ONE OF THE District’s largest environmental projects planned for coming decades is a system to prevent a noxious mixture of urban runoff and raw sewage from flowing into Rock Creek and the Anacostia and Potomac rivers every time there is a big storm. As The Post’s Darryl Fears reported last week, a legally binding agreement requires the D.C. Water and Sewer Authority to construct, at a cost of $2.6 billion, three huge tunnels into which this filthy water could be stored until treatment. But everyone in government seems to agree the city might be better served by a different approach: investing in “green infrastructure” that absorbs rainwater — things such as retention pools and grass rooftops. These have the potential not only to project local rivers but also to improve the city’s air quality and provide buildings with added insulation.

Why, then, did Christophe Tulou, who used to head the District Department of the Environment (DDOE), lose his job in the wrangling over the issue? Mr. Tulou says that he and his agency were cut out of the process as city officials, including Mayor Vincent C. Gray, considered a green infrastructure pilot program to test the feasibility of forgoing the tunnels project. When the Environmental Protection Agency (EPA), a key player in the cleanup effort, asked for thoughts from Mr. Tulou and his staff, he gave them. Green infrastructure could be great, he still maintains, but the city must make sure that a system of rain gardens and green roofs can function as well as the tunnels would; that it’s clear who would pay to maintain it all; and that the pilot project doesn’t delay the whole effort unnecessarily, possibly for many years.

Mr. Tulou’s concerns are fair, as none other than D.C. Water’s general manager, George Hawkins, agrees. Mr. Hawkins says that the point of the pilot project — which, with a price tag in the tens of millions, would be no small effort — would be to assess how well green infrastructure would perform in lieu of the tunnels. And, he says, there are many points, some early on, at which the experiment could be called off if the city or the EPA determined it’s likely not to work. Environmentalists who worry that the pilot project would only delay water cleanup in the Washington area should balance the many possible benefits of a greener strategy against their concern. Even if the experiment determined that green infrastructure alone wouldn’t do the trick, what might result is a mixed approach — perhaps smaller tunnels along with some grass roofs.

What is less clear is why Mr. Tulou had to lose his job following the submission of his agency’s questions to the EPA. True, it appears that Mr. Tulou dispatched the critique without full vetting from the mayor’s office or City Administrator Allen Y. Lew. But he claims that he did show the DDOE’s criticism to both before sending it to the EPA. By the accounts we heard, that criticism was intended to be constructive, part of a debate the city must have about the trade-offs involved in experimenting with green infrastructure.

Mr. Lew did not respond to requests for comment. The Post reported Mr. Gray felt “upstaged.” The mayor’s feelings aside, Mr. Tulou hardly seems to have acted outside the public interest.