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page 3, 24100 Lammers Road <br /> Monitoring wells have not been installed to discrete y monitor the vertical extent of the <br /> contamination, and there is no data from the lower and unit to determine whether it is a <br /> conduit to the area drinking water wells. Moreover, the existence of the "upper sand" and <br /> "lower sand" referred to in the CAP are questionab!e and cannot be verified due to the <br /> incorrect boring logs. <br /> Excavation of source material is the only alternative presented that will protect future <br /> beneficial uses of the groundwater at this site. By r moving a large volume of <br /> hydrocarbon-impacted soil at the former UST site, t e future mass of contaminants <br /> leaching into the groundwater will be substantially reduced. Additional corrective action i <br /> may be required once the vertical extent of the groundwater contamination is known. <br /> i <br /> Recommendations <br /> 1. Excavate the source material, and initiate quarterly groundwater <br /> monitoring. The extent of soil contarnination is limited to the area <br /> surrounding the former UST. Removing the impacted soil should minimize <br /> future ground water impacts of site constituents. <br /> 2. Install a monitoring well immediately down gradient of the former tank pit <br /> area. A deep monitoring well may a so be necessary to determine the <br /> vertical extent of the groundwater cc ntamination and to determine the <br /> vertical groundwater gradient. Additional deep monitoring wells may also <br /> be needed to determine the deep gr undwater flow direction. All water <br /> samples should be analyzed for all oxygenates and gasoline additives by , <br /> EPA Method 82606. <br /> 3. A sensitive receptor survey was submitted for this site, but did not provide <br /> the well construction details for the t ree domestic water supply wells that <br /> I <br /> were identified as being the only sensitive receptors located within a 2000- <br /> foot radius of the site. This informat on should be determined and provided j <br /> to PHSIEHD. The closest municipal well is approximately one mile from i <br /> the site. The on-site water supply w9ll should also be included in the <br /> quarterly monitoring and sampling program. <br /> Submit to PHSIEHD a work plan that addresses the above recommendations by March 5, <br /> 2001. If you have any questions please call Lori D incan at (209) 468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> rr __ C�t k tiw,, <br /> Lori Duncan, Senior REHS Dot Lofstrom, RG i <br /> LOP/Site Mitigation Unit IV Registered Geologist, Unit IV <br /> cc: Marty Hartzell, CVRWQCB <br /> Mike Kloberdanz, MJK <br /> Robert Fourt, P O Box 1029, Sutter Creek CA 95685 <br /> R <br /> i <br />