The U.S. Army Corps of Engineers works in mysterious ways. Part of that mystery involves an expectation on the part of the Corps that you sign off on whatever it is they’re planning to do before they tell you exactly what they’re doing and how much it’s potentially going to cost you.

In a nutshell, that was the message from the Corps in October as it sought to receive from Riverside a signed “Letter of Intent” to support flood-control improvements along the Des Plaines River.

The trouble is the draft letter the Corps helpfully sent was ambiguous in stating what improvements it would be completing. Indeed, the letter included references to flood-control measures that left more questions than answers.

When the village president asked for more detail and estimates of cost, the Army Corps asked that those costs, if given to the village, be kept secret. As for project details, the Corps sent Sells a 2009 study that included many measures they have already decided they’re not doing.

In addition, the Corps, in both the letter and the 2009 study, refers repeatedly to an extension of the Groveland “levee,” south of Forest Avenue. While it may seem a quibble, that’s not the term the Corps uses for that floor barrier in its most recent report, which was released in September.

In that report, the Corps calls the extension a “flood wall.” The difference? A levee is an earth berm. A flood wall is just that — a wall of concrete. It makes a bit of a difference to those who would end up looking at such a structure in their backyards.

The Riverside village board last week chose not to sign the letter of intent, and as such is not officially supporting whatever the Corps will eventually bring to the U.S. Congress as they seek funding.

As far as we can tell, not signing the letter of intent will not prevent the Corps from moving ahead with its plans. It also does not mean Riverside is not interested in flood mitigation in this area.

Flooding remains a critical issue for places like Riverside and Brookfield and the flood-control efforts that eventually get built will need the support and input of the people who live and govern here.

That could be years down the road. It took more than a decade for the Hofmann Dam removal project to happen. It could take another decade or more before any of the plans the Corps is now setting in motion see the light of day.

But Riverside is correct in letting them know up front that it isn’t about to be steamrolled into supporting measures the Corps can’t coherently articulate, much less put a price tag on.

At the same time, Riverside needs to keep the lines of communication open with the Corps to ensure the village receives all the information it will need to either support or fight such plans in the future.