BY GLENN PUIT
TRAVERSE CITY — An investigation into what caused Brown Bridge Pond to rush into the Boardman River could take months to complete, and investigators aren't sure if they'll figure out what caused the flooding.
"I don't know if we will ever really know for sure exactly what happened," said Jim Pawloski, a member of the Michigan Department of Environmental Quality's Dam Safety Unit. "Often, when we have incidents like this, much of the evidence is washed downstream."
The DEQ is investigating what caused the pond to empty into the Boardman during work to remove Brown Bridge Dam. A construction crew was at work on a "dewatering structure" adjacent to the dam on Saturday morning when the breach occurred.
The dewatering structure is supposed to allow for a slow release of water, but the pond flushed into the river in the space of a few hours, and caused the Boardman to rise as much as five feet.
Property damage claims tied to the flood surged to 49 by Tuesday, said Dan Scott, Grand Traverse County's Emergency Manager.
DEQ investigators are investigating whether a contractor, Molon Excavating, accidentally caused the pond to empty into the river or if there was an equipment failure.
Byron Lane, the DEQ's chief of Hydrologic Studies and Dam Safety, said the plan is to draw down water on the Brown Bridge Dam and the adjacent dewatering structure for inspection. Right now, key components of the structure remain underwater.
"With something like this, when you have an earthen embankment, during the flooding, the evidence can be destroyed," Lane said. "Right now it seems as though the structure that failed is reasonably intact."
Pawloski said the investigation is an engineering-related inquiry, not a criminal investigation.
"From the DEQ's perspective, we've initiated an investigation into what's happened, and we have conducted interviews with most of the people who were on site, trying to correct information, data and observations to try to gain an understanding of technically what was the situation, and, from an engineering situation, what exactly occurred," Pawloski said.
Lane said a comprehensive analysis of the flooding's impact on the Boardman fishery is ongoing. Teams of biologists with the DEQ and the Michigan Department of Natural Resources will be on the river today to assess the damage.