From Ordnance Plant to Native Plants in Central Illinois

Built in 1942, the Green River Arsenal is located nearly ten kilometers south of Dixon, Illinois, in the Green River watershed, a tributary of the Lower Rock River basin. It was the first, and probably the only, plant in the country to produce the rocket-propelled bazooka's ammunition. After World War II ended in 1945, production stopped and the arsenal was closed down, and by the spring of 1946, the land had been returned to agricultural use. Today, Allied Waste Services owns 240 ha and operates the 107 ha Lee County Landfill. Located directly in the center of the former arsenal site, Lee County Landfill replaces the munitions assembly facilities.

Figure 1.

Looking east in March 2009, across the seeded wet meadow area in the foreground, with the open water pond community in the background of the Green River Arsenal wetland mitigation site in Lee County, Illinois.

Photo courtesy of Mark Smith

Allied Waste has plans to expand the landfill, which entails destroying wetlands and relocating a creek and pond. The company has purchased 12 ha of adjacent farmland just 1.6 km east to satisfy the Army Corps of Engineers' requirement for compensatory wetland. When the rich wetland complex, once the area's most distinctive ecological asset, was originally converted to agriculture, the meandering creek was channelized and the wetlands tiled, changing stream hydrology and resulting in serious erosion and sedimentation downstream.

Apart from the clearing of the prairies, no change to the Lower Rock River basin has had a more profound ecological impact than the altering of the hydrology by the channelization of streams. In an attempt to reduce flooding, all but 38 km of the Green River has been dredged and straightened to increase its water-carrying capacity as it flows from its source in northern Lee County until it joins the Rock River at the boundary of Rock Island County in the Quad Cities area. The region still supports a wide variety of ecological communities with an impressive diversity of species that compensates for the scarcity of high-quality habitat. There are 71 km of streams designated as "biologically significant" because of their fish and mussel diversity; 43 Illinois Natural Area Inventory sites that include marshes, seeps, two types of forest, and eight types of prairie; and the Nachusa Grasslands, a 400 ha prairie restored and owned by the Nature Conservancy.

The mitigation at the Lee County Landfill is a restoration project in that it is reestablishing wetland and riparian zones by dechannelizing the creek with the goal of returning it to its natural functions and characteristics and provides a net gain of wetland area. Through a competitive bid process, Weaver Boos Consultants was hired to design, permit, and monitor the wetland project, while Tallgrass Restoration was contracted for the on-the-ground restoration portion. An excavation contractor contoured a basin, creating a small, shallow pond for water to feed into the wetland areas from the creek that flows into the Green River.

The first phase of Tallgrass Restoration's work in 2008 included seeding a nine-meter-wide perimeter around the new lake with a mixture of emergent wetland plants, and seeding a larger perimeter up to 90 m away with mixed native vegetation (Figure 1). Weather-related delays posed the most difficult challenges during the initial phase of the project, according to Tallgrass Restoration project ecologist Tim Moritz. "We expected to get started in May of 2008, but bad weather delayed the excavation of the pond, which pushed our work back into September," Moritz recalled. "Because of the delay, we were unable to get everything planted as expected during the 2008 season, but we're back on track this year and everything is shaping up well." The native seed was planted in the fall of 2008 as scheduled, but saturated ground delayed tree planting until the spring of 2009 (Figure 2).

Natural communities that were planted included a forested buffer, wet meadow, emergent wetland, and shallow open water aquatic vegetation. Tallgrass Restoration planted approximately 830 bare-root trees of various native...