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r r, V � Wright ��lP�`�{�� fiAL I�I+AI-Tli Environmental September 16, 19% r' + '? Services, Inc. cis SEP I g AM It 06 San Joaquin County Ms.Linda T urkatte Public Health Services Environmental Health Division 304 E. Weber Ave. Third Floor Stockton,CA 95201 RE: Naomie King Trust,Workplan to Investigate Subsurface Contamination,King Island, San Joaquin County,California,Site Code 506032. Dear Ms.Turkatte: Wright Environmental Services, Inc. (Wright)has prepared this workplan on behalf of the administrator of the Naomie King Trust and Estate regarding the above referenced site. Wright has performed previous work at this site and the current workplan is in response to the San Joaquin County Public Health Services Environmental Health Division(PHS-EHD)date stamped letter of August 8, 1996. BACKGROUND The site is located at 21334 West State Route 4, Stockton, California (Figure 1 and 2). In November 1995 an underground storage tank was located and removed from the ground at the site. The last use of the tank is not known,but the tank had apparently been used for gasoline storage. The tank was estimated to be about 500 gallon opacity and was observed to have numerous small hoes in the tank bottom. Sampling and analysis of soil from the tank pit bottom revealed low levels of degraded petroleum compounds and analysis of water collected from the tank pit and soil from the tank pit sidewalls revealed no detectable concentrations of petroleum compounds.(see Wright report dated June 21, 1996). SAMPLING-TECHNICAL RATIONALE DISCUSSION The PHS-EHD indicated in their August 1996 letter and in subsequent telephone conversations with Wright staff that additional sampling beyond the former tank pit would be necessary to verify if the documented release was limited to the former tank pit area as suggested in Wrights June 21, 1996,report. PHS-EHD specifically requested additional data on the lateral extent of the contamination noted at six feet below ground surface(bgs). PHS-EIID indicated it will use the data collected as a result of this workplan to rule out a potential threat this contamination may pose to the aquatic ecosystem and the users of nearby surface waters. In our opinion, the previous chemical analysis showed low levels of degraded Total Petroleum Hydrocarbons as Gasoline (TPHG) Diesel (D) and or Benzene, Toluene, Ethyl Benzene and Xylene (BTEX). Evidence of a large release was not indicated and no reports of river impairment have been noted at or near this site. The levees, around the island contain old river and related water ways (waterways) which surround the Island. The land level of the island is somewhat below the levees. The flowing waterways are subject to tidal changes and without considering major storm events (100 year) normally crest 2-3 feet below the lard level of the island. This and observed geology of the former tank pit indicates an inward groundwater flow gradient to the island given the larger hydraulic head through the levee relative from the river to the island Thus a relatively static flow in the vicinity of the tank pit is envisioned based upon existing data Hence,a reconnaissance groundwater sampling approach will be used for this study. 4220 Commercial Dr.#5 - Tracy,California 95376 Telephone (209) 833-0758 - Fax(209)832-5152