SITE INFORMATION AND CORRESPONDENCE FILE 1

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Geologicallle hnics Inc. 2741 Riva Road Ma&to,Calif—95351 (209)538-6424iFaC#538-5852 '-',. r,- -- P'. 9 I I 5 September 13, 1999 Project No.: 425.2 Project Name: George's Service Ms. Carol Oz San Joaquin County Public Health Services Environmental Health Division 304 East Weber Street, Third Floor Stockton, CA 95202 Re: Response to September 8, 1999 Letter George's Service, 1600 Durham Ferry Road, Tracy, California Dear Ms. Oz: This letter is an initial response to your September 8, 1999 letter, for George's Service, 1600 Durham Ferry Road in Tracy. As the investigation project proceeds, additional information requested in you letter will be submitted. On-Site Domestic Wells • As per our September 1, 1999 field meeting, the on-site domestic well that tested positive for 0.37-ppb benzene was re-sampled. A bailer could not be used to sample the well, as the access port was only `/2 inch diameter. The sample valve between the tank and pump was repaired and used to collect a sample after the well had been purged for approximately `/2 hour. It was decided to give this well the designation of 1600-A Durham Ferry Rd. • The other domestic well on the 1600 Durham Ferry Road property was also sampled. domesticl waterwill b y supply fore ethe Georgenatd 1600-B e&ham Mea Teranishi. This Road and the well primary ell isfl for farther tothe southeast then is 1600-A. • Construction details of 1600-A Durham Ferry Road have not been located during review of DWR and county files for well logs. The well is very old and may have been installed without a log being prepared by the driller. While we were on site, the total depth of the well was measured and found to be 77 feet below ground surface. This well has a similar depth as MW-202 (—' 80 ft deep). Once the data for this last monitoring event has been received from the lab, decisions will be made regarding the need of performing an aquifer pumping test and to have the construction of the well determined by down-hole camera. If the well is non-detect it may not be necessary to perform these tasks. The two domestic wells on Teranishi's property, as well as the two down-gradient domestic wells, are sampled on a quarterly basis. These wells are displayed on the site uded gradient domestic wellswater gradient are designated as 31448that is 15. Hwy 33 and 16h each 97ort. The two down Durham Ferry Rd. Former UST Locations The four former USTs are clearly labeled on the site maps and gradient maps that are submitted with each report. Plume Migration • Fate and Transport modeling will be performed to determine the potential for off site migration of the plume. Geophysical parameters, porosity, specific gravity, moisture, bulk density and permeability were tested for on samples collected in June and July of