WORK PLANS - Laserfiche WebLink

Home Browse Search

parameters including temperature, pH, specific conductance, turbidity, dissolved oxygen, and oxygen reduction potential (ORP) will be recorded using a YSI Multi System Probe, or equivalent. Purging will continue until water quality parameters stabilize. Purging and groundwater sample collection activities will be completed at flow rates of less than 200 milliliters per minute. Groundwater samples will be collected into appropriate laboratory-supplied containers. The groundwater samples will be labelled, placed on ice, and transported under chain-of-custody to a State certified laboratory. The sample labels will be unique and identify the boring and sample media from which the sample originated. Once the groundwater sampling is complete, the temporary casing will be removed, and the sampling point will be backfilled with neat cement grout in accordance with the drilling permit requirements and patched at the surface as necessary to match the surrounding Site conditions. The groundwater samples will be analyzed for VOCs using EPA Method 8260B. 4.2.3 Installation of Soil Vapor Sampling Points Roux will advance five borings for the construction of permanent soil gas probes (SG-42 through SG-46), Figure 4). Note that proposed soil vapor sampling points SG-42, SG-43, SG-45 and SG-46 are located offsite on privately owned residences,access for which has yet to be coordinated and is therefore subject to change. The soil vapor probes will be constructed following the most recent California DTSC guidelines. Soil gas probes will be installed at a depth of 5 ft bgs. The probes will consist of a new stainless-steel filter probe tip with a 1/4-inch push-to-connect fitting attached to 1/4-inch diameter Teflon tubing. The probes will be installed using a downhole rod to support the well tubing and probe in the borehole and ensure that the probe tip is placed at the proper depth. This down-hole rod will be removed during the placement of annulus materials. A 12-inch sand pack of#3 sand will be placed surrounding the probe tip to minimize the disruption of airflow to the sampling tip. A 12-inch-thick layer of dry granular bentonite will be emplaced above the sand pack, which will be overlaid with neat cement grout up to approximately 6 inches below the surface. The soil gas wells will be completed at the surface with a flush-with-grade traffic bearing road box. 4.2.4 Soil Vapor Sampling Soil vapor samples will be collected using batch certified clean Summa canisters at least 48 hours after the installation of the new soil vapor probes per DTSC guidance. In addition, soil vapor samples will be collected from the existing soil vapor probes after verifying that a leak check meets the acceptable quantitative air leakage conditions (i.e., < 5% air leak when sampling with a shroud). If soil vapor samples do not meet the acceptable air leak conditions, a new soil vapor probe will be installed using the methodology described in Section 4.2.3. Prior to the collection of soil vapor samples, a "shut in" test will be performed to check for leaks in the above ground soil gas sampling equipment. Following the shut-in test, approximately three purge volumes will be purged from the sampling tubing using a sample syringe or a purge Summa canister before soil gas sample collection begins. Purge activities will be conducted at the same flow rate used for soil gas sample collection (approximately 150 milliliters per minute). During purging and soil gas sample collection activities, a leak test will be performed using 1) a shroud, which will enclose the soil gas probe vault, probe tubing, and the entire sampling manifold, and 2) helium as a tracer gas. A minimum helium concentration of 20 percent will be maintained within the shroud during the purging and soil gas sample collection period. 3989.0001S101/R Revised Data Gap Investigation Work Plan I ROUX 19