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Lawrence Livermore National Laboratory June 26, 1987 r-Z ;Z y t`+J, ENVIRU''v",ENTAL HEALTH Ms. Wendy Cohen FERMIT/SERVICES, Regional Water Quality Control Board Central Valley Region 3201 S Street Sacramento, CA 95816-0270 Dear Ms. Cohen: Subject: Building 834 Area Remedial Effort: Short-duration Experimental Testing for Soil and Ground Water Cleanup. As previously reported, a shallow plume of TCE exists in the soil and perched ground water beneath the Building 834 area of Site 300. We are designing a cleanup system to reduce TCE concentrations to acceptable levels for soil and ground water use and quality. A series of short-duration pumping tests will provide the necessary first step toward soil characterization, the basis for the ultimate process design. The general purpose of these tests is to determine an empirical value for the gas permeability of the soil interval .containing the contaminant. Our choice for the soil-cleanup system is a vacuum-induced soil-venting process. The process involves the application of vacuum in a series of wells that have been screened in the soil interval containing high concentrations of TCE. The test will incorporate a series of four shallow test wells completed on an azimuth line running generally west of Building 834-D. These wells will be spaced laterally at varying intervals to provide a range of spacing data. With an approximate total depth of 40 ft, each will have a 10-ft screened section near the bottom and should show the perched water level at about 25 ft. During the test, the contaminated soil interval will be dewatered concurrent with the application of vacuum to the region. The extracted water, expected to flow at 1 gpm and to contain an average of about 200 ppm TCE, will be processed (treated) through a surface-mounted stripping system and discharged onto the ground near the test site. This processed water will contain only trace levels of TCE (upper limit of 5 ppb) and is expected to run below detection limits during most of the tests. The vacuum system will draw a mixture of TCE vapor and air from the wells at a maximum flow rate of 100 scfm. This vapor and air stream will contain concentrations of TCE in a range from 100 to 2000 ppm by volume. These levels are based on data from a preliminary test performed on one of these test wells, 834-D-3, last year. We anticipate that the initial TCE concentrations will be higher and show a gradual decrease over time. We expect that the average concentrations will be about 1000 ppm. This air stream, discharged from the vacuum system, will be vented to the atmosphere. This process will discharge TCE to the atmosphere at an average of 0.022 lb/hr. An Equal Opportunity Employer•Universityof California•PC.Box BOB Livermore,Caktrnia 94550•Telephone(415)422-1100•TL:x 970-386-8339 UCLLL LVY1R