In 2010, after a series of regionally severe rain events, Oak Lawn began an aggressive effort to reduce basement sanitary sewer backups during wet weather. Many of these sewer problems are caused what is called Infiltration and inflow (I/I) to the sanitary sewer system, by downstream capacity restrictions, localized bottlenecks, or a combination of these. Infiltration and Inflow is when unwanted clear water enters the sanitary sewer system. I&I reduces the capacity of the sewer which can result in basement backups. For more information on how residents can protect their basements from sewer backups click here. For information on I&I laws, including "illegal hookups" click here.
As a first step in the process, in 2010 the Village retained CDM, a national expert in sewer and water resources. CDM worked closely with staff to develop a Sanitary Sewer Master Plan. The master plan comprehensively
evaluates the sewer system, identifies areas with the worst problems at the
highest frequencies, and determines the cause of those problems. It
provides a set of solutions to address the problems. As part of the master planning process a substantial number of flow meters were installed in Village and MWRD sewers. The results of the flow metering were used to factually model the entire system - for the first time in Village history.
In 2013, based on the findings of the Master Plan the Village televised, cleaned and rehabilitated _____ linear feet of sewer pipe and _____ manholes. Rehab work consists of lining pipes using cured in place pipe, and chemical grouting of manholes. Lining the pipes prevents "clear water" from entering the sanitary sewer and re-enforces the aging pipes structurally to prevent them collapsing, extending their lives by as much as 75 years. Pipe lining is cost effective and minimally disruptive because it does not require digging of a trench.
In 2013 Oak Lawn passed a sewer rate increase dedicated specifically to sewer rehabilitation. Oak Lawn will use the funds generated by this rate to rehabilitate the Oak Lawn sanitary sewers and manholes on an annual basis, incrementally decreasing the amount of I&I entering the sewers, and incrementally increasing each sewer's capacity so that they can better handle flows during wet weather conditions without backing up. The goal of the program is to target the oldest sewers in the worst condition first, and rehabilitate 2% of the entire system annually.
For more information on the Sewer Master Plan click the below.
The Oak Lawn sanitary system discharges to the Calumet 20 Interceptor owned by the Metropolitan Water
Reclamation District (the District), and is eventually conveyed to the District’s Calumet Water
Reclamation Plant for treatment.