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Gooding, Idaho
Y-Siphon Replacement
Replacing a Critical Canal Crossing Near Gooding, Idaho
The North Side Canal Company’s irrigation system near Gooding, Idaho, crosses beneath Dry Creek through an inverted siphon about 175 feet upstream from the Big Wood River. The pressurized crossing carries canal water below the natural drainage channel.
The siphon serves the lower portion of one of southern Idaho’s largest irrigation networks—approximately 900 miles of mainline canal serving about 160,000 acres. Its two 80-foot-long, 60-inch-diameter corrugated metal pipes and concrete headwalls had reached the end of their useful life after nearly a century of service.
Morrison-Maierle’s* team developed a durable solution to improve conveyance reliability and extend the life of the Y-Siphon, addressing maintenance, channel stability, and flood exposure at a sensitive crossing near the Big Wood River. Without this project, a siphon failure could have disrupted irrigation deliveries across a significant portion of the canal system.
Client
North Side Canal Company
Location
Gooding, Idaho
Size
100-ft. crossing with twin 60-inch HDPE pipes
Project Snapshot
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Project support from beginning to end: Services included funding assistance, topographic surveying, hydrologic and hydraulic analysis, alternatives evaluation, engineering design, permitting, construction documents, bidding support, and construction administration. The team balanced irrigation operations, stream hydraulics, channel stability, constructability, regulatory requirements, and a limited construction window.
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New features: The team replaced a century-old inverted siphon beneath Dry Creek near Gooding, Idaho, with twin 60-inch fusion-welded HDPE pipes, new concrete headwalls, and flood-protective riprap to improve long-term irrigation reliability.
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Taking care of the surroundings: Morrison-Maierle’s engineers incorporated several measures to protect the surrounding environment, including silt fences and straw wattles for sediment control, a design that avoided wetland impacts, and permitting coordination for work within and near the Dry Creek channel.
Planning, Design, and Coordination
The design replaced the corrugated metal pipes with two nominal 60-inch fusion-welded HDPE pipes. Extending the crossing from about 80 feet to 100 feet allowed the new concrete headwalls to be set farther from Dry Creek, improving channel stability and reducing exposure to stream forces. Crushed-gravel bedding provided uniform pipe support, while a rock riprap curtain protected the crossing from flood damage.
The site sits where an irrigation canal intersects a natural stream, requiring a dewatering plan that isolated construction from both water sources. Dry Creek’s mean annual flow is about 4 cubic feet per second, and late-fall canal deliveries were expected to reach about 20 cubic feet per second. Morrison-Maierle coordinated the diversions so excavation, pipe installation, and concrete work could proceed in dry conditions.
Excavation of the proposed Y-Siphon site where the canal crosses Dry Creek. The siphon serves the lower portion of one of southern Idaho’s largest irrigation networks.
The design replaced the corrugated metal pipes with two nominal 60-inch diameter fusion-welded HDPE pipes.
New concrete headwalls were constructed in the dry to reduce the risk of turbidity in the Big Wood River and shortened the construction schedule.
Building Within a Low-Flow Window
Morrison-Maierle scheduled the construction after the irrigation season, when Dry Creek flows were expected to be manageable. Temporary upstream and downstream cofferdams isolated the work area. Creek flows were diverted into the adjacent canal, carried about 400 feet to an existing turnout, and redirected to the Big Wood River. The downstream cofferdam prevented river backwater from entering the site.
Additional canal cofferdams isolated the site from late-fall irrigation deliveries, which were routed around the work area. The contractor then removed the existing pipes and headwalls, excavated the crossing, installed the twin HDPE pipes on prepared bedding, and built new concrete headwalls. Contractors removed materials and excess soil to an off-site location.
Completing the work in the dry also reduced the risk of turbidity to the Big Wood River and shortened the construction schedule. Dewatering discharge was directed to an upland area away from flowing water, and silt fence and straw wattles controlled sediment during rainfall. The design avoided wetland impacts, while Morrison-Maierle coordinated permitting for work within and near the Dry Creek channel.
Improving Long-Term Irrigation Reliability
The completed Y-Siphon Replacement modernized a critical link in the North Side Canal Company’s water-delivery system. Twin fusion-welded HDPE pipes, new concrete headwalls, greater setbacks, and flood-protection measures provide a more durable crossing with fewer long-term maintenance concerns. Through integrated civil engineering, hydraulic analysis, permitting, construction documents, and field support, Morrison-Maierle helped the client replace century-old infrastructure while maintaining water deliveries and protecting nearby waterways.
*This project was designed and completed by QRS Consulting prior to its 2026 acquisition by Morrison-Maierle.
We love to discuss irrigation solutions. Contact us today!Meet the Team
Nick Kraus
Senior Fisheries Engineer | Boise Natural Resources Market Group Office Leader
PE
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