Hibernia Brook Restoration & Lake Hudsonia Dam Removal

The Lake Hudsonia Dam was constructed in the early 1900s as part of a scout campground and impounded the headwaters of Hibernia Brook. The lake and dam are owned by Rockaway Township. For years, the Township was trying to determine the best path forward regarding the dam: repair or removal. Around 2010, it was determined that the removal of the dam would create significant wetlands and, therefore, it qualified for NJDEP Wetlands Mitigation Council funding. The removal of Lake Hudsonia Dam was designed in concert with a restoration component, which optimizes environmental benefits to the Hibernia Brook system. Hibernia Brook is a freshwater, non-trout producing, C1 stream (FW2-NTC1). Lake Hudsonia is typically 6 feet deep and likely contributes to elevated water temperatures, due to direct insolation, that is a exported to downstream reaches.

The project benefits include:

• Restoration of a man-made impoundment to a free-flowing stream bordered by riparian floodplain wetland community

• Increased flood storage capacity of the Hibernia Brook corridor

• Improved water quality of C1 stream through enhanced removal of in-stream pollutants by restored riparian floodplain wetland

• Reduction in summer in-stream water temperatures

• Re-creation of stream habitat in the former impoundment

• Restoration of fish passage and movement of other aquatic organisms

• Re-connection of formerly isolated populations and stream habitats upstream and downstream of the dam

As part of the restoration element of this project, the lake bed was reshaped to reestablish a geomorphically appropriate streamchannel, to re-naturalize grades, and to re-establish vegetation. Accumulated sediment was moved within the impoundment and placed along the eastern shoreline, which is nearly vertical along the existing edge of water, to re-naturalize grades and create a gradual transition from the proposed floodplain wetland to the existing surrounding grades. Impounded sediments were sampled and analyzed for NJDEP Soil Remediation Standards (Residential, Non-Residential, and Impact to Groundwater) and determined to be suitable to remain onsite.

The proposed design to remove Hudsonia Lake Dam is focused on the restoration of Hibernia Brook and its floodplain to a native riparian wetland plant community. This restoration project seeks to convert the artificial impoundment of Hibernia Brook into a freshwater wetland complex of emergent and scrub/shrub wetland. Permit applications were simultaneously submitted to the NJDEP LURP for GP 16 and GP 18. In 2021, the project was bid and awarded to a contractor and construction was completed in November 2021, with oversight by Princeton Hydro. The impoundment area will be planted as an emergent wetland community with scattered patches of shrubs in order to stabilize the site. Over time, the site is anticipated to develop into a forested plant community similar in composition to the forested wetlands surrounding the site.