CORRESPONDENCE_2005-2006 - Laserfiche WebLink

Home Browse Search

Pa.U.�N G UQ1 ?< c )p Q�/PORN THOMAS M. GAU DEPUTY DIRECTOR MANUEL SOLORIO DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR THOMAS R. FLINN DIRECTOR ROGER JANES BUSINESS ADMINISTRATOR s � } 1b wy�� ♦ ' � reg„ s �o June 14, 2006 Mr. Todd Del Frate, RG California Regional Water Quality Control Board 11020 Sun Center Drive, #200 Rancho Cordova, California 95670-6114 P. O. BOX 1810 - 1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201-3018 (209) 468-3000 FAX (209) 468-2999 www.sigov.org 2006 JUN 15 PM 4: 09 V .6A A rR I`:: 4�fi18` 8 1 HEt,LTI H DEPARTMENT SUBJECT: CRITERIA FOR ACCEPTANCE OF ET FINAL COVER, FOOTHILL SANITARY LANDFILL, CLEANUP AND ABATEMENT ORDER R5-2004-0706 Dear Mr. Del Frate:Tm j" 1 Enclosed, please find the Performance Criteria for the evapotranspirative (ET) cover at the Foothill Sanitary Landfill, as requested in your letter of May 1, 2006. In general, the ET cover will be considered a successful closure cap if the percolation measured over the five-year test period through the test pad is no more than the percolation predicted by the HELP model through the prescriptive cover without desiccation cracking. The HELP model parameters are specified in the attachment, the most significant of which will be the actual measured rainfall at the site. Because the first year of the test pad will be non -representative, we propose that the five-year test period start with the rains of the winter of 2006/2007. We also suggest that annual reports be submitted after the winter rains, rather than in January, so that each full rainy season can be assessed. Your letter also identified several improvements to the test pad, which we will incorporate, along with some additional improvements for which I believe you have expressed support. They include: • Per your direction, we will install moisture sensors at three locations in the closure cap. The leads from these sensors will be carried in trenches to a monitoring station at the edge of the closure area. Data will be recorded in thirty -minute intervals, and retrieved monthly. • We have offered to increase the area of the test pad from 660 to 2200 square feet to match the ACAP dimensions. Because of the larger size, the larger test pad will be located uphill of the closure cap side berms. We have also offered to revise the test pad design to allow construction with the same equipment used in the construction of the ET cover. The test pad was originally required by Ms. Kim Schwab, and was to be constructed one year prior to the construction of the cover area. In this original scenario, the test pad soil was to be placed at the same density as the ET cap, but using smaller equipment than would be used for the cap. Now that the ET test pad will be installed with the closure cap, we can use the same equipment used for the cap. Filter fabric and a protective gravel layer will be needed to protect the plastic membrane under the test pad soil during construction.