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Performance Criteria and Procedure for Acceptance of the ET Test Pad Foothill Sanitary Landfill June 12, 2006 47717-5 B Purpose of Performance Assessment The purpose of the test pad is to confirm whether the evapotranspiration (ET) test pad, and therefore the ET final cover constructed in the Foothill Sanitary Landfill site improvement project, is an acceptable engineered alternative to the Title 27 prescriptive final cover. Pass/Fail Criterion If, during the test period, the amount of water found by direct measurement percolated through the ET test pad is no more than the amount predicted by the HELP model for the an intact prescriptive closure meeting the minimum standards of Title 27 under the same conditions experienced at the test pad, then the ET cap at the Foothill Landfill will accepted as an engineered alternative to the Title 27 prescriptive final cover. Study Period The study period will begin July 1, 2007, and will continue for five years. Data will be collected from the test pad starting with the completion of the test pad. In accordance with the San Joaquin County letter dated October 24, 2005, in order to speed the development of the test pad vegetation to a point that long-term evapotranspiration is approximated, the test pad will be planted with young, plants (rather than seeds), and irrigated though the first dry season. Therefore, measurements taken during this period would not represent the long-term performance of the test pad, or of the seven -acre closure cap, and will not be included in the assessment of ET cover effectiveness at the Foothill Landfill. Test Pad Data Collection Over a 5 year study period, the following data will be collected at the test pad accordance with the Landfill Closure Method Selection Report, September 21, 2004: • Storm water runoff • Percolation escaping from the bottom of the test pad • Soil moisture content of ET soil in the test pad at three depths below the surface (Figure 1) • Precipitation • Air temperature • Solar radiation Data logged at 30 minute intervals, collected monthly. Volume measurements of percolation from the test pad during the test period will be summed and expressed as inches percolation (TPTs)• Foothill Sanitary Landfill 1 Public Works/Solid Waste ET Test Pad Performance Criteria County of San Joaquin — June 7, 2006