CORRESPONDENCE_2005-2007 - Laserfiche WebLink

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a surface under the pipe settles, new low spots are created, causing blockage by accumulating condensate. At the Harney Lane Landfill, a trench fill method was used to place the refuse, exaggerating differential settlement. Off-site migration was previously controlled by the LFG collection system, with the last detection above regulatory limits occurring in April 2005. The LFG system therefore appears to be adequate in controlling LFG migration if fully functional; however, combustible gas was detected at above regulatory limits (5%methane) in soil gas well GW-1 on May 5, 2007. Recent operational data, concurrent with the reported exceedence at GW-4, indicates that the collection of LFG from the northwest corner of the Primary Site compromised by differential settlement and associated accumulation of condensate within the main LFG pipe (the LFG "header"). MITIGATION STEPS The following Plan describes the steps that will be taken, which will continue until regulatory limits are reached. The steps to re-establish control of LFG migration are as follows. 1. Determine the problem Reduced and inconsistent vacuum along the LFG header indicates that differential settlement has created low spots, and the accumulation of LFG condensate within the header is reducing the LFG collection from the wells in that portion of the LFG system. SCS Field Services has been directed to investigate the situation. They believe they have located a length along the LFG header which is allowing condensate to accumulate. The County has asked SCS to immediately formulate a plan to correct the improper slope of the header. 2. Locate the areas along the LFG header where condensate is accumulating. a. Expose the header at select locations and install temporary test ports to measure vacuum. A significant decrease in vacuum from one location to another along the header indicates a low spot with accumulated condensate between those two locations. b. Remove vegetation along the alignment of the header in question, expose the header approximately every 25 feet, and survey to locate the low spot if necessary. c. Remove condensate blockage by re-establishing proper drainage across the low Tots . Expose the length of pipe with the low spot and raise the pipe to the proper elevation, eliminating the low spot. Remediation Plan for LFG Migration 2 San Joaquin County Public Works/Solid Waste Harney Lane Sanitary Landfill May 23,2007