Westfield, Ma – The Connecticut Society of Civil Engineers (CSCE) presented Tighe & Bond with the 2010 Water Resources Award for an innovative engineering achievement that has significantly reduced flooding in the neighborhood located downstream of Olmstead Pond in Norwalk, CT. Presentation of the award took place at the Third Annual Achievement in Civil Engineering (ACE) Awards Program on May 11 at the Aqua Turf Club in Southington, Connecticut.
As part of a citywide drainage studies to address chronic flooding problems in Norwalk, Tighe & Bond recommended modifications to convert an existing manmade pond into a dry basin to increase its stormwater detention capacity. This solution was the most viable and cost-effective alternative to reduce the magnitude and frequency of flooding in the neighborhood.
Prior to the pond modifications, the neighborhood regularly incurred extensive street, building and yard flooding during rainy periods. According to Michael M. Yeosock, P.E., Senior Engineer for the Norwalk Department of Public Works, “This project appears to have worked well and has certainly helped to reduce flooding in the area. It was a difficult project to undertake, especially due to its impact on so many residential properties.”
Tighe & Bond engineering techniques included excavating the pond’s accumulated sediments, raising the embankment crest elevation, and providing a multi-level outlet control structure to regulate water discharges from the basin. A meandering stream channel now flows through the former pond basin and is immediately bounded by shrubs to help shade surface waters. Beyond the stream banks, a broad wet meadow floodplain was created within the footprint of the former pond.
Tighe & Bond also used bioengineering restoration methods within the basin to establish a natural regime including the installation of the pilot stream channel with a sediment forebay at the headwaters, and a stilling basin at the outlet structure. The channel banks were formed using coconut fiber coir logs and then planted the banks with native wetland shrub species to encourage natural vegetation that resists erosion. The floodplain which is subject to intermittent inundation, was restored using sediments excavated from the pond which were then seeded with a wetlands vegetation mixture and planted with interspersed native wetland shrub species. The success of the Olmstead Pond Modifications continues to advance acceptance of bioengineering for civil engineering construction, while also promoting a more sustainable environment.
Tighe & Bond kept in close coordination and communication with the City of Norwalk throughout the study, design and construction phases of this project. According to Richard Linnartz, Principal Engineer for the Norwalk Department of Public Works, “Our rapport with Tighe & Bond on this project was seamless; it was if they were an extension of my own department.” He adds, “The City of Norwalk has benefitted from Tighe & Bond’s services on a variety of projects. They have been very responsive to our needs and complete work within allocated time and budgets.”