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Jeff Wong 4PRION <br /> San Joaquin County Environmental Health Department <br /> 30 October 2019 <br /> Page 4 <br /> Recommendations <br /> Based on the site conditions and rationale described in this letter, Orion recommends <br /> destroying wells OS-57, OS-48, OS-47, OS-46, OS-45, OS-1613, OS-44, OS-15B, OS-43, <br /> OS-1313, OS-41, OS-12B by grouting rather than overdrilling. For these 12 wells, Orion <br /> proposes to destroy each well using the following procedures, in accordance with SJCEHD <br /> standards for grouting: <br /> 1. Tag the total depth of the well to confirm the well casing is free of <br /> obstructions. <br /> 2. Clear the annular space around the well casing using air-knife to a depth of <br /> approximately 3 feet below ground surface (bgs) and cut and remove the well <br /> casing to a depth of approximately 2.5 feet bgs. <br /> 3. Using tremie pipe, fill the well casing with neat Portland cement. Allow <br /> cement to overflow the top of the well casing and fill the cleared boring to a <br /> depth of approximately 2 feet bgs. <br /> 4. Complete the surface with a 2-feet-thick concrete surface seal. <br /> If you have questions or comments regarding this report, please call either Scott Stromberg <br /> or Mike Purchase at 510/525-2180. <br /> Very truly yours, <br /> ORION ENVIRONMENTAL INC. <br /> Scott Stromberg, N.G. Michael P. Purchase, P.E. <br /> Project Geologist Vice President <br /> Attachments: Figure 1 —Site Plan—East Array <br /> Attachment A— Photographs <br /> Attachment B —Boring Logs <br /> References <br /> Central Valley Regional Water Quality Control Board, 2016. "Request to Remove Ozone Injection <br /> Systems, Stockton Terminals Technical Committee, Port of Stockton, Stockton, San Joaquin County," <br /> 14 October. <br /> S:\Clients\52STTC\LTR\LTR002.docx 10/30/19 <br />