SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

San Joaquin County DIRECTOR oP "' n, REHS Donna Hera Environmental Health Department � _��'•.O ASSISTANT DI ADIRECTOR OR 600 East Main Street Laurie Cotulla, REHS a.l Stockton, California 95202-3029 PROGRAM COORDINATORS •' -- - Carl Borgman, REHS Mike Huggins, REHS, RDI Q�iFOR`'� Website: www.sjgov.org/ehd Margaret Lagorio, REHS Phone: (209) 468-3420 Robert McClellon, REHS Fax: (209) 464-0138 .teff Carruesco, REHS, RDI Kasey Foley, REHS October 15, 2008 Mr. Dung Thanh and Ms.Nhuan Le 2224 Manthey Road Stockton, California 95206 Subject: California Stop 2224 Manthey Road Stockton, California 95206 The San Joaquin County Environmental Health Department (EHD) has reviewed Additional Site Assessment Work Plan dated September 29, 2008, prepared by Advanced GeoEnvironmental, Inc. (AGE) on your behalf for the above-referenced site. In the work plan, AGE proposes to characterize subsurface lithology and identify potentially permeable subsurface soil units using cone penetration test (CPT) technology by advancing eight CPT soil borings to approximately 150 feet below surface grade (bsg) at locations on- and off-site. Based on the acquired information, AGE proposes to collect approximately thirty-five grab groundwater samples from discreet borings advanced adjacent to the eight proposed CPT soil borings. The grab groundwater samples will be submitted to an environmental laboratory certified by the State of California for chemical analysis. The work is proposed to delineate the vertical and lateral extent of the petroleum hydrocarbon plume at your site. The EHD approves the advancement of one CPT boring (CPT-2) to approximately 150 feet bgs in the source area. However, the EHD believes the depths for the remaining seven proposed CPT borings should exceed 100 feet bsg only if justified by findings from soil boring CPT-2. Grab groundwater samples collected should decrease from the proposed thirty-five samples since the number of samples collected is based on subsurface permeable intervals to 100 feet bsg instead of 150 feet bsg. Please summit an encroachment permit from the California Department of Transportation (Caltrans), a boring permit application and permit/inspection fee of$404 per parcel to the EHD,and complete the fieldwork by December 15, 2008. The EHD has reviewed the analytical results for groundwater samples collected during the first two quarterly groundwater monitoring events of 2008. It appears the dissolved petroleum hydrocarbon plume in the monitored shallow groundwater zone is unstable. This is apparent by comparing concentrations of total petroleum hydrocarbons quantified as gasoline (TPH-g) and methyl tertiary- butyl ether (MTBE) in groundwater samples collected from monitoring wells MW-1 and MW-8 during these two sampling events. Results for groundwater samples collected from MW-1 went from 1,200,000 micrograms per liter(pg/L)to less than 50 µg/L for TPH-g, and from 910,000 µg/L to 48 gg/L for MTBE; while results for groundwater samples collected from MW-8 went from 400 pg/L to 360,000 pg/L for TPH-g,and from 250 µg/L to 140,000 pg/L for MTBE.