It’s disorienting to look up through a sewer grate from below — but at least the concrete floor of the massive, square-shaped stormwater drainage culvert is bone dry.
Come June, when the system is set to begin operating after project delays, this is the last place you’d want to be during a spring downpour, as several feet of water rushes through the 15-by-12-foot pipe. It will be the final leg of the journey from city streets in northeast Denver to the South Platte River, letting out at Globeville Landing Park.
The box culvert, among the largest in Denver, is part of the $70 million-plus Globeville Landing Outfall project, the first of four main components planned in the city’s largest storm-drainage project of the modern era.
“We’re very proud of what you’re going to see today,” Patrick Riley, a project manager, said as he and other city officials began a media tour Thursday morning. He called the large outfall replacement — and the gargantuan pipes leading to it — a legacy project.
The Platte to Park Hill program, with an estimated $298 million price tag, has proved controversial, not least because some parts involve digging into contaminated soils. The City Park and Park Hill golf courses are being shut down for long periods to allow for regrading that will create stormwater detention areas.
And the entire behemoth has ties to the contentious Interstate 70 expansion project.
The Colorado Department of Transportation is sharing some of the cost because the city’s large new system will divert more storm runoff from the expanded highway. That reduces the scope necessary for CDOT’s planned drainage system for a 2-mile portion that will be lowered into a trench.
During Thursday’s visit, the culvert had not yet been buried. Made up of 5-foot sections that weigh about 48,000 pounds each, it can carry twice the normal summer flow of the South Platte, said Bruce Uhernik, a wastewater engineering supervisor for the city.
The culvert will be fed by an open channel along the East 39th Avenue alignment as well as pipes under Brighton Boulevard. It stretches 560 feet before the bottom drops into a bay that feeds into three smaller, side-by-side culverts that will carry the water under the Denver Coliseum parking lot.
And then the water will emerge into a natural-filtration channel in the park, before flowing into the river.
