Sodom/Shearer Dams Fish Passage Improvement and Flow Management

2013 Update on the Sodom Channel Restoration Project from Project Manager Denise Hoffert-Hay

Download the PowerPoint Presentation


 OSU Monitoring Data at Sodom and Shearer Dam sites 

Calapooia River and Sodom Ditch Discharge 


Archived-Preferred Alternative Design
Archived-Permits and Bid Documents, Sodom and Shearer
Archived-Sodom Dam Project Monthly Updates
2011 Dam Removal Construction Footage and Photos
4/12/12 Project Performance Presentation by River Design Group


Sodom and Shearer Dams Background

The Calapooia Watershed Council partnered with Oregon Parks and Recreation Department (OPRD) in spring 2008 for addressing fish passage and water management issues at a series of structures formally used to control flows to the historic Thompson’s Mills.

The Sodom and Shearer Dams were managed by OPRD to control operational flows delivered to the Mills. The Mills became a State Heritage Site in 2004, with the property’s special significance being the oldest water-powered grain mills in the state with a system of waterways, dams, control gates, ditches and dikes that had diverted water from the Calapooia River to the Mills’ head gates since 1858.

The Sodom ditch was built in the late 1800’s upriver of the Mills to serve as a high water over-flow channel to divert water around the Mills and minimize flooding along that reach of the Calapooia River.  Unfortunately, the Sodom ditch was too effective and shortly after its construction, began to capture nearly the entire flow of the Calapooia River.  The Sodom Dam was built around 1890 to divert river water during low flows out of the Sodom ditch and back into the Calapooia River.

The Mills operated to provide flows to power the Mills’ grain processing facility for over 120 years.  Beginning in the 1970s, it was no longer economically feasible to grind grain – little grain was being produced in the area – and the Mills began to instead generate electricity that was sold to the energy company, PacifiCorps.  The 1998 listing of winter steelhead and spring chinook as  “threatened” under the federal Endangered Species Act, spurred state and federal natural resource agencies to examine this site more closely when it came time for the site to renew its Federal Energy Regulatory Commission (FERC) license.  NOAA Fisheries, the federal agency responsible for enforcing the Endangered Species Act (ESA), determined fish passage at the dams associated with the Mills would be a necessity.  This led to a lengthy multi-year discussion between the natural resource agencies, Pacificorps, Oregon Water Trust (now The Freshwater Trust) and the private owner over how to satisfy the new regulatory framework (cascading from the ESA listing) in order to surrender the property’s FERC license.  After several years of discussions and negotiations, in 2004, OPRD purchased the property, including the dams.  Also in 2004, dam’s private owner sold 12 cfs of the property’s historic 1858 water rights to the Trust for transfer to instream rights.

Over-arching problems associated with the managed water system included the following (details on the concerns with each dam are outlined in subsequent sections):

  • Water control facilities were 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 this technical assistance and outreach effort, there had not been community outreach efforts to develop a sustainable solution to the managed flow system that was dependent on significant partial barriers to fish passage, Sodom and Shearer Dams.
  • The bifurcation becomes plugged with sediment and woody debris and requires maintenance in order to keep the Calapooia River channel active.
  • All the watershed’s spawning and rearing habitat for salmonids is upstream of these former dam sites.  Steelhead and chinook once had to negotiate one or the other of these dams in order to reach the cool pools and spawning gravels in the upper watershed.

Sodom Dam

The original structure was a push-up dam, then later a wooden crib dam and finally in 1957, the concrete structure that was recently removed.  The dam was an integrated weir and pool fishway.  The dam was located approximately 1,400-ft downstream of the bifurcation of the Sodom Channel and the Calapooia River, just downstream from Calapooia RM 19.  The Sodom Channel flows parallel to the Calapooia River before the channels converge approximately 7 miles downstream.  (Note on nomenclature – due to the fact that the Sodom Channel now conveys a majority of the winter flows for the Calapooia River and is expected to convey 50% of the summer flows after this project’s implementation, the Sodom ditch is now referred to by a more accurate description as the Sodom “Channel”.)

The Sodom Dam was approximately 11-ft in height from the outlet apron to the crest of the dam.  Across the crest and the width of the fishway, the dam was 85-ft wide.  The sides of the dam were bounded by concrete abutments that extend to a height of 10-ft above the crest of the dam.  The abutments had concrete wingwalls that extend into the bank.  The fishway was located on the west side of the dam.  It was a pool-weir fishway with six pools.  The fishway entrance was on the west side, in the scour pool below the dam.

Sodom Dam, Spring 2007

Sodom Dam, Spring 2007

Problems associated with the Sodom Dam included:

  • The dam was an aging structure that reaching its as-built life expectancy.
  • There was significant deterioration of the fishway’s concrete with daylight visible through the fishway wall in a number of locations.  Flows actively seeped through the wall of the fishway.  Two of the six pools had severe abrasion from bed load with exposed rebar along the walls and floor.
  • Some areas of concrete along the scour apron and lower portion of the dam had deteriorated or been abraded by bed load.  Exposed rebar was evident at the toe of the three buttresses.
  • Scour under the outlet apron had occurred along the center portion of the outlet edge in excess of 4-ft.
  • The existing fish ladder did not meet current design criteria established by ODFW and NMFS.  It did not have the appropriate jump/drop height in the pools.  Attraction conditions during high flows were inadequate because the first two pools of the fishway were submerged.  Attraction conditions during low flows prevented migrating fish from finding the inlet to the ladder because the fish congregate at the spillway where flows are higher.  The ladder was frequently non-functioning due to accumulated debris from winter storms that is not removed because there was no access to the fish ladder during high flow conditions (the fish ladder was on the opposite bank from the only road to the dam).
  • Steelhead have been observed spawning in the Sodom Channel.  Spawning in this channel is a concern because the juvenile winter steelhead do not likely survive the high summer water temperatures in this reach (ODFW, 2003).
  • Sodom Dam interrupted movement of gravels along the Sodom Channel.

Shearer Dam

The Shearer Dam was also originally a push-up dam, then later a wooden crib dam and finally the concrete structure that was removed, built in 1956.  The dam’s purpose was to divert Calapooia River flows to the Mills via a human-dug channel (mill race).

The Shearer Dam was located on the Calapooia River at approximately RM 23.  The dam was a 40-ft wide concrete structure, 5 feet in height from the scour apron to the crest of the dam.  The crest of the dam was 7.1 feet higher than the water level in the downstream scour pool under stagnant conditions.  The weir and pool fishway was comprised of three pools 6-ft wide by 9.5 ft long by 3-ft depth.

Problems associated with the Shearer dam included:

  • The dam had a fishway along the west bank of the dam which did not meet current fish passage criteria and did not provide passage during low flow conditions, due to the presence of rock ballast at the outlet that extends above the water level.
  • Additionally, the fishway pool weirs were not appropriately sized, allow too much water through them, thus creating adverse hydraulic conditions for fish passage.  Under stagnant conditions this was a barrier to fish.  At low stream flows the flow depth may have been too shallow for fish to traverse and jump into the fishway entrance.

These dams have been known fish passage problems for decades, but because of their complexity and lack of a simple, inexpensive solution, nothing had been done to address them until recently.  Over the past four years, the Calapooia Watershed Council (CWC), with the support from State parks and an active Technical Team composed of local, state and federal natural resource officials and local landowners, has built the relationships and done the outreach necessary to obtain stakeholder support for removal of Sodom and Shearer Dams in 2011 and continued maintenance of the project site in the coming few years.