WORK PLANS - Laserfiche WebLink

Home Browse Search

rated well box set in concrete, and a lockable expanding well plug with lock. Proposed well construction details are presented on Figure 3. The monitoring wells will be constructed and developed in accordance with the Winzler&Kelly's Standard Operating Procedures (SOPS)for Soil Boring and Monitoring Installation and Development(Appendix A). The new wells will be developed a minimum of 72 hours after installation of the sanitary seal. 2.3 SOIL GAS PROBE INSTALLATION Soil gas probes will be either advanced using a hand operated rotary hammer drill with attached direct- push tooling or using a limited access direct push drill rig, following theguidelines presented in the Draft Advisory-Active Soil Gas Investigations, provided by the Department of Toxic Substances Control (DTSC), dated March 2010(DTSC Guidelines).A copy of the DTSC Guidelines is provided in Appendix B. In accordance with this advisory, borings will be advanced to approximately 5 feet bgs or first encountered groundwater,whichever occurs first. The depth was selected as it will provide the most relevant data for the proposed human health risk evaluation. Additionally, 5 feet bgs is the minimum sample depth identified by the DTSC Guidelines. The direct push rod will be driven down to the sample depth of 5 feet bgs,creating a boring for the installation of a temporary soil gas probe. The soil gas probe will be temporarily installed in each of the two proposed locations. To complete the installation, clean, dedicated nylon tubing with an attached new 1-inch porous foam block will be inserted at the bottom of the borehole,with the other end of the tubing extended to the surface.A total of 12 inches of sand will be placed around the porous foam block(6 inches below and 6 inches above). Approximately 1 foot of dry bentonite chips will be added to the borehole. The remainder of the borehole will be backfilled with hydrated bentonite to the ground surface. 2.4 SOIL GAS SAMPLING AND ANALYSIS The DTSC Guidelines recommend that the soil gas probes be allowed to equilibrate after installation and before sample collection. To comply with the DTSC Guidelines,30 minutes of time will be allotted to allow each probe to equilibrate before the soil gas samples are collected. Soil gas sampling will be collected through the dedicated porous foam block and nylon tubing installed at each location.At the surface,the tubing will be connected to a sampling manifold using Swagelok®fittings and a Summa canister. The sampling manifold consists of a stainless steel tube with a pressure gauge, a vacuum gauge, and connections for the sample canister and purge device. The dedicated porous foam block and nylon tubing will be isolated from the ambient air using a manifold valve. The soil gas probe will be purged using either a syringe or hand pump and will be purged a minimum of seven(7)purge volumes prior to sample collection. Samples will be collected using laboratory prepared Summa canisters. During the soil gas collection process, a leak check will be performed as part of the sampling quality assurance/quality control(QA/QC). As a leak check compound, 1,1,1,2-Tetraflouroethane will be used at the sample collection point to ensure to verify that no air is leaking into the manifold during the sample collection Soil gas samples will be analyzed at lower detection limits using United States Environmental Protection Agency(USEPA)Test Method TO-15. Samples will be collected in Summa canisters and delivered to the laboratory within 24 hours of collection under proper chain-of-custody documentation. The laboratory's reportable detection limits are listed in the following table in micrograms per cubic meter(pg/m). 03009-10017-37020 3 WINZLER&KELLY August 2011