GLEN ELLYN – As part of efforts to curb Lake Ellyn flooding, Glen Ellyn officials will work with engineers to determine the maximim output rate possible for water that leaves the lake and enters surrounding bodies of water.
At the Glen Ellyn Village Board meeting Aug. 12, trustees approved a $38,000 agreement with Engineering Resource Associates to perform the necessary computer modeling services to determine the maximum discharge rate possible for Lake Ellyn.
The lake currently drains at 37 cubic feet per second, according to village documents, but based on the recommendations of a Lake Ellyn drainage study, the village is seeking to increase that amount to improve the lake's performance during a serious storm event, such as the one the area saw in April.
"Our goal, really, in terms of what we found, is to maximize discharge from Lake Ellyn," village Professional Engineer Bob Minix said.
The maximum rate allowed by DuPage County for the size of the Lake Ellyn watershed is 61.4 cubic feet per second. However, Glen Ellyn may be able to increase the discharge rate further with the county's approval, depending on pipe capacity, effects on downstream areas such as Perry's Pond and available room in the DuPage River's East Branch, officials said.
Water drains from Lake Ellyn through an outlet structure at the north end of the lake into a storm sewer under Riford Road, according to village documents. The sewer delivers the water to a channel betwen 725 and 717 Riford Road and then brings it to Perry's Pond, eventually reaching the East Branch of the DuPage River.
"We are charged with the responsibility of making sure that if we increase the rate of beyond the current 37 (cubic feet per second) that there are no adverse impacts either downstream in the channel area, downstream at Perry's Pond, downstream in the river itself," Minix said.
Officials previously approved a $59,000 agreement with RHMG Engineers in June to design proposed modifications to the outlet control structure, including increasing the structure's weir length and expanding the structure's opening into the drainage pipe.
Engineering Resource Associate's modeling studies are expected to be completed this year, officials said.
The proposed timeline from RHMG, which is the firm that performed the village's Lake Ellyn drainage study, includes a June 2014 construction completion date for outlet control structure changes that would increase the lake's discharge rate beyond 61.4 cubic feet per second, based on the findings by Engineering Resource Associates.
"We are hopeful that we can do a sweep of possible discharge rates, come up with what our maximum would be before we start getting to the threshold that we're causing adverse impacts or impacts that we cannot do something about per se," Minix said.