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LCRS Design - Area 28 Foothill Sanitary Landfill Section D.1 under "Construction Specifications" reiterates the EAD requirements for the base liner system, and continues under Section D.6 to note that the following: "The Discharger may propose changes to the liner/final cover system design prior to construction provided that approved components are not eliminated, the engineering properties of the components are not substantially reduced, and the proposed liner/final cover system results in the protection of water quality equal to or greater than the design prescribed by Title 27 and this order [R5-2015-0058]". 3.0 LCRS DESIGN OVERVIEW The Area 2B proposed design incorporates a LCRS that consists of all the components of the approved EAD LCRS (i.e. blanket drainage and collector pipes in drainage troughs). Specifically, the LCRS in Area2B incorporates a ridge and valley drainage system wherein parallel ridges drain to several perforated high density polyethylene (HDPE) collection pipes in swales that are plumbed to a single LCRS sump for Area 2B. The HDPE pipes are designed to collect drainage from the module's blanket leachate collector component. The LCRS will be sloped on the floor areas to convey leachate by gravity to a new LCRS sump located at the eastern side of Area 2B's. The leachate is removed from the landfill sump by pumping through a riser pipe and pumped into leachate storage tanks. The transmissivity of the LCRS drainage layer has been designed to prevent the build-up of hydraulic head on the liner to no more than 12 inches and to accommodate at least twice the anticipated peak daily flow volume as required by Title 27 and the FSLF's WDRs. The LCRS pipes have also been designed to resist collapse under the weight of the final waste mass resulting from the final configuration of the landfill after closure. While the proposed LCRS consists of all the WDR required components, the proposed EAD for Area 213's base LCRS blanket collection layer is a geocomposite drainage net (GDN) in lieu of a 9 - inch -thick GDL. The base LCRS is described in detail in the following section. No EADs have been considered or proposed for the side slope LCRS system. 3.1 Base Liner LCRS The proposed base LCRS drainage layer will have a minimum slope of 2 percent to the leachate collector pipes, which collect and convey leachate by gravity to the LCRS sump by virtue of the gradient provided. An EAD drainage layer (relative to the 9 -inch -thick granular drainage layer specified in the site's WDR's) consisting of a single or double sided GDN is proposed for the Area 2B base liner. The EAD is proposed for the base LCRS due to the limited availability of nearby gravel material meeting LCRS drainage layer requirements along with the resulting prohibitive cost of importing such material. The GDN should have a minimum 100 -hour transmissivity of 7.1x10-4 m2/s or greater under a vertical stress of 1,000 psf, and a minimum 100 -hour transmissivity of 2.9x10-4 M2 /s at a vertical stress of 11,000 psf, considering the current landfill Master Plan. Assuming the above flow capacity of the base liner drainage layer and considering the published data on available GDN products meeting these requirements, the GDN can be considered as good, or better, than the 9 -inch -thick GDL and will accommodate the Project No. AU 17.1254 1 LCRS Design 2 May 2018