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3 Workplan for Soil Gas Study—Subslab Sampling Cardne 807 N. Hunter Street Stockton,California ATC 25,2014 Shaping the Future Ms. Terrell stated that the pilot project had appeared to result in a reduction of the CVOCs concentrations detected in collected groundwater samples. Furthermore she said Geomatrix was preparing to scale up the pilot project to inject more of the HRC material to facilitate additional reductions in the CVOC concentrations in groundwater. SCOPE OF WORK The scope of work to take place at the building designated as 807 N. Hunter includes: 1. The installation of six temporary subslab soil gas sampling points 2. The collection of soil gas samples from these sampling points 3. The analysis of the collected samples 4. An evaluation of the potential risk to human health associated with the CVOCs. The 807 N. Hunter section of the"U-shaped" building was selected because of its close proximity to where the CVOC release is believed to have occurred on the 819 N. Hunter property. If CVOCs are found to be threatening to occupants of this portion of the building, additional sampling in other portions of the building may become prudent. 1 PREPARATORY ACTIVITIES 1.1 HASP and JSA Development Cardno ATC will develop the site's HASP and JSA as is required by OSHA regulations. 1.2 Permitting Cardno ATC will obtain the necessary SJCEHD permits and pay the associated fees for the advancement of the six subslab borings. 2 FIELDWORK 2.1 Utility Clearance Cardno ATC will notify Underground Services Alert to locate underground utilities as required, and perform other necessary field preparation and job start-up activities. A private utility locating service will be used to locate underground utilities that may be present in the work areas. 2.2 Installation of Soil Gas Sampling Points This task includes mobilization to the site, installing six sub-slab sampling points. The temporary subslab vapor points will be installed to depths of approximately one foot below ground surface (bgs) in three locations within the enclosed office building onsite and within in three locations within the covered parking structure. The locations of the soil gas sampling points are shown on Figures 2 and 3. Drilling will be conducted by TEG Northern California Inc. (TEG) (State C57 license No. 706568). TEG will use an electric Roto Hammer equipped with a 1.5 inch bit to drill 1 inch into the cement slab. The cuttings are removed and a 5/8-inch bit is the used to drill through the remainder of the slab and up to 3 inches into the sub base material. The hole is cleared of any cuttings and debris. The sample train, constructed of 1/8 or% inch Nylaflow or Teflon tubing with a plastic or stainless steel air diffuser attached, is inserted through the slab into the sub base. #30 kiln dried sand is poured into the hole up to the base of the slab. One (1) inch of dry granular bentonite is poured into the hole, surrounding the tubing. Hydrated bentonite is placed in the hole and up to the surface of the slab. The sub slab soil gas sampling point is allowed to equilibrate for a minimum of 30 minutes and up to 2 hours before sampling. After a sample is obtained the tubing and bentonite are removed and the soil gas sampling point is backfilled with grout. To protect the integrity of the sampling point until sampling is complete, the aboveground portion of the sampling point will either be installed in a clearly marked protective container or attached to a wall or www.cardnoatc.com