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San Joaquin County PQ�'lMEnvironmental Health Department DIRECT°R C M ° •'°' ''• Donna Horan,RENS ?: =i 600 East Main Street PROGRAM COORDINATORS y < Stockton, California 95202-3029 Margaret Lagorio,REHS �. RobertMcClellon,REHS ' Jeff Carruesco, REHS,RDI ;.��P Website: www.sjgov.org/ehd Kasey Foley,REHS l°a Phone: (209) 468-3420 Fax: (209)464-0138 December 29, 2009 Port of Stockton IL� Mr. Jeff Wingfield 2201 W. Washington St Stockton, CA 95201 Subject: UST Site#3 LOP Case #: 1282124 Port Rd 13 at G St CUF#: 013777 Stockton, CA 95201 Global ID #: T0607700817 The San Joaquin County Environmental Health Department (EHD) has reviewed Site Assessment dated November 13, 2009, Remediation Bench Tests - Bioremediation Study Report dated November 13, 2009, and Semi Annual Monitoring Report — Fourth Quarter 2009 dated December 4, 2009, submitted by your consultant, WGR Southwest, Inc. The reports cover the April 2009 installations of monitoring wells MW3-8, MW3-9, MW3- 10 and soil borings 133-20 through 133-24, soil and groundwater sample analytical results, a semi-annual groundwater monitoring event, and a discussion of steps taken to evaluate the need and use of chemical oxidant injection and biological injection to remediate the petroleum contaminated soil and groundwater at the site. The monitoring report covered the collection and laboratory analyses of groundwater samples from all the monitoring wells onsite November 23, 2009. The bioremediation and bench test reports discussed plans to inject chemical oxidants (ozone and peroxidelperozone) into the subsurface to enhance existing bacterial breakdown of petroleum hydrocarbons in the subsurface. Also included was a discussion about the possibility of injecting macronutrients into the subsurface after special regulatory approval is received. The results of the bench scale test indicated that no metals or byproducts of concern were formed from the use of ozone or peroxidelperozone. Conclusions included in the site assessment report stated that the extent of dissolved petroleum hydrocarbons toward the north—northeast and the west-southwest has not been fully delineated. The elevated concentration of total petroleum hydrocarbons as gasoline (TPHg) in monitoring well MW3-8 identify a potential new concern at the site and the EHD will require an additional lateral and vertical groundwater investigation in this quadrant if similar concentrations continue to be detected from samples collected from this well. Although the site has been required to reduce sampling of the monitoring wells to semi-annual, the EHD recommends that new monitoring well MW3-8 be sampled quarterly for a full annual period to provide additional data.