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Del Monte Foods One Market ' � Rk P.O. Box 193575 Steven P.Ronzone San Francisco,CA 94119-3575 Director/Real Estate&Facilities Telephone: (415)247-3000 (415)247-3520(Direct) (415)247-3540(Facsimile) October 8, 1999 Mr. Ronald Rowe, Sr. REHS LOP/Site Mitigation Unit Ms. Margaret Lagorio,Supervisor Site Mitigation Unit ' Public Health Services U San Joaquin County Environmental Health Division OUT 111999 304 East Weber Avenue, Third Floor Stockton, CA 95202 ENVIRONMENTAL. HEALTH PERMIT I SERVICES Re: Amended Work Plan for Additional Site Characterization Disco Property, Stockton, California Dear Mr. Rowe and Ms. Lagorio: Enclosed is an amended work plan for additional site characterization for the Disco property. This amended work plan has been prepared in response to your September 13, 1999 comments and directives to the most recently submitted work plan (August 17, 1999). The amended work plan incorporates the comments and directives outlined in the September 13, 1999 letter, with exception of the following: • Laboratory derived permeability. As directed by PHS, a CPT rig will be used to collect CPT logs, soil samples, and grab groundwater samples. Permeability cannot be measured in the laboratory with soil cores recovered using a CPT rig due to the small diameter (1.125-inches) of the soil core. Two geotechnical laboratories were contacted by CH2M HILL and asked about the feasibility of testing for permeability using.CPT soil cores: URS-Greiner Woodward-Clyde, in Pleasant Hill (personal communication, Sam Capps, September 1999), and RGH Environmental in Santa Rosa (personal communication, Terrence McCue, September, 1999). Both laboratories informed CH2Mhill that they could not perform permeability tests on the small diameter soil cores. The minimum required soil core diameter for laboratory derived permeability testing is 2- inches. • Estimates of transmissivity and groundwater flow rate. An aquifer pumping test is the standard method used to estimate transmissivity and hydraulic conductivity. An aquifer pumping test was previously performed at this site, on February 16 and .17, 1995. The results of this pumping test are presented in the Problem Assessment Report and Final Remediation Plan'(CH2M HILL, 1995). The groundwater flow rate can be derived from the estimated hydraulic conductivity and the groundwater gradient. These calculations will be performed when assessing the fate and transport of a groundwater plume.