Laserfiche WebLink
Engineering Analysis in Support of the <br /> Use of Crushed Rock in LCRS Drainage Layer <br /> Module 4, North County Recycling Center and Sanitary Landfill . <br /> San Joaquin County, California <br /> 1.0-Introduction <br /> San Joaquin County is seeking approval from the CVRWQCB for substituting a crushed rock <br /> drainage layer in place of the rounded gravel. Crushed rock with a uniform size of '/2 inch is <br /> proposed to be used for the LCRS drainage layer. This design will provide drainage <br /> characteristics equivalent to the gravel layer. To provide protection against puncture of the <br /> 60-mil HDPE geomembrane from the crushed rock, a geotextile cushion layer will be placed <br /> directly above the geomembrane before placing the crushed rock. <br /> The construction documents for the LCRS drainage layer within Module 4 of the North County <br /> Recycling Center and Sanitary Landfill specify rounded or sub-rounded gravel placed directly <br /> over the 60-mil high density polyethylene (HDPE) geomembrane liner. During the design of <br /> Module 4, it was envisioned that on-site soil deposits at the Foothill Sanitary Landfill (FSL) <br /> would be mined and screened to provide the rounded gravel. However, subsequent subsurface <br /> investigation and testing of the on-site soil deposits at FSL determined that the on-site gravel at <br /> FSL is significantly larger in size than that required by the construction specifications. <br /> The use of the crushed rock and the geotextile cushion result in the following two design <br /> considerations that need to be addressed: <br /> 1. The minimum mass per unit area (ozlyd2 or g/m2) of the geotextile cushion required to <br /> . protect the geomembrane from the crushed rock;and <br /> 2. The shear strength of the interface between the geotextile cushion and the 60-mil HDPE <br /> geomembrane should be adequate for slope stability of Module 4. <br /> This report addresses the above design considerations. The calculations provided below <br /> determine the mass per unit area of the geotextile cushion required to protect the geomembrane <br /> from the proposed crushed rock. A discussion of the shear strength of the geotextile-textured <br /> geomembrane interface is also presented. <br /> N:\sacDP\2003\Prj\83\835608.3ap.doc <br /> (NCRCSL) <br /> 1 <br />