The City of Jersey
Identifying Combined Sewage Overflow Patterns
StormSensorTM collected data at two locations during the preliminary Pilot Test. The Scutes™ provided reliable data sets that established baseline conditions at two tidally influenced locations and identified combined sewage overflows (CSOs). Data collected during the pilot test showed more frequent overflows than the current EPA SWMM model predicted, which suggests a need to further validate source data for future model runs.
Several opportunities to improve the ScuteTM sensors usability were identified. These modifications, including further waterproofing and the addition of forward/ reverse velocity measurements, will be applied to the next iteration of sensors, released to selected pilot consumers in September, 2018.
The Jersey City Municipal Utilities Authority (JCMUA) operates the sewerage systems in Jersey City. Begun as the Jersey City Sewerage Authority in 1949, the JCMUA built two sewage treatment plants where the current JCMUA offices are located. The treatment systems were upgraded in 1990 as a result of tightened regulations managing wastewater discharge.
Both of the sites selected for this pilot study are under tidal influence; therefore, establishing baseline conditions was required in order to accurately identify any contributions to the system due to storm events. These contributions were identified as “anomalies” and were flagged as potential CSOs.
StormSensor Scutes™ successfully established baseline tidal conditions by monitoring water level and temperature within the pipes. Figure 5 shows an example of the tidal baseline conditions at the downstream Site 1 location at the Hackensack River outfall point. Tidal conditions were observed at Site 2; however, because the downstream sensors at Site 2 were located at an outfall that discharged to a rocky tidal canal, instead of directly into the Hackensack River, only higher tides were consistently documented at the downstream Site 2 locations.
During the duration of the pilot study, one likely CSO event was identified at Site 1 and four were identified at Site 2. A definite pattern indicative of a CSO was consistently observed across each of the Scute™ monitoring locations throughout the course of the pilot study.
Both of the sites selected for this pilot study are under tidal influence; therefore, establishing baseline conditions was required in order to accurately identify any contributions to the system due to storm events.
Figure 9 shows a single CSO event at the Site 2 outfall.
Here, the observed two-phase CSO pattern can be clearly seen. After the rain begins (1), the water level in the pipe increases (2), followed by a small dip in water temperature. This is followed by a clear spike in water temperature (3) as sewage enters the system and water level in the pipe is maxed out. The CSO continues as water temperature equalizes.
Water level returns to normal several hours after the rain event ends.