WORK PLANS - Laserfiche WebLink

Home Browse Search

Geosptec consultants 3.3.2 Soil Vapor Sampling Prior to soil vapor sample collection, above ground sampling equipment will be tested to ensure that ambient air would not become entrained into the sample. A"shut-in"test will be performed once the above ground sampling equipment is assembled. A vacuum of approximately 100 inches of water will be applied to the assembled aboveground sampling equipment.Vacuum will be monitored for approximately 1 minute to confirm the integrity of the aboveground sampling equipment assembly. During the purging process and prior to sample collection, a leak test will be performed. A shroud filled with approximately 10 to 30 percent (%) helium will be placed over the soil vapor probe and all aboveground sampling equipment.The concentration of helium in the shroud will be measured using a field helium detector. Three well volumes will be purged from each soil vapor probe prior to sample collection to avoid sampling ambient or stagnant air.One purge volume is equivalent to the sum of the internal volume of tubing,the annular pore space within the sand pack at the well tip,and the annular pore space within the dry granular bentonite above the sand pack. Soil vapor will be purged from each probe using a flow rate between 100 and 200 milliliters per minute(mL/min). Following the purging and leak check activities,the soil vapor samples will be collected using I Summa' canisters.Vacuum will be maintained at less than 100 inches of water(approximately 7 inches of mercury) during sampling. After samples are collected, Summa' canisters will be closed and secured pending shipment to the analytical laboratory under chain-of-custody procedures. The sampling matrix is presented in Table 1 and includes a summary of samples to be collected and analytical methods for each proposed sample location.All soil vapor samples will be analyzed for VOCs by EPA Method TO-15,and 50%of the samples will be analyzed for helium by modified American Society for Testing and Materials (ASTM) Method D-1946. 3.3.3 Soil Vapor Probe Decommissioning Following sampling activities, the soil vapor probes will be destroyed, and the borings will be backfilled with cement grout in accordance with San Joaquin County and City of Stockton requirements. 3.3.4 Grab Groundwater Sampling In addition to soil vapor samples along the sewer main on West Hammer Lane, groundwater samples will be collected utilizing a HydroPunch'sampling system or an equivalent sealed screen sampling device. A grab groundwater sample will be collected from the boring with a new, dedicated Teflon bailer. The samples will be collected in accordance with the USEPA groundwater sampling and monitoring with DPT guidance (USEPA, 2005) and the attached SOP (Appendix B). Three primary groundwater samples and one duplicate will be collected and analyzed for VOCs by EPA Method 8260B. Upon completion of data collection and sampling activities at each soil boring, the location will be backfilled with cement grout in accordance with San Joaquin County and City of Stockton requirements. 3.4 On-Site Investigation Activities 3.4.1 Indoor Air Sampling Prior to sample collection,a building survey and questionnaire form will be completed,and when available, the owner/occupant will be interviewed regarding chemical usage and ventilation system operation. 8 September 2025