2018-02-13_REVISION - M1977342 - Laserfiche WebLink

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0.s W. W. WHEELER 9,+7 & ASSOCIATES, INC. Water Resources Engineers WWW.WWWHEELER.COM 3700 S. INCA STREET I ENGLEWOOD, CO 80 110-3405 303-761-4130 I FAX 303-761-2B02 TECHNICAL MEMORANDUM October 31, 2017 To: Brandon Beggs From: Doug MacLaren, P.E. Re: 1333.01.11 Henderson Mill Seepwater Collection System Piping Hydrostatic test On October 18 and 19, 2017, the discharge pipelines for Phase III of the Henderson Mill Seepwater Collection system were hydrostatically tested. Phase III consisted of two new wells, MLEX-4 and -5, along with the associated vaults and pipelines, etc. The two new wells were drilled, and vaults and discharge pipelines were installed earlier in the summer/fall of 2017. Well MLEX-4 is connected to the existing well pipeline system that includes wells MLEX-1 thru -3, which discharges into the storage pond at the base of the tailing dam. Well MLEX-5 uses a separate discharge line that discharges the flow directly into the sump at Ute Park Pump Station. Due to their locations, the two well systems use separate discharge lines and were therefore tested independently. The line from well MLEX-5 was hydrostatically tested first. The date of the test was October 18, 2017. The end of the new pipe where it is to be connected to the existing discharge box was closed off with a blind flange, which was modified to add a pressure and fill port. The 1-1/2 inch valve in the concrete vault was closed and the 4-inch HDPE line pressurized with water to between 85 and 90 psi. For the next 4 hours the line was kept at this pressure by adding water as required. Once the line was determined to be holding pressure, Wheeler was contacted and visited to the site to witness the 1-hour hold period, which is the most important part of the test procedure. After being pressurized to a minimum of 85 psi for 4 hours, the line pressure was reduced to 75 psi and no water was added to the line during the 1-hour period. After the 1-hour