The Nevada Irrigation District is planning an emergency repair project after leaks were detected in a large 90-year-old pipeline that runs through a tunnel beneath the rockfill dam at Bowman Reservoir.
In a report Wednesday (Mar. 13) to the NID Board of Directors, General Manager Rem Scherzinger said the district is moving forward with plans to reactivate a bypass to supply water while permanent repairs are completed.
He said the district anticipates having the bypass in operation prior to this year’s irrigation season, which begins Apr. 15 and when seasonal demand for water begins to rise. He said the permanent fix is expected to be complete this summer.
District officials are placing high priority on the repairs because Bowman is at the center of NID’s Upper Division water storage system. Water from several mountain reservoirs runs through Bowman and the Bowman-Spaulding Canal to PG&E’s Lake Spaulding where it is routed to NID customers in Nevada and Placer counties.
Bowman is located at the 5600-foot elevation on the western slope of the Sierra. Officials said this year’s light snowpack and early runoff should benefit the district in providing the temporary supply and making the permanent fix.
NID Associate Engineer Keane Sommers, who is heading the repair effort, said the leak was first detected by NID’s resident laketender at Bowman. Inspections showed cracks in the old riveted 48-inch-diameter steel pipe that dates to the dam’s construction in 1925-26. Damage to a butterfly valve was also found.
Sommers said the damage is confined to a 20-foot section of the pipeline just above its outlet. He said a new section of pipe and a new outlet valve house are being planned.
Meanwhile, to keep water flowing, the district plans to spill water over another dam at Bowman, the South Arch Dam, and divert this water into the Bowman-Spaulding Canal. Sommers said an inlet taken out of service in this area in the 1980s to divert water when the nearby powerhouse was being built, would be uncovered and reactivated for the temporary supply.
District officials have been meeting with a specialty contractor, who will be expected to quickly mobilize and complete the repairs as soon as possible. Approval of an emergency contract is expected soon.