C+S January 2020 Vol. 6 Issue 1 (web)

Rocky Mountain Redo Hammered by a Major Flood Earlier in the Decade, Denver Decided to do Some Digging. By Sam Stevens

Severe flooding in Colorado caused the loss of lives, destruction of property and the evacuation of more than 11,000 people in 2013. Fol- lowing this and numerous other instances of flooding, the City and County of Denver committed to an ambitious, $298 million stormwater infrastructure initiative – Platte to Park Hill: Stormwater Systems Proj- ect. The coordinated and community-led approach consists of a series of engineering-focused projects that will address flood protection in northeast Denver neighborhoods. Denver’s Montclair Basin, which encompasses the area affected, expe- riences a high flood risk given it lacked an adequate drainage system and is the City’s largest watershed basin. It is also challenged from a water treatment perspective, with no open waterway to allow natural or man-made facilities to address water quality. Stormwater modeling and evidence from previous storms shows that during moderate to large storm events, the existing pipe systems reached capacity quickly and the excess runoff is carried into neighborhoods at depths of three feet or more – causing a many issues for these at-risk communities. In order to address these flooding and environmental issues, as well as improve community amenities, multilayered goals for the project were established early, including providing critical flood protection, improv- ing water quality, increasing neighborhood connectivity, enhancing public spaces, and upgrading infrastructure with green elements. The three projects are currently underway with expected completion of the water treatment elements by Fall 2019 and the entire project by the end of 2020. The projects include: • City Park Golf Course Redesign • 39th Avenue Greenway and Open Channel • Globeville Landing Outfall and Park Integrating a 200-acre-foot detention basin into an urban golf course To begin, the City knew it needed to uncover existing storm canals and drainageways that had been buried under 150 years of urban de- velopment, forcing stormwater into pipes. The “daylighting” of buried channels started at the golf course — cutting through pavement and re- engineering old streams and canals to ultimately create over a mile and a half of naturalistic riparian corridors across the three projects – and allowing the team to create natural bioswales throughout. The first part of this takes place at City Park Golf Course, where 800 linear feet of brick pipe installed in the early 1900s was removed, opening up the system to a 1,200-linear foot meandering stream. The stream was then seamlessly integrated into the golf course – control- ling stormwater and enhancing playability of the course. A trash vault

Photo: City and County of Denver

was also installed offline of the storm system, intended to collect debris picked up by stormwater during rainfall events, and up to 2,200 cubic feet of trash prior to emptying. Another essential part of the course redesign was the inclusion of a 200-acre-foot detention basin. Golf courses have a proven track record of providing neighboring communities with effective water quality and flood control protection and integrating stormwater detention basins into golf courses allows the course to capture and temporarily hold floodwater, slowly releasing it over time. The new regional trash vault, forebay and wetland channel form the first treatment train in the re-engineered Montclair Basin, enhancing the quality of the water as its conveyed to the South Platte River. Precast, reinforced concrete boxes were installed underground on both sides of the greenway, connecting the overall system and allowing for future extension further into the basin. Photo: City and County of Denver


csengineermag.com january 2020

Made with FlippingBook Annual report