Sodom Dam Fish Passage Improvement and Flow Management

Stakeholder reference documents from CWC & project engineers at River Design Group, Inc.
Design Process & Technical Reports
Preferred Alternative Design
Project Maps & Photos
Sodom Dam Project Monthly Updates

Sodom Project Background
The Calapooia Watershed Council has partnered with Oregon Parks and Recreation Department (OPRD) for the Sodom Dam Fish Passage Improvement and Flow Management Project in spring 2008 and has commenced technical assistance activities and landowner outreach. The Sodom Dam, located on the Sodom Ditch, is operated by Oregon Parks and Recreation Department’s (OPRD) staff at Thompson’s Mills to manage operational and ecological flows delivered to the Mills and Calapooia River. The ditch was built in the late 1800’s upriver of the Mills to serve as a high water diversion to ultimately direct high flows around the Mills and to have the effect of minimizing flooding along that particular reach of the Calapooia River.

Sodom Dam, Spring 2007

Unfortunately, the Sodom Ditch was too effective, thus, the Sodom Dam was originally built around 1890 to help divert river water during low flows out of the Sodom Ditch and back into the Calapooia River.  The dam has an integrated weir and pool fishway along the left bank.  The Sodom Dam is located approximately 1,400-ft downstream of the bifurcation of the ditch and the Calapooia River. Problems associated with the dam and managed water system, as identified by the CWC, OPRD and fisheries agencies, include the following:

• The existing fish ladder does not provide adequate passage.
• Sodom Dam is an aging structure that is reaching its as-built life expectancy.
• Sodom Dam interrupts movement of gravels along the Sodom Ditch.
• Current water control facilities are inadequate to ensure water availability for fish in the Calapooia River, and flows are too warm in Sodom Ditch during hot summer months to support migrating and juvenile fish.
• Prior to CWC project activities, there have not been community outreach efforts to develop a sustainable solution to the problems presented by a managed flow system that is dependent on a significant partial barrier to fish passage, Sodom Dam.

The Council has secured technical assistance funding to contract a part-time project manager and has to date facilitated the first of a series of 3+ community meetings to discuss what the stakeholders envision for long-term management of the river system and to determine the technical information needed to move the project forward. Consultants will provide technical input throughout the Council’s outreach process to answer questions pertaining to river processes and management and to provide information that will facilitate discussions.

The CWC has also begun to coordinate meetings with permitting and regulatory agencies such as DEQ, ACOE, NOAA Fisheries, ODFW, WRD, and DSL to ensure that alternatives and the final design address regulatory requirements. Project engineers will be attending and presenting deliverables at these Technical Team meetings to ensure their work is on track. The engineers will complete a detailed analysis for the Calapooia channel and Sodom Ditch in order to fully evaluate the complex river system. The nearly completed geomorphic assessment of the system will result in a document that details how river processes shape the existing system and provide insight into future conditions and water conservation scenarios. Field surveys have also been conducted in order to use with future LiDAR data to develop a hydraulic model.