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Onondaga Lake Capping, Dredging, Habitat and Profundal Zone (SMU 8) Final Design- March 2012

The remediation plan for Onondaga Lake, which was selected by the New York State Department of Environmental Conservation (NYSDEC) and the U.S. Environmental Protection Agency (USEPA), calls for a combination of dredging and capping. These methods are proven environmental cleanup
methods that address contamination in water and lake sediment. This document provides information on the design for remedial areas, sediment cap, habitat restoration and enhancement, areas and depths of sediment to be dredged, and dredging and capping methods. This report also provides the design for the profundal zone-the deeper water portion of the lake where water depths exceed 30 ft. [9 meters]). This area is referred to as Sediment
Management Unit (SMU) 8 in the ROD. The remedy for SMU 8 includes thin-layer capping, monitored natural recovery, and nitrate addition to reduce release of methyl mercury. The design team for this work consists of more than 100 local engineers and scientists working with nationally recognized experts from various universities, research institutions, and specialty engineering firms, and with input from community stakeholders. The design generated through this collaboration is effective and meets the objectives for remediation and long-term protection of health and the environment outlined in the ROD.

Restoring diverse, functioning and sustainable habitats to the remediated areas of Onondaga Lake is one of the top priorities of this remedial program. Therefore, habitat considerations are at the forefront of the various design evaluations for the lake and have been fully integrated into this document. Habitat considerations are a major factor in developing the habitat layer and the total thickness of the cap. The cap will provide a suitable habitat layer for plants, animals, and fish to use without impacting the chemical isolation layer. The cap will also provide long-term chemical and physical isolation of underlying material from the lake and will resist erosive forces such as wind/wave-generated currents, tributary and other inflows, and ice. Capping, Dredging, and Habitat Restoration Detailed technical evaluations demonstrate that capping will be effective in Onondaga Lake. Sediment caps are a proven technology and have been implemented at numerous sediment remediation sites, including the Fox River in Wisconsin, the St. Louis River Interlake Duluth Tar site in Minnesota, and Commencement Bay in Washington.

In the littoral (shallow) zone of Onondaga Lake, the cap will include the following layers: habitat, erosion protection, and chemical isolation layers. The cap will also include an allowance for mixing of the bottom of the chemical isolation layer with underlying sediment. The different layers will provide long-term protection of human health and the environment, and will ensure that goals are met for habitat restoration, erosion protection and chemical isolation. The design team performed detailed evaluations to ensure each layer meets the remedial goals and is designed to withstand expected conditions in the lake. The evaluations include the following:

  • Extensive laboratory bench-scale analysis
  • State-of-the-science numerical and computer modeling designed to conservatively predict long-term effectiveness
  • Evaluation of capping successes and lessons learned at other remediation sites
  • Evaluation of post-remediation habitat considerations and
  • Continuous consultation with national and local experts

The total thickness of the cap includes the habitat layer, erosion layer, and chemical isolation layer, as well as the mixing layer. As part of the habitat restoration goal, areas will be developed near the mouth of Ninemile Creek where floating aquatic plants (such as lily-pads) will thrive.

Onondaga Lake Capping, Dredging, Habitat and Profundal Zone (SMU 8) Final Design- March 2012

Onondaga Lake Capping, Dredging, Habitat and Profundal Zone (SMU 8) Final Design- March 2012, Text and Appendix A, (PDF) (225 pages, 4.4mB)

Appendix B and C (PDF) (213 pages, 4.2 mB)

Appendix D (PDF) (93 pages, 1.9 mB)

Appendix E 1 (PDF) (100 pages, 3.6 mB)

Appendix E 2 and F (PDF) (96 pages, 4.0 mB)

Appendix J, K and L (PDF) (138 pages, 2.8 mB)

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