ARCHIVED REPORTS_2004 - Laserfiche WebLink

Home Browse Search

Leachate in WMU FU-04 will drain to a permanent double composite lined sump at the southern WMU FU-04 edge. The primary and secondary sumps are each lined with 60-mil HDPE geomembrane and GCL. The primary and secondary sumps are each 2-ft deep and sized to accommodate leachate from WMU FU-04. Within the primary and secondary sumps will be a perforated section of 18-inch diameter HDPE pipe surrounded by coarse gravel. The perforated 18- inch pipes will be connected to nonperforated 18-inch leachate riser pipes. The leachate riser pipes will extend from the primary and secondary sumps to the ground surface. Submersible pumps will be extended through the leachate riser pipes to the sumps for pumping out leachate. All leachate will be directed via a header pipe to the new Class II Leachate Impoundment, where it will be evaporated. Specifications for the granular drainage material, coarse gravel, HDPE pipe, filter and cushion geotextile, and geocomposite drainage layers are included in Appendix C. Quality assurance testing of the LCRS materials is outlined in the CQA Manual (Appendix D). The testing includes particle size and hydraulic conductivity for the granular drainage material and coarse gravel and manufacturer's certification of material properties for the geotextile and GDN. Details of the composite liner and LCRS components are shown on the Construction Drawings in Appendix A. 5.2.3 Base LCRS in Northeastern Portion of WMU FU-04 The base LCRS in the northeastern portion of the cell will be constructed of a 6-inch-thick layer of clean granular material with a minimum hydraulic conductivity of 0.1 cm/sec draining towards leachate collection pipe trenches. The particle size of the granular drainage material has been limited to a maximum of 1/2-inch to protect against puncture of the adjacent geotextile filter fabric, and to a maximum of 3 percent of particles finer than the No. 200 sieve to maintain its permeable nature. The leachate collection trenches will contain 3-inch diameter SDR 11 perforated HDPE leachate collection pipes (see pipe sizing and loading calculations in Appendix B). The pipes will be placed within each leachate collection trench to increase the drainage capacity of the LCRS. Each pipe will be surrounded by coarse gravel wrapped with a nonwoven geotextile to prevent migration of fine particles from the overlying LCRS granular drainage material. The minimum hydraulic conductivity of the coarse gravel will be 1.0 cm/sec. The coarse gravel will be washed and have a maximum particle size of 1 inch with less than 15 percent of particles smaller than 1/2 inch, 5 percent finer than the No.4 sieve, and 2 percent finer than the No.200 sieve. The leachate collection pipe will be perforated at fourth-points,with 1/4-inch-diameter holes, spaced 6 inches on center. Termination berms will be constructed around the perimeter of the unit. The interior slopes of the termination berms will be lined with a 60-mil HDPE geomembrane to contain leachate within the unit. The geomembrane also extends into the vegetative layer around the perimeter of the unit to block and route any leachate that may potentially seep through the vegetative layer into the LCRS. The granular drainage material of the base LCRS will be underlain and overlain by a sheet of nonwoven geotextile filter fabric.The geotextile functions as a filter to separate and prevent intrusion of fine materials from the adjacent soils into the granular drainage material. This will allow the granular drainage material to retain its specified hydraulic conductivity by preventing clogging from piping of fines. Leachate collected within the northeastern portion of WMU FU-04 will drain to leachate collection header pipes at the southern edge. The leachate header pipes will gravity drain to the base of the central portion of WMU FU-04. FU-04 REPORT.DOC 5-6