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California '.egional Water Quality Cot of Board <br /> Central Valley Region <br /> Karl E. Longley,ScD, P.E.,Chair <br /> Linda S. Adams Sacramento Main Office Arnold <br /> Secletarvfor 11020 Sun Center Dine 9200.Rancho('ordoNa.California 9�'670-6114 Schv�arzenegger <br /> bivironmental Phone(916)464-3291 -FAX(916)464-464 0_01ep'1101' <br /> Protection <br /> hnp,'/%vN%-N%.xNatcrboards ca p0centrahallev <br /> ��� �SG�G <br /> BGG <br /> 13 June 20079��Gs���h oo� <br /> Mr. Allan Fetters <br /> 3705 Portsmouth Circle North <br /> Stockton, CA 95219-3842 <br /> REQUEST FOR SUBSURFACE INVESTIGATION, RIPON FARM SERVICE, <br /> 938 FRONTAGE ROAD, RIPON, SAN JOAQUIN COUNTY <br /> Ripon Farm Service formulates and distributes nitrogen fertilizer products to the retail market <br /> and is investigating whether nitrogen found in groundwater and in the City of Ripon Municipal <br /> Well 12 is related to historical operations at the Frontage Road facility. In January 2007, <br /> Ripon Farm Service installed six off-site monitoring wells to the north, south, east and west of <br /> the Ripon Farm Service facility. Regional Water Quality Control Board, Central Valley Region <br /> (Regional Water Board) staff reviewed the following reports relating to the groundwater <br /> investigation. <br /> • 28 February 2007 Monitoring Well Installation Report by Genesis Engineering and <br /> Redevelopment, LLC. <br /> • 5 March 2007 Quarterly Report— First Quarter 2007 by Advanced GeoEnvironmental Inc. <br /> • 26 April 2007 Summary of Groundwater Sampling Data by Genesis Engineering and <br /> Redevelopment, LLC. <br /> Four of the off-site monitoring wells are screened in the shallow water-bearing zone at about <br /> 30 feet below ground surface (bgs), which is comparable to the screen interval of the on-site <br /> shallow monitoring wells. Two of the off-site monitoring wells are screened in a deeper water- <br /> bearing zone, at about 160 feet bgs, which coincides with the upper interval of the water- <br /> bearing zone that provides water to Municipal Well 12. <br /> The off-site shallow wells were sampled using similar procedures to those used to obtain <br /> samples from the on-site wells. <br /> Groundwater Data Review <br /> The first two rounds of sampling data from the off-site monitoring wells show elevated nitrate <br /> concentrations in shallow groundwater northeast, southeast, and west of Ripon Farm Service. <br /> The shallow well to the north did not contain nitrate concentrations greater than the water <br /> quality objective. The highest concentration was found in the off-site well to the southeast, <br /> RMW-3S, located near a former truck wash operation. The onsite monitoring well with one of <br /> the highest nitrate concentrations is in the southeast portion of the Ripon Farm Service facility <br /> (MW-101). While this data identifies that there is an off-site source of nitrate that is migrating <br /> California Environmental Protection Agency <br /> Re,v(led Paper <br />