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0 �1 John Yoakum [EH] From: Larry Witwer <larryw@amiadini.com> Sent: Wednesday, September 04, 2013 3:32 PM To: John Yoakum [EH] Subject: RE:420 W Yosemite - Rainwater car wash Attachments: Elder 2013-08-01 CVRWQCB_install new down-gradent wells.pdf John, Perhaps you did not receive my email update I sent on August 16, 2013. The following is a summary of the most recent developments on the subject case. We recently received the attached directive from the Oversight Agency (Central Valley RWQCB). Following our submittal of an MTBE Plume Travel Model (Fate and Transport Model) that was requested to estimate the fate and transport of the groundwater contaminant plume, the Agency responded as follows. The Agency concluded that the Model results do not support closure under the State Water Resources Control Board Low Threat Closure Policy (LTCP), which does not allow petroleum releases to impact water supply wells. The Agency further directed that the proposed off-site wells as we had permitted with your office now be installed, with a further condition that depth-discrete well clusters must be constructed to monitor at least the first three water-bearing zones down-gradient of MW-11. The wells we had previously proposed and permitted with your office included two separate split wells at four locations (MW14A, MW14B, MW15A, MW15B, MW16A, MW168, MW17A, and MW17B), which will be located next to each other and each having a different screen interval and depth (one 2-inch well to a depth of 30 feet below ground surface (bgs) and one 2-inch well to a depth of 70 feet bgs.). The objective here was to monitor the first two water-bearing zones. We are now required by the Agency to provide an additional well in each location to monitor the third water- bearing zone, which is estimated to be at a depth range of 135 to145 feet bgs. Installing three separate depth-discrete wells in clusters at each location would be a very expensive undertaking, as would installing triple-nested wells in a single borehole at each location. We are therefore working with the Central Valley RWQCB to see if we can reduce the number of proposed off-site wells. We will keep you informed of the progress. At this point in time it seems like any new well installation work would most likely occur in 2014. There is a possibility it could occur in late 2013. Best regards, fix; Larry Witwer Sr. Project Manager Ami Adini &Associates, Inc. 4130 Cahuenga Blvd., Ste 113 Toluca Lake, CA 91602 Tel. (818) 824-8102 Fax. (818) 824-8112 t I