with lesser strengths may be acceptable if supporting calculations are provided.
- (2) Perforations. Pipes shall contain a minimum of two (2) rows of perforations no greater than 5/8 inch in diameter. Pipe perforations shall be drilled at an angle between 45° and 60° from the vertical and shall be spaced according to design loading and anticipated volume of leachate.
(3) Pipes. The piping system shall be designed and installed as follows:
- (A) Orientation. Pipes shall be installed on top of the FML with perforations facing down.
- (B) Pipe bends. The piping system shall have gradual sweep bends that are tied into one or more sumps designed to remove collected leachate from the system.
- (C) Pipe slopes. Secondary collection lateral pipes shall maintain adequate slope after allowances for settlement. Primary centralized removal pipes shall maintain a slope of at least 0.5% after settlement.
- (D) Spacing. Pipe spacing shall be based on the anticipated volume of leachate.
(E) Cleanouts. Cleanouts shall be placed so that all collection pipes can be accessed.
- (i) Spacing of cleanouts shall be not exceed 1200 feet or available equipment, whichever is less. A larger spacing may be proposed if equipment is available that will accommodate the larger spacing.
- (ii) Cleanouts shall be at least the same diameter as the collection pipe.
- (iii) Penetrations of the liner shall be minimized.
- (4) Backfill. Each pipe of the piping network shall be covered with a minimum of twelve inches (12") of material with a hydraulic conductivity of 1 x 10-2 cm/sec or greater.
- (5) Geotextile. Backfill around the piping network shall be covered with suitable geotextile fabric.
Added at 20 Ok Reg 1151, eff 6-1-03