SITE INFORMATION AND CORRESPONDENCE

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• • Page 2 of 4 ` Below is Section 3.1.2 from the work plan with revisions proposing a new soil-vapor sampling method and materials, and including the items/conditions outlined in the EHD letter dated 11 March 2014: 3.1.2 Soil-Vapor Sampling A soil-vapor sample will be collected at approximately ten (10) feet bsg in the boring advanced north of the former UST area at 615 East Main Street. The soil-vapor sample will be collected utilizing '/4-inch diameter Teflon tubing and a Y4-inch diameter, two-inch long, disposable polyethylene vapor implant with speed-fit fitting installed to 10 feet bsg. The soil-vapor sampling boring will be advanced to 10 feet bsg using a truck mounted AMS Powerprobe 9600 or Geoprobe direct-push probing unit equipped with 1.25-inch probing rods. Once the total depth is reached, the 1.25-inch probing rods will be removed and the vapor implant, with Teflon tubing attached, will be installed in the borehole. Once the implant is set a filter pack material consisting of pre-washed #2/12 Lonestar sand will be added from total depth to approximately 9.5 feet bsg. A dry bentonite seal will be placed above the filter pack to a depth of 8 to 9.5 feet bsg and pre-hydrated bentonite will be placed above the dry bentonite from 8 feet bsg to near surface. The bentonite will be allowed to hydrate for a minimum of one half hour. Approximately, 3 feet of extra tubing will be run above ground for soil-vapor sample collection. Additionally, hydrated bentonite will be placed around the tubing at ground surface to prevent ambient air intrusion. A minimum of 120 minutes equilibrium time will be allowed at the soil- vapor boring location prior to purging and sample collection. One six-liter Summa canister will be utilized for purging and soil-vapor samples will be collected in one-liter Summa canisters (TO-15) and four-liter sorbent tubes (TO-17). Based on the EHD letter dated 11 March 2014 and the phone conference held between AGE and EHD personnel on 07 May 2014, a duplicate TO-15 and a replicate T01 soil-vapor sample will be collected during the investigation. The sampling and purge canisters will be connected together with a dedicated and serialized sampling inlet manifold. The sampling inlet manifold will consist of a vapor-tight valve; a particulate filter; a calibrated flow restrictor, calibrated to 200 milliliters per minute (ml/min); a stainless steel tee-fitting; two vacuum gauges at either end of the flow controller and connections for both purge and sampling canisters (manifold assembly). The manifold assembly will be attached to the Teflon tubing from the vapor implant; for the duplicate TO-15 sample, a tee-fitting will be used to attach the tubing to two separate manifold assemblies. The purge canister will be attached to the end of the sampling manifold while the sample canisters will be attached to the tee-fitting between the tubing and purge container. A manifold assembly will not be used for sorbent tube sample collection. The inlet of the sorbent tube will be attached directly to the Teflon tubing and a low-flow pump will be attached to the outlet of the sorbent tube. The low-flow pump will be calibrated to approximately 100 ml/min and will used to extract soil-vapor through the tubing and into the sorbent tube. Approximately four liters of soil-vapor will be collected into each sorbent tube. This step will repeated for collection of a replicate TO-17 soil-vapor sample. Leak tests will be performed on each assembly by attaching and securing the sample and purge canisters to the manifold and opening the valve on the purge canister and the manifold. The leak test will be performed for approximately 10 minutes on each assembly. The soil-vapor boring location will be isolated from ambient air by enclosing the borehole, tubing and manifold/canister assembly in a plastic shroud, which will be weighted at the surface. Isopropyl alcohol (IPA) as a liquid will be placed in a stainless steel bowl within the plastic structure and allowed to volatilize into the air enclosed within the plastic structure surrounding the borehole, tubing and manifold/canister assembly. 6/20/2014