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DUDEK <br />Soil Gas Survey <br />Soil gas surveys are a useful tool to identify and evaluate potential impacts at a site. A direct push drill <br />rig is typically used to advance boreholes to the targeted subsurface depth. Dudek will partner with <br />Millennium Environmental, Inc. for direct push and sub -slab drilling services. Following borehole <br />advancement, temporary soil vapor probes will be constructed in accordance with the DTSC Advisory — <br />Active Soil Gas Investigations. Probe inlets will be placed in sand, topped with dry granular bentonite, <br />then sealed with hydrated bentonite chips. Each probe will be allowed to equilibrate for a minimum of <br />two hours prior to sampling. A tracer gas compound will be used to test for leaks around the temporary <br />soil vapor probe penetration seal at the ground surface and within the sampling system. A default of <br />three purge volumes will be extracted prior to sampling from the probe locations. The soil vapor <br />samples will be collected in accordance with the DTSC Advisory. <br />Dudek will partner with Jones Environmental Laboratories, Inc. (Jones), to provide mobile and stationary <br />analytical services for soil gas samples. Dudek will ensure that the laboratory reporting limits will meet the <br />project objectives. At the end of the sampling event, all soil boring locations will be resurfaced matched to <br />the existing ground surface. Drilling equipment will be appropriately decontaminated before the <br />commencement of any drilling activities and in-between boreholes. The findings of the soil gas survey will <br />be presented in a standalone report or incorporated into a Phase II report. <br />Drilling <br />Dudek will provide support for the permitting, drilling, installation, development, and sampling of deep <br />borings and groundwater monitoring wells. Dudek will partner with BC2 Environmental for hollow -stem <br />auger, mud rotary, air rotary, and sonic drilling services. The drilling methods previously described <br />provide capabilities to drill through various media, including consolidated and unconsolidated <br />sediments, rocks, asphalt, concrete cement, and waste materials. Each boring will be logged using <br />ASTM Standard D2488-09a—Standard Practice for Description and Identification of Soils (Visual — <br />Manual Procedure). Boring logs will also include descriptions of the lithologies and grain sizes, color, <br />moisture content, cohesive characteristics, odors, and any other pertinent information (e.g., blow <br />counts, photoionization detector readings, anthropogenic materials, etc.). The subsurface lithologies will <br />be used to determine the well screen slot size and filter pack materials best suited for the site. Wells will <br />be constructed in accordance with the Department of Water Resources (DWR) California Well <br />Standards Bulletins. <br />Groundwater monitoring wells will be developed at least 24 hours following the completion of <br />construction. The drilling activities, including permits and DWR documentation, will be presented in a <br />standalone report or incorporated into a Phase II ESA report. <br />Sampling <br />The media to be sampled at a site (air, soil, soil vapor, and/or groundwater) is dependent on the type of <br />contamination present or suspected. The work plan/field sampling plan will outline the suspected concerns <br />and include proposed sample locations, media, sample depth(s), and targeted analytes. All sampling will be <br />performed in accordance with applicable regulatory protocols and/or standard industry practices. For <br />example, soil samples to be analyzed for volatile components (e.g., gasoline -range hydrocarbons and <br />VOCs) will be collected in accordance with EPA Method 5035. Dudek will ensure that the samples for all <br />media (soil, soil vapor, or groundwater) are placed in proper containers and that the laboratory reporting <br />Various Environmental Services 14 <br />