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California r _ 'oual Water Quality )ntrol Board ;D� 4 <br /> Central Valley Res on <br /> Robert Schneider, Chair <br /> instoo H.Hidcox Gray Davis <br /> Secretary for Sacramento Main Office Governor <br /> ' En.ronneemal ftimmet Address: httpd/"w.sw b.ca.gov/— gcb5 <br /> Protection 3443 Routley Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> ' 2 March 2001 <br /> Mr. Jeffrey Wong RECEIVED <br /> ' Senior Registered Environmental Health Specialist 14AR 2001 <br /> San Joaquin County Environmental Health Division <br /> ' 304 East Weber Avenue <br /> Stockton, CA 95202 <br /> ' REQUIREMENT FOR INTERIMREMEDIATION, RAINWATER CAR WASH <br /> 420 WEST YOSEMITE AVENUE, MANTECA,SAN JOAQ UIN COUNTY <br /> ' During our 28 February 2001 meeting,we discussed the Cone Penetrometer Testing Site Investigation, <br /> Fourth Quarter 2000 and the January 2001 draft sampling results for monitoring wells MW-1 through <br /> MW-4, both submitted by Advanced GeoEnvironmental (AGE). Groundwater samples collected from <br /> ' on-site monitoring wells in January 2001 contained up to 120,000 µg/1 TPHg; 9,900 µg/1 benzene; and <br /> 730,000 µg/1 MtBE. The current depth to water in the on-site monitoring wells is about 17 feet bgs, and <br /> the reported groundwater flow is north/northeast. Results of the depth-discrete groundwater samples <br /> t collected from the cone penetrometer testing (CPT) borings at 130 feet show MtBE at 39 µg/1. <br /> Tetrachloroethylene and trichloroethylene also were identified in the groundwater samples at maximum <br /> concentrations of 1,600 µp/1 and 28 µg/1, respectively. At this time, it is uncertain where the source of <br /> ' these solvents originated, and we are greatly concerned that the aquifer, which is used for domestic and <br /> municipal water supply, has been impacted. <br /> As presented in AGE's 8 September 2000 Sensitive Receptor Survey, two municipal water supply wells <br /> are within 2,000 feet of Rainwater Car Wash. One well (Almond Street Well) is about 1,900 feet <br /> northwest of the site and reportedly is non-operational. The other well (Jessie Street Well), which is <br /> ' operational, is about 1,500 feet south of the site. This well is cased to 100 feet and"open-hole"from <br /> 100.to 325 feet. The reported pumping rate for this well is 1,100 gallons per minute. <br /> AGE recommended in the CPT Site Investigation to install an interim remediation system to reduce <br /> off--site migration of the groundwater plume. The system is appropriate to reduce contaminant mass and <br /> control the lateral and vertical movement of contaminated groundwater until the completion of the site <br /> assessment. Therefore, require Rainwater Car Wash to complete the following: <br /> ' By 16 April 2001, install and continuously operate an interim pump and treat system in the area <br /> of the highest on-site groundwater contamination. The system should remove product and <br /> stabilize the groundwater plume. <br /> ' California Environmental Protection Agency <br /> 0 Recycled Paper <br /> ' The energy challenge facing California is real. Every Califomuo needs to take immediate action to reduce energy consumption. For a list of simple ways <br /> you can reduce demand and cut your energy costs,see our Web-site at httpJ/www.swrcb.ca.govimgcb5 <br />