COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Mr. Alan Buehler Page 2 of 3 will be collected at approximately 4 and 8 feet using a drive-sampling device containing clean brass or stainless steel sample tubes. Soil type will be described in accordance with the Unified Soil Classification System (USCS) and the samples will be field-screened for contamination with a photoionization detector (PID). After sampling, the boreholes will be backfilled to grade with neat cement or hydrated bentonite and capped with concrete. The rationale for the proposed soil sampling is explained in greater detail in our March 28, 2017 Workplan. Soil Vapor Sampling Ground Zero proposes installing up to three (3) temporary soil vapor monitoring wells in the vicinity of the northeast corner of the southern "shop" building near MW-5. The proposed vapor sampling locations are shown in Figure 2. The final location of the boring located within the "shop" will have to be positioned based on indoor access. Sampling Procedure The temporary soil vapor sampling points will be installed in general accordance with the Department of Toxic Substances Control (DTSC) and RWQCB guidelines set forth in the California Environmental Protection Agency's Advisory — Active Soil Gas Investigations (DTSC and RWQCB, July 2015), which is included in Attachment C. C-57 licensed Transglobal Environmental Geochemistry (TEG) of Northern California will advance direct-push sample rods to a depth of 5 feet. A vapor flow test will be performed to determine if the soil can yield vapor flow at a rate of 100 — 200 milliliters per minute at a vacuum less than 100 inches of water column. If so, then the vapor wells will be screened at that depth. If not, consecutive flow tests will be performed at 1-foot depth intervals until satisfactory yield can be obtained. TEG will construct temporary vapor wells in the borings using Nylaflow tubing and nylon screen. The screen will be placed in the middle of a one-foot thick sand filter pack. The filter pack will be overlain with six inches of bentonite chips followed by hydrated bentonite to the surface. Prior to purging and sampling, the wells will be allowed to sit for two hours to equilibrate. A shut in test will be performed to ensure that no leaks are present in the sample train. The wells will then be purged of three tubing volumes and sampled using 1-liter Summa canisters at a flow rate between 100 — 200 ml/minute and at a vacuum of less than 100 inches of water column. During the collection of each soil vapor sample a leak detection test will be conducted to insure no intrusion of ambient air into each respective vapor sample. During the collection of each vapor sample 1,1-difluoroethane (DFA) will be applied to towels or clean rags and placed directly around the rod/surface interface and all associated connections. During sample analysis the lab will analyze for the presence of DFA; its presence would indicate a leak. Following the completion of sample collection, the well materials will be retrieved, the borings will be backfilled with bentonite and the pavement surface restored. Soil vapor samples will be submitted under chain of custody protocol to State-Certified BC Laboratories, in Bakersfield CA for VOC and oxygen analysis. Final Soil Sampling WP 2017 Addendum.doc