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i PUBLIC 1EALTH SERVICES SAN JOAQUIN COUNTY ENVIRONMENTAL HEALTH DIVISION Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer : P 445 N. San Joaquin Street • P.O. Box 388 • Stockton, CA 95201-0388 c,FOR� (209) 468-3420 k I� f Py JOHN STROH SAN JOAQU Ilv MOSQUITO ABATEMENT DISTR 7759 SOUTH AIRPORT WAY STOCKTON CA 95206 MAR 2 8 1994 � Re: San Joaquin Mosquito Abatement District If Site Code: 1798 7759 South Airport Way Stockton CA 95206 } i1 } San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has completed review of the "Work Plan" dated March 14, 1994 and prepared by ' Weston. PHS/EHD has the following comments for your consideration and action. The work plan proposed to investigate soil contamination associated with the four M underground storage tanks (USTs) which were removed m 1987 and included two soil borings (SB1 and SB2) two soil borings with hydropunches (HP1 and HP2) and three soil borings converted into monitoring wells (MW1 - MW3). Soil contamination documented is associated with former UST#1 and UST#2, at a maximum depth of 27 feet below ground surface (bgs). T'he work plan indicated that only two soil samples from each soil boring, SBI and SB2, would undergo analysis. Since this area has been reportedly over-excavated and sidewall samples not collected it will be necessary to analyze additional soil samples to verify that the Horizontal extent of contamination was adequately remediated. PHS/EHD suggests that soil samples be E collected for analysis at 15, 20, 25, and 30 feet bgs along with the capillary fringe sample. Field screening may indicate that additional soil sample collection for analysis is ,. warranted, in which case PHS/EHD recommends addition al samples undergo analysis. All soil samples should be analyzed using the detection limits outlined in the Tri-Regional Guidelines which was referenced in the work plan. The detection limits for BTEX are 0.005 ppm and for TPH-gas or diesel are I ppm. The detection limits used previously for BTEX were 0.2 ppm. The work plan indicated that soil samples would not be reserved and would be stored in P P P i a "cooler" pending transport to the laboratory. The State Water Resources Control Board's "Leaking Underground Fuel Tank Manual" indicates that soil samples should be stored at 4° Celsius pending analysis. Therefore, the soil samples collected for analysis 1 should be stored in the same way as the groundwater samples;collected for analysis, in an ice chest with adequate ice. jY 1 A Division of San Juaquin County Health Careirervices; ;