St. Charles, Missouri
Client: City of St. Charles
Terra Technologies was approached by the City of St. Charles to stabilize rapidly eroding stream banks adjacent to several residences. Two separate areas in the same subdivision were experiencing similar erosion problems.
The main channel of Cole Creek passes through an outer bend immediately adjacent to the residence at 1787 Buckingham Green Court. The nearly vertical stream bank is rapidly eroding and the top of bank is only approximately 25 feet from the house. An outer bend of a tributary to Cole Creek is eroding near 1803 Buckingham Green Court, similarly threatening the residence.
Large gabion basket retaining walls were considered for each of these failing slopes but the geotechnical analyses of the sites showed that both locations had stream banks with low levels of global stability and soils that prohibited the gabion walls from providing sufficient protection against rotational slope failure without having to excavate so far into the bank that the construction of the retaining walls would threaten the stability of the houses. After assessing all of the options, it was determined that soil nail walls with decorative shotcrete faces would be the most appropriate engineering solution. Gabion basket walls will stabilize other nearby stream banks that were not as close to residences and a grade control structure will maintain the current slope of the side tributary to Cole Creek adjacent to 1803 Buckingham Green Court.
Terra Technologies also handled the Clean Water Act Section 404 and 401 permitting for the projects. Additionally, hydraulic analyses were performed in order to determine that the projects would not increase the 100-year flood water elevation as both project areas were within the FEMA regulatory floodplain.
Construction of both projects occurred in 2010.