Evaluation of Alternative Options for Freshwater Emergent Wetland Compensation at Naval Air Station Patuxent River

Abstract

At Naval Air Station (NAS) Patuxent River, 3.6 acres of freshwater emergent marsh were filled as part of a remedial action. A qualitative functional analysis indicated that flood flow alteration, sediment/toxicant retention, and nutrient removal/transformation were the primary functions of the filled wetland. The compensation evaluation included consideration of a tidal, brackish wetland restoration; a constructed freshwater marsh; and a stream restoration. The project, which required the preparation of conceptual level designs and costs, involved wetland design, water balance modeling, flow control engineering, and a watershed hydrologic model. The scaling of alternative mitigation options for the impacted wetlands was based on lost ecological services. The selection of the preferred alternative centered around compatibility with the NAS Patuxent River mission, balancing service equivalency, the need for extra service credit for future liabilities, cost, and design feasibility. This approach will enable the Navy to obtain full credit for water quality services created as part of the compensation package.