NID purchases a new outlet valve for Rollins Lake

The Nevada Irrigation District (NID) continues to work with state and federal regulators to ensure its dams and reservoirs are operated in a safe, efficient manner. To that end, a replacement for an aging outlet valve at Rollins Lake near Chicago Park has been ordered, and District officials offer assurances that public safety was never at risk.

NID’s Board of Directors approved the purchase of a new valve and support structure for nearly $470,000 during its Nov. 8 meeting. The valve currently is being designed and manufactured with installation scheduled for the winter of 2018-2019.

An outlet valve is like the plug on the bottom of the bathtub used to drain the tub. At Rollins Lake, which holds 66,000 acre-feet of water (1 acre-foot of water equals about 326,000 gallons, or enough water to cover a football field 1-foot deep), the outlet valve has a five-foot diameter.

The valve serves as a backup and is not used as part of normal operations. When NID needs to manage reservoir water levels, it does so through its power plant and a spillway “designed to pass the most severe flood that is reasonably possible based on meteorological and hydrologic conditions in the watershed,” said Keane Sommers, NID’s hydroelectric manager.

An earlier routine inspection by the California Division of Safety of Dams (DSOD) noted the old valve could not be fully opened. Following the discovery, the District quickly completed significant maintenance on the valve and requested two independent engineering evaluations of the valve. Following that work it was concluded that the valve should be replaced.

A follow-up inspection report by DSOD dated January 19, 2017 noted the outlet valve “still cannot be fully operated” due to corrosion. Importantly, the report concluded, “From the known information and visual inspection, the dam, reservoir, and all appurtenances are judged safe for continued use.”

The new outlet valve will be built with stainless steel to reduce corrosion and will include modern controls and redundant operating systems to ensure the dam continues to be safe for years to come.

NID owns and operates 15 dams under the jurisdiction of California Division of Safety of Dams and 13 under the jurisdiction of Federal Energy Regulatory Commission (FERC). In addition to the District’s weekly and monthly inspections of its dams, DSOD and FERC perform annual inspections.

The District’s seven power plants generate approximately 82.2 megawatts of electricity each year. That’s enough electricity to supply the equivalent of more than 60,000 homes. The Rollins Lake power plant has a generation capacity of 12.15 megawatts.



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