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Below are the details regarding soil gas sampling for the property 434 Dr. Martin Luther King Jr. Blvd in <br /> Stockton.This document is a part of the soil boring permit application submitted to the San Joaquin County <br /> Environmental Health Department on October 5, 2017. <br /> Soil Gas Probe Installation <br /> Soil gas probes will be constructed within the boreholes upon completion of soil sampling. Boreholes will <br /> be backfilled with grout cement to approximately six inches below the desired sampling depth. A new <br /> section of 1/4-inch diameter polyethylene tubing with a new 1/4-inch diameter polypropylene filter at the <br /> terminal end will be inserted into the borehole to the desired sampling depth. One-inch diameter polyvinyl <br /> chloride (PVC) casing will be used as a guide for the tubing to ensure that the desired sampling depth will <br /> be achieved. Sand will be poured into the boring annulus to form an approximately one-foot long sand <br /> pack around the polypropylene filter, at which time the PVC piping will be withdrawn. Approximately one <br /> foot of dry, granular bentonite will be placed atop the sand pack and the remainder of the borehole will be <br /> backfilled with grout cement to the ground surface to form a seal. <br /> Soil Gas Sampling Methodology <br /> Soil gas samples will be collected in general accordance with the July 2015 Department of Toxic Substances <br /> Control (DTSC) and Los Angeles Regional Water Quality Control Board (LARWQCB) "Advisory—Active Soil <br /> Gas Investigations." <br /> Soil gas samples will be collected using one-liter, stainless-steel, cylindrical SUMMA canisters. Partner will <br /> receive the SUMMA canisters evacuated to approximately-30 inches of mercury. The SUMMA canisters will <br /> be fitted with stainless-steel flow controllers, which will be calibrated to maintain constant flow <br /> (approximately 0.1 liter per minute) for approximately five to 10 minutes of sampling time. <br /> Each probe will be allowed to equilibrate for a minimum of two hours after installation prior to sampling. <br /> After equilibration, the sample tubing and sampler screen will be purged of three volumes of ambient air <br /> using a separate one-liter SUMMA purge volume canister evacuated to approximately 30 inches of mercury. <br /> Tracer gas 1,1-diflouroethane will be placed around each probe at the ground surface while sampling to <br /> detect ambient air intrusion. Once the one-liter purge volume canisters are filled, the sampling end of the <br /> tubing will be fitted to the sampling canister and the port valve will be opened, causing air to enter the <br /> sample container due to the pressure differential. Partner will close the valves after the canister was <br /> evacuated to approximately minus one to two inches of mercury, with pertinent data (e.g., time, canister <br /> vacuum) recorded at the start and end of sampling. <br /> Partner will disconnect individual one-liter SUMMA canisters from each sampling point. Soil gas samples <br /> will be collected from each boring at five feet bgs. <br />