Riverside officials have backed off a threat to seek legal action against the U.S. Army Corps of Engineers and the Illinois Department of Natural Resources after grilling representatives of the agencies at a closed-door meeting on April 26 at the Riverside Township Hall.

The emergency meeting was called early last week in response to information that the agencies had hidden data that predicted lower-than-expected water levels on the Des Plaines River once the Hofmann Dam is removed.

Meeting with the Army Corps and IDNR officials last week were Village Manager Peter Scalera, trustees James Reynolds and Lonnie Sacchi, Public Works Director Edward Bailey and residents who brought the previously hidden data to light.

“They provided the group with the information we requested,” said Scalera.

As a result of the closed-door session, Riverside canceled a special board meeting it had scheduled for the evening of April 27 to discuss possible legal action to halt the project.

The Army Corps contends that the difference between the two sets of figures won’t make that much difference in terms of predicted impact once the dam is removed.

But the new information, which indicated that the figures released to the public last September understated the impact the dam removal would have on river levels, alarmed residents and village officials alike.

The agencies had the data at their disposal at the time of a public hearing on the project in Riverside in September 2011. However, they chose instead to use older data that was more optimistic in terms of river flow and future water levels.

On April 19, in an email exchange with the Army Corps’ project manager for the Hofmann Dam removal, Maplewood Road resident Jeff Miller learned of the conflicting sets of data.

He and more than 20 other residents signed a letter calling for work to halt until an investigation could be done. The Frederick Law Olmsted Society, which had supported the dam removal project, also called for a suspension of work in light of the new information.

On April 25, state Sen. Martin Sandoval, whose new district will include a portion of Riverside after the November election, added his voice to those calling for work to be halted until the Army Corps and IDNR could explain themselves.

“I am demanding that no work begin on the removal of the Hofmann Dam until the agencies can earn community support with full public disclosure of all studies and data at your disposal,” Sandoval wrote in a letter to the director of the IDNR.

Scalera said there will be a public meeting in the next couple of weeks where representatives from the Army Corps and IDNR will give an “explanation for the disparity in information pertaining to flow rates and river hydrology, additional information on the impact of the project to the river and the riverbank from 31st Street to Hofmann Dam, and a verification of all data by an independent agency.”

That independent agency reportedly will be the U.S. Geological Survey, which collects and publishes data about the nation’s waterways.

While village officials are cautiously optimistic that the IDNR and Army Corps will be able to calm the fears of those alarmed by the discovery of an alternate data set regarding river flows and water levels, some remain skeptical.

Miller, the Maplewood Road resident who received confirmation of the existence of the alternate data in an email exchange with the Army Corps’ Hofmann Dam project manager on April 19, said the Corps’ analysis relies on plugging that data into current conditions.

Once the dam is removed, however, those conditions will change and the Corps has not done that kind of data modeling.

“All of this is a roundabout way of saying that it is easy to predict the past. The future is another matter,” Miller stated in an email summary of his thoughts about the April 26 meeting at the township hall.

“To summarize, I don’t really know how to assess the Corps’ predictions because they themselves provide no guidance about the range of expected outcomes – we just get one set of numbers, (presumably) their best guess.”

In the meantime, the riverbank stabilization work that began two weeks ago will continue in preparation for the dam notching, which will likely happen sometime in June.