Laserfiche WebLink
4 <br /> San Joaquin County DIRECTOR <br /> oma,°.�'" Environmental Health Department Donna Heran, REHS <br /> .... c <br /> ASSISTANT DIRECTOR <br /> 'ZA 600 East Main Street Laurie Cotulla, REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> ' Mike Huggins,REHS, RDI <br /> Website. www.sjgov.org/ehd Margaret rio, REHS <br /> Robert M Cellon,REHS <br /> Phone: (209)468-3420 .teff Carruesoo,REHS, RDI <br /> Fax: (209) 464-0138 Kasey Foley,REHS <br /> May 27, 2009 <br /> Terrence Fox <br /> California Department of Transportation District 6 <br /> 2015 E. Shields Avenue, Suite 100 <br /> Fresno, CA 93726 <br /> Subject: Cal Trans Shop 10 Site Code: 1018 <br /> 1603 B Street <br /> Stockton, CA 95201 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed First Quarter 2009 <br /> Operations Maintenance and Monitoring Report (Report) dated May 15, 2009, submitted on <br /> your behalf by Stantec and has the following comments. <br /> The Report documents routine groundwater monitoring and sampling activities, and soil vapor <br /> extraction/air sparging (SVE/AS) system operation and maintenance activities conducted during <br /> the first quarter of 2009 at this contaminated underground storage tank (UST) site. <br /> Citing low influent vapor sample concentrations ( 200 parts per million volume [ppmv]), and <br /> very low contaminant concentrations reported in the most recent groundwater samples, Stantec <br /> recommends shutting down the SVE/AS system and initiating site closure procedures. <br /> The EHD agrees with this recommendation. As stated in the Report, contaminant <br /> concentrations in soil vapor did not rebound to higher levels following a 6-month system <br /> shutdown in 2007, and the only contaminant currently reported in the groundwater is <br /> 1,2-dichloroethane (1,2-DCA). The 1,2-DCA is reported at low and declining concentrations in <br /> five of the sites twelve wells. <br /> Please proceed with preparation and submittal of a closure report that includes the following: <br /> 1. A calculation of the contaminant mass remediated and the contaminant mass remaining <br /> at the site in both soil and groundwater. <br /> 2. An estimate of how long it will be until the dissolved contaminant concentrations onsite <br /> will reach water quality goals. <br /> 3. A discussion of the risks of indirect exposure, gross contamination and vapor intrusion <br /> from the contamination left behind. <br /> 4. Confirmation that a sensitive receptor survey has been completed and a discussion of <br /> the potential threat to those receptors, and <br /> 5. Any other requirements listed in the Tri-Regional Guidelines Appendix A. <br />