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Denmar US American Soda Ash Terminal at the Port of Stockton 19113.000.001 Work Plan for Groundwater Characterization FIELD EXPLORATION Site Reconnaissance We performed an initial site reconnaissance to identify access constraints for field explorations. After approval of this work plan, we will conduct a pre-exploration site visit to mark the proposed boring locations on the ground using wooden construction stakes. We will locate the borings using a handheld GPS unit with sub-meter accuracy. As part of the pre-exploration site visit, we will mark and ticket the exploration locations for Underground Service Alert (USA) North. Supplemental Borings We will perform two shallow borings within the planned excavation footprint at the approximate locations shown on the Site Plan, Figure 1. We will retain the services of a contractor perform a hydropunch to a depth of approximately 10 feet below the existing ground surface from a track- mounted exploration rig at each boring location. The hydropunch will be advanced with the screen protected to the sample depth, at least 5 feet below the groundwater level at the time of sampling. The screen will then be exposed and the hydropunch allowed to fill. The vendor will then purge the hydropunch of at least two volumes with a bailer and then we will collect a grab sample; the operator will allow time for the hydropunch to fill after each bailing. We will measure the depth to groundwater during the sampling process. After sampling, the vendor will grout the hole left behind from sampling. Sampling Existing Wells We will also collect samples from five existing wells around the perimeter of the planned excavation. These wells were previously constructed for environmental studies and monitoring at the site. The wells we intend to sample from are shown in Figure 1. If a well is not able to be located or if the well has been damaged, we will substitute the planned well with a nearby well such that the distribution of sampling and distance is similar to that shown on Figure 1. Prior to sampling, we will purge at least two well volumes from each well. Before sampling, we will allow each well to fill to equilibrium after bailing. We will measure the depth to groundwater during the sampling process. SAMPLE COLLECTION, TRANSPORT, AND ANALYTICAL TESTING We will use disposable bailers to collect the groundwater samples in clean, laboratory-provided containers. Upon collection of samples, we will place a sample label on the container that will include a unique sample number, sample location, time/date collected, laboratory analysis, and the sampler's identification. We will place the groundwater samples in an ice-cooled chest and submit under documented chain-of-custody to California Laboratory Services Laboratory, a State-accredited, fixed-base analytical laboratory located in Rancho Cordova, California. Each of the seven samples with be tested on a discrete basis for the constituents listed in Table 1-1 under "Groundwater Source"as well as the priority pollutants listed in Table 1-3,VOCs listed in Table 1-5, and Petroleum Fuel parameters listed in Table 1-6. ENGEOApril 6, 2023 Expect Excellence