Goose Lake in Lake in the Hills, IL, was completely filled with sedimentation in excess of 180,000 cu. yds. (137,620 cu m). The lake, approximately 12 acres (4.9 ha) in size, acted as a natural silt trap for the Crystal Creek watershed. The creek system drains hundreds of acres of urban development and accommodates the effluent discharge from two wastewater treatment plants, approximately 6 million to 8 million gal. (22.7 to 30 million L) per day. Previous farming operations combined with recent development caused silt to deposit in Goose Lake until it was filled to the top.
The water control structures allowed the lake pool to be lowered only a couple feet, fully exposing most of the sedimentation. The creek then flowed through the material across the remainder of the lake 6 to 8 in. (15 to 20 cm) deep; the water continuously flowed across the surface to the dam. Due to the vast area of the upstream watershed, even a small amount of rain caused the entire 12 acres (4.9 ha) to re-fill and then discharge to the dam.
Access to the lake for mechanical dredging was limited due to existing homes and the steep elevation change from the nearby roads to the lake. The lack of a local spoil site made hydraulic dredging impractical. An access point though a local park was provided to the water’s edge for staging. Shoreline access to the remainder of the lake was not available. The depth of the muck was 6 to 13 ft. (1.8 to 4 m) to the hard bottom.
A previous contractor employed a number of pumps in an attempt to keep up with the flow from Crystal Creek. After approximately one year of non-performance by that contractor, the exposed sedimentation was covered with weed growth causing the residents to voice even more displeasure.
In February 2001, C&C Dredging Services Inc. was called in to take over the project. Due to Illinois Department of Transportation (IDOT) and local restraints, the bypassing of the water by breaching the dam was not allowed. The company obtained the approximate daily discharge rates from the treatment plants; and also considered the influx of water from the Crystal Creek watershed during rain and flood events. It was determined that trying to maintain dewatering by pumping was not practical, said Timothy Cantwell, president of C&C.
The test excavations determined the lake did have a hard clay, sand and gravel bottom which would allow crews to work from within the basin. The remaining problem that faced the original contactor and now C&C was what to do with the influx of water as the dredging work was in progress, he noted.
The company’s answer to the access problem was quite baffling to some of the homeowners. Trucks starting arriving on the job site but instead of hauling the muck away, clay was deposited and dozed into the lake forming berms. “Before we could haul out the muck, we had to fill the lake even more. Utilizing thousands of yards of clay, the existing sedimentation was capped to form separate cells within the lake,” said Cantwell.
During excavation, the water was diverted around each cell by the berms. The berms also served as haul roads. To reduce the water content prior to hauling, the sedimentation was excavated and stockpiled to de-water before it was loaded. By constructing the berms to act as haul roads the trucks hauling the material were able to drive into the lake bottom to be loaded. The diversion berms/haul roads were at an elevation that kept the truck traffic on fairly dry ground, thus the amount of material deposited on the streets as they exited the job site was minimal.
As each cell was completed, the clay material from the berms was utilized in the shoreline restoration. The existing shores were in bad shape with muck; once the dredging work in a cell was completed, the shoreline was rebuilt to a three to one slope, stabilization fabric and stone rip-rap was installed, explained Cantwell.
Utilizing a Case 9330B long front excavator on wood mats, the material was excavated and stockpiled for drying. A loading station was constructed and another excavator loaded trucks. A number of specialized low ground pressure excavators and dozers were utilized to complete this project. “Ernie Prudhomme, of McCann’s Industries, in Addison IL, kept us up on the latest Case equipment for this type of work,” Cantwell noted.
The 9030B long front excavator with a 50 ft. (15 m) reach, combined with a 550LGP wide track dozer, allowed crews to excavate and stockpile the material for drying. “Working with McCann’s enabled us to deploy a variety of equipment to achieve the difficult excavation and stockpiling of the wet sedimentation,” he added. McCann Industries and Case Credit Inc. provided financing plans to make purchasing equipment possible.
With dredging spoil, muck or sedimentation, disposal is difficult due to the moisture content. It cannot be used as structural fill and if one finds a landfill that will accept the material, disposal fees per load for wet material are high. What was C&C to do with more than 180,000 cu. yds. (137,620 cu m) of muck? A local gravel pit had recently completed its mining operations, as part of the restoration process the side slopes were to be stabilized by vegetation. C&C Dredging Services Inc. deposited the nutrient rich material, allowed it to dry and utilized it as topsoil. After a few weeks, the sedimentation was graded over the existing surface and any remaining moisture in the sediment dissipated. Utilizing the new Case 1150G, the dredged material was spread on the side slopes, the slopes were seeded and erosion control matting was put into place. Substantial growth occurred within a few weeks. Dredged material that can be a contractor curse to dispose of, also can be an important commodity by recycling it as topsoil, Cantwell said.