Removal of the low-head dam at the former Humboldt Generating Station site southeast of Humboldt began in November as river levels were low enough for work to proceed. Corn Belt Power hired Richards Construction, Sac City, to complete the project.
In 2000, when it was clear that Corn Belt Power Cooperative’s Humboldt Generating Station would not be operated again, the cooperative’s board of directors decided that dismantling the plant was the most responsible option.
At that time, the nearby low-head dam in the Des Moines River was left in place. Located downstream of the confluence where the east and west forks of the Des Moines River come together, the five-foot dam stretched approximately 220 feet across the river. Constructed in the early 1950s, the dam provided adequate water level for the cooling water intake used to cool the condensers for the four steam turbines.
Estimates for tearing out the dam were not in the scope of the plant demolition project. Because it was cost prohibitive to take out the dam at that time, the structure was left in place in the river.
The dam, however, has presented a safety concern due to its potential as a drowning hazard. The flow of water over low-head dams can form a dangerous recirculating current that can trap and drown victims immediately downstream. Swimmers and people in small watercraft like kayaks, canoes and inner tubes are often unaware of hazards these types of dams present.
Although Corn Belt Power posted warning signs over the river for many years, the potential for tragedy still existed as long as the dam was in place.
Mike Thatcher, vice president, generation, explains, “Low-head dams are notorious for being drowning hazards. In fact, many years ago there were three drowning deaths in the vicinity of the dam. It presented a liability to members.”
Last year, when the Iowa Department of Natural Resources offered grant money to share the cost of dam removal projects, Thatcher applied for funds to help pay for dismantling the Humboldt dam. Applicants’ projects were ranked and those selected were sent on to the Natural Resources Commission for approval. With its 92.2 score out of 100 possible points, Corn Belt Power’s project received the second-highest ranking of all applicants.
Thatcher said, “I appreciated the help from the DNR staff in regard to the impact the dam removal would have on river life. During the grant approval process, the DNR commented that sometimes removing a dam will improve fishing upstream, which in this case would be at Gotch State Park.”
The grant narrative explained how removing the dam would have a positive impact on aquatic life, increase recreational boating on the river, reduce security concerns around high voltage facilities and eliminate the drowning hazard to the public.
The Natural Resources Commission approved funding a portion of the project.
Richards Construction was chosen as the successful bidder among three bids requested. Work began across the river from the plant site, which has better access to the dam. The contractor is using an excavator with a jack hammer attached to break up the dam and then remove concrete pieces. An access road was built in the river to allow equipment to reach the dam, which will be torn out down to the riverbed. As progress is made removing concrete pieces, the access road will also be removed.
The project will likely be completed by year end. Rubble from the dam will be buried at the Corn Belt Power plant site. Total cost of the project is approximately $200,000.