Glen Ellyn making changes to reduce flooding
Glen Ellyn is planning to make changes to a device at Lake Ellyn that controls how much water leaves the lake during storms to help alleviate flooding in the area.
The village has hired a consultant to design changes to an outlet control structure that would allow the discharge rate to be increased.
It was one of the recommendations in a hydrologic and hydraulic study conducted over the course of the past two years by the same consultant, RHMG Engineers, a Mundelein-based firm.
The lake, located north of the village’s downtown, acts as a stormwater detention facility for a one-square-mile area. It releases water north of the lake through underground pipes that lead to nearby Perry’s Pond and then the East Branch of the DuPage River.
Currently, water is released from the lake at a rate of 37 cubic feet per second. But changes to the outlet control structure would allow it to go to 61.4 cubic feet per second, which equates to about 40 million gallons a day.
To increase the rate, RHMG Engineers will design plans to increase the length of the lake’s weir — a device that influences how fast water can leave early on in a storm event — by eight feet. Plans also call for upsizing the opening of the outlet control structure from 24 inches to 31.5 inches.
Village engineer Bob Minix said there’s a complex amount of permitting required before changes can be made to the structure, including a revised dam permit from the Illinois Department of Natural Resources.
“It might be the controlling factor of when we can make physical changes to the structure,” Minix said.
Construction on the outlet control structure is scheduled to begin early next year, with completion anticipated in June 2014.
The current discharge rate is the maximum allowed under the DuPage County stormwater ordinance, but there are ongoing discussions between county and village officials that would allow the rate to be increased to 85 cubic feet per second.
As part of its analysis, RHMG will assist another consultant in evaluating the possibility of returning an abandoned 24-inch storm sewer to service and verifying that downstream areas wouldn’t be adversely impacted by greater flow rates.
RHMG is being paid $59,000 for its latest round of work.
Minix said the village also will have to commission a mini-watershed/flood control study before consideration would be given to raising the rate to 85 cubic feet per second.
Minix said county officials have been helpful; in fact, they first proposed the rate be increased.
The county’s stormwater committee, and then county board, would have to approve any changes.
Minix is hopeful that could take place by the end of the year.
“The more we can increase the discharge of Lake Ellyn, the more benefits we think there are,” he said.