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a • • Page 3 of 5 Email: vmccartnev(cDsicehd.com x. From: Brian Millmanrmailto:bmillman(&advaeoenv.com] Sent: Monday,June 16,2014 2:15 PM To:Vicki McCartney[EH] Cc: Nuel Henderson[EH] Subject: RE: Collecting a material blank Hello Vicki/Nuel, I apologize for the delay with this project since last speaking with you and Nuel. I have been reviewing soil-vapor sampling investigations that we have performed over the past year. Over the past year we have performed several vapor investigations using a new procedure to collect soil-vapor samples. The new procedure consists of a sampling train with less components and a much reduced chance of cross-contamination or contamination from the sampling materials. Because documentation is required to demonstrate that the equipment being used for collecting soil gas samples do not contain any contaminants of concern,AGE would like to addend the procedures for soil-vapor sampling that were proposed in the AGE-prepared, Site Assessment and Vapor Intrusion Investigation Work Plan, dated 11 February 2014. The addendum is proposed for two reasons: 1) to update the procedures and equipment now being used by AGE to collect soil-vapor samples and 2)to provide documentation from current soil- vapor investigations to demonstrate that the equipment being used does not contain any contaminants of concern. Below is Section 3.1.2 from the work plan with revisions proposing a new soil-vapor sampling method and materials, and including the items/conditions outlined in the EHD letter dated 11 March 2014: 3.1.2 Soil-Vapor Sampling A soil-vapor sample will be collected at approximately ten (10) feet bsg in the boring advanced north of the former UST area at 615 East Main Street. The soil-vapor sample will be collected utilizing '%-inch diameter Teflon tubing and a'%-inch diameter, two-inch long, disposable polyethylene vapor implant with speed-fit fitting installed to 10 feet bag. The soil-vapor sampling boring will be advanced to 10 feet bsg using a truck mounted AMS Powerprobe 9600 or Geoprobe direct-push probing unit equipped with 1.25-inch probing rods. Once the total depth is reached, the 1.25-inch probing rods will be removed and the vapor implant,with Teflon tubing attached, will be installed in the borehole. Once the implant is set a filter pack material consisting of pre-washed#2/12 Lonestar sand will be added from total depth to approximately 9.5 feet bsg.A dry bentonite seal will be placed above the filter pack to a depth of 8 to 9.5 feet bsg and pre-hydrated bentonite will be placed above the dry bentonite from 8 feet bsg to near surface. The bentonite will be allowed to hydrate for a minimum of one half hour.Approximately, 3 feet of extra tubing will be run above ground for soil-vapor sample collection. Additionally, hydrated bentonite will be placed around the tubing at ground surface to prevent ambient air intrusion. A minimum of 120 minutes equilibrium time will be allowed at the soil-vapor boring location prior to purging and sample collection. One six-liter Summa canister will be utilized for purging and soil-vapor samples will be collected in one-liter Summa canisters (TO-15) and four-liter sorbent tubes(TO-17). Based on the EHD letter dated 11 March 2014 and the phone conference held between AGE and EHD personnel on 07 May 2014, a duplicate TO-15 and a replicate T017 soil-vapor sample will be collected during the investigation. The sampling and purge canisters will be connected together with a dedicated and serialized sampling inlet manifold. The sampling inlet manifold will consist of a vapor-tight valve; a particulate filter; a calibrated flow restrictor, calibrated to 8/8/2014