St. Charles, Missouri

Client: City of St. Charles

Terra Technologies was asked by the City of St. Charles to design stream bank stabilization measures adjacent to the residence at 145 College Drive in order to prevent potential property damage. The project area is an approximately 300 linear foot long segment of Boschert Creek which includes a roughly 100 linear foot long portion of the stream bank immediately behind the house.

Upstream development has been increasing the volume of storm flows in the stream and the stream banks have been eroding as a result. The homeowner had created several improvised erosion control structures that were intended to stabilize the banks of Boschert Creek adjacent to their house but formally engineered structures were required to successfully protect the residence from future stream bank migration.

Terra Technologies took a biotechnical engineering approach to bank stabilization and considered the geomorphic stream characteristics within the subject area, the hydraulics and hydrology of Boschert Creek, the watershed conditions, and our previous experience on similar stream systems. A geotechnical soils analysis determined that there was very little risk of significant slope instability that could result in large bank failures would threaten the home. As a result, the house could be protected by bank stabilization alone. The design approach consisted of a combination of toe armoring, grade control, bank stabilization, and ecological restoration. Gabion baskets will be used to stabilize the stream toe at its present location, angular rock weirs will provide grade control, and high tensile turf reinforcement matrixes, erosion control blankets and the roots of native vegetation will stabilize the stream bank slopes.

In addition to the design of the project, Terra Technologies guided the City of St. Charles through the Clean Water Act Section 404 and 401 permitting process necessary to authorize any bank stabilization activity. Hydraulic analyses were also performed in order to determine that the project would not increase the 100-year flood water elevation as the project is within the FEMA regulatory floodplain.

Construction of the project occurred in 2010.