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� <br /> Page lof2 � <br /> � <br /> � <br /> Natalia Subbotnikova [EH] <br /> From: Michael Carroll |@sj0ovorg] <br /> Sent: Tuesday, February 07. 201311:05AK8 <br /> To: Robert McCNdlonOEH8 <br /> Cc: Natalia8ubbotnikov [EH] <br /> Subject: GoaPnzbeyWodificaUona-onomn*noboqueotiona <br /> Good morning Robert, <br /> Thanks for forwarding these questions. ihave inserted mnyresponses,which | hope will provide assurance that <br /> inserting the tubes within the existing pipes does not conflict with the objectives of soil gas monitoring, and may <br /> enhance our ability todoso. <br /> Best regards, <br /> Mike Carroll <br /> VV.Michael Carroll,pE <br /> Senior Civil Engineer,Public Works/Solid Waste <br /> 181UsHazelton Way <br /> Stockton,CA95ZO5 <br /> Phone(0nect):3O9-468'85O4 <br /> Phone(Office Kxa\n):ZO9468'3O66 <br /> Fax:209-468-3078 <br /> From: Robert McC|aUon [EH] (mmailto:RMcC|eUun@ 'cehd'onmnl <br /> Sent: Tuesday, February O7, 2O1Z8:O8AM <br /> To: Michael Carroll <br /> Cc: Natalia Subbotn|ko*a [EH] <br /> Subject: Gas Probe Modifications <br /> Mike here are comments from Ca|nao/destaff- <br /> Hello Nata|ia: Thank you for forwarding the proposed revision toCounty landfills gas compliance wells. We do <br /> understand the Operator would like to reduce their purge time by inserting polyethylene tubes inside the existing <br /> PVC pipes. <br /> Perhaps this is not important, but most of our probes are W High density polyethylene (HDPE),although we do <br /> have some PVC. <br /> Based on Calrecycle's landfill gas monitoring procedures, we have recommended againstpurBingthegaapnobee <br /> and have recommended readings once steady state has been achieved. Purging might actually defeat the <br /> purpose of true gas monitoring since by purging, gas that might have had the potential to migrate and accumulate <br /> within the probes will be purged. <br /> This method ofmonitoring isexactly what xveplanned. Perhaps"purQed" was the wrong term; itisour intent <br /> to clear the probe of gas pulled during the previous measurement so that we measure the current <br /> concentrations. VVedon't intend 10pull more gas from the soil than that, but gas from the previous <br /> measurement could be trapped in the probe, and should be removed before making a new measurement. The <br /> tubes will greatly reduce the volume needed to clear the probe for the new measurement. <br /> 2/7/7m <br />