SITE INFORMATION AND CORRESPONDENCE FILE 2

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ENVIRONMENTAL HEALTH DEPARTMENT SAN JOAQUIN COUNTY Q ?� Donna K.Heran,R.E.H.S. Unit Supervisors N: 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. J. Director Al Olsen,R.E.H.S. Stockton, California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. Douglas«'.Nilson,R.E.H.S. Program Manager Telephone: 209 468-3420 <�FORd Laurie A.Cotulla,R.E.H.S. p ( ) ret Lag Program Manager Fax: (209) 464-0138 Robert loo,R.E.H.S. Mark Barcellos,R.E.H.S. DANIEL SILVA WEST CLAY PROPERTIES PO BOX 6152 STOCKTON CA 95206 RE: West Clay Properties Site Code: 1065 639 West Clay Street Stockton,CA 95206 Three cone penetrometer soil borings CPT-01 thru CPT-03 were advanced in the vicinity of the former No. 3 underground storage tanks(UST)located on the south end of the above referenced site,and two CPT borings CPT-04 and CHB-01 were advanced in the vicinity of the former UST cluster located on the northern part of the site in June 2004. CPT-01 was advanced to approximately 100 feet below surface grade(bsg),CPT-02 to 170 feet bsg,CPT-03 to 210 feet bsg,and CPT-04 to 175 feet bsg. Grab groundwater samples were collected from 11 separate soil borings located immediately adjacent to the corresponding CPT. The results of the CPT investigation were documented in Cone Penetrometer Testing and Ground Water Sampling Report(the report)dated September 14,2005 prepared by Advanced GeoEnvironmental,Inc. (AGE). AGE identified in the report the presence of 6 hvdro- geological units HU-1 through HU-6 at the former No.3 USTs area: • HU-1 from 18 feet bsg to maximum of 40 feet bsg composed of clay and fine sand • HU-2 from 31 feet bsg to maximum of 72 feet bsg composed of silt and clay • HU-3 from 62 feet bsg to maximum of 90 feet bsg composed of silty sand to gravelly sand • HU-4 from 83 feet bsg to 170 feet bsg composed of clayey silt and silt • HU-5 from 166 feet bsg to maximum of 191 feet bsg composed of sand and gravelly sand,and • HU-6 from approximately 191 feet bsg to at least 210 feet bsg composed of clave silt and silt. Although CPT-03 was advanced to approximately 210 feet bsg,grab groundwater sample was not collected at that depth due to refusal. The deepest grab groundwater sample collected in the area of the former No. 3 USTs was collected from the boring next to CPT-03 at between 176 feet bsg and 180 feet bsg in what is interpreted to be HU- 5. Analytical results of this CPT-03 grab groundwater sample were 5,400 micrograms per liter(ug/1)of Total Petroleum Hydrocarbons as gasoline(IPH-g),3,000 ug/1 of TPH-diesel(IPH-d),23 ug/1 of Benzene,and 1,180 ug/I of Total Xylenes. The highest contaminant concentrations detected in the same area was detected in the grab groundwater sample collected from the boring next to CPT-02 at 137 to 141 feet bsg(HU-4). Analytical results of this sample were 30,000 ug/1 of TPH-g,25,000 ug/1 of TPH-d,170 ug/1 of Benzene,and 6,600 ug/l of total Xylenes. Grab groundwater samples collected from the former UST area to the north at depths of 80 feet to 84 feet bsg,78 to 82 feet bsg,and 166 feet to 170 feet bsg,were all non-detect(ND). San Joaquin County Environmental Health Department(EHD)concurs with AGE's conclusion that the vertical and deep lateral extent of the groundwater contamination plume in the former No.3 UST area is not defined. Submit a work plan-that will define the extent of the contamination plume in this area to EHD by April 1,2005. Please feel free to direct any questions to Jeffrey Wong at(209)468-0335. Donna Heran,REHS,Director Environmental ealth Department Jeffrey Wong,Senior RENS Nuel C. Henderson,Jr.,RG LOP/Site Mitigation Unit IV LOP/Site Alitigation Unit IN' C: RWQCB,Central Valley Region—James L.L.Barton,RG C: Advanced GeoEnvironmental,Inc.—Bill Little,RG