Delphia-Melstone Water Users Association History

• Infrastructure completed in 1952 and funded by the Montana State Water Conservation Board
• DMWUA formed in 1995 when ownership was transferred from DNRC
• Primary purpose: Irrigation
• Acres Irrigated: 6,085
• Number of users: 52
• Primary Diversion Point: Two diversions on the Musselshell River, with storage from Deadman's Basin Reservoir

Project History

In 2011, the Musselshell River experienced a significant flooding event, which damaged numerous ditches and irrigation structures operated by the DMWUA. Of these damaged structures, the largest and most technically challenging, the Delphia Canal Long Span Pipe over the Musselshell River, was put on hold for repairs until 2012, so funding and proper design could be established. The damage to the Long-Span Pipe included pier damage, pipe failure and outlet transition structure loss.

The Long-Span Pipe was originally constructed in the 1950’s and consisted of a 150 foot aerial pipe span with a 30-inch diameter pipe. The pipe was supported by numerous support piers. Prior to the 2011 flooding event, the aerial span had significant damage on numerous occasions, including damage that resulted in a full rebuild.

The preferred replacement structure was identified as an inverted siphon, due to the historic issues with an aerial span at the project location. Some challenges were present at the project site, including shallow bedrock and proximity to a private irrigation dam. The new siphon utilized an HDPE pipe with new concrete transition structures.

Work Breakdown

• Removal of existing aerial span
• New HDPE Siphon
• Associated concrete siphon transition structures

Project Funding

The total cost of the project was $299,151. To finance the project, the DMWUA used the following grant and loan programs:

• DNRC RRGL Grant - $100,000
  • Redirected RRGL Grant that was utilized due to flooding damage and importance of critical irrigation infrastructure
   
• USDA Rural Development Loan - $150,936
• USDA NRCS Cost Share - $48,215
  • Cash contribution specifically dedicated to concrete and transition structures

Project Status & Results

• Project successfully completed in 2012
• Replacement of the aerial span with a siphon has ensured irrigation system functionality, even in high flow events
• Project was a team effort; landowner allowed access for borrow source and upstream dam owner cooperated during construction

Project Partners

Owner: Delphia-Melstone Water Users Association

Engineer: DOWL

Contractor: Western Municipal Construction, Inc.

Construction Oversight: DOWL