Riverside officials hope to begin tackling the problem of basement flooding throughout the village now that they have a comprehensive picture of the sewer system and several recommendations to improve the situation.
In February, the village’s engineering firm, Christopher B. Burke Engineering Ltd., delivered its report, which was commissioned last year by the village board. The report gives a detailed picture of what’s contributing to flooding in various parts of the village and provides eight potential solutions.
The plan calls for building storm sewers to separate that runoff from the combined sewer system, which tends to back up into people’s basements during even relatively common storm events.
While the village has seen isolated overland flooding in historic storm events where water overtops the banks of the Des Plaines River, most of the flooding experienced by homeowners results from combined storm/sanitary sewers overflowing into basements.
“The major cause of flooding throughout the village is sanitary sewer backup,” the report states.
The capacity of the combined sewer system is so limited, according to the report, that in many locations in Riverside, the sewer can’t even handle a “1-year” storm event, defined as 1.48 inches of rain within a two-hour period.
If implemented, the plan would create separate storm and sanitary sewers for approximately half the village, roughly doubling the area of the village served by separate storm sewers. But it won’t be cheap. If completed, the village would have to spend about $7 million.
“One of the things we have to do now is bring projects to the board for consideration,” said Village Manager Peter Scalera.
According to Scalera, projects can be funded through reserves in the village’s water and sewer fund. It also may be possible to obtain grant funding from the Metropolitan Water Reclamation District of Cook County, said Scalera.
And coupled with a new street-condition study in the hands of village officials, the village board can couple street-improvement projects with improvements to the sewer system.
“We can now plan intelligently,” said Scalera. “We can do street and sewer projects combined.”
The recommendations in the sewer study range from the relatively affordable to expensive. In the former category is a $64,000 plan to build a storm sewer that would drain the area of Riverside west of First Avenue directly into the Des Plaines River. Now that pipe connects to the combined storm/sanitary sewer serving the First Division, and it contributes to basement flooding during big storm events in that area.
Related to that plan is a $1.6 million proposal to connect the various small storm sewer lines in the First Division in order to completely separate storm runoff from the combined sewer system.
Completion of the two plans would “greatly reduce the risk of sanitary backup in the Scottswood watershed,” according to the report.
Another rather expensive project is a plan to completely separate storm and sanitary sewers that run down Longcommon Road. The $2.8 million plan also calls for the construction of an underground storm water detention vault, which would be tentatively located under the Downing/Longcommon/Evelyn triangle.
The plan would have a variety of benefits, including freeing up capacity in the combined sewers draining into the Deep Tunnel system and allowing for additional sewer improvements in north-central Riverside.
Another proposal in the report addresses the kind of backyard flooding that occurs in some areas of the village in the aftermath of heavy rains. Connecting storm sewers to the low points of those areas could reduce the flooding and the length of time it takes to drain water away. The plan estimates it would cost about $75,000 for those individual neighborhood storm sewers to be constructed.
Scalera said he and Public Works Director Edward Bailey will refine their recommendations on how to move forward with sewer improvements and bring options to the village board during the 2015 budget process in the fall.
“We’ll try to identify a project we have with the lowest cost and the greatest return,” said Scalera.