The city of Denver's $300 million stormwater diversion project has already generated significant community resistance, from complaints over the sharp hike in stormwater fees needed to finance the plan to protests over the impacts the construction will have on north Denver neighborhoods and the City Park Golf Course to heated debates over who truly benefits from the project.
But as more details of the plan become public, opponents of the Platte to Park Hill Stormwater Systems are increasingly focusing on a little-discussed aspect of the project: the decision to direct storm runoff to the South Platte River through a heavily polluted Superfund site, a process that some fear could expose the river and nearby neighborhoods to a toxic brew of contaminants from arsenic-laced groundwater and a long-buried landfill.
"This is authentically nuts," says civil engineer Adrian Brown, who's raised questions with city engineers about the viability of the storm runoff outfall design. "If this thing fails, it's just going to deposit the whole landfill into the river."
Public works officials say the project is safe and will actually improve river quality. They have touted Platte to Park Hill (or "P2PH") as a necessary fix for long-festering drainage problems in the northeast part of the city — water that flows north and west from Fairmount Cemetery through the Montclair, Park Hill, Cole and Whittier neighborhoods to Elyria, Swansea, Globeville and ultimately the South Platte River. Officials have stressed that some of the city's poorest neighborhoods will benefit from the improvements, which include a fifteen-block channel along East 39th Avenue, an expanded outfall area at Globeville Landing Park, and a thirty-acre detention "pond" at the golf course, which won't fill up except in the worst storms.
But residents in the affected areas have argued that the primary beneficiary of the improvements appears to be not the neighborhoods south of the 39th Avenue channel, but the controversial I-70 expansion through east Denver planned by the Colorado Department of Transportation, which is helping to fund the drainage work. The project also offers flood relief for industrial areas flanking the highway and targeted for future development, as well as for one of Mayor Michael Hancock’s legacy projects: a billion-dollar makeover of the National Western Complex.
Community groups and the Sierra Club have filed a federal lawsuit against the EPA over the I-70 project. Another lawsuit is challenging the city's right to turn its premiere golf course into a detention area, which would involve regrading the course, relocating the clubhouse, and removing more than 200 trees. But in many ways, the final component of the P2PH plan — getting the runoff safely into the river — may be the most challenging and environmentally complex engineering piece of all.
The plan calls for greatly expanding an existing drainage channel at Globeville Landing Park in order to convey the runoff to the river. Brown believes that's the wrong place to be sending such a tremendous volume of water — as much as 3,750 cubic feet per second in a hundred-year storm event. The outfall is located within what's known as Operable Unit 2 of the Vasquez Boulevard/I-70 Superfund site, a four-square-mile area loaded with chemicals, metals and other contaminants from smelter operations many decades ago. Although residential properties in the area went through a lengthy process of soil decontamination, part of the outfall will be on top of a landfill that contains construction debris and a small amount of asbestos — and groundwater that far exceeds stream standards for arsenic, lead, cadmium and several other contaminants.
"It's not the Rocky Mountain Arsenal, but it's metals and other meaningful contaminants," observes Brown, who's worked on numerous groundwater cleanup projects in several countries. "We shouldn't be letting them loose."
The final design report for the environmental components of the Globeville Landing Outfall Project — GLOP, for short — calls for removal and off-site disposal of some waste materials in the landfill. During the construction phase, the site will also have to be "dewatered," meaning the current water table might have to be lowered by up to ten feet, requiring treatment and disposal of contaminated groundwater. Brown notes that the city has obtained a permit allowing it to discharge GLOP effluent into the river with concentrations of arsenic, zinc, sulfates and hazardous chlorinated hydrocarbons far in excess of stream standards. For example, he likens the project's allowable level of zinc to that found in acid mine drainage. The rationale for such discharge is that the dewatering flow is far exceeded by the river flow, which will dilute the contaminants to an acceptable level — but Brown believes the river will be badly degraded during the process.
"For the city to be proposing to dump dirty water into the system on our behalf is just unreal," he says. "We're killing our own freaking river, when you could spend a few more bucks per thousand gallons to do it right. I think it's outrageous."
In a written response, Denver Department of Public Works planners say that the treated groundwater discharge will not degrade river water quality, and that the monitoring of the project will include "toxicity testing to protect sensitive aquatic species." They maintain that the project will improve water quality by reducing the concentration of contaminants entering the South Platte River through stormwater runoff: "The open channel design...along with other open channel and detention features planned in the larger Platte to Park Hill project, will help capture pollutants from the Montclair Creek drainage basin prior to discharge to the South Platte River. The project is part of the City’s efforts to improve water quality, to make the South Platte River a more valuable amenity to the City, and to promote active, healthy lifestyles for the City’s residents."
The final design report estimates the cost of removing some landfill materials, dewatering and construction of the outfall at around $20 million. That includes the cost of installing special compressed-gravel columns to support the outfall and an impermeable barrier system to keep the groundwater from contaminating surface water (and vice versa). Brown has questioned whether the design can truly withstand a hundred-year storm, with flow rates at twenty times the normal flow of the South Platte. "There's no ability to hold this in place," he says. "If the trash around it washes away, then you've got nothing."
The city's engineers disagree. The actual outlet structure will be founded on native soil or bedrock, not the shifting landfill material; portions of the channel liner and walls to be constructed in what is now part of the Coliseum parking lot (and which lies over the landfill) "will be supported by soil that will be stabilized using stone columns." The average flow in the channel should be relatively low, they insist, with minimal risk of eroding the structure or its liner system; additional improvements to the river bank should make the entire area more stable than it is now.
Critics of the project, though, have objected to the lack of public participation. Although EPA guidelines call for a "community involvement plan" when Superfund removal activities are initiated, there's been no such engagement concerning the GLOP construction. Neighborhood activist Christine O'Connor says the city managed to have the project designated by EPA as a "time critical removal action," which allowed the public participation process to be truncated. Such a designation is intended to "protect public health and safety," but O'Connor suggests the most time-critical element of GLOP is the intergovernmental agreement the city entered into with CDOT to get the drainage work done ahead of the highway expansion, or face a fine of $5,000 a day in damages. "As best as I can tell, the thing that was critical was the IGA said they had to get this done so they wouldn't get fined," she notes.
Construction on the outfall is expected to begin soon. Brown has an alternative proposal for solving Denver's stormwater problems, one that relies largely on residents retaining storm runoff on their property for a few hours with modest dams, until the water can percolate into the soil. He says he got a "lukewarm reception" to the idea from city planners. "There's no way in hell that they're going to invite the citizens of Denver to do this," he says. "But every citizen could put in their own stormwater protection system for peanuts."
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