Combined Sewer Overflow (CSO) reporting requirements vary from state to state, but every jurisdiction has mandated some form of overflow monitoring. Some of the toughest legislation requires that overflows be reported on a daily basis, 365 days per year. Reports often require that duration and volume of each overflow event be documented.
Attempting to satisfy these requirements, several cities have implemented daily or weekly visual inspections of CSO sites. Techniques for confirming events include fluorescent chalk, wooden bobbers and similar rudimentary tools. Complications can arise from these methods including storms washing away the chalk or bobbers, overflow points being located far away from manholes and the inability to accurately determine if an overflow has occurred or not. In addition, volumes and durations can only be guessed. Others have installed flow monitoring equipment that is downloaded on a regular basis and reports generated from recorded data. Flow monitors can provide durations and measure volume, but if a sensor becomes fouled or damaged, data that is required to meet reporting requirements can be lost, and fines will result.
If there were a way to confirm integrity of data as it was recorded, then flow monitoring would be a viable solution. Well, GEOtivity is able to do just this. Wireless flow monitoring systems can range from 2 to more than 100 sites with many projects being installed over the five or six years. Data is sent wirelessly, via the Internet, where it is made available on website maps, customized for each community. GEOtivity data analysts as well as clients are able to view this data real-time as it is uploaded to the Internet at user-defined intervals. This means that if there is a problem with data or equipment, it will be identified the same day, not two weeks later when the data is downloaded.
GEOtivity uses a redundant sensor system consisting of two pressure depth sensors and a float switch with a capacity up to 16 sensors. By having three sensors in place, actual overflow events can be confirmed, and there is always a back-up sensor if one gets damaged due to environmental conditions. The sensors and data logger electronics are housed in a waterproof enclosure and powered by batteries that last six to twelve months. A small wireless antenna is installed to transmit the data using existing cellular tower networks and the new Global Packet Radio Service or Cellular Digital Packet Data (CDPD) communications services.
In addition to uploading real-time data, the system also can be used to send alarms. When flow reaches a pre-defined depth, an alarm can be sent via e-mail or text message to cell phones and pagers. By integrating the CSO monitors with wireless rain gauges, the system can even check rainfall and differentiate between wet and dry weather events. In some instances, this ability has prevented dry weather overflows by alarming city maintenance staff to remove blockages.
All of the recorded data is archived on the website map where it also can be plotted in line and scatter graphs, or downloaded into an Excel spreadsheet for further analysis. No costly proprietary software is required. At anytime, from any location in the world, data can be viewed, analyzed and discussed by one or several people.
With growing populations, aging municipal infrastructure and a stressed natural environment, the need to monitor and prevent sewage discharges is crucial and mandatory. Wireless flow monitoring has proven to be an affordable replacement for old-fashioned visual inspection methods. It conserves valuable human resources and provides much more detailed and useful flow data for reporting to your regulatory body, as well as for your own long-term infrastructure planning and development.