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The lake's southwest corner preserves wetlands and provides access to recreation.
© Photo courtesy of the Delavan Lake Sanitary District

April 2012

Delavan lake restoration efforts deliver

It's a case study in clean water economics.

Julia Riley

Showcasing innovative dewatering technology

Is it possible to put a value on clean water? Many Delavan Lake residents think it is.

They know that a clean water resource there helps preserve more than 800 local jobs.

They know that managing pollutants from urban areas and agricultural lands within the watershed is critical to protect the lake's recreational and aesthetic values, and its fishery.

And they know that making a long-term commitment to lake protection means finding the right mix of technology, partnerships and funding.

Delavan Lake residents in Walworth County have worked hard to improve their lake's water quality during the last three decades.

The Delavan Lake Sanitary District formed and oversaw the installation of wastewater collection sewers around the lake in the 1980s. That project cost $50 million and received federal and state funding. The sewers helped eliminate wastewater discharges from faulty residential septic systems into the lake.

The town and city then undertook an ambitious $7 million massive lake rehabilitation project that was completed in 1992. The lake's water level was lowered and the entire fish population was killed to remove carp. Alum was added to the bottom of the lake to help trap phosphorus in the sediments. Three ponds were constructed to capture sediment and phosphorus from a tributary, Jackson Creek. A peninsula was constructed near the inlet to divert sediment-laden water from the main part of the lake. A dam near the outlet was reconstructed and more desirable game fish were restocked.

Those lake rehabilitation actions increased water clarity to a depth of 26 feet and eliminated carp and severe blue-green algal blooms. Partners in the project included Walworth County, the U.S. Geological Survey, the U.S. Environmental Protection Agency, the U.S. Army Corps of Engineers, the Department of Natural Resources, the Southeastern Wisconsin Regional Planning Commission, the University of Wisconsin's Department of Civil and Environmental Engineering and The Nelson Institute for Environmental Studies.

In 2005, the Delavan Lake Improvement Association and the University of Wisconsin-Whitewater, released a comprehensive economic impact study, "What is the Value of a Clean and Healthy Lake to a Local Community?" The study calculated that "$77 million is generated annually as a result of Delavan Lake and its improved water quality."

The economic analysis estimated that 812 jobs were generated, the average value of lake shoreline property appreciated $177,000 between 1987 and 2003, and the aggregate land value increased $99 million.

The study states, "Delavan Lake is a crucial component to the financial, physical and social fabric of the region. Delavan Lake affects not only the quality of life for local residents, but also has regional economic implications... Deterioration of lake water quality (water clarity, milfoil) could be expected to lead to reductions in time spent in Delavan by property owners and visitors, which in turn would have economic implications for the local economy."

Back to work

To keep up with nutrient loadings from agricultural areas and the watershed's growing urban areas, the community went to work again!

This time it tapped a new partnership, additional tributary improvements and innovative dewatering technology to take lake restoration to a higher level.

A network

The Delavan Lake Watershed Initiative Network (WIN) was established in 2010 as a coalition of 11 municipalities and organizations. WIN's focus is protecting the lake from industrial, agricultural and storm water pollution. Priorities are controlling urban storm water runoff, restoring wetlands, creating buffers of natural vegetation along waterways and expanding monitoring.

Delavan Lake WIN Project Manager Maggie Zoellner describes some of the outreach work WIN will accomplish with a $250,000 three-year grant awarded in 2010 by the U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS).

"We are working with local farmers with funding from the NRCS's Mississippi River Basin Healthy Watershed Initiatives to reduce sediment, nitrogen and phosphorus loadings and improve water quality not only in Wisconsin, but also ultimately in the Gulf of Mexico," Zoellner says. "Cost sharing at 75 to 100 percent is available for the development of nutrient management plans, the installation of grassed waterways, filter strip, winter cover crops and the use of no-till practices.

"Walworth County Conservation staff is working with local farmers to identify areas that could use management practices to preserve the quality of the soil and reduce erosion. Not only do these practices improve water quality, they benefit farmers because they help maintain agricultural productivity. WIN is truly an organization that coordinates grassroots-level support with local, state and federal partners."

Tackling tributary improvements

The Department of Natural Resources also awarded a $10,000 river protection grant for 2011-2013 to fund an inventory of Jackson Creek and its tributaries that enter Delavan Lake at its northern end.

The grant allows scientists to study Jackson Creek and nearby areas to develop site-specific recommendations for reducing sediment loads in the creek, protecting local natural resources and improving the quality of water entering the lake.

WIN's outreach work will help phosphorus-laden sediment stay on agricultural lands and not end up as inlet sediment.

Dredging gets to the bottom of things

The Town of Delavan conducted three maintenance projects during 2005-2011 to help support the original massive lake rehabilitation projects.

The north inlet dredging project (see companion story on page 20) was the last of the maintenance projects and Town of Delavan Administrator John Olson explains the town's rationale for the $1.6 million project:

"Following several public meetings, the town board and lake committee undertook the project understanding that a clean and healthy Delavan Lake is one of the town's single most important assets," Olson says. "Maintenance steps taken to help protect that asset will yield multiple and compounding economic and social benefits to the local economy."

