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♦./ Ll vapor sampling, the temporary wells will be removed under approved EHD permits (see below). 2.0 Vapor Sampling Procedure A minimum of 48-hours after well construction will be allowed for equilibrium of conditions prior to sampling. Wright will then sample the vapor wells assisted by SCV Environmental, Inc. The sampling procedures are summarized as follows: The tubing emanating from the vapor point affixed to a sample shut-off valve in the off position will first be connected to a 167 milliliters-per-minute flow regulator inclusive of particulate filter and a "T" fitting. One end of the "T" will be connected to the sampling Summa canister. The other end of the "T" will be affixed to a digital vacuum gauge and a I-liter Summa canister utilized for purging. A ten (10)minute minimum vacuum tightness test will be performed on the manifold and connections by opening and closing the 1-liter purge canister valve and monitoring the applied vacuum on the vacuum gauge. The sample shut-off valve on the downhole side of the sampling manifold will refridin in the closed position. When gauge vacuum is maintained for ten (10) minutes without any noticeable decrease (less than 0.1 inches of mercury (Hg) for properly connected fittings), then purging may begin. The down-hole shut off valve will be opened and approximately three pore volumes removed utilizing the purging Summa. Purge volumes of vapor will be removed and verified by the calculated pressure drop in the 1-liter Summa canister utilized for purging. Isopropyl alcohol will be utilized as a leak detection compound during sampling by applying 10 to 15 drops to cotton gauze and placing near the borehole. Sampling will begin by opening the Summa canister valve. Immediately upon opening the sampling valve, a shroud will be placed over and enclose the atmosphere of the borehole and entire sampling train including all connections. Sampling will continue until the vacuum gauge indicates approximately five (5) inches of Hg remaining (approximately five [5] minutes for a 1-liter canister equipped with a 167 milliliter-per-minute flow regulator). A flow controller will be utilized in the sample train to control the flow of soil gas into the Summa canisters for sample collection. Limiting the purging and sampling rate to between 100 and 200 milliliters per minute is recognized to produce representative samples and aids in preventing ambient air from diluting the soil gas samples. During sampling, a data logging photoionization detector (PID) will be utilized to monitor the atmosphere inside the shroud through a bulk-head fitting. The logged data (at minimum thirty [30] second intervals) will be corrected to parts per million by volume isopropyl alcohol concentrations and utilized to evaluate the integrity of the sampling train. All field data, including equilibrium time, purge volume calculations and leak check measurements recorded will be included in the report. Page 3 of 8