COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

Proposal No. P1-410-0587 August 27,2010 Page 4 soil-gas sample will be collected from the interval estimated to be 5 and 10 feet below the existing surface materials. Based on the presence of an existing structure that partially occupies a portion of the footprint of the proposed Fresh & Easy Neighborhood Market, access to the sampling locations beneath the concrete slab floor of the existing structure is limited. As such, SALEM proposes to use both a Geoprobe Model 540M Limited Access Rig capable if fitting though the existing structure doorway, and a standard Geoprobe 5400 truck mounted rig for outside borings. The sampling equipment will be cleaned prior to sampling and between borings to minimize the likelihood of cross-contamination. Based on previous drilling results at the subject site that noted the presence of naphthalene at depth of 5 feet below grade, the proposed 5 and 10 feet deep vapor sample intervals appear appropriate for the conditions previously noted. 4.2 Drilling And Soil Gas Probe Installation The soil-gas sampling probes boreholes will be advanced using a either a Geoprobe 5400 truck mounted rig or a limited access direct-push rig (Geoprobe 540M Limited Access Rig) as 4 of 10 borings will be inside the building. Following coring of the concrete floor, 10 soil-gas sampling probes will be installed using either the hydraulic ram or in combination with the percussion hammer option of the drill rig (as needed and based upon drilling resistance). The soil-gas sampling probes will be generally installed at depths of approximately 5 or 10 feet bgs. The locations of the borings completed as part of this investigation are presented in Figure 1, Site Plan. During the survey,once a probe is installed to the target depth,the 1.5-inch diameter hollow probe drive-rods will be withdrawn, leaving a steel probe point and '/a -inch NylaflowTM sampling tube in the subsurface soils. The lower 2-inches of the tubing installed is slotted. The end of the tubing at surface will be plugged with a sheet metal screw or cap.Approximately 6 inches of clean,graded(#3),kiln-dried RMC Lonestar sand will be poured around the slotted section of Nylaflowrm sample tubing to allow for diffusion of soil vapors, with approximately 12 inches of hydrated bentonite pellets placed as a temporary seal above the sand. The points will remain in place for a minimum 30 minutes to equilibrate prior to sampling. Once the soil vapor samples are collected and analyzed, the sample tubing will be withdrawn from the borehole and the remaining borehole annulus will be backfilled and sealed with neat cement and capped at the surface to match existing materials. During sampling, a tracer gas (n-propanol) or isopropyl alcohol (IPA) will be used to confirm that the soil vapor monitoring probes and sample train are leak free. This compound will be analyzed by the analytical laboratory to determine if there were surface leaks into the subsurface due to improper installation of the vapor inlet probe. The soil vapor samples will be recorded onto a chain-of-custody document that accompanies the samples from the point of collection to the analytical laboratory. 5.0 CHEMICAL ANALYSES A maximum of ten (10) soil vapor samples will be collected depths of 5 and 10 feet below grade from below the proposed Fresh & Easy Neighborhood Market concrete slab. Soil vapor samples will be analyzed at an on-site State of California certified mobile analytical laboratory for VOCs (including dry cleaning solvent constituents) using EPA Method 8260B.An additional three soil vapor samples will be collected to adhere to