St. Peters, Missouri
Client:
City of St. Peters
Terra Technologies was retained by the City of Saint Peters to develop natural stream channel stabilization alternatives to improve water quality discharge through approximately 2,000 lineal foot segment of a tributary to Dardenne Creek. The improvements are located between the Homestead Estates and Crystal Lake Estates residential subdivisions. The section channel loses most of its grade, and the active channel is almost non-existent as the bottom swale turns into more of a wetland than a stream corridor. This has resulted in the accumulation of silt and poor maintenance.
The restoration goal of the project was three-fold: 1) create a geomorphically stable low flow channel capable of sustaining minor sedimentation independent of occlusion, thus improving in-stream aquatic habitat, 2) create a riparian system complete with numerous species of indigenous plant materials, thus improving the aesthetic and conservation value of the ecosystem, while buffering the impact of non-point source residential lawn pollutants, and 3) demonstrate the applicability and functionality of in-stream wetland biological filtration for protection of stream quality from residential and commercial solid waste and chemical pollution.
In order to capture solid waste debris, the design included expanding the in-bank capacity of the stream while protecting the existing low flow channel and corresponding aquatic habitat. The newly formed fluvial accumulation pool and corresponding wetland will allow for de-acceleration of stream velocity, providing a predictable biological filtering location for collection of upstream pollution. This was accomplished through the installation of a V-configuration weir across a portion of relocated stream, in conjunction with a pipe through the weir to allow uninterruptible base flow through the weir. In order to achieve the correct stream physics associated with de-acceleration and solids settling, the stream thalwag was diverted through a curvilinear segment prior to weir obstruction. Along the inside bend, an area was reforested, providing necessary overbank roughness to ensure maintenance of the relocated thalwag.
No less than 60 species of native grasses, wildflowers, wetland plants, shrubs, and tree species were established from local sources of seed and containerized plantings. Modern erosion protection technologies including biodegradable blankets and permanent geotechnical matrices will protect developing plants during periods of large storm events.
The project represents the manipulation of physical, chemical, and biological characteristics of the site with the goal of returning natural/historic functions to a former degraded riparian ecosystem. The project included enhancement of existing aquatic habitat through the biological filtration of both point source and non-point source pollution. Improvements in herbaceous elements along the low flow channel will provide natural rehabilitation of aquatic habitat. The improvements are preserved by the management of a permanent drainage easement through the project area. The project was successfully completed in the spring of 2004 under the direction and field inspection oversight of Terra Technologies. |
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