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5.4.4 Purge Volume The sub-slab soil gas probes and the shallow soil gas probes will be purged of three purge volumes prior to sample collection using a gas tight glass syringe. Specifically, the mobile laboratory technician will use a gas-tight glass syringe to purge and sample the probes. The sample tubing will be connected to the syringe via a three-way valve. It is anticipated that one purge volume will be approximately 500 ml. 5.4.5 Soil Gas Sample Analysis The cumulative soil gas samples will be analyzed by an on-site mobile laboratory operated by TEG of Rancho Cordova, California, a laboratory certified by the State of California for analysis of soil gas samples. Samples will be provided to the laboratory under a sample chain of custody. To protect sample integrity, soil gas samples to be analyzed were not chilled, will be analyzed within 30 minutes of sample collection, and will be kept in a cool dark location protected from exposure to light until the analysis is performed. The samples will analyzed in accordance with EPA Method 8260B. Laboratory QA/QC will be performed in accordance with the project QC/QA Plan. 5.5 Proposed Groundwater Assessment for the Quality Cleaners Five proposed groundwater monitoring wells will be installed to assess groundwater quality and gradient pertaining to the impacts related to the Quality Cleaners. Initially, three groundwater monitoring wells (MW-2, MW- 4, and MW-5) will be installed in a triangular array so that an expedited survey of the three monitoring wells can be conducted. The results of the survey, available within approximately 48 hours, will be used to assess the flow direction of groundwater at the time the wells are installed. Based on the survey, the remaining two monitoring wells will be installed as proposed. If, however, the groundwater flow direction is other than to the north-northeast, the DTSC will be contacted so that alternative locations of the remaining two monitoring wells can be selected for subsequent installation can be discussed. The five monitoring wells as currently proposed are shown on Figure 10 and will be installed as follows: MW-1 will be installed approximately 40 feet southwest of the Quality Cleaners in the general area of Partner's 2015 groundwater samples from borings B3 and B4. This well is intended to be the upgradient groundwater monitoring well. MW-2 will be installed within the sidewalk immediately to the northeast of the Quality Cleaners in the general area of Partner's May 2015 groundwater sample from boring B5-GW. This well is intended to be a proximate downgradient groundwater monitoring well related to the anticipated source areas of the dry cleaning machine and boiler room. MW-3 will be installed approximately 150 feet north-northeast of the Quality Cleaners in the general area of Partner's May 2015 groundwater sample from boring B6-GW. This well is intended to be a downgradient groundwater monitoring well. Sampling and Analysis Plan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 17