SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

I Former Fayette Manufacturing Page 2 of 3 7675 West Eleventh Street January 16, 2013 i Tracy, California iE I r I r • Collect a minimum of one duplicate soil gas sample immediately after the original soil gas sample has been collected. • Collect one indoor air sample in the business office and one outdoor ambient air sample approximately 100 feet up-wind of the office structure over a period of six to eight hours using time-release certified-clean Summa canisters. • Transfer all indoor, ambient and soil gas samples to a State-of-California-certified on-site laboratory for analysis by Environmental Protection Agency (EPA) method TO-15 that includes the analysis of 1,1-DFA at a detection limit less than 10 micrograms per liter (pg/L). (EPA method 8260B was proposed for analysis of some samples if dilutions are required resulting in elevated reporting limits by method TO-15.) • Remove the vapor probe assembly and backfill the borings with neat portland cement from boring terminus to surface grade following collection of the soil gas samples. Cardno ATC proposes to follow the sampling guidelines established by the Los Angeles Regional Water Quality Control Board (LARWQCB), the Department of Toxic Substances Control (DTSC), and the Interstate Technology & Regulatory Council (ITRC) in documents titled Advisory-Active Soil Gas Investigations dated January 28, 2003; Interim Final — Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air dated December 15. 2004, revised February 7, 2005; and Vapor Intrusion Pathway. A Practical Guideline, dated January 2007. Instead, the EHD recommends that the latest publication of two of these guidance documents be employed. They include Advisory-Active Soil Gas Investigations dated April 2012, issued by California EPA DTSC, LARWQCB and San Francisco Regional Water Quality Control Board (SFRWQCB); and Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air(Vapor Intrusion Guidance) dated October 2011, issued by the California EPA DTSC. The EHD does not approve the proposals as submitted in the work plan largely because the proposals lack specificity; please resubmit the work plan to the EHD by 01 March 2013 with the following additions and revisions: • The EHD is of the opinion that the two proposed soil gas probe locations east and west of the office are too distant from the contaminant source. Please relocate these two soil gas probes between the former underground storage tank (UST) area and the office building. • In 2011, during the last two sampling events, depth-to-groundwater measurements were reported approximately 5.5 feet bsg; when installing the soil gas probes at the proposed five feet bsg, assure that the probes are not within the capillary fringe. • Complete a "shut-in" test to check for leaks in the above-ground soil gas sampling system following the equilibration period once the vapor probes have been installed. • Confirm that the syringes used to purge three volumes are made of glass and not plastic. • Prior to soil gas sampling, a Material Blank consisting of an assembled soil gas probe, tip and tubing should be blank tested for chemicals of concern. • Quantify the leak check compound 1,1-DFA, at the reporting limit of the target analytes. (A method detection limit of less than 10 pg/L is not acceptable.)