The Methow Valley Irrigation District’s East Canal was initially an open irrigation canal extending south from its point of diversion on the Methow River for approximately 9.5 miles. This project replaced a portion of the canal with a gravity pressurized piped system beginning at Mill Hill and extending down to a drain near Beaver Creek. The piped system is approximately 23,590 feet in length. The pipe utilizes the existing East Canal route to supply water to over 150 individual parcels. Pipe diameters range from 24 to 26 inches at Mill Hill to 10 inches at Beaver Creek. The pipe material is HDPE. Because of the possibility of eventually extending the East Canal pipe up to the existing Methow River diversion, the pipe design considers the pressures that will result when the canal is piped along its entire length. All trees within eight feet on either side of centerline of the existing canal were removed for pipe installation.
Located in Twisp, Wash., the project presented several challenges. Pipeline had to be installed along a 10-foot bench with cliff above and below. The tight access didn’t allow for any equipment larger than a mini excavator, which made pipe installation difficult. It also snowed around this time, and instead of packing up and waiting for the snow to melt, Tapani took full advantage of the slick surface. The crew welded up the run of HDPE and chained a CAT 730 haul truck to the back end of it. The haul truck pushed the pipe from behind, sliding it on the snow, and the mini excavator guided the front end of the pipe around bends and kept it aligned correctly in the canal.