SUPPLY IRRIGATION DIVERSION STRUCTURE
The Supply Irrigating Ditch Company diversion structure was a multipurpose project on the St. Vrain Creek. S2o was hired by the ditch company to design a diversion dam that maintained the ditch company’s decreed flow, facilitated fish passage, and created recreational amenities for other users on the St. Vrain Creek.
Historically, the structure was a barely noticeable, at-grade concrete dam. Flooding in September, 2013 caused significant erosion downstream of the structure, degrading the channel to the extent that a new at-grade diversion structure could not be built.
S2o used it’s creative innovation in multi-purpose river engineering to design a grouted rock ramp structure which ensured that the ditch company’s decreed flow was diverted to the headgates, and provided added benefits to the fish and the recreational users. The structure was designed to facilitate fish passage at a variety of flows. The structure included a low flow fish passage notch, as well as designed interstitial spaces. This was created by holding grout back from the surface of the rock on the low, medium and high flow tiers of the structure. The design of the structure also promoted recreation at the site; the hydraulic conditions across the grouted rock ramp and in the tail water pool were designed in the same manner as a whitewater park structure, thus allowing the water not diverted down the ditch inlet to be enjoyed by recreational users.