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Date: March 3, 2022 Ramboll 2200 Powell Street Suite 700 Emeryville, CA 94608 USA T +1 510 655 7400 F +1 510 655 9517 www.ramboll.com Jeffrey Wong Environmental Health Department San Joaquin County 1868 East Hazelton Ave Stockton, CA 95205 1681 EAST GRANT LINE ROAD, TRACY, CA PERMIT APPLICATION SCOPE OF WORK Dear Jeff, Ramboll US Consulting, Inc. (Ramboll) has prepared this scope of work for installation of multi-depth (nested) soil vapor probes at the site located at 1681 East Grant Line Road, Tracy, California (the “site”). Soil vapor probes will be installed as stepouts to an abandoned gas well. This letter provides a brief background for the site, a summary of pre-field activities and a description of the drilling, sampling and destruction methods for nested soil vapor wells to be drilled at the site. BACKGROUND The site is located at 1681 East Grant Line Road in Tracy, California and is associated with parcel numbers (APNs) 213-070-017, 213-070-039, and 213- 070-041 (See Figure 1). The site is mostly undeveloped and covered by former agricultural fields. In the center of the site there is a single family residence, a detached garage, a detached shop, and stored vehicles and farm equipment. Proposed sampling activities will be performed as part of site due diligence related to an on-site abandoned gas well. It is Ramboll’s understanding that the gas well was abandoned in the 1940’s following common gas and gas well abandonment procedures for that time period, however the current condition of the well is unknown. The location of the gas well was recently confirmed by a magnetic survey and the well was exhumed using a mini excavator. PRE-FIELD ACTIVITIES Prior to mobilizing to the site for drilling activities, Ramboll will prepare a site-specific health and safety plan (HASP), mark the proposed drilling locations with white flags, and will notify Underground Service Alert (USA) at least 72 hours prior to the scheduled drill date. Ramboll will also contract with a private utility locator to perform a subsurface utility clearance at the proposed drilling locations. DRILLING AND SAMPLING METHODS Ramboll will subcontract with PeneCore Drilling of Woodland, California, a California C-57 licensed drilling company to install up to eight stepout, multi-depth (nested) soil vapor probes in the vicinity of the abandoned oil well. Stepout soil vapor probes will be installed at distances of approximately 25 and 75 feet from the oil well, in each cardinal direction (north, south, east, and west), for a total of eight stepout soil vapor probes. Sample locations are shown on Figure 1. During drilling of each soil vapor well, a minimum 2.25-inch diameter borehole will be advanced using direct-push technologies (DPT) drilling equipment to a total depth of approximately 20.5 feet below ground surface (bgs). The subsurface lithology in each boring will be logged according to the Unified Soil Classification System (USCS), soil will be field screened for with a photoionization detector (PID) for the presence of VOCs and a flame ionization detector (FID) for the presence of methane, and soil will be observed for visual and olfactory indications of impacts. The borings will be converted to temporary multi-depth soil vapor probes in accordance with California Environmental Protection Agency (Cal/EPA) Department of Toxic Substances Control’s (DTSC) Active