About the data

A combined sewer carries sewage and stormwater in the same pipe. During heavy rain or snowmelt the combined volume can exceed what the system is able to convey, and the excess discharges to a nearby waterway. That discharge is a combined sewer overflow.

How the outlook is calculated

For each permittee we total the observed precipitation over the previous hour and the previous four hours, and weigh those totals against the amount of rainfall that has been associated with overflows in that community. As the totals climb, a CSO event is reported as becoming more likely, and then as likely to be occurring.

The rainfall that a community's sewer system can take before it overflows differs from one community to the next, so the outlook is an estimate of likelihood rather than a measurement of what is happening in the sewer.

Where the precipitation data comes from

Precipitation observations come courtesy of the Iowa Environmental Mesonet at Iowa State University. Values are gridded estimates for a representative point in each permittee, not readings from a gauge inside that permittee, so local totals can differ.

Observations are collected on a recurring schedule. The time of the most recent successful update is shown on the current conditions page; if that update is more than a couple of hours old, the affected permittees are marked as having no current data rather than being shown as unlikely to be experiencing a CSO event.

How times are shown

Every date and time on this site, including the ones you enter when checking past conditions, is Eastern time, adjusting for daylight saving time as New Jersey does. Readings are recorded by the hour, so past conditions are chosen on the hour.

What this site does not tell you

This site does not confirm that an overflow occurred, does not report its volume or duration, and is not a substitute for official notifications from a permit holder or from the New Jersey Department of Environmental Protection. Treat it as an early indication only.