Overcoming Wet Weather Overflows, Pittsburgh, PA

 

      Reviewing wet weather overflow data
Reviewing wet weather overflow data

 

For the Pittsburgh region as little as one-tenth of an inch of rain (an average Pittsburgh rainfall is one-quarter inch) can result in untreated wet weather sewage overflowing into area streams and rivers. The extra volume of storm water overloads the sewage collection system pipes, which causes raw sewage to overflow at hundreds of locations during the wet weather before it reaches the treatment plant. In 2001 3 Rivers Wet Weather (3RWW) contracted with Vieux & Associates of Norman, Oklahoma to create a calibrated radar wet weather network because accurate rainfall data is critical for communities dealing with this issue. Local agencies needed reliable information to design sewer rehabilitation projects and to develop long-term maintenance plans for wet weather overflows.

Using RainVieux, 3RWW is able to provide local municipalities with online access to actual, as well as estimated radar wet weather rates. The primary radar source is the National Weather Service NEXRAD radar, located in Moon Township. The radar data gathered during a wet weather event is calibrated with the rain gauge data collected during the same time period for every square kilometer in Allegheny County, Pennsylvania. The combination of radar and gauge data ensures accurate wet weather information.

3RWW operates and maintains thirty-three rain gauges throughout Allegheny County. Initially the wet weather network was designed as a telephone dial-up interrogated system with rainfall totals acquired every fifteen minutes. However in 2004 the impact of Hurricane Ivan caused malfunctions with the dial-up system and erratic wet weather reporting. The area sustained record-breaking rainfall and heavy flooding, which caused 3RWW to re-examine the system and consider a real-time wet weather overflow data reporting network.

PEMA (Pennsylvania Emergency Management Agency) already uses the ALERT/IFLOWS format for their statewide rain gauge network and served as an example for 3RWW. Officials liked the benefits of converting to an ALERT wet weather overflow monitoring system: reliable, low cost, real-time data, automated warnings, and it would be easy to incorporate with RainView. They also liked the idea of collaborating with PEMA and strengthening their partnership with the National Weather Service. So with a recommendation from Vieux & Associates, 3RWW approached HSE for assistance.

HSE conducted a radio path study and assisted 3RWW with telemetry requirements for their upgrade wet weather overflow project. It was agreed that the existing tipping bucket rain gauges would remain and be interfaced with Model 3206 ALERT Data Transmitters. The terrain also dictated the need for a repeater system, the Model 3300 Store & Forward Repeater, as well as directional antennas and power amps for wet weather overflow monitoring sites with marginal signals. A new fully equipped base station utilizing specialized software was added for processing of real-time data. The specialized monitoring software enables 3RWW to archive the data, trigger alarms, create graphs, and to incorporate many other data management tools. HSE staff also helped 3RWW acquire funding for the project by introducing them to the National Weather Service AFWS Program for which they received a grant in 2005.

Today, 3RWW utilizes over thirty Model 3206 ALERT Data Transmitters and three Model 3300 Store & Forward Repeaters with a rain gauge input. The system is similar to Harris County's rain and stream gauge network in Houston, Texas where Vieux & Associates and HSE have collaborated for many years.

SPECIAL NOTE: In 1997, the U.S. Environmental Protection Agency initially cited more than fifty communities in the Allegheny County Sanitary Authority (ALCOSAN) service area for sewage wet weather overflows that violate the Federal Clean Water Act. ALCOSAN, located in the Woods Run section of Pittsburgh, Pennsylvania provides sewage treatment for nearly one million people over a 300-square mile area of Allegheny County. To address this critical wet weather overflow issue, ALCOSAN and the Allegheny County Health Department joined forces to create the 3 Rivers Wet Weather Demonstration Program.

Since its inception, 3RWW has helped the ALCOSAN municipalities tackle the region's aging and deteriorating sewer and storm water infrastructure. As a non-profit organization, 3RWW helps promote the most cost-effective, long-term solutions; i.e., benchmark sewer technology, providing financial grants, educating the public, and advocating inter-municipal partnerships.

 


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