Seeing the Benefits of GI at the Sewer Meter
April 15, 8:35 – 9:05 a.m. | Eric Carlson
Flow meters provide information on sewer system performance by aggregating upstream characteristics into a single flow response. When green infrastructure (GI) is installed and inflows reduced, a change in hydrology is expected to appear in the meter’s response. However, observing trends can be challenging if GI is a small part of the drainage area, variations occur in infiltration rates, rainfall, and antecedent moisture conditions, and GI performance is affected by environmental impacts.
Peoria, IL is using GI to reduce inflows to the combined sewer system as part of its combined sewer overflow (CSO) control program. The City needs to meet CSO reduction targets per its Consent Decree (CD), so quantifying benefits of GI is critical to show progress towards compliance and for project planning. The CSO control program incorporates data from an extensive network of flow meters and rain gauges to document existing conditions and quantify GI performance.
Since a large portion of the drainage area is managed by GI, targeted meter locations allow benefits to be observed and quantified. Also, level meters installed at GI facilities can verify that benefits seen at the meter are attributable to GI performance. A calibrated sewer model is used to evaluate reduction in CSO frequency and volume and attribute the reductions to GI and other system improvements. The combination of metering and modeling allows Peoria to have confidence the GI is working and CD compliance is being met.
