From The Denver Post (Bruce Finley):
Denver drainage carries contaminants into waterways at levels up to 137 times higher than federal safety limit
Colorado health officials this week declared water quality in the South Platte River as it flows through Denver highly deficient, pointing to E.coli contamination at levels up to 137 times higher than a federal safety limit.
This intestinal bacteria indicates fecal matter and other pollution from runoff after melting snow and rain sweeps Denver pollution through drainage pipes into the river. To deal with the problem, the Colorado Department of Public Health and the Environment has imposed, in a permit taking effect next month, stricter requirements for managing runoff water pollution.
But Denver officials are fighting those requirements and twice petitioned the state health department to relax the new permit.
“What the new requirements do is drastically increase the amount of expensive system maintenance beyond what could make a meaningful impact on E.coli concentrations,” city spokeswoman Nancy Kuhn said.
Colorado public health officials last month rejected Denver’s latest appeal. They issued a statement standing by their demands for the city to reduce its water pollution, saying the agency hopes to avoid litigation.
A more aggressive approach is required, state health officials said in the statement, “because the South Platte remains in bad shape for pathogens.”
Denver officials told The Denver Post on Wednesday “no lawsuit has been filed” challenging the permit in state court and that they are “having conversations with the state on five or so new requirements with the hope of reaching compromise.”
“Denver’s storm sewer system is a clear part of the problem,” CDPHE permitting officials said in an email. When inspectors in 2019 sampled water flowing out of city drainage “outfall” pipes into the South Platte, they detected E.coli at levels as high as 1,970 cfu from one pipe and 8,400 cfu from another, state data shows…
“Denver has never opposed the numeric limit of 126 cfu per 100 milliliters,” [Nancy Kuhn] said, but opposes “the specific measures that CDPHE is mandating to achieve that limit.”
A consultant analyzing Denver stormwater runoff in 2018 proposed, in a document included in a 419-page state fact sheet accompanying the new permit, a comprehensive effort to slow down drainage flows, treating runoff water as a useful resource for re-greening in a semi-arid area. He recommended wide use of low-cost measures such as flattening crowned streets, installing small dams in alleys to re-direct culvert-bound gushing runoff, and converting sidewalks to “semi-pervious” surfaces that let water sink between stones into the soil.
Denver’s population growth and development boom have worked against greening to improve water quality. Developers have paved over more surfaces, leaving Denver as one of the nation’s most paved-over cities — especially in newly developed areas — sluicing away runoff water at high velocity without removing contaminants.
Denver officials directed contractors at the city’s new Globeville Landing outfall drainage pipe, in a park built over a former toxic dump site, to install an ultraviolet light. This light, city officials say, zaps away more than 90% of E.coli before runoff water reaches the river.
Wild animals such as raccoons in storm sewers add to the fecal pollution contaminating runoff, Kuhn said, and “dog waste that people don’t pick up is a huge problem and a significant source of E.coli.”