EXECUTIVE SUMMARY
The New Orleans Sewerage and Water Board has proposed restoring degraded cypress swamp— including the Bayou Bienvenue Wetland Triangle— by diverting the treatment plant’s partially treated effluent into the wetland. This practice, known as wastewater assimilation, may aid the restoration of the degraded swamp by increasing inputs of nutrients and fresh water. Potential benefits of this proposed project include increased cypress growth, decreased operating costs for the East Bank Sewage Treatment Plant, and a restored environmental resource for area residents.
The surrounding community, the Lower Ninth Ward of New Orleans, is still recovering from the devastation and chaos caused by Hurricane Katrina in 2005. Current awareness of potential protective benefits from intact wetlands and fond memories of the cypress swamp of earlier years have earned the Bayou Bienvenue Wetland Triangle restoration a place in the community’s ambitious, long-term, sustainable recovery plans.
For Lower Ninth Ward residents this project is a source of hope and inspiration, but there are serious obstacles and numerous uncertainties. The New Orleans Sewerage and Water Board is evaluating several locations as potential sites for this wastewater assimilation project; it is possible that the Bayou Bienvenue Wetland Triangle may not be chosen as one of these sites, or that its conditions may even make it unsuitable for consideration.
In order to better understand the Bayou Bienvenue Wetland Triangle’s potential for restoration, the Holy Cross Neighborhood Association of the Lower Ninth Ward requested that Water Resources Management students from the University of Wisconsin–Madison study the wetland and share their findings with the community. In the summer of 2007, the Water Resources Management group conducted an environmental characterization of the Bayou Bienvenue Wetland Triangle, researched wastewater assimilation techniques, and examined the post-Katrina social context surrounding this restoration proposal.
The Bayou Bienvenue Wetland Triangle is a 427- acre body of open water with an average depth of about two feet, and approximately one foot daily variation in response to tidal forces. The wetland’s primary water sources and sinks are currently tideinduced surface water flow into and out of the Bayou Bienvenue Wetland Triangle. Through the years, engineering projects have dramatically altered the natural hydrology of the area, resulting in decreased sediment, nutrient, and freshwater input, and enabling a gradual intrusion of salt water.
The Bayou Bienvenue Wetland Triangle supports a functioning ecosystem, although it contrasts starkly with the former cypress swamp. A sole surviving cypress tree exists in the extreme northwestern corner of the Bayou Bienvenue Wetland Triangle. The wetland is now open water dominated by submerged aquatic vegetation and dotted with stumps of dead cypress trees. Surprisingly, the standing stumps and submerged snags of former cypress trees still provide habitat for a variety of aquatic life and waterfowl.
Based on the Bayou Bienvenue Wetland Triangle’s current (2007) environmental conditions, it is unlikely that the area can be restored to a sustainable cypress swamp solely by means of wastewater assimilation. However, supplementing this approach with a secondary supply of sediment to the Bayou Bienvenue Wetland Triangle would increase the probability of success; the current water depth and insufficient exposure of sediment to oxygen due to lack of water level fluctuation are critical obstacles to restoring a self-sustaining cypress community. Salinity levels are higher than the optimal range for reintroduction of cypress trees. The impending closure of the Mississippi River-Gulf Outlet may slow, and perhaps reverse, the trend of increasing salinity.