High Line Canal Crossings & Overflow Structure for Solstice Development
High Line Canal Improvements, Crossings, & Overflow Structure
Douglas County, CO
The High Line Canal is a 71-mile waterway that provides irrigation and recreational uses across Denver and is managed by Denver Water. JR’s proposed civil design for 4,000 LF of the canal with the Solstice residential development included two roadway crossings over the canal, Lake Breeze Drive & Bright Sky Lane. The new bridge crossings span lengths of approximately 80 feet & 60 feet, respectively. An overflow structure along the canal was also incorporated into the design to prevent the canal from overtopping during major storm events. Recreational trails and maintenance access along the canal were incorporated into the design along with existing canal features.
JR Engineering partnered with ERO Resources Corporation to obtain environmental clearances. A Natural Resources Assessment and Level II Historic Resource Documentation was completed to observe the existing biological resources and identify potential historical impacts associated with the project. The historic resource documentation and public outreach were completed to resolve the possible “adverse effect” of construction near and within the canal identified by the Army Corps and SHPO.
Bridge Structure Selection & Design
A hydraulic analysis was performed on the channel during the design of the bridges & overflow structure. Proposed topography was used to determine the characteristics of the ultimate canal conditions. HEC–RAS & SWMM software was utilized to determine the water surface elevations within the canal at a design flow rate of 600 cfs per the High Line Canal Stormwater Operations Master Plan. JR Engineering worked with San Engineering LLC to create a bridge structure that would not interrupt flows in the canal and provide adequate structural capacity for the given spans. Understanding the above constraints, 32” H x 58” W pre-stressed concrete box girders were selected.
Overflow Structure Design & Hydraulics
Established on the hydraulic analysis of the High Line Canal Operational model, JR Engineering integrated an overflow structure to release any overtopping flow from the canal and prevent flooding of the Solstice Development. The structure was designed to capture runoff that might otherwise overtop the canal and safely route it into the adjacent tributary. The inlet structure is a 4’ x 60’ area inlet built into the slope paving of the canal bank. In the event this inlet capacity is exceeded, there is also an overflow spillway that will route excess into the existing tributary and ultimately Chatfield Reservoir.