SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

4) Quantitative measurements of soil porosity and permeability have not been made. However, with over twenty (20) borings drilled to date on this site, the site should be regarded as densely drilled, yielding excellent quantitative data on lithology and stratigraphy. This information is depicted graphically in Cross-sections included in the FRP. Two moderately sorted to well-sorted, permeable sand units are present beneath the site, and both interfinger with, and are underlain by thinner units of low- permeability silty clay. The organic matter content has not been measured, but casual observation indicates that it is low. Silty clay beds are either blue-green (reduced) or reddish-brown (oxidized), and sandy beds are yellow-brown to gray. No dark gray to black beds were encountered. Pore moisture ranges from zero in parts of the vadose zone to 100% saturation below the water table. Further discussion of soil characteristics is provided in #8, below. 5) For several reasons, no vapor extraction test has been performed. After discussions with their consultants and legal counsel, Geweke Land Development & Marketing has concluded that vapor extraction does not offer a feasible or cost-effective approach to remediation at this site. Previously, PES Consultants had suggested that remediation by vapor extraction could require ten (10) years at this site (PES Problem Assessment Report, July, 1991). In prior correspondence regarding the Final Remedial Plan submitted by Geological Audit, neither San Joaquin County PHS/EHD nor the Central Valley Regional Water Quality Control Board (CVRWQCB) requested that a vapor extraction test be performed, or that such data be submitted (see memo dated September 20, 1993 from Elizabeth Thayer to Gordon Boggs). Vapor extraction technology is not planned or recommended for this site. An aquifer test was performed by PES Environmental on June 5, 1991, and reported in a Problem Assessment Report (PAR) dated July 31, 1991. The data collected during this test are more than adequate for our purposes. Furthermore, since pumping of groundwater is not planned or required for the chosen remediation method (bioremediation), an additional aquifer test would only be superfluous. 6) Testing for background CO2 and OZ is scheduled for the month of January. We anticipate monitoring twice a week until inoculation to obtain baseline data on CO2 and 02. Testing/monitoring equipment is currently being secured; it is likely that a GasTech 3252 will be utilized to measure both the CO2 and 02 concentrations. The data will be incorporated in the first quarterly report (March 1994). 7) Adding moisture by one well volume [approximately 35 gallons for a 4-inch diameter well and 9 gal for a 2-inch well] per well will insure some moisture level above wilt. The water is being added to counteract the desiccating effect of the low-pressure air source, and is unlikely to cause a measurable change in the net moisture content of the soil or movement of the groundwater plume. p 1,"l ASM Service.,h. 2