Rainwater Recycling

Did you know that University Operations Services (UOS) uses recycled rainwater to wash hundreds of University-owned vehicles each year? It’s true. In addition to conserving water, recycling rainwater helps control pollutants washing into the Charles River and recharges groundwater supplies for the dry summer months.

"We're directly on the Charles. This [project] reduces pollutant loading into the river and makes the river more usable," said Director of Environmental Health and Safety Joseph Griffin.

Rainwater recycling reduces runoff surging into the Charles River and saves 25,000 gallons of water used for washing vehicles each year, Griffin said. Nigel Pickering, a senior engineer with the Charles River Watershed Association (CRWA), applauded the Harvard project, saying it changes the way people think about rainwater.

Rainwater has typically been diverted into gutters and drains and allowed to run into rivers and streams. Urban areas such as Boston and Cambridge present so many hard surfaces⎯rooftops, sidewalks, roadways, and parking lots⎯that the rain runs immediately off the property and into nearby streams and rivers.

This has a couple of negative effects, Pickering said