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Integral Consulting Inc. 545 Sansome St Suite 875 San Francisco, CA 94111 telephone: 415.393.4750 www.integral-corp.com January 6, 2020 Project No. C2074 Rachel Kerr Ahtna Environmental, Inc. 296 12th Street Marina, California 93933 Subject: SHAD-007 & -008 C Zone Groundwater Capture Analysis Dear Ms. Kerr: Integral has performed a groundwater capture study for potential new C Zone extraction wells within the SHAD-007 & -008 areas at the Sharpe Army Depot (“the Site”). Groundwater at the Site is currently impacted by a number of contaminants, particularly tetrachloroethylene (PCE), trichloroethylene (TCE), and carbon tetrachloride (CT) within the A, B, and C flow Zones. Groundwater at the SHAD-007 & -008 areas, near the northwest corner of the Site, is primarily impacted by TCE, as observed in onsite and offsite monitoring well and grab samples. Integral reviewed the current state of groundwater capture in this area of the Site and evaluated alternative new extraction well configurations in conjunction with guidance from Ahtna. This analysis used a version of the Site groundwater model that has been updated to simulate flow conditions through October 2019. The details of this model update and calibration effort were provided to Ahtna in a separate memorandum and were included as an appendix to the FFA Annual Progress Report. A similar analysis for groundwater capture in the SHAD-153 area had been done with the previous 2018 version of the model, and the results of that analysis were transmitted to Ahtna in a separate letter. The predictive period of the updated 2019 model extends for 30 years from the end of the calibration period in October 2019 to October 2049. The boundary conditions and other inputs to the model were retained from the updated 2019 version of the model, but all anticipated changes to the extraction well network during the 30-year predictive period, including an additional extraction well in the SHAD-153 area, were included in the analysis presented herein. Documentation of these extraction well network changes are provided in the FFA Annual Progress report and in a letter to Ahtna dated September 27, 2019. New extraction wells were simulated as fully penetrating the C Zone (Layer 4) of the groundwater model. A representative extraction flowrate of 40 gallons per minute (gpm) was assigned to the new well locations, which were estimated to begin pumping in October 2019. A particle tracking analysis was performed for each potential new C Zone well