Major repairs to the Malheur Siphon, an above-ground irrigation pipe in southeastern Oregon, are under way and slated to be completed by March if not Christmas 2018, Owyhee Irrigation District general and project manager Jay Chamberlin said.
The siphon, a landmark in the valley, delivers up to 325 cubic feet per second of irrigation water from the Malheur Reservoir to farmers on the northern part of the OID system.
Crews recently finished repairing four bends in the 4.5-mile, 80-inch steel pipe that previously was held up by a support structure with concrete legs placed two feet into the bentonite clay soil. In the old system, wet conditions expanded soil and lifted supports — which dropped when the soil dried. “The problems were stress, wrinkle and misalignment” to the pipe, he said.
Improvements under way in the roughly half-mile affected area include placing the pipe on a beam-mounted slide plate that sits atop concrete, steel-reinforced piers drilled 22 feet underground — some 20 feet deeper than the old supports. Chamberlin said the plate is designed to allow the pipe to move independently of any soil shifting, such as when the pipe expands slightly due to heat.
“The support structure has not been supporting the pipe to allow thermal expansion and contraction of the pipe itself,” he said.
The siphon runs south to north, crossing U.S. 20-26 between Cairo Junction and Vale. Supplied by Owyhee Reservoir, it serves about 20,000 acres of irrigated farmland. The section under reconstruction is on the north end, starting at the Malheur River and running north.
So far in the project, groundwater has posed a challenge close to the Malheur River, Chamberlin said. Here, holes for concrete piers are encased in steel.
“And because it is so close to Malheur Butte, there are some challenges with land and slopes and terrain,” he said. A couple of repairs are slated where the siphon traverses a draw and sits on an elevated, trestle-like steel structure.
The approximately $1 million project, paid for by OID reserve funds, also involves JC Constructors of Meridian, Idaho, engineering firm Stantec’s Boise office and the U.S. Bureau of Reclamation.