The Town of Delavan financed the inlet project with contributions from the City of Delavan's room tax revenue, a grant from the Wisconsin Waterways Commission and general borrowing. The project almost stalled because of debt financing issues, and it was bid three times in an attempt to get lower bids. Identifying funding for future projects remains a key priority for local decision makers.

Watchdogs on duty

Today, Delavan Lake's Improvement Association labels itself the "watchdog" for the long-term health of the lake. In July 2011, the association released a study, "How Do Towns Take Care of Their Lakes? A Search for Lake Management Best Practices." The study investigated how other communities finance lake projects and recommended that the Town of Delavan establish a dedicated lake fund with annual contributions held for future maintenance projects.

Olson acknowledges that economic times are tough and the town's 2012 budget is tight. Setting aside additional funds for future maintenance projects is probably not realistic right now. But he is optimistic that town board dialogues on maintaining water quality will include establishing a dedicated lake fund in the future. Proper protections on the use of those segregated funds solely for lake projects must be included to prevent diversion of the money for other purposes.

Audrey Green, a lake specialist for Walworth County, notes that during the summer of 2011 over 17,400 boats used the boat ramp at Highway 50 to access Delavan Lake and enjoy recreation on its waters.

For a detailed view of the dredging project, visit Town of Delavan.

Read more about Wisconsin's efforts to reduce phosphorus in lakes and rivers.

The partnerships and organizations formed to protect Delavan Lake demonstrate an impressive coordinated and cooperative watershed management effort. With a continued longterm commitment to lake management and restoration as demonstrated over the past 30 years, county residents will ensure the beauty of Delavan Lake's waters and its economic benefits will be enjoyed for future generations.

Julia Riley is a water resources management specialist in DNR's Bureau of Water Quality.

Showcasing innovative dewatering technology

Richard Raschke, a project supervisor for JND Thomas Company Inc., cradles a moist clump of soil in his hand. The soil was reclaimed from the bottom of Delavan Lake's northern inlet and Raschke shares a story about its source.

Standing in front of a new hydraulic dredging system used for the first time in Wisconsin, Raschke explains, "I had a farmer stop by last week to take a look at what we were doing with the dreg from the bottom of the inlet. The farmer pointed to these piles and said, ‘That came from my field and I'd like to have it back!' You could sell this, people want it."

Some 900 feet away, a DSC Moray articulating dredge works its way up Delavan Lake's inlet channel. The dredge is precisely positioned using GPS equipment and the operator guides the "walking" dredge according to cross-sectional engineering drawings prepared by Peter Berrini of HDR Engineering Inc.

Berrini and the HDR team are involved in every step of the Lake Delavan dredging project from permitting to project management.

The dredged sediment is then pumped through a pipe to dewatering equipment set up behind the Town of Delavan Fire Station #1. It takes about 20 minutes to complete the four-stage dewatering process and what emerges is stackable material referred to as "cake."

The "cake," which was dewatered to approximately 60 percent dry, is then hauled by dump trucks to a local gravel pit and used to reclaim a 40-acre quarry site.

Extracted water is eventually returned to the main part of the lake with 6-18 mg/l suspended solids – lower than the average lake concentration of 18-22 mg/l suspended solids.

The Delavan Lake northern inlet project also included dredging a 3,000-foot navigational channel that was 177 to 267 feet wide and 4 to 6 feet deep. Some 45,330 cubic yards of sediment (1,489 truckloads) were removed during the sum mer of 2011. The project avoided disturbing high-quality aquatic habitat in DNR-designated sensitive areas.

The Town of Delavan removed this phosphorus-enriched sediment from the inlet to prevent it from washing into the main lake. That section of the inlet drains about half of Delavan Lake's 26,000-acre watershed and contributes an estimated 60 percent of the phosphorus entering the lake. Phosphorus is often added to agricultural soils to help crops grow. But over time, phosphorus can accumulate in soils, wash off agricultural lands when it rains and end up in waterway sediment.

HDR Engineering Inc. calculated that approximately 33,350 pounds of phosphorus were removed from the inlet as a result of the dredging project.

One pound of phosphorus can grow 300-500 pounds of wet algae. Removing the inlet's sediment and its phosphorus cache will help improve water quality and prevent excessive algal growth that diminishes recreation.

Martye Griffin, the DNR's statewide waterway science and policy coordinator, explains why this hydraulic dredging site was more efficient and economical than other types of dredging operations:

"With some types of dredging operations of this size you'd normally have to construct large earthen settling basins to dewater the dredged materials," he says. "The dredge slurry is pumped to the settling basin and either filtered out or allowed over time to settle out in the bottom of the basin. After settling, the water is drained off, treated and returned to the waterway."

The remaining sediment is usually removed with a backhoe and hauled away for disposal, or in some cases the sediment is allowed to remain in place and "capped."

"Sometimes communities have to purchase land for the sedimentation basins, which is expensive," Griffin says. "Then you have to restore the site once the dredging and dewatering is completed. At this unique hydraulic dredging site, the dewatering equipment fit into a small footprint on the landscape and produced drier sediment, which equated to lower truck hauling costs. The restoration costs for this site were much lower compared to a dewatering site that relies on earthen settling basins."