Wastewater: Monitoring Green Roof Runoff

June 1, 2011
Pittsburgh-area county officials, facing an expensive wastewater system upgrade, hope reducing stormwater will help reduce the severity of combined sewage overflows.

Part of the plan involves putting a “green roof” on an 87-year-old government building. Monitoring the roof’s success in reducing runoff is critical, according to Darla Cravotta, special projects coordinator with Allegheny County.

Allegheny County has four companies working on the project, including Civil & Environmental Consultants, Inc. (CEC, www.cecinc.com) whose job it is to monitor a multitude of data points over the next six years. CEC is using Web-based weather stations from Bourne, Mass.-based Onset Computer Corp. (www.onsetcomp.com). John Buck of CEC will use eight Onset HOBO U3O weather stations with approximately 90 sensors to track soil temperature, soil moisture, runoff duration, and more.

In a 2005 job, Buck used Onset data loggers at a solid waste disposal site. “We had a pretty hot setup for the time,” Buck said. “We created a 900 MHz network that relayed data and emailed me three times a day.” But that system had weaknesses that the U30 devices have overcome, he said. “When you consider the dependence of that system on the computer at the site, and the power outages, MS Windows updates, and the fact that the computer hated zero degree weather, you’ve got a lot of variables,” he explained. “The HOBO U30 cut out the intermediate computer and 900 MHz radios and simplified the system.”

Originally, Buck wanted to use Wi-Fi communications for all eight weather stations, but Wi-Fi did not transmit through the roof.  Instead, he put two Ethernet-enabled U30s inside the building and placed an access point on the roof so that the other six Wi-Fi devices up there could communicate. Buck is using Onset’s HOBOlink web server as a data repository and a way to monitor the system remotely, sensor-by-sensor.

June 2011, Related Perspective – Comparing Automated Label Inspection Solutions
To read the perspective, visit

Civil & Environmental Consultants, Inc. (CEC, www.cecinc.com)

Onset Computer Corp. (www.onsetcomp.com)

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