WORK PLANS - Laserfiche WebLink

Home Browse Search

• Work Plan for Soil and Groundwater p"stigation ECOR Former ARCO Service Station#0760 December 13,2006 Page 5 Soil Vapor Sample Collection Soil vapor sampling will be performed after a minimum time duration of one week, to allow the neat cement grout to cure, and to allow the subsurface vapor concentrations disturbed during installation activities to equilibrate. Vapor sampling will not be scheduled until after a minimum of five consecutive precipitation-free days. If there are any landscaped areas near the vapor probes, the landscape irrigation will be turned off for five days prior to sampling. The sampling apparatus will consist of two six-liter Summa canisters(one forvaporsample collection and one for system purging) connect via a manifold to a vacuum gauge, a %2-hour (100 to 200 ml/minute)flow regulator, and a filter(Figure 4). The sampling apparatus will be assembled and a leak check performed prior to mobilization to the field. The leak check will be performed by closing the system at the down-hole side of the filter and opening the valve on the purge Summa canister. If the negative vacuum pressure of 30 inches of mercury (inHg) is maintained over a fifteen minute period,the apparatus passes the leak check. Once the sampling apparatus is assembled in the field, Tygon®tubing will be attached to the down-hole side of the filter and connected to the Swagelok® type valve on the soil vapor sampling probe. The apparatus will be leak checked again. Once the apparatus passes the field leak check, the system will be purged of three system volumes. The purge time will be calculated by adding the volume of the length of Tygon®tubing between the soil vapor probe and the Swagelok® type valve, the volume of the length of tubing between the Swagelok®type valve and the sampling apparatus,and the volume of the sampling apparatus(minus the Summa canisters). This volume will be divided by the flow rate of 200 ml/minute to derive the purge time. After the system purge, the soil vapor will be collected by closing the valve on the purge Summa canister and opening the valve on the sampling Summa canister. The sampling start time will be recorded on afield data sheet. Isopropyl alcohol (IPA),or the equivalent,will be used as a leak check compound. A piece of gauze will be attached to the down-hole side of the Swagelock®type valve and moistened with IPA, taking care not to apply the IPA directly to the tubing, valves, and fittings. The gauze will be re-moistened with IPA every five minutes. After approximately one'/2 hour,orwhen the vacuum pressure of the system reaches 5 inHg, the sampling canister valve will be closed and the end time will be recorded. Prior to sampling subsequent sample locations,the used tubing will be discarded. The sampling canister(s)and chain of custody will be labeled with the site name, sampling ID, time and date of sampling, final vacuum pressure, and the canister serial number. The sampling canister(s)will be shipped to a California certified laboratory for analysis. Vapor Sample Laboratory Analyses The vapor samples will be submitted under documented chain-of-custody control, to a California State-certified laboratory and analyzed for TPHg, BTEX, MtBE, di-isopropyl ether(DIPE), ethyl-tert- butyl ether(ETBE), tert-amyl methyl ether(TAME), tert-butyl alcohol (TBA), and 1,2-dichloroethane (1,2-DCA) using EPA method TO-15. Once laboratory analysis is complete, SECOR will compare the site results to Region Two Environmental Screening Levels (ESLs). Comparative analysis of the ESLs and Site data will determine if a human health risk assessment (HHRA) of indoor vapor intrusion is required. ARCO 00760 Soil and Groundwater Investigation W P.doc