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Mr. Soon Kim Page 10 December 19, 1995 E Remediation Progress The remediation system consists of two well pairs, a vapor monitoring well cluster(NP-2) that was converted to a vapor extraction well, a sparging blower, a vapor extraction blower, and a.set of two granular activated carbon vessels in series. New Well Construction Two additional multi-purpose wells SVE-3 and SVE-4 were completed December 11 and 15, 1995 as directed by PHS/EHD. The installation procedures followed the November 1, 1995 work plan submitted to PHS/EHD. The construction of these wells is similar to the other groundwater monitoring wells on site. The new wells consist of a 20 screen interval from 55 to 75 feet below ground surface, a 2 inch diameter PVC casing, and a lockable well head. The intended purpose of these new wells is (1) to provide additional ITB monitoring points in I ' the contaminated groundwater zone, (2)provide additional soil vapor extraction points for vadose zone NAPL removal, and (3) to serve as passive soil venting wells that may enhance the extraction of soil vapor from adjacent SVE wells. A plan is being formulated to connect SVE-4 (the more contaminated of the two new wells) to the vapor extraction and treatment system. SVE-3 was drilled and installed 30 feet north and 15 feet west of NP-2. SVE-4 was drilled and installed 14 feet north and 23 feet west of NP-2Fi ure 1 . The borehole wa ( g ) s drilled with an 8-inch diameter hollow-stem auger. Soil was sampled every 5 feet using a standard penetration test sampling device. A portion of each soil sample was saved in a zip-lock style plastic bag and, after several minutes of equilibration, the vapor inside the bag was monitored j . with a photo ionization detector (PID). The total vapor concentration is reported in parts per million (ppm) on the geologic logs. In addition, the soil was geologically logged and characterized using the Unified Soil Classification System. The boring logs and well completion logs are attached. SVE-4 was the first borehole drilled and installed. The PID data reveal that the soil beneath SVE-4 is impacted from a comparatively shallow depth (10 feet bgs) down to groundwater. The first odors and measurable vapors occur at 10 feet bgs at a concentration of 45 ppm. The concentration of these vapors becomes increasingly greater with depth. The increased concentration continues to approximately 40 feet where it stabilizes around 390 ppm. The stabilized concentration of 390 ppm continues to approximately 65 feet bgs (depth to groundwater) where it increases slightly to 402 ppm. i . SVE-3 was installed December 15, 1995. PID measurements made on the soil reveal that the soil is not impacted by volatile hydrocarbons from the surface to 55 feet bgs. The first }