Milton Ditch Piping Consolidation & Efficiency

Historically, a gravel and rock push up dam was constructed each year in the Walla Walla River just upstream of Milton-Freewater in order to divert flows into the Milton ditch. Degradation in the system over time made a gravity diversion into Milton Ditch impossible. Consequently, the diversion was moved upriver to the confluence with Couse Creek.  In the summer, the gravel berm often blocked off the entrance to Couse Creek and sent all the water down a ditch parallel to the river.  ESA listed steelhead and threatened bull trout, unable to enter Couse Creek, tried to swim up the juvenile fish bypass located at the drum screen for the Milton ditch fifty yards downstream of the diversion at Couse Creek. Steelhead smolts leaving Couse Creek may have had difficulty entering the Walla Walla River and ended up in the beginning of the Milton ditch. 

Usage of this problematic diversion site has been discontinued as a result of this project.  The Walla Walla River Irrigation District (WWRID) applied and received OWRD approval for a change in the point of diversion of the water for Milton ditch to relocate it 1.5 miles downstream to consolidate with the Little Walla Walla diversion at Cemetery Bridge.  The Little Walla Walla diversion has a state-of- the-art set of fish screens, an inflatable dam diversion and fishway installed in 1998.

The largest portion of the funding for the project was contributed by the Bonneville Power Administration (BPA) .  Other partners included the Walla Walla River Irrigation District (WWRID) and district patrons, the Oregon Watershed Enhancement Board (OWEB, grant #204-246), the Walla Walla Watershed Alliance (NRCS funds pass-through), Oregon Department of Fish & Wildlife (ODFW), Confederated Tribes of the Umatilla Indian Reservation (CTUIR), and the Columbia Basin Water Transactions Program.  After several years work by the partners to secure the funds, the piping was completed between November 2003 and June 2005.  The total project installation cost was $1.72 million.

Under contract from BPA, the engineering firm Montgomery-Watson-Harza completed a final design, managed the project, and communicated with affected landowners.  Becker Construction installed the pipeline and pump station.  The system consists of an intake structure, pump station and associated yard piping, forcemain, and turnouts.  BPA warranted the completion and operation of the project for two years and will then give title to WWRID for long-term operation and maintenance. WWRID users donated easements and will pay the long term pumping and maintenance.  Three small pastures and around 20 lawns were previously irrigated using the upper (now un-used) portion of the old Milton Ditch.  Mitigation funds are being shared among those users not served by the new pipeline.

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This project has left an estimated 7.5 cfs flowing in the mainstem Walla Walla River channel for an additional 1.5 miles downstream from Couse Creek to the Little Walla Walla diversion.  It also eliminated the need for a gravel push-up dam requiring annual disturbance of the streambed, thereby allowing for improved fish passage in the Walla Walla River and into the Couse Creek tributary.  The project eliminated the use of a fish screen that did not meet NOAA Fisheries criteria and improved irrigation delivery efficiency and operation by shortening and piping the leaky Milton ditch system.

The pipeline is functioning as designed and installed. Because it is an “on-demand” system, water is only used as needed. The Milton Pipeline irrigators are now using approximately 1/3 less water as a result of this project. This has allowed efficient distribution of very tight summer water supplies. The automation contained in the pump house has also decreased the workload for WWRID staff as adjustments to the water needed at the diversion off of the Powell-Pleasantview ditch are taken care of by the electronic controls. Funding has been secured to begin piping the Powell-Pleasantview ditch that brings the water to the Milton Pipeline and to automate the headgate operation so that no more water is taken out of the river than is actually needed.

An application for transfer of the conserved water to an instream right has been drafted to be submitted to the Oregon Water Resources Department (OWRD) for approximately 2.5 – 3 CFS of senior (pre-1900 summertime) water rights. WWRID is currently going through a district remapping process (under HB3201). Once that is completed, the water rights will be reviewed again for conserved water, and the conserved water application finalized and submitted to OWRD.

Where the Milton ditch used to run along the edge of Yantis Park, a trail has now been created above it, heading up the hillside.  Some grading work has been done by the City of Milton-Freewater, perhaps to make the old ditch area more aesthetically pleasing. This may need to be redone later to accommodate better the stormwater runoff that will likely flow through the old ditch path. The portion of the ditch that previously flowed along city sidewalks in town is no longer being used or maintained by WWRID and the easements may eventually be ceded to the City of Milton-Freewater for stormwater runoff.

Information updated 7/28/06