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iA i E 3F'cAL1FORNIA - tnvirnnme., i <br />-ALIFORNIA REGIONAL WATER QUA <br />'ENTRAL VALLEY REGION <br />1443 Routier Road, Suite A <br />iacramento. CA 95827-3098 <br />'NONE: (916) 255-3000 <br />:AX: (916) 255-3015 <br />19 January 1995 <br />Ms. Donna Heran <br />Director, Division of Environmental Health <br />San Joaquin County Public Health Department <br />P.O. Box 2009 <br />Stockton, CA 95201 <br />NOTIFICATION OF POTENTIAL THREAT TO DRINjUVG WATER <br />Al- T11 <br />Jd,q 2 Q PH I= <br />50 <br />(C(D[Ply <br />Over the last several years, Regional Board staff have overseen a site investigation at the former <br />PureGro/Brea Ag facility at 1905 N. Broadway Avenue in Stockton. Pesticides and nitrates were <br />detected in facility soils, and four monitoring wells were subsequently installed. Quarterly <br />monitoring has identified a plume of the pesticide 1,2-dichloropropane (1,2-DCP) beneath the <br />facility. At staff's request, the Discharger installed and sampled two off -size monitoring wells in <br />November 1994. <br />The two wells are located on Sutro Avenue. The well to the north, at Sutro Avenue and Charles <br />Street, contained 42 ppb of 1,2-DCP. The California Maximum Contaminant Level for 1,2-DCP is <br />5 ppb. The extent of the plume has not yet been determined; the Discharger will soon be required <br />to install additional off-site monitoring wells. <br />The discovery of the off-site plume of 1,2-DCP does not meet the criteria for a Proposition 65 <br />notification. However, because of the shallow domestic wells in the Sutro Avenue area, we feel that <br />San Joaquin County Public Health should be formally made aware of the potential threat to drinking <br />water posed by this plume. This letter serves as chat notification. <br />Staff will continue to oversee the investigation and remediation of this plume, and will continue to <br />keep your staff informed as to our progress. <br />If you have any questions, I can be reached at (916) 255-3101, or you may contact Wendy Wyels at <br />(916) 255-3104. <br />RUDY J. SCHNAGL, Chief <br />Agricultural Regulatory Unit <br />cc: Mr. Nick Nickerson, Unocal Environmental Remediation & Technology, San Ramon <br />