ARCHIVED REPORTS_2012_4 - Laserfiche WebLink

Home Browse Search

groundwater quality has not changed throughout the year,which is also an indication of no impact from the landfill. PROGRESS OF EVAPOTRANSPIRATION COVER The purpose of the evapotranspiration cover is to capture rain water during the wet months, allowing the vegetation growing on that cover to remove the water from the soil during the dry months,restoring the storage capacity of the soil for the next rainy season. Providing storage for rainwater each year prevents the percolation of water into the refuse. The intention of this closure method is to minimize water percolating into the refuse at least as effectively as the prescriptive barrier layer(one foot thick with permeability of 10-6 cm/sec or less). A key component of this method is the vegetation on the cover. Perennial plants, such as purple needle grass and California Brome, send roots deep within the soil to gather moisture,providing storage capacity during the rainy season. In contrast,annual species, such as rye grass,may produce a thick cover during their growing season,but produce shallow roots which cannot remove moisture from deep within the cover layer. The ET cover was established in December 2008 when the soil of much of the top deck area was amended, fertilized and reseeded. The cover vegetation continues to flourish(Photos 1 and 2). Results of monitoring in the 20011-2012 rain year indicate that the ET cover is successful. Because of the dryness of that rain year,the run-off from the ET cover was too little to measure with the equipment installed at that time. Previous rain years show that that the measured percolation in the test area is approximately one-half of that calculated for an intact prescriptive cover(report previously submitted). The original measuring equipment(dosing siphon in 55 gallon drums)was replaced in 2012 to allow for better measurement of small amounts run-off. The new equipment(tipping bucket)will allow measurement of much smaller quantities (Photos 3 and 4). The surfaces of the landfill, including the ET cover area, are grazed annually to facilitate inspection by the LEA. ANNUAL FACILITY INSPECTION Foothill Landfill was inspected to assess damage to the drainage control system, groundwater monitoring equipment in September 22,2011. The report of this inspection was transmitted to RWQCB staff on or about November 10, 2012. Generally,the site was found to be in excellent condition due to the improvement of drainage in 2006 and ongoing drainage system maintenance by the site superintendent. Groundwater monitoring equipment remained in good condition. Foothill Sanitary Landfill 13 Department of Public Works/Solid Waste 2nd Semester and Annual 2012 Groundwater Monitoring County of San Joaquin—January 15,2013