Iowa plans to drain Lake Geode to improve water quality
Iowa plans to drain Lake Geode to improve water quality
By JULIA MERICLE
Jul. 15, 2017
DANVILLE, Iowa (AP) — Looking at Lake Geode, it may seem crazy to think the 174 water-filled acres, which reach a maximum depth of 44 feet, can be drained through a 24-inch pipe on the bottom of the lake.
But before year's end, in a bid to improve water quality and get the lake off Iowa's impaired waters list, the plug will be pulled and the lake will begin to drain just like a bathtub. Before it is filled again, the lake-bottom will be reconstructed using methods designed to promote a healthier lake.
Iowa Department of Natural Resource's impaired waters list now identifies 283 impairments in 145 of the state's monitored lakes, reservoirs and wetlands, according to Tom Wilton, of the department's water quality bureau. Elevated levels of pH and bacteria, specifically E. coli, landed Lake Geode on the list, which is defined by the federal Clean Water Act.
Chad Dolan, a fisheries management biologist for the DNR, told The Hawk Eye (http://bit.ly/2tBn6Dd ) that the seemingly high number boils down to the fact Iowa is a highly agricultural state.
"It's a competition between human use and animal use and maintaining excellent water quality," Dolan said. "The battle is really to find the balance between the two. The reality is, there are events and things that throw it out of balance."
Dolan said Iowans should not be alarmed by the number of impairments, but instead be conscious of how they are using the landscape if they want water quality to improve.
A pH impairment means water monitoring data demonstrated a pH level exceeding 9, the water quality standard, Wilton said. High pH levels are phosphorus-related, and often linked to algae blooms. Algae growth, as in the case of Lake Geode, can be triggered in agricultural watersheds where fertilizers are applied to crops make their way into the lake.
However, Dolan said the cause lies not only in the hands of farmers, but all who live in or near the watershed — the 10,327 acres surrounding Lake Geode that drain into the lake.
"People fail to realize that when they wash their car, where do all the soap suds go?" Dolan said. "Down a drain and make their way to a ditch and a larger waterway and that soap carries nutrients and they get to the lake and cause algae bloom."
High bacteria levels stem from excrement — whether from deer in the woods or geese on the beach, or pigs on farms — making its way into the water. People, too, when septic systems fail.
To get Lake Geode off the impaired waters list, park employees, DNR and other partners set goals to reduce total phosphorus and sediment entry into the lake by 6,351 pounds per year and 2,499 tons per year, respectively.
"You want to turn off the sink before you fix it," Michelle Balmer of the DNR lake restoration program said, meaning problems in the watershed had to be addressed before in-lake work could proceed.
Achieving that started with implementing conservation efforts in the watershed, which is larger than most in relation to lake size among restoration projects.
Successful lake restoration projects tend to have smaller watershed-to-lake area ratios than exists with Geode, Balmer said. The DNR lake restoration program works primarily with projects with ratios of 40-to-1 or less, meaning that for every 40 acres of land there is one acre of lake. The ratio at Lake Geode is 56 to 1.
Caleb Waters, the Lake Geode watershed project coordinator, has been addressing these problems since the project began in 2010. He has worked to install conservation practices in the state park, including the construction of 13 ponds and some sediment basins to reduce erosion and slow runoff and sediment from reaching the lake.
Waters has also worked with about 170 landowners in the watershed to encourage things like installation of terraces and planting cover crops, practices which further protect Lake Geode from runoff and sediment from watershed farmland and properties.
Waters and Dolan have taken conservation measures at the shoreline, too, such as placing large rocks resistant to erosion from small waves that further halt sediment and runoff.
Divers inspected the underwater drawdown pipe in Lake Geode on June 16 and found it plugged with a steel plate. DNR design engineer supervisor Heath Delzell said the plate must be removed before drainage of the lake can proceed.
This plate pushed back the best-case scenario drawdown start date. But Delzell said project coordinators still hope to get the drawdown started before December when ice forms on the lake.
Several plate-removal methods are being considered. One would require a confined-spaces operator to inspect the dry side of the drawdown pipe and the condition of the current valve, both constructed in 1950. The operator would determine if the condition would allow for a new valve to be installed before drainage commences.
If a new valve could be installed, it would equalize pressure on the steel plate for it to be taken out. This method, however, would require the design and manufacture of a new valve, which might put the team behind its drawdown schedule goal.
Another method suggests the 350- to 400-pound plate be removed with brute force. This method would require lifting equipment on a barge in the lake directly above the pipe that could overcome the 55 feet of head pressure and 30- to 40-ton load on the plate.
A third possible method would poke holes in the steel plate or the pipe itself, which is made of reinforced concrete, for the water to flow through. This method would require heavy equipment and is still undergoing cost, feasibility and safety analysis.
Delzell said the benefit of choosing the first method is that even if the valve cannot be replaced before the lake is drained, it will be replaced after. The valve replacement-plus-divers option would cost somewhere in the $50,000 to $75,000 range, he said.
Once the plate is removed, water will run through the valve to the other side of the lake's dam and into Cedar Creek, a tributary of the Skunk River.
Delzell said the water must not come down faster than one foot per day, and takes about a month to fully empty. Most in-lake dams are made primarily of clay, which becomes saturated with water. If all the water was removed at once, the moisture in the dam would not have time to leech out and could lead to flooding or damage to the dam itself.
As the water level drops, some fish will go through the drainage pipe into Cedar Creek and the Skunk River. Other Iowa fisheries will come to Lake Geode to take some fish to restock their own ponds and lakes. The park itself also will relocate some of the fish to its new ponds, Dolan said. Fishing regulations also have been relaxed in preparation of the drawdown process.
However, there are millions of fish in Lake Geode.
"Inevitably, at the tail end of a mass exodus of fish some will get trapped in the lake itself and some may perish," Dolan said.
Once Lake Geode is empty, sediment will be removed from the lake bed through a process of mechanical dredging. Heavy, earth-moving equipment, such as excavators, scrapers, bulldozers and dump trucks will run along the bottom of the lake and scoop out sediment.
The material may be trucked to a disposal site, but more likely will be moved from shallower areas of the lake to deeper areas of the lake.
This method would create ridges and variability along the bottom of Lake Goede, which promotes better fish habitat and aquatic health, Delzell said. Additionally, it would encourage fish to congregate in certain areas, providing great fishing spots.
Delzell said when in-lake work — which will cost in the range of $2 million to $3 million — is complete, workers will "close the valve and let nature take its course to fill up the lake." The money comes from the DNR lake restoration program fund, which Balmer said receives $9.6 million each fiscal year.
Entirely dependent upon rainfall and groundwater seeping in, the lake could take up to two or three years to refill completely.
However, Dolan said once water deepens to 4 to 6 feet, reintroduction of fish will begin, starting with bluegill. Crappies will be added last, almost a year after the first bluegill.
Dolan said that while water quality will never be perfect, and heavy rainfall always will bring unwanted elements into Lake Geode, the project aims to leave Lake Geode with good water quality a majority of the time.
"Just like you have to maintain roads or houses," Balmer said, "you have to update the infrastructure of lakes, too."
Information from: The Hawk Eye, http://www.thehawkeye.com