Duke pond to help with water conservation

May. 03, 2014 @ 06:28 PM

Duke University is creating an on-campus lake that should reduce the school’s draw on Durham’s water system by about a fifth.
The $9 million “reclamation pond” is going in on a highly visible site just off Erwin Road. It will collect the rainwater that runs off about 22 percent of the campus and feed it into the machinery that cools Duke’s many buildings.
The project is a child of the 2007 drought, a worst-on-record run of dry weather that saw stockpiles in the city’s two primary reservoirs, Lake Michie and Little River, drop to less than two months’ worth of high-quality water.
Since then, the university has done “a lot of small things” to cut down on its use of potable water, which before the drought had peaked at about 645 million gallons a year, said Steve Palumbo, Duke’s energy manager.
But committing to building the pond “was a big play,” Palumbo said, explaining that once online, it should trim about 100 million gallons off Duke’s annual water buy from the city.
The school of late has been using about 470 million gallons a year, with about 30 percent of that going to run its chiller plants, he said.
Cutting its use of city water also means cutting its payments to the city, to the tune of about $400,000 a year.
But Durham Water Management Department officials aren’t fretting about the likely loss of revenue. To the contrary, they welcome the move as one that relieves a bit of the pressure on the city to build new infrastructure.
“We wouldn’t be getting as much revenue from selling water to them, but our overarching goal is to make sure we’re providing safe drinking water for potable-water purposes,” department Assistant Director Vicki Westbrook said.
She added that she suspects there will “be a lot of innovations in the next 30 years” on the conservation front given that the city is facing the need to expand its water supply, a job that could consume $115 million in present-day dollars if it taps Jordan Lake.
Duke started digging its new pond last year. The weather has caused some delays, but Palumbo said the project’s on track to be finished in the spring of 2015.
The site covers about 12 acres and is next door to the larger of Duke’s two campus chiller plants. Workers are damming a small creek, and will eventually install a pavilion, a walking path and plantings that can thrive both in the wet and the dry.
“We decided we weren’t just digging a hole,” Palumbo said. “We’re making it more of a campus amenity.”
The pond will be up to 10 feet deep in places, and should be a year-round feature.
“It’s designed with a 4-foot [depth] flux to keep the plant growth feet-wet,” Palumbo said. “It’s not going to be like a traditional farmers’ pond where we drain it dry.”
He added that Duke will still use city water for some of its chiller-plant needs, and continue to count on it as a back-up supply for the chillers in the event of a drought.
Duke’s move parallels what UNC Chapel Hill did in response to the two big droughts that happened last decade.
The Chapel Hill school in cooperation with the Orange Water and Sewer Authority put in a “reclaimed” water system that recycles the effluent of OWASA’s sewage-treatment plant.
The system at UNC among other things feeds several chiller plants and also supplies water used to irrigate athletic fields.