SITE INFORMATION AND CORRESPONDENCE

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j + Mr. John Welty April 10, 1990 Page 5 Soil-Vent System. The soil venting system consists of eight venting points on the site which includes four groundwater monitoring wells which had gone dry by May of 1989 (Wells 1, 2, 3, and 4). The vapor points are connected to a high-vacuum vapor control system. The points are manifolded to vapor phase carbon adsorption canisters. The system was expanded to include e . a catalytic scavenger vapor-treatment systerrL The system draws vapors at a rate of approximately 90 cubic feet per minute (cfm). A soil-vent test was conducted on the four dry monitoring wells to determine the vacuum and flow rates required for optimum use, prior to connection to the soil-venting system. The soil-vent test was conducted in April of 1989 and results of the test indicated that the dry monitoring wells could handle a flow of 100 standard cfm and a 15-foot radius of influence could be achieved. Groundwater Remediation System. A total of 20 monitoring, recovery, or pumping wells have been installed on or around the site since May of,.1986. Of the 20 wells, 9 have gone dry or ceased being usable. Free product was found in Wells 1 and 4 initially. Free product was recovered from Well 4 initially by hand bailing and then by using a small diameter double pumping system installed in July 1986. Two pumping wells (PW-1 and PW-2) were installed by October 1986. Pumping Well 3 (PW-3) was installed by November 1986. PW-1, PW-2 and Well 4 were used to pump groundwater to a carbon filtration treatment system which was replaced by an air stripper in February 1987. In February 1988, Recovery Well 1 (RW-1) was installed and the remediation abatement system's underground line and electrical systems were upgraded. A pump test was performed by GTI on the site wells and reported in the April 1988 Update Report. Based on the results, a capture zone 'radii was calculated using the values of transmissivity and storativity calculated. The results indicate that a pumping rate of between 5 and 10 gallons per minute (gpm) would capture the contamination plume beneath the site, based on average value for transmissivity of 5,160 gallons.per day per foot. Figure 3 shows the capture zones developed by GTI for different pump rates. As shown on the figure, a pump rate of greater than 10 gpm would be needed for one well-on the 7-Eleven property to capture a plume extending to the Tomato Growers Association (TGA) property. In a January 1987 report prepared by GTI, it was reported that groundwater was extracted from PW-1, Well 12, PW-3 and Well 4. In May 1989, only PW-1 and RW-1 were being used to extract groundwater at a total rate of 1.3 gallons per minute (gpm). Since June of 1989, the groundwater remediation system has consisted of groundwater extraction only from RW-1 because the water table declined so PW-1 could no longer be used. Currently, pumping is maintained at an average rate of 1 to 2`gpm. By June 8, 1989, over 900 gallons of free product have been recovered from the groundwater remediation system. Brown and Caldwell