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V,JLIFA Camp Drener&Md(w4 <br /> Mr.Mike <br /> January 31,2000 <br /> Page 2 <br /> Downdrains <br /> a Downdrains were constructed at law spots around the ton deck soil berm, as required to <br /> convey top deck flows to the perimeter drainage channel. The downdrains were <br /> constr=tedof 4_mch Iugh-demts polyethylene (HDPE)pipe and discharge into erosion <br /> cor.=Iling hay bales before entering the ditch. Frequent Inspection and maintenance of the <br /> downdrains is required throughout the rainy season. Broken or separated downdrains <br /> may lead to accelerated cover erosion due to concentrated runoff flows. <br /> South Perimeter Drainage Channel <br /> ■ The City completed a survey pronie d the south penme►er drain ge channel in September <br /> 1999 to identify depressed areas or areas of reverse grades within the channel. CDM <br /> identified six distinct areas totaling 2,860 linear feet requiring regrading. <br /> r CVWS regraded the south channel in December 1999 in the six areas identified by CD'.�i..A <br /> field survey performed by the City in January 2000 confirms that a positive drainage <br /> gradient exists along the entire channel. Frequent inspection and maintenance of the south <br /> perimeter drainage ct+Am.el is required throughout the rainy season in order to clear any <br /> brush or localized erosion,which may impede flows. <br /> North Perimeter Drainage Channel <br /> ■ CVWS cleared the north perimeter drainage channel and road crossings to promote <br /> positive flow along the channel toward the retention/infiltration basin. <br /> South Perimeter Road <br /> ■ CVWS placed rock on the south perimeter rcad in October 1999 to allow all-weather access <br /> along the south perimeter of the landfill. <br /> Cover Vegetation <br /> ■ CVWS spread hay on the side slopes of the landfill prior m November 1999 to promote the <br /> gxowth of vegetation on all exposed soil surfaces. Frequent inspection and maintenance ' <br /> the cover vegetation is required throughout the rainy period in order to repair arias of thee <br /> cover where vegetation was not successfully established,or where point runoff flows may <br /> have eroded:he vegetative layer. <br /> Feel free to call se at(925)933-2900 if you have any questions regarding the information <br /> provided in this correspondence. <br /> Very truly yours, <br /> CAW DRESSER cSCM INC. <br /> Wayne Pickus,P.E. <br /> Project Manager <br />