Flooding in the Eastgate subdivision had been a concern for many years with flooding reports dating back to the 1970's and 1980's. In July 2010, a significant storm event caused substantial flooding throughout the area, including structure flooding at nine or more homes. Flooding was caused by both an undersized storm drain system within the neighborhood and high water conditions in the Northeast Drainage Ditch (NEDD), which the storm drain system flows into. The project consisted of two phases: Phase 1 to lower the flood elevation in the NEDD at the location where the subdivision discharged into the NEDD, and Phase 2 to address the storm drain system within the residential area.
The Phase 1 design involved realigning and widening the NEDD to improve conveyance through the channel. The improved channel had a bottom width of 40-feet and an average depth of 6-feet. Cascading gabion baskets were used to dissipate energy, protect against erosion, and trap sediment. The final design included approximately 1,000 feet of gabion-lined channel, 1,500 feet of improved earthen channel, over 600 feet of concrete box culvert, and other pipe improvements. This design included work within a gas main easement for a 24-inch high pressure gas main. The final design lowered flood elevations within the NEDD by as much as 2 feet. The channel realignment of the NEDD included revisions to the existing FEMA floodplain and floodway. Map revisions for this area are currently being conducted by SAI.
The Phase 2 design included improvements to the storm drain system within the subdivision. This consisted of upgrading existing storm culverts and inlet structures throughout the neighborhood that SAI identified as ineffective and the construction of new culverts and inlets in key locations. The final design included over 4,400 feet of concrete pipe, over 600 feet of box culvert, and nearly 30 special high capacity curb inlets.
This project earned a 2014 Top Stormwater and Erosion Control Project award by the Storm Water Solutions Magazine and received special mention in the February 2016 edition of Municipal Sewer & Water Magazine.