While other Fox River dams face removal, Yorkville's dam's uniqueness has it staying put

Along its 202-mile journey down the Fox River, a drop of water must pass through 15 dams before spilling into the Illinois River. The U.S. Army Corp of Engineers recommend removing nine of these dams, to return the river to its natural ecological state. While some Fox Valley communities, like Carpentersville and St. Charles, are facing dam removal, the uniqueness of Yorkville’s dam means it’s expected to remain.

According to the Illinois Department of Natural Resources, the Glen D. Palmer Dam in Yorkville is not scheduled for removal or any modifications. The innovative engineering was designed to create a safer and more environmentally-friendly dam than the one previously spanning Yorkville’s shores.

Far from the current multi-step dam design abridging the water today, featuring a man-made island accessible by bridge and the Marge Cline Whitewater Course, the pummeling flow over the previous low head dam devoured the riverbed beneath the dam. Low head dams allow uncontrollable volumes of water to flow over its raised crest, which is difficult for boaters to see. This created the dangerous, and often inescapable, roller hydraulic effect, resulting in the tragic drowning of 26 people between the dam’s re-construction in 1961 and 1993.

“I remember how dangerous it was, I used to paddle above and below the old low head dam,” Yorkville native Wally Werderich said. “As you’re traveling down river towards the town, it’s hard to see the dam as you approach the bridge.”

In 1993, the Yorkville Police Department contacted the Illinois Office of Water Resources to see how the dam could be made safer. State officials previously used riprap boulders to reduce the undertow effect, increasing safety, until the rushing waters eroded away the constructed safety precautions.

Engineers at the University of Illinois proposed a modified concrete four-step spillway design, creating a safe passageway for canoes along the river’s south bank. The design also established a passageway for fish and aquatic life to travel both upstream and downstream unabated. The dam’s north abutment even featured a first-of-its-kind Denil fish ladder, further restoring fish mobility.

The re-modified dam, costing more than $8.25 million funded by the state, opened to the public in 2010. Grouted boulders sculpt the river’s flow into rapids for recreational kayakers. The bypass channel includes two whitewater courses, one for novices and one for more experienced paddlers, and a standard boat passage route allowing multi-directional traveling.

Concrete block stop logs enable city staffers to increase flows through the 1,100-foot-long whitewater courses during competitions.

“It’s fun going downtown and not only seeing the recreation on the river, but all the recreation happening on land around that focal point of our community,” Werderich said. “People really congregate to that area. The Fox River is a jewel of a natural resource. Anybody who enjoys the river needs to take care of it and be wise how they use it.”

In an interview, IDNR officials said while Yorkville’s dam has largely been a safety and environmental success, other towns exploring alternatives ranging from dam modification to full removal, are hesitant to replicate the design because of its significant costs. A similar design can total 10 times more than the standard dam removal. Many towns are still exploring similar whitewater features.

“The Yorkville dam is one step in restoring connectivity to the Fox River,” said Tristan Widloe, stream specialist for the IDNR. “Allowing not only fish but other aquatic organisms to move around the dam. Flathead catfish tagged downstream of the dam were later collected upstream, demonstrating fish can and will move past these barriers if given the opportunity.”

Widloe said reconnection of the Fox River and other state rivers is an important management objective for state agencies.

“The present problem is that dams restrict the movement of fish to other reaches of the river,” Widloe said. “Many native freshwater fish that were originally thought to not make seasonal movements are now known to migrate in the spring or move to over-wintering pools if conditions allow that movement.”

In addition to the bypass channel, a fish ladder provides a solution to restore fish mobility. An IDNR study found fish species like bluegill, and the threatened Shorthead Redhorse frequently use the ladder.

Widloe said while habitat and water quality is most vastly improved by complete dam removal, waterfowl still congregate near the tailwater, the shallow waters beneath the dam that are often abundant in fish. However, all waterfowl, including bald eagles, seek the least-degraded habitat and water quality, preferring open water to man-made ecosystems.

While the multi-step dam and the fish ladder increase environmental friendliness, Widloe warns the dam still poses ecological challenges. The dam creates an upstream pool containing excessive nutrients, sediment, and silt trapped by the dam. Widloe said the decomposition of all that organic upstream material impairs water quality containing low dissolved oxygen levels. The slow, shallow water above the dam also increases water temperatures, providing unnatural ecosystems for aquatic wildlife.

IDNR officials are continuing to monitor the ecological effects of the dam on both upstream and downstream water quality and aquatic life.