In December, the Pittsburgh Water and Sewer Authority installed a solar-powered smart valve at Panther Hollow Lake as part of a pilot project to manage storm water. Seven months later, the engineers behind the project say it's been a success.
The lake is a man-made body of water in Schenley Park; on a normal day it holds 1.3 million gallons of water. The valve system created by Boston-based company Opti, essentially turns Panther Hollow Lake into a natural holding tank for stormwater, increasing its water volume capacity by about 70 percent.
Here's how it works: a valve and motor sit at the bottom of a manhole near the lake, and are connected to a nearby solar-powered control panel. The internet-enabled panel gets information on weather forecasts from the National Weather Service, and this data feeds into an algorithm that calculates when to open and close the valve and by how much.
"When it anticipates a rain event coming, it will actually close the valve here at the lake and allow the lake level to rise up an extra foot to get extra storage in the lake," said ecological engineer Barton Kirk. Kirk is with the Ethos Collaborative, a partner in the system's implementation.
Allegheny County has a combined sewer system, which means both stormwater and sewage end up in the same pipes. When these pipes get too full, as can happen during a storm, they overflow into the rivers. PWSA engineer Ruari Egan said the system at the lake reduces combined sewer overflows to Pittsburgh's rivers.
"Essentially, the system acts as a detention basin during rain events and then it draws back down to normal lake levels with a 48 hour draw down period," Egan said. "It's slowly releasing back into the combined sewer system once the rain has stopped."
Opti CEO David Rubinstein said since the system went live in February, it's diverted 16 million gallons of water from Pittsburgh's sewer system. He said the company plans to tweak the system based on the data collected so far.
"[That's] so we can hold even more wet weather back in the future," Rubinstein said. "I view what we're able to do here as continuous improvement."
PWSA estimates more than 30 million gallons of sewage and stormwater overflow from near Panther Hollow Lake every year.