Des Moines River Dam Removal

Des Moines River Water Quality Concerns

As of 2014, the Iowa Department of Natural Resources listed 572 bodies of water as impaired, which has garnered strong publicity with Iowans becoming increasingly concerned about water quality. Common pollutants include nutrients, sediment, and chemicals. While the majority of Iowa waters are only impaired on a minor to moderate level, now is the time to act before the issue grows in severity.

One area of concern, the Des Moines River, holds a strong significance both locally as well as regionally. First and foremost, it serves as a primary water source for numerous communities within the Des Moines River watershed. In addition, it’s a popular recreation destination for anglers, water sports enthusiasts, and people who enjoy the beauty of rivers. At approximately 525 miles long, it’s also the largest river in Iowa and is a tributary of the Mississippi River.

Due to bacteria levels, it was identified as impaired in Iowa’s 2012 Integrated Report: Category 5: EPA-Approved Section 303(d) Impaired Waters. Recognizing existing opportunities to restore the original beauty and function of the Des Moines River, the City of Fort Dodge dedicated a large part of its comprehensive plan to improvement efforts.

Restoring Beauty & Function of the River

In order to fund water quality improvement initiatives within the watershed, the City of Fort Dodge was recently awarded funds from the Clean Water State Revolving Funds program. Specific water quality objectives for restoring the river’s original beauty and function are as follows:

  • Improve the integrity of the river by preventing future degradation
  • Restore natural in-stream habitat conditions
  • Meet the designated uses for the river

Central to the project is the removal of the Fort Dodge hydroelectric dam and Little Dam, which lies two miles south. Constructed in 1916, the Fort Dodge damn generated electricity for downtown street lights until 1971 when it was decommissioned. It has since been abandoned, with subsequent gate failures contributing significantly to the decline in water quality.

Studies completed in 2006 and 2010 both concluded that redevelopment of the dam for hydroelectric power was not economically feasible. Recently, the deteriorating power plant building next to the hydroelectric dam and its gates were removed. As part of a riverfront plan, Snyder & Associates, Inc. has recommended removal of the Fort Dodge damn along with Little Dam.

“Removing the dams will restore the natural flow of the river to improve water quality,” states Jeff Walters of Snyder & Associates.

It will also improve safety for kayaking and other recreational uses once the dam structures are removed.

Additional Steps 

Dam removal is only part of the overall plan to improve water quality, restore in-stream habitat, and meet the river’s designated use. Recently, the staff of Snyder & Associates completed several tasks as part of a fluvial geomorphological assessment:

  • Bathymetric survey to determine river geometry and provide insight on the depth and shape of underwater terrain
  • Depth of refusal probing to quantify the volume of silty material located upstream from each dam
  • Cross-sectional survey to develop a profile of the river

The staff has also reviewed original drawings, construction plans, and historic data to aid in planning for removal of the dams. Ongoing work includes the completion of a wetland delineation, to determine the upper limits of wetland within the corridor, and a threatened and endangered species habitat survey, to determine if listed species may be impacted. Particular species of concern include the Northern Long-Eared Bat and several mussel species.

Noteworthy items from recent fieldwork include:

  • Sediment probing completed above the upper and lower dams to determine sediment loading quantities in the river showed a maximum sediment depth of 9.5-feet for the upper dam and no sediment for the lower dam.
  • Bedrock outcroppings, or locations where bedrock is visibly exposed, were observed along the length of the studied segment. The area above the dam had the most outcroppings.
  • Logjams were found to be quite common below the lower dam, with none noted elsewhere within the studied segment.

Future work includes engineering design for dam removal, dam removal and riparian enhancement cost estimates, permitting with the Iowa DNR and US Army Corps of Engineers, and final design.

“It’s going to take time, but we’re confident this plan will improve water quality of the Des Moines River.”  Jeff Walters, Environmental Scientist, Snyder & Associates.