East Branch Channel and Regional Water Quality Facility at Black Arroyo Dam
The East Branch Channel serves as the outfall for a 200 acre watershed located in the southern portion of the City of Rio Rancho.
This segment of the channel, meandering through the newly developed Cabezon Communities with an ultimate outfall to the Black Arroyo Dam, is approximately 9530 LF in length and is designed to convey a peak discharge of 3750 cfs. The channel discharges to a 44 acre-foot water quality facility located in the Black Arroyo Dam.
The design incorporated landform topography resembling a valley environment with landscaped floodplain. The water quality facililty was strategically located to treat flows from both the east and west branches of the Black Arroyo, reducing floatable and suspended solids and sediment discharges below Black Arroyo Dam, and ultimately to the Rio Grande.
The channel was designed with the bank full elevation at the 100 year water surface elevation with a three foot freeboard integrated into the construction on the edge of the 150 foot right of way. The section minimized the footprint of the channel to allow for a sinuous channel alignment with room to accommodate multi-use facilities including plazas, and bike and pedestrian facilities tying this created passive open space into the surrounding community. Tinted Shotcrete was used to "soften the edges" of the lined portion of the channel and provide a more natural feel for the open space users.
The creative design of the water quality structure using large diameter inclined pipes allows for large volume treatment for two significant watersheds. This project was completed in 2009, and was a 2011 Engineering Excellence Award Winner in the Water and Stormwater category, from the American Council of Engineering Companies.
After construction of the water quality facility, but before the landscaping was complete, the water quality elements were already working properly, as is demonstrated in the picture below, taken during a rainstorm:
(All photos link to larger photos for greater detail.)