Frankenmuth Fish Passage at the Cass River Dam

The Frankenmuth Fish Passage Project at the Cass River Dam

This photo is graciously provided by the project contractor, CTI and Associates of Wixom, Michigan.

About the Project!
Located in the heart of Frankenmuth, at the Cass River Dam, Frankenmuth’s Fish Passage project reconnects the fish of the Saginaw Bay to more than 73 miles of historically significant spawning areas. While the focus of the project is on fish passage, the project maximizes opportunities to benefit Frankenmuth’s local economy – keeping the river profile as it is today and adding opportunities for recreation that sustain the tourism industry and employment center through eco-tourism. Regionally, the project benefits the Saginaw Bay Watershed, supporting local and regional efforts to improve the premier water resource, creating a desirable recreation center, and a successful and sustainable tourism destination.

Live Webcam!   


FAQ's Frequently Asked Questions About the Dam Project

What kind of wildlife has been seen around the area? The construction crew has scouted a variety of wildlife including mink, osprey, a variety of fish, and clams in the construction area.

How long is the "rock ramp" ? The rock ramp is about 300 feet long from the dam, downsteam to the last weir or arch. At the base of the ramp, nearest the first overlook west of the Lager Mill, the contractor will dig a pool, one that will naturally be maintained over the years. This will be the new "fisherman's pool," a resting place before the fish enter the ramp to go upstream

What is different about this dam and rock ramp project than others? Dr. Sandy Verry noted in an interview yesterday that the Cass River Dam is built on a curve of the river. Normally, dams were built on a straight section of waterway. To accommodate this location and the rock ramp design, the weirs are closer together on the north bank than they are on the south bank.

What is a “rock ramp?” This project is a constructed rapids, also known as a rock ramp. From the top 4-ft. of the existing dam to 300-ft. below the dam, this area is replaced with a wedged-shaped stone ramp. Large stone weirs (which look like arches) are constructed on top of the ramp to form a step-pool rapids allowing fish “passage” upstream to spawn (or reproduce.) When the project is complete, the water depth upstream of the dam will remain as it is today. Fish can move through the weirs in both low and high water conditions, accommodating more diverse fish species. The estimated cost of the project is $3.5 million.

Who built the Fish Passage Project? The U.S. Army Corps of Engineers (USACE) is the project manager. The City of Frankenmuth is the project sponsor. CTI and Associates of Wixom, Michigan, is the contractor of record. The USACE has worked with the City’s consultant, Dr. Elon (Sandy) Verry, of Ellen River Partners, to provide the basis of design for the project. Dr. Verry will was on-site during construction of the project guiding the placement of rock in the river.

What is the timeline for the project? CTI began construction activities in 2014 focusing on the land projects. Working under a permit from the Michigan Department of Environmental Quality (MDEQ,) the permit required the construction sequence to complete the land projects first, including bringing Frankenmuth’s levee system (at the lowest point)on the north bank to the 100-foot flood plain level and providing additional storage for a high water event in the immediate area. With voluntary agreement from Zehnders of Frankenmuth and the Fortress Golf Course, the driving range was excavated to achieve the needed storage space (for water) in the event of a future high water event. With the project completed, it’s “Golfing as Usual” on the driving range today. (The City expresses its gratitude to the Zehnder family for their good will and partnership on this community project.)

Most of the work to build the ramp will be completed below the dam before the dam itself is modified. Modifications to the dam will include removal of about the top 4-feet of the dam, replacing that area with new stone. The dam itself will serve as the upstream anchor. River levels will be lowered after Labor Day weekend to complete the work in this area. Levels will return to pre-construction levels when the dam returns to its current height through the addition of new stone.

The project was substantially completed by fall of 2015.

How is the project funded? The project is funded from a variety of sources. The City and the USACE entered into a Project Partnership Agreement (June 2014) that details how the project is funded. The federal share of the project (65%) was provided through the USACE by the Great Lakes Restoration Initiative (GLRI,) a federal source. The Great Lakes Restoration Initiative was launched in 2010 to accelerate efforts to protect and restore the largest system of fresh surface water in the world – the Great Lakes. The City of Frankenmuth funded the balance of project costs (35%) or about $1.27 million. The local match is comprised of an equal share of funding totaling $850,000 (using municipal bonds) from the City of Frankenmuth and from the Downtown Development Authority (DDA) with the remainder provided from contributions received through the generosity of local foundations and businesses. Additional funding for Dr. Verry’s services was provided by a grant from the U.S. Fish & Wildlife Service.

Why is fish passage important at the Cass River Dam? The Fish Passage project achieves ecological and economic goals, both locally and in the Great Lakes Bay Region.

With the arrival of European settlers in the Saginaw Bay area and the resulting expansion of logging, agriculture and industrialization of the area, the construction of dams increased significantly over time. By 2005, over 300 dams were located on the Saginaw River and its tributaries in the Saginaw Bay Watershed. The Cass River is one of six of the major tributaries, and the Cass River Dam at Frankenmuth, is one of its three most impacting dams. (The other two are the dams at Chesaning on the Shiawasee River and the Dow on the Tittabawassee River. A similar project has been successfully completed in Chesaning.)

