A tiny creek weaving through Northeast Baltimore has cost the city a lot of money.

In part, the city alleges in a lawsuit filed last month, that’s due to the oversights and errors of a contractor it hired over a decade ago to plan the environmental engineering for the stream known as Chinquapin Run — shoddy work Mayor Brandon Scott’s administration now says has cost the city nearly $14 million extra.

The work on Chinquapin Run, a tributary of Northeast Baltimore’s Herring Run, is required under a long-standing U.S. Environmental Protection Agency mandate that the city address backups and overflows in the sprawling system of pipes that collect its sewage and deliver it to wastewater treatment plants.

In this case, the city tried to kill two birds with one stone. Since these sewer lines often run under low-lying areas like creek beds, repair on sewage lines sometimes happens alongside work to rehabilitate and restore tributaries like Chinquapin to control stormwater runoff — another requirement under state environmental regulations.

But the work at Chinquapin Run didn’t go according to plan, the city says, in part because of sloppy work by the consultant it hired to scope out the area, the global firm AECOM Technical Services. The project itself dates to 2011, when the city hired a company for the planning called URS Corp., which was acquired three years later by AECOM.

In its suit against AECOM, the city cites more than a dozen problems with the design AECOM ultimately delivered.

Among them, according to the lawsuit, AECOM gave bad estimates for the types and amount of rock the city’s contractor would have to excavate to install a sewer line, misinformation the city says cost it an additional $6 million. The company failed to identify five tributaries feeding into Chinquapin Run that needed work to control erosion and sediment flows, the lawsuit adds, resulting in a citation by environmental regulators, and its worst case predictions for storm scenarios were off-base, leading to nearly half-a-million dollars in damage and recalibration work when a bad storm came through. The tally of trees AECOM said needed to be removed to make way for the work wasn’t even close: It undercounted by more than 700.

In all, the city says its contractor billed an unexpected $13.8 million for the additional work — a cost overrun the Scott administration argues was AECOM’s fault.

On top of the work on Chinquapin Run, AECOM was coordinating the city’s work on its sewage system consent decree. Because the company failed to give notice about some of the challenges affecting the consent decree response, the city says, it couldn’t give federal officials proper warning that it was going to miss its deadlines, causing it to rack up $2.5 million in fines under the EPA consent decree.

AECOM, which has not yet responded in court, also did not respond to requests for comment on the city’s claims.

An outside attorney representing Baltimore in its case against AECOM deferred comment to the city’s Department of Public Works, which declined to elaborate on the lawsuit.

The company that Baltimore hired to conduct the work on Chinquapin Run and billed the city for these unanticipated costs, New Jersey-based Spiniello, also did not respond to requests for comment.

Among environmentalists, stream restoration is already a divisive practice, in part for some of the same issues highlighted in the city’s lawsuit.

When storms roll into Baltimore, heavy rains can overpower streams like Chinquapin or Herring runs, flushing sediment and other pollutants toward the Chesapeake Bay. By reengineering stream banks and deploying stone or earth constructions to direct water flow, restoration projects are designed to control stormwater, slow currents and prevent these pollutants from washing downstream.

But projects often don’t work as intended.

Some environmentalists point out that the work can be unreliable at best in cities, where blacktop surfaces like roads and parking lots funnel huge amounts of stormwater into urban waterways. They argue that the work can be costly and sometimes wasteful: In some cases, big floods can wash away expensive engineering jobs overnight. Some stream restoration projects require cutting down trees to allow access to the waterway, a step that became controversial in an ongoing $5.5 million project on part of Herring Run north of where it meets Chinquapin.

For some environmentalists, the city’s lawsuit is just the latest in a history of frustrations — both with the city’s efforts to comply with its federal sewer line mandates and with a proliferation of stream restoration projects.

Alice Volpitta, Baltimore Harbor Waterkeeper for the nonprofit Blue Water Baltimore, said the revelations of the new lawsuit are both infuriating and validating. Progress on Chinquapin Run and on the city’s decades-old consent decree always have felt slow, she said, and this lawsuit helps explain why.

“It constantly feels like we’re being undercut,” said Volpitta, who predicts that the city and federal regulators will need to revise the 2032 deadline on their sewer system consent decree, a step they already took to push the end date back from 2016. “We’re undercutting ourselves, and we cannot resolve the problems quickly enough.”

Volpitta pointed out that her organization cited the work on Chinquapin Run five years ago as a case study in Baltimore’s struggles to get a handle on its stormwater problems.

In the 2019 report, Blue Water expressed frustration that the city removed 70 trees the nonprofit had planted along the Chinquapin to access the sewer line and stream restoration project. In addition to undoing work Blue Water had performed over close to six years, the removal of those trees weakened the stream bank, the report argued.

This was outlined as the primary example in a section of the Blue Water report titled, “Communication Breakdowns.”

Baltimore Banner reporter Giacomo Bologna also contributed to this story.

Correction: A previous version of this story incorrectly described the location of ongoing stream restoration work on Herring Run.