FLOW 5th Avenue Dam Pre-construction Project Site
Olentangy Riverbanks are prepared for planting in May 2013
Dams transform a stream system of riffles, pools and runs to something closer to a lake environment, reducing the habitat structures that harbor wildlife and restricting flow so that water and polluted urban runoff stays impounded above the dam. Dams restrict the migration of fish and other aquatic species as well as reducing the natural transport of bed-load materials (sand and rocks) down the river.
Friends of the Lower Olentangy Watershed (FLOW) recommended the removal of low head dams in their Watershed Action Plan more than a decade ago as a means of improving water quality in the Olentangy River. Water-quality studies showed the Olentangy River was far from meeting aquatic use standards for modified warm water habitat. Removal of the dam is expected to improve water quality almost immediately, and the planned ecological restoration will further help improve water quality along the stretch of the river from West 5th Avenue to Lane Avenue.
Water quality is evaluated by examining several different characteristics including physical, chemical and biological attributes. Physical characteristics such as water temperature, substrate of the river bottom, and the presence of twists and turns in the course of the river can suggest whether a river is capable of supporting a healthy river ecosystem. Chemical measurements such as the amount of dissolved oxygen and the levels of pollutants and heavy metals are used to gauge whether the river is capable of supporting life. Biological criteria measure the variety and abundance of species, and indicate whether those species are tolerant of contaminants present in urban runoff that drains to local waterways.
The dam was removed in August 2012, and the ecological restoration project began as pool levels were reduced above the 5th Avenue Dam. The ecological restoration includes construction of three shoreline wetlands on the western bank and a fourth wetland on the eastern shore of the Olentangy River. Seven riffles will be constructed near the center of the river channel, and 21 scour pools will be built along the river's edge to reconnect storm water outfalls to the new lowered elevation of the river.
After water levels in the Olentangy River are reduced by removing the dam, muddy banks that were once underwater will be planted with grasses, sedges and forbes that don't mind being underwater during high-water events. Further up the bank, native trees and shrubs will be planted to eventually provide shade to help regulate water temperatures in the river and provide food and habitat for wildlife that live in or migrate through the Olentangy riparian corridor. The project is scheduled for completion by the end of 2013, but it will take many more years for plants and trees to fully mature. In addition to the benefits of improved water quality, the dam removal and ecological restoration will enhance safety and recreational opportunities for small watercraft.
The following is a summary of answers to questions that the community have asked about the project. If there is a question you would like to ask, contact FLOW at email@example.com
What is the purpose of the project and what are the project limits?
The purpose of the project is to help restore the river to a more natural free-flowing condition and to improve aquatic and riparian habitat. These changes are expected to have a positive impact on water quality in this stretch of the Olentangy River.
The stream restoration effort starts just upstream of the Lane Avenue Bridge and extends south to 900 feet downstream of the 5th Avenue Bridge. Construction is limited to the area between the pre-dam removal shoreline and the new location of the shoreline now that water levels are lowered. Work does not extend up the existing river banks.
Where will the new park be located?
Although no park will be dedicated along the land created by the removal of the 5th Avenue Dam, there will be new greenways along the river’s edge. The Olentangy Trail parallels the river from downtown Columbus northward to the Franklin County Line. This heavily traveled, multipurpose trail is used by bike commuters, bird watchers, walkers and more, and the views of the Olentangy River are expected to improve as the Lower Olentangy River Ecosystem Restoration is completed and new plantings become established. Metro Parks personnel maintain the Olentangy Trail, but within the project area, the land is owned or managed by the City of Columbus (City), The Ohio State University (OSU), and Ohio Department of Transportation (ODOT).
To help preserve what is anticipated to be an aquatic, scenic and natural resource, environmental covenants have been placed across the land within the project limits. The environmental covenants place restrictions on the land in an effort to keep it more natural. Example restrictions include no mowing within the covenant area and no planting of non-native species.
What are the costs of the project?
The construction cost for the dam removal and ecosystem restoration project is approximately $6.9 million dollars. The cost of the dam removal is approximately $200,000, with the remaining funds to be used to reconstruct river features, create 4 large wetlands, reconnect approximately 40 stormwater outfalls to the river, and establish native vegetation along the 1.5 mile long project area. Almost 3 miles of river bank will be restored during the project.
