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5-Dam Seep-water Collection Area,Secondary Containment System <br /> Submitted with TR-36 <br /> The following narrative describes the purpose and need for the project, including technical details <br /> such as basin, pump and pipe sizing, and the proposed construction sequence and QA/QC process. <br /> Purpose and Need <br /> • The project involves addition of an Environmental Protection Facility(EPF) and is entirely within <br /> the currently permitted affected lands boundary. <br /> • The project is intended to prevent events similar to that which occurred on August 5, 2022 at <br /> Climax, when a fitting on a primary seepage conveyance pipe failed and a small amount of <br /> process water ultimately flowed outside of containment. The system will also capture potential <br /> shallow process water seepage from the Mayflower Tailings Storage Facility(TSF) and nearby <br /> seepage collection ponds and infrastructure. Ultimately,the project will help protect water <br /> quality in Tenmile Creek(which begins about 0.5 miles north/downgradient of the project site). <br /> • The project involves constructing a seepage collection and pump-back system to collect <br /> potential impacted seepage and direct this water back into the Mayflower seepage water <br /> management system. <br /> Major Project Components <br /> • The project involves relocating a small —2,500 cy topsoil stockpile from the future pipeline route <br /> to another location adjacent to 5-Dam (to be used for dam reclamation in 2024). <br /> • Project involves removing an existing concrete headwall at the inlet of the 120-inch diameter <br /> corrugated metal pipe (CMP)that currently conveys water under Old Hwy 91 (downstream of <br /> the Mayflower Clear Pond). This will make room for construction of the new cutoff wall and <br /> collection sump. <br /> • The project involves constructing a cutoff wall, collection pond, and pumping infrastructure <br /> downstream of the Mayflower Clear Pond. Any water collected in the sump would be conveyed <br /> back to the Mayflower Clear Pond. This system is similar to another seep-water <br /> collection/secondary containment EPF below Robinson Lake. <br /> • Pumping infrastructure would consist of an 18-inch diameter corrugated HDPE (CHDPE) intake <br /> pipe from the sump to a wet well, a wet well, submersible pumps, and an 8-inch diameter <br /> pipeline consisting of Steel (inside the building footprint) and HDPE piping from the pumps to <br /> the Mayflower Clear Pond. The wet well and pumps would be contained/covered inside a small <br /> 12' x 15' building. <br /> • Detailed plan and design drawings are attached to this submittal. <br /> Project Location and Background <br /> • The project's general location is depicted on Drawing No. 6-807-00101.The site is located <br /> downgradient of the Mayflower Tailings Storage Facility(TSF) and below the Mayflower TSF <br /> seepage collection facilities. The site is fully within Climax's affected lands boundary. <br /> • Currently, seepage emanating from the toe of Mayflower TSF (known as 5-Dam) is captured <br /> using an engineered drainage collection network of pipes. This captured seepage water is <br /> initially routed into two parallel concrete-lined seepage collection ponds. This water then flows <br />