Lake Dredging: The Ultimate Face-Lift

Dredging, or lake deepening, has been described as the “ultimate face-lift.” By why is that?

During a dredging project, not only are accumulated sediments removed, but the accumulated nutrients such as phosphorus and nitrogen are removed as well. This prevents the nutrients from recycling back into the water column, fueling algae blooms and excessive plant growth. Aquatic weeds that may have rooted in the shallow water as sediments accumulated are removed and any invasive species can  be eradicated. If the lake is drawn down during dredging, shoreline stabilization and drainage improvements can be more easily accomplished.

Lake dredging can be accomplished in one of two ways: mechanical dredging where the lake is drawn down and heavy machinery is used to manually scoop out the sediment, and hydraulic dredging where a dredging barge equipped with a cutter head and suction hose is used to dislodge and suck up the accumulated sediment and pump it to a disposal basin on shore. Sediment disposal options must be considered carefully as hydraulic dredging requires adequate area for a sediment dewatering basin close to the lakeshore. Even if mechanical dredging is employed, sediments must be trucked to an adequate disposal location. This can prove tricky if the sediments are contaminated. For a more detailed discussion of lake dredging, please consult the Pennsylvania Lake Management Society's Lake Management Handbook. 

Fall is a good time to begin dredging projects so that any potential adverse impacts to fish and wildlife species are minimized. Most species have completed their breeding process by that time and winter hibernation has not yet begun. However, it is important to keep in mind that planning for a dredging project may take up to a year. First, a dredging feasibility study must be completed that includes sediment testing, a bathymetric survey, and disposal site determinations. Extensive permitting is typically required before the design phase can begin.

Although dredging may be necessary to remove accumulated sediments from a lake, dredging is not the right solution for all lake problems. Dredging is very expensive and funding for dredging projects is not easily obtained without extensive water quality and watershed surveys. If the source or sources of sediment entering the lake from the surrounding watershed are not addressed, the sedimentation will continue to occur and the lake will need to be dredged again. It is preferable to complete a watershed survey of nonpoint source problem areas and develop a watershed management plan to determine other appropriate lake and watershed best management practices (BMPs) before dredging a lake.

F. X. Browne, Inc. has extensive experience in designing dredging projects, watershed assessments, and BMP design. Our Lake Lily dredging project in Cape May, NJ uncovered freshwater springs and led to the return of the Lake’s namesake white water lilies. Visit the F. X. Browne, Inc. website to read an article about the project.