Funds to complete the project were provided by the Ohio EPA, the City, and OSU. Costs for the dam removal are in line with costs for other dam removals in the area. Some of the costs are allocated to reconstruct necessary infrastructure such as the storm-water outfalls, and to protect utility lines that cross beneath the River. The ecological restoration is the largest project of its kind in central Ohio, so it is difficult to compare costs with other similar projects.
What new recreational opportunities does the project offer?
Small watercraft will be able to maneuver their boats along a free-flowing Olentangy River between the Dodridge Street lowhead dam and downtown Columbus. Ohio State University is looking forward to the Olentangy River being an iconic part of main campus, with educational and pastoral recreation opportunities all along the river bank.
Will trash and debris exposed by the lowering of the dam pool be cleaned up?
Exposed trash and debris located in the channel bottom will be removed within the project limits by the contractor as construction progresses upstream throughout the remainder of 2012 and 2013.
During November 2012, FLOW organized a River Clean Up event to remove trash from the riverbanks between Lane Avenue and Woody Hayes Drive. Volunteers comprised of University and high school students, Eco-Summit volunteers, and individuals helped to haul debris like shopping carts, tires, and trash from the riverbanks to dumpsters provided by OSU. Clean up efforts were coordinated with the City and OSU and they provided assistance with disposal of the debris collected.
Will invasive species like shrub honeysuckle be removed?
During construction, the contractor will remove invasive species that come up within the project limits. To help planted materials get established, spread and mature the project area will be monitored and invasive species controlled for 5 years after the end of construction. Removal of existing invasives along the river banks is not part of the project; however, the City, OSU and FLOW are investigating potential options for removing these invasives.
The plans call for a lot of fill material to be used in reconstructing the floodplain. Why will so much fill material be placed in the floodplain?
The removal of the 5th Avenue Dam has allowed the river to return to its more natural characteristics; however, the existing banks are now too wide for a river of this size. Imported, clean fill material, as well as existing material excavated from the river bed, will be used to construct narrower banks. At the completion of construction, the width of the river in the project area will match existing widths found south of Dodridge Street Dam and south of 5th Avenue Bridge.
Why was this project initiated?
The City offered to look at either modification or removal of the dam as a Supplemental Environmental Project as part of the settlement of an enforcement order and agreement with the Ohio Environmental Protection Agency. The agreement was reached to enhance water quality and stream habitat in this portion of the Olentangy River.
Why was only a portion of the dam removed?
The entire height of the dam was removed only where the new active river channel will be located. The top 3 feet of the structure was removed from the remaining portions of the dam along either bank. Those remaining portions of the dam will be buried under 2 foot of fill that will be used to create the new riverbanks.
Does removal of the dam increase the chances for flooding in that area?
Does the dam removal make the River safer?
Removal of the dam will create a safer environment for small watercraft to maneuver between the north campus area and downtown Columbus. The biggest reason for removing the dam is to improve water quality in the lower portions of the Olentangy River. This improvement in water quality makes the River safer for the entire community.
What will the river look like eventually?
Although no one knows exactly how the river will look at the completion of the project, the City of Columbus contractor in charge of the design of the dam removal and ecological restoration of the Olentangy River created a rendering showing a predicted appearance of the river of the river over time. These projected views are available on the City of Columbus Department of Public Utilities website. The views show the predicted appearance of the river shorelines as plantings mature and increase the function of the floodplain over time.
Will we see more wildlife and fish species as a result of the dam removal?
Removal of the dam will certainly change the river environment within the project area. The Olentangy River is already home to many species of wildlife, and the project should result in a better environment for them to thrive. The ecological restoration work will make this stretch of the River more attractive to migrating birds and shoreline wildlife. Removal of the dam will allow fish and other aquatic species to migrate up and down this stretch of free-flowing river.
How will the project affect the bike trail?
The Olentangy Trail is a multi-purpose recreational trail that parallels the river from downtown Columbus northward to the Franklin County line. The path is a busy with bicycle commuters, bird watchers, and recreational users walking along the trail. Project construction will cause some momentary closures of the multi-purpose path to permit construction equipment to cross into their work areas, but will remain available to the public throughout the project. Signage and flagmen will be used to keep these momentary closures of the Olentangy Trail safe for users.