Peshastin Irrigation District Pumpback Design

This project involved the completion of the Icicle and Peshastin Irrigation District (IPID) Pump Exchange Project Feasibility Study. This project would provide an alternate source of water supply to portions of the IPID delivery system by pumping water to the system from the Wenatchee River at two locations. This would enable IPID to reduce diversions and increase streamflow in both Peshastin and Icicle Creeks during the entire irrigation season, thus improving fish passage and habitat conditions. All of the alternatives evaluated in this report would eliminate the need for the Peshastin diversion and result in the removal of that dam infrastructure.

This work builds on previous work that has spanned 15 years. Preliminary design was completed for a preferred pump station located near Dryden, WA under a separate RCO grant. This work builds on that as well as a Value Planning Study completed by the U.S. Bureau of Reclamation in 2019. This feasibility study included the following work. An Alternatives Evaluation was completed initially to identify alternative pump station locations to be considered and compared against one another. Based on that work, the stakeholders selected the Stines Hill and near the Cashmere Waste Water Treatment Plan (CWWTP) as the two pump stations to consider with the Dryden location. Site investigations at these two sites included topographic survey; hydrology and hydraulic investigations with use of an ADCP and water level monitoring; reconnaissance-level geologic investigation through desktop research of geology and site visits; property owner coordination; and environmental and permit review. The study also included the completion of engineering and cost analysis, and instream flow benefit evaluation to demonstrate the range of flow improvements to each stream from different pump station configurations. Conceptual design drawings for Stine Hill and CWWTP sites were completed to be included with the site at Dryden. This project will ultimately include either two pump stations - one at CWWTP plus Dryden or Stines Hill - or one large pump station located at Dryden.

Next steps for this project are to evaluate all three pump stations (Dryden, Stines Hill, CWWTP) and select the preferred combination to implement and then define design paramters. Landowner and funding coordination are ongoing.

Complete an alternatives evaluation to identify and design two preferred pump stations that will move surface water withdrawal from Peshastin and Icicle Creeks to the Wenatchee River. The reduced water withdrawal in the two creeks will enhance instream flows for ESA-listed spring Chinook and steelhead.