Fish species including walleye and lake sturgeon are important to the Saginaw Bay Fishery. Both are non-jumping fish species and use rivers and tributaries for spawning before returning to the Saginaw Bay where they spend most of their adult lives. Because the Cass River dam (and other dams) prohibits access to historically significant spawning grounds, there has been a significant decline in fish population in the Saginaw Bay. While the Saginaw Bay is home to more than 90 fish species, walleye is an important sport fish and lake sturgeon is listed as an endangered species. Improving fish passage has been an important goal of organizations such as the Partnership for the Saginaw Bay.

Why is the project important to Frankenmuth? Constructed in 1850, the Cass River Dam has been a community workhorse and landmark for more than 160 years. A failure at the dam would result in the loss of water depth upstream, eliminating commercial boating, changing the river profile for properties along the river, and releasing silts and soils from behind the dam. Over time, the original wooden dam was covered with concrete, more concrete and more concrete. Needing major upgrades requiring a minimum investment of $350,000 to repair half of the dam in 2005, the City chose to make its investment go farther, leveraging other funds to construct a permanent solution while providing for an ecological improvement (fish passage) and new recreational opportunities. Not only does the project forever remove the requirement to maintain the dam, but the project stabilizes the south riverbank and the critical M83 Bridge, enables the continuance of existing commercial boating and maintains the river profile property owners and park users enjoy today. The project is a keystone activity to developing new tourism markets through eco-tourism. The project can help to sustain local employment levels in addition to spurring new business development oriented toward the river and its recreational value in Frankenmuth.

How does project benefit the region? The decline of the number of fish species associated with the loss of spawning habitat was a significant deficiency (impairment) cited when the International Joint Commission designated the Saginaw River/Bay as a national environmental AOC (area of concern.). Dams, like this one in Frankenmuth, are a contributing factor to the loss of habitat. Maximizing the opportunity to support natural fish reproduction, the project restores fish passage in Frankenmuth, continuing to rebuild the Saginaw Bay and Lake Huron fishery – a very good thing. The Great Lakes Fishery Commission (a joint taskforce of Great Lakes states (US) and provinces (Canada)) rated the project a ”High Priority” when evaluating the fisheries and ecosystem benefits of the proposed project. Because of the area-wide benefit from the project, the region attracted national funding of approximately $2.3 million.

The high visibility of Frankenmuth’s location provides a natural forum for environmental education on water quality, environmental sciences, and stewardship to the millions of guests who visit annually.

Why is an abundant fish supply good for the Saginaw Bay Watershed? The presence of healthy fish marks the presence of good water – something very important for people of the region and the Great Lakes.

How much stone will be placed in the ramp? Stones to be used on the project will be limestone from the Alpena Quarry. The weir stones (footer and header) will be comprised of over 2,200 stones with a total weight of over 6,000 tons. The ramp wedge (or the weir foundation) is made up of smaller sized stone (sourced from Bay Port and Alpena) is expected to consist of over 14,000 tons of stone.

Will spring ice thaws or wood jams damage the rock ramp in future years? Dr. Sandy Verry recently evaluated the wood jam on the Chesaning rock ramp from the spring of 2015 stating that “a large wood jam that is stuck at the top of the ramp … (may) always be the case for dams or rock ramps that back up water in the river.” He explains that the wood jam was left during a period of lower than average water flow, as has been the case this spring and summer in Frankenmuth. When comparing the two locations -- one with a rock ramp and one with dam, it appears that low water flow is the culprit for the wood jam in both situations! Which would indicate that Frankenmuth may still have wood jams in the future.

Dr. Verry continues, “Given the large amount of wood that backed up (which could be similar to wood on the Cass River or to ice jams), I am pleased there was no damage to the sides of the river where we used vanes to protect the (amenities in Chesaning) and the bridge abutments downstream in the park.” The Frankenmuth rock ramp has similar design features including vanes that will direct large floating objects and ice towards the center of the river as the water flows, protecting Cass River-banks from erosion.

While the design concepts are similar between the Chesaning fish passage project and Frankenmuth’s project, there are significant differences. Chesaning’s dam had already failed and their project purpose to build the rock ramp was much different than Frankenmuth’s. Much of the stone in Chesaning was donated field stone, irregular in size and undersized. Frankenmuth’s stone will be significantly larger, with the size ordered and cut. The symmetry and placement of the Frankenmuth stones are critical, assuring its stability when placed in the ramp. The distance between each weir (or arch) is less in Frankenmuth than in Chesaning, with a shallower pool and less of a drop between weirs. Regardless of the differences, Chesaning’s fish passage project is deemed a success with recent studies showing fish are finding passage through this once barrier dam.

Will "bad" fish like sea lamprey also be able to pass beyond the dam? With the removal of the Cass River dam as a barrier, all fish species can move freely within the river system including sea lamprey. Because sea lamprey are already found upstream of the dam on the Cass River, and during high water events the dam is an ineffective barrier to sea lamprey moving upstream beyond the dam, the benefits of building the rock ramp are considered greater than the risk of the sea lamprey. Earlier this spring, the U.S. Fish & Wildlife Service treated the Cass River for sea lamprey, turning the river a bright green -- a surprise for many! This is an annual event.

Interested in learning more?

For information about the Cass River Greenway, visit

For information about the Saginaw Bay Watershed, go to

To find out more about the project and the studies completed by the regulatory agencies, read the U.S. Army Corps of Engineers Finding of No Significant Impact (FONSI) Report on the Cass River Dam Project, which can be found at: