Climate change was incorporated into the design by adding one foot of height to the breakwater. Given the current data on water rise, the extra foot should be sufficient over the next several decades. More information is available at http://www.corpsclimate.us/ccaceslcurves.cfm regarding Sea Level Rise.

Construction of the breakwater and stone sill will not have significant impacts on boating and fishing. There will still be able plenty of areas to fish and boat in and around Dyke Marsh. In addition, the breakwater will not impede boating in the existing navigation channel. National Park Service will mark the waterward end of the breakwater with lights and signs to caution boaters.  

Dyke Marsh is viewed as a national treasure that holds extensive value not only for plants and animals, but for its recreational, educational and cultural purposes. It is estimated that the southern marsh has existed for 2,200 years, and the northern marsh has existed for 500 years. Dyke Marsh is one of the largest remaining freshwater tidal wetlands in the Washington metropolitan area.

Dyke Marsh provides a storm buffer for the George Washington Memorial Parkway, a natural filter for the Potomac River, and habitat for a variety of plants and wildlife, including six state-listed species of special concern (two bird species and four plant species).

It is critical to act now to protect and restore Dyke Marsh. Approximately 270 acres of marshland were damaged from the 1940s to the 1970s through the dredging of sand and gravel. In 2009, National Park Service partnered with U.S. Geological Survey to investigate the state of Dyke Marsh. USGS found that the post-mined marsh is rapidly shrinking as a result of erosion caused primarily by storm waves driven northward up the Potomac River. Erosion in the marsh averages between 6 and 8 feet per year. USGS found that without intervention, this unique ecosystem would be entirely lost by 2035. 

There will be temporary impacts to water quality due to the short-term disturbance/turbidity in the water from the construction efforts. Construction will be conducted to minimize these impacts as much as possible, such as careful placement of marine mattresses. After the project has been completed, it will assist in nutrient reduction in the Potomac River and positively impact long-term water quality in the area.

This is a National Park Service, George Washington Memorial Parkway, project that the U.S. Army Corps of Engineers is authorized to design and construct through the Interagency and International Support program. NPS is providing funding to the Corps through the Hurricane Sandy Mitigation Program. 

The cost to construct the recommended project outlined within the Environmental Impact Statement (EIS) far exceeds National Park Service's available funding. The U.S. Army Corps of Engineers worked with NPS to design a project based on the recommended project that still meets intended objectives and fits within the existing budget.

This design has been set up to allow for expandability. Remaining construction work that cannot be completed as part of this effort could be identified as future phases of the project to be constructed as more NPS funding becomes available.

The breakwater is the most critical aspect of the project and will help protect the existing marsh from erosion and will help reestablish the marsh’s ability to regenerate naturally.

The ecological benefits of preserving Dyke Marsh outweigh the impacts to the submerged aquatic vegetation (SAV) at the site.

While an analysis shows that construction will result in permanent and temporary impacts to the existing SAV within and adjacent to the footprint of the proposed project, the SAV consists primarily of Hydrilla verticillata, which is an invasive (non-native) species and a federally-listed noxious weed that has been shown to displace native submerged plants. There are numerous NPS policies and federal executive orders and laws that direct federal agencies to remove or protect against exotic and invasive species, hydrilla being one of them.  

Dyke Marsh is viewed as a national treasure that holds extensive value not only for plants and animals, but for its recreational, educational and cultural purposes. Dyke Marsh is one of the best studied wetlands in the U.S., and is one of the largest cattail marshes in the national park system. Dyke Marsh provides a storm buffer for the George Washington Memorial Parkway, a natural filter for the Potomac River, and habitat for a variety of plants and wildlife including six state-listed species of special concern (two bird species and four plant species).