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• San Joaquin County 12066.000.000 PCCP Mountain House Property May 7, 2015 ENVIRONMENTAL ASSESSMENT WORKPLAN Page 3 • The sample train will consist of a stainless steel twin Summa manifold with built-in flow controller set to 100-200 ml/min. A purge vacuum pump will be attached to the manifold connection that is closest to the well casing, and the sampling canister will be connected to the manifold fitting furthest away from the well casing. Prior to connecting the sample train to the well casing, we will perform a "shut-in" test to assess for potential leaks. The shut-in test will consist of capping the end of the manifold,then cracking and closing the purge canister to apply a vacuum.We will observe the vacuum gauge for two minutes to determine if there is a leak. • The sample train will be connected threading the permanent Swagelok® fitting on the well casing onto the manifold. Three well volumes will be purged from the wells. • After purging is completed, the purge valve on the manifold will be closed, and the vacuum pump can be removed and connected to another well if desired. Samples will be collected by opening the sample canister valve and allowing the sample canister to extract soil gas until the vacuum in the sample canister reaches approximately 5 inches of mercury. The leak detection compound 1,1-Diflouroethane will be applied by wrapping a doused rag around the manifold fittings during sample collection. • We will label each sample canister with a unique identification number, sampling time, and pre- and post-sample vacuum readings. The four soil gas samples will be submitted to a State certified laboratory under documented chain-of-custody for analysis of VOCs, TPH-g, and TPH-d by Test Methods TO-15 and TO-17. Laboratory analysis for soil gas samples will be performed on a standard 5-day turnaround. • We will review of the laboratory test results with comparison to applicable residential environmental screening levels. Soil cuttings, rinsate, and purge water generated during the field exploration will be contained in 55-gallon drums. These materials will be transported to an offsite disposal facility within 90 days in compliance with applicable laws. Appropriate analytical testing will be performed on these materials for characterization purposes prior to transportation and disposal. Following completion of the soil borings and vapor wells, the borings will be grouted and abandoned in accordance with San Joaquin County requirements. EQUIPMENT DECONTAMINATION All reusable sampling equipment that comes into contact with potentially contaminated soil or water will be decontaminated. Decontamination will occur prior to and after each use of a piece of equipment. The following decontamination procedure will be carried out in sequence: • Non-phosphate detergent(e.g., Alconox®and tap water solution), using a brush if necessary, or steam cleaning. • Tap-water rinse.