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e rn o r a n d u In <br /> CnLIFORNin R WnTE R UnLITY CONTROL BOnRO CENTnnL URLLEY REGION <br /> 3443 Routier Road phone: (916) 361-5600 <br /> Sacramento,California 95827-3098 AT SS: 8-495-5600 <br /> TO: Seniors and Supervisors FROM: Jon B. Marshack <br /> Environmental Support Unit <br /> Ground Water Protection & <br /> Investigations Section <br /> DATE: 29 January 1988 SIGNIATURE: <br /> SUBJECT: SHOULD I.REQUIRE THIS CLASS III LANDFILL TO BE LINED? <br /> THE PROPOSED RCRA SUBTITLE D LANDFILL REQUIREMENTS <br /> Under g2533(b) of Subchapter 15, Class III landfills are to be sited such <br /> that natural hydrogeologic conditions at the landfill are sufficient to <br /> Imensure no impairment of beneficial uses of surface water or ground <br /> water beneath or adjacent to the landfill." Where <br /> e the site does not <br /> provide this level of protection for water quality, a single clay liner is <br /> required. Insufficient guidance is given in Subchapter 15 to easily and <br /> clearly determine whether natural conditions are sufficiently protective <br /> of water quality so that a liner is not needed. A recent draft guideline <br /> from EPA could aid in this determination.. <br /> EPA Is In the process of setting requirements for non-hazardous waste <br /> management units under Subtitle D of the Resource Conservation and <br /> Recovery Act (RCRA). , A draft of these requirements divides all <br /> non-hazardous waste landfills into four categories, based on two simple <br /> factors: "net precipitationv' and "time-of-travel" for leachate to reach <br /> ground water. The overall goal of the draft requirements is that <br /> leachate should not reach ground water during the active life of the <br /> landfill unit. <br /> Category Net PreCLipiLt-ation Time-of-Travel <br /> low long <br /> II high long <br /> III low short <br /> IV high short <br /> Net Precipitation (NP) is defined as [Mean Annual Precipitation] minus <br /> [Mean Annual Evapotranspiration] . The dividing line between "high" <br /> NP and "low" NP is 0 inches/year. The theory behind this division is <br /> that for low JVP sites, rainfall is less likely to contribute to leachate <br /> formation. Sites with "high" ' NP must have leachate collection alld- <br /> g <br /> removal systems and caps which contain a drainage layer above a <br /> synthetic barrier. Sites with "low" NP may have a cap composed only <br /> of earthen materials. <br /> Time-of-Travel (T) is the time for leachate to migrate between the base <br /> of the landfill and the top of the first ground water. It, is calculated by: <br /> [Depth to Ground Water] x [Porosity] -L [Hydraulic Conductivity] <br />