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California R Yonal Waterual
<br /> Q qty Control Board : ~-
<br /> - Central Valley Region
<br /> Winston H. Hickax Robert Schneider,Chair �
<br /> cratary for Gray Davis
<br /> vtronmental 9acramentn i[ain Office Governor
<br /> Protechorr Internet Address http 11www swrcb ca gov/—rwgcb5
<br /> 3443 Routuer Road,Suite A,Sacramento,California 95827-3003
<br /> Phone(916)255-3000•FAX(916)25.5-3015
<br /> 2 March 2001
<br /> Mr Jeffrey Wong RE CE MED
<br /> Senior Registered Environmental Health Specialist
<br /> San Joaquin County Environmental Health Division MAR P 9 X1111
<br /> 304 East Weber Avenue
<br /> Stockton, CA 95202
<br /> REQUIREMENT FOR INTERIM REMEDIATION, RAINWATER CAR WASH
<br /> 420 WEST YOSEMITE A VENUE, MANTECA, SAN JOA Q UIN CO UNTY
<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 GeoEnvlronmenta.l (AGE) Groundwater samples collected from
<br /> on-site monitoring wells in January 2001 contained up to 120,000 ug/1 TPHg, 9,900 1ig/1 benzene, and
<br /> 730,000 99/1 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
<br /> collected from the cone penetrometer testing (CPT) bongs at 130 f et show MtBE at 39 gg/lwater amples
<br /> borings
<br /> Tetrachloroethylene and tneliloro ethylene also were ldentificd m the groundwater samples at maximum
<br /> concentrations of 1,600 gg/1 and 28 gg/I,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 1s 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 Iateral and vertical movement of contaminated groundwater until the completion of the site
<br /> assessment Therefore, requirc Rainwater Car Wash to complete the following
<br /> r By 16 April 2001, install and continuously operate an intenrn 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
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