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FRITZ BUCHMAN <br />DEPUTY DIRECTOR <br />MICHAEL SELLING <br />DEPUTY DIRECTOR <br />STEVEN WINKLER <br />DEPUTY DIRECTOR <br />ROGER JANES <br />BUSINESS ADMINISTRATOR <br />THOMAS M. GAU <br />DIRECTOR <br />'W(DR iEIRg fi),r Yc0) X17 <br />January 20, 2012 <br />Mr. Robert McClellon, Program Coordinator <br />Environmental Health Department <br />600 East Main Street <br />Stockton, California 95202 <br />P. O. BOX 1810 - 1810 E. HAZELTON AVENUE <br />STOCKTON, CALIFORNIA 95201 <br />(209) 468-3000 FAX (209) 468-2999 <br />www.sjgov.org/pubworks <br />RECEIVE[ <br />JAN 2 4 2012. <br />ENVIRONMENTAL HEALTH <br />PERMMSERVICES <br />SUBJECT: ADDITIONAL INFORMATION REGARDING THE PROPOSED UPGRADE OF <br />PERIMETER LFG MIGRATION MONITORING WELLS AT SAN JOAQUIN <br />COUNTY -OWNED LANDFILLS <br />Dear Mr. McClellon:,,4 <br />This information is sent in response to questions asked by Ms. Natalia Subbotnikova on or <br />about January 5, 2011. 1 hope these answers address any concerns that you and she may <br />have. <br />As identified in our letter of December 7, 2011, we propose to insert 1/4" diameter polyethylene <br />(PE) tubes within the existing probe pipes, thereby greatly decreasing the purge time at each <br />probe and (we believe) increasing the accuracy of our measurements. <br />Method of attaching the tube to the probe top: We intend to use standard threaded and <br />compression fittings designed for use with the pipe and tube proposed (Figure 1). This <br />will provide a secure, leak -free conduit from the surface to the sampling area below. <br />Please also note that we do not intend to install the tubes hanging from the connection <br />at the top, rather, tubes will extend fully to the bottom of the existing probe pipes with the <br />weight of the tube supported by surrounding pipe. The tubes will be installed under <br />slight "compression". <br />Size of perforations: Perforations will be 1/10" diameter. <br />Number of perforations: The minimum number of perforations will be 12, providing <br />adequate open area for sample collection. This minimum number occurs at the Shallow <br />probes of the Corral Hollow Landfill, where the perforation length of the probe pipe is <br />three feet (Table 1). <br />Length of Perforations: The tube perforations will extend at least to the top of the <br />perforations of the existing probe pipe. Tube perforations may be provided above the <br />pipe perforations. <br />