The goal of the Devins Ditch storm water separation project was to decrease street flooding and remove storm water flow from an existing combination sewer system. The watershed for the project (400 acres) is one of the few in the city that still predominately rural into an urban section of the city. CDP designed one new detention basin and retrofitted an existing basin that are in series to reduce flooding and provide storm sewer and sanitary sewer separation. Both storm water wetlands are hydraulically regulated by a pumping station that diverts the storm water into a nearby drainage ditch. The wetland design incorporated ground water wetlands that were hydraulically connected by meandering E channels. When water levels are low, the meandering channel is visible as it flows in and out of wetland pools, improving habitat for fish and wildlife while treating run-off. Small ephemeral wetlands were built along the edges of the wetland and channel system to provide habitat for frogs, toads, and salamanders to lay their eggs. Zones of shallow water, less than 6-inches deep, were formed to provide habitat for shorebirds such as the spotted sandpiper and killdeer. As the shallow portions of the wetlands dry in summer, the exposed mudflats provide critical feeding sites for migrating birds and unparalleled bird watching opportunities. Additional wetland features included the incorporation of large woody debris. Logs were partially buried throughout the wetland to provide tip-ups and resting placing for wildlife. Large dead trees were installed to create vertical snags, which also provided habitat. Trees and shrubs adapted to growing in moist ground were planted in and around the new wetlands.
- field survey of the project area to locate existing drainage patterns, utilities, trees, and existing channel cross sections.
- detailed hydrologic study of two watersheds
- detailed hydraulic study of two drainage ditches using XP SWMM to compute peak discharges for all flow events
- innovative wetland design that focused on habitat creation and water quality improvement utilizing both groundwater and surface water wetlands
- preparation of final construction plans, easements, specifications, and construction oversite.
- annual wetland monitoring – first report was submitted to KDOW in October 2011