St. Elizabeths Stream Restoration and Wetland Mitigation, St Elizabeths West Campus, SE, Wash. , DC

The project consists of the work required to regrade and restore approximately 1200 linear feet of stream channel and the construction of approximately 0.15 acres of new forested wetlands.

The proposed stream restoration project includes relocating the origin of the project reach to begin at the proposed 24" Reinforced Concrete Pipe (RCP) upstream.  The existing 24" RCP will be shortened and replaced with a 15" RCP. The remaining length will be daylighted and restored. Both the tributary and mainstem stream resources were designed as stable BA-type channels. Drop pool structures and rock-and-roll cascades have been designed to dissipate energy; maintain stable dimension, pattern, and profile along the stream continuum; and provide stable, structural habitat favorable for aquatic life use. To the greatest extent practicable, natural channel design techniques will be followed. Detailed hydrologic and hydraulic modeling have been used in conjunction with geomorphic assessments as the basis of the proposed design. Native riparian buffer plantings will be installed to augment water quality benefits, restore the forested corridor, and maintain stream bank stability throughout the project area.

Wetland creation is also proposed as part of the project. The proposed wetland system will receive groundwater contributions from existing seeps and springs, as well as direct inputs via rainfall and surface water runoff. Soils will be amended to create suitable substrate for propagation of native, forested and scrub-shrub hydrophytic plants. The wetland system will create a habitat niche inside of the much larger, approximate five-acre stream and buffer restoration corridor.