WORK PLANS - Laserfiche WebLink

Home Browse Search

AdvancedGeo 09 January 2019 Environmental AGE Project No. 99-0559 1V Page 6 of 7 For installation of soil-vapor wells, 1/4-inch diameter, 2-inch long polyethylene soil vapor implants and nine feet of '/4-inch Teflon® tubing will be lowered to the base of the borings; three feet of tubing will remain outside the boreholes for vapor sample collection. However, before installing the vapor implant and tubing, approximately six inches of#2/12 sand will be placed at the bottom of the boreholes for the vapor implants to be placed on. Once the six inches of sand, tubing and vapor implants are in place, the filter pack of #2/12 sand will continue to be added from the bottom of the boreholes to approximately six inches above the base of the vapor implants. Following placement of the filter pack, approximately 12 inches of dry granulated bentonite will be placed atop the filter packs. The remaining annular space will be filled to the ground surface with a cement grout. The grout mixture will consist of Type 1/11 Portland neat cement with approximately 3-5% bentonite content. A flush mounted well box will then be installed over the wells. Approximately, 3 feet of extra tubing will be run above ground for soil-vapor sample collection. A well construction diagram illustrating the proposed design is included as Figure 4. Once soil-vapor wells are installed, a minimum of 48-hours equalization time will be observed prior to sampling the wells. 3.4. SOIL-VAPOR SAMPLING Soil-vapor samples will be collected from the vapor wells using Summa canisters. For this method, one 6-liter Summa canister will be utilized for purging and each soil-vapor sample will be collected in a 1-liter Summa canister. 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 '/4-inch Teflon® tubing from the vapor sampling locations. 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. Leak tests will be performed on each manifold 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 3-5 minutes on each assembly. Each soil-vapor sampling location will be isolated from ambient air by enclosing the borehole, tubing and manifold/canister assembly in a 300-liter 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.