Army Corps Prepares Greenbelt Lake Water Diversion
Work crews began installing aqua levee systems recently on Pistol and Brown Creeks that will act as makeshift coffer dams. Pumps capable of moving up to 6,900 gallons per minute are in place and ready to divert water collected from these streams through pipes around Greenbelt Lake.
As the water is diverted and once the lake bed dries up, the U.S. Army Corps of Engineers Nashville District plans to dredge and make other enhancements as part of an ongoing aquatic ecosystem restoration project at Bicentennial Park nestled along the city’s Alcoa Greenway.
The project is set to enhance wetlands, provide for bank stabilization, remove sediment, and include aquatic plants and boulders around Greenbelt Lake.
David Bishop, Nashville District’s project manager, met with city officials today and provided the latest project schedule that begins with the installation of the diversion structure. He indicated that the lake has already been drained and pumps are in place to begin pumping out water in discharge pipes so that the lake and stream bed can completely dry up. A test of the diversion system is planned in the coming days.
Bishop also reported to the city that excavation of an estimated 40,000 cubic yards of sediment is part of the next phase of the project, which begins in March. This phase includes erosion control, equipment mobilization, mechanical excavation, drying of soil, hauling soil, grading, shaping of the bank, and an initial survey.
Future phases include installation of a weir structure that is designed to catch sediment and prevent it from moving into the lake and downstream; putting in riprap, boulders and wetland seeding; and planting, fertilizing and turf seeding.
Bishop said the lake should be refilled about July 2012, provided there are no weather and construction delays.
“We’re happy to be here and we’re glad that the city hung in there with us, and that we actually have equipment on site and are getting closer to actually removing sediment from the lake,” Bishop said.
This project has been in the works since 2001 when the city of Maryville first requested an aquatic and ecosystem restoration study at Greenbelt Lake. In 2004 the Corps completed an assessment of Pistol Creek, and in 2007 finished a feasibility study. Design plans, technical specifications and bid packages were completed in 2011.
Greg McClain, Maryville city manager, said, “I think the fact that we’re all still here at the table says a lot. I think we’ve all known this is an important project to get done. It’s going to be valuable to the community. And the Corps has stuck with us and we’ve stuck with the Corps, and we’re extremely excited to see it come to fruition.”
The city manager added that the environmental aspects of the project, although great, are not the sole overriding interest the city has in its completion.
“I know from our standpoint if you see how many people actually use the Greenway and how many children come and want to feed the ducks or fish, it is a tremendous asset right here in the center of town,” McClain explained. “So again, it’s a valuable asset, (and it’s important) that we spend this money and time and effort to get it done.”
The Corps is participating in this cost-share project with the city of Maryville under Section 206 of the Water Resources Development Act, which provides authority for the Corps to restore aquatic ecosystems. This project was accepted for construction after a detailed investigation showed it was technically feasible, environmentally acceptable, and provided cost effective environmental benefits.
As stipulated under Section 206, the federal government pays 65 percent and Maryville pays 35 percent of the project’s $1,956,888 total cost. Costs of lands, easements, and rights-of-way are non-federal and are creditable towards the 35 percent non-federal cost share.
“Financially, there is a big benefit to communities like the city of Maryville to work with the Corps on these types of projects,” Bishop said.
The contractor working on this project is Environmental, Safety & Health, Inc., of Knoxville, Tenn. The Nashville District awarded the construction contract Sept. 30, 2011.
Dredging Today Staff, March 5, 2012; Image: usace