Century-Old Storm Sewer Discovery Halts Denver Construction, Costs Millions

Denver’s $149 million, 3.5-year 16th Street Improvement Project was halted in May 2022 after construction crews unearthed a centuries-old brick storm sewer, discovered to be undocumented in city records.

Significant Delays and Cost Overruns

The discovery triggered a 301-day delay and an additional $18 million in costs, a figure the Denver City Council did not learn of until after it had been paid, according to a recent report by the City of Denver Auditor’s Office.

Extensive Brick System Remains Unmapped

Denver still possesses over 69 miles of brick storm sewers, constructed between 1880 and 1937 and designated for National Register of Historic Places listing in February 2013. Despite this, a comprehensive map of their locations does not exist, leaving the exact location of many sewers unknown.

Project Oversight and Resolution

The DOTI consulted with Colorado’s State Historic Preservation Office during the project’s environmental assessment, but the brick sewer system was initially not identified as a ‘historic resource.’ Following the discovery, work ceased, and a 30-day review was required. The city initially argued that all utility risk was on PCL, but ultimately settled for an $18 million compensation due to the lack of mention of potential brick sewers in the original project proposal.