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�Q.viry e �•' �a THOMAS M. GAIL DIRECTOR FRITZ BUCHMAN DEPUTY DIRECTOR MICHAEL SELLING DEPUTY DIRECTOR STEVEN WINKLER DEPUTY DIRECTOR ROGERJANES BUSINESS ADMINISTRATOR n,ill)i=1i� fh&i YC -R-1 December 13, 2011 Mr. Robert McClellon, Program Coordinator Environmental Health Department 600 East Main Street Stockton, California 95202 P. O. BOX 1810 -1810 E. HAZELTON AVENUE STOCKTON, CALIFORNIA 95201 (209) 468-3000 FAX (209) 468-2999 www.sjgov.org/pubworks SUBJECT: REVISION TO LFG MIGRATION MONITORING PLAN FOR IMPROVEMENT OF PERIMETER MONITORING AT SAN JOAQUIN COUNTY -OWNED LANDFILLS Dear Mr. McClellon: 6r r Please consider this a request to allow San Joaquin County to improve the perimeter landfill gas (LFG) migration monitoring wells at the four County -owned landfills. The objective 'of this improvement is to greatly reduce the purge time required for monitoring. Our present monitoring wells are comprised of either 1/2" or 3/" (nominal) pipes, with interior diameters of 0.62" or 0.73". At a sampling rate of 18 cubic inches per minute (Landtec GEM 2000), many minutes are required to purge each probe. To shorten the sampling time, we propose to install polyethylene tubes inside the existing probe pipes (Figure 1). These tubes will have an inside diameter of approximately 1/8" thereby reducing the sampling time by a factor of 30. Our deepest probes will require less than two minutes to purge. The internal tubes will be easily removable, allowing the insertion of a camera, if the need for camera inspection arises in the future. All materials used will be non -biodegradable, avoiding contribution of degradation products to the sampled gas. The tube will be polyethylene (PE), consistent with the probe pipe material of the most recently -installed wells at our North County Recycling Center and Sanitary Landfill and Foothill Sanitary Landfill. To ensure the tube reaches the bottom, a length of stainless steel rod or tube will be affixed to the end of the plastic tube, providing some weight. The inserted PE tubes would extend without joint to the perforated section of each probe pipe, and would be perforated in the pipe perforation area, allowing sampling up to the top of the pipe perforations (Table 1). The lengths of the tube will be pre -measured, and documented as to the insertion length, to ensure the tube reaches the perforated pipe section. The upper end of the tube would be attached to a cock valve at the top of the probe pipe for sampling. In addition to significantly decreasing the sampling time of most of the wells, we will make the probes uniform throughout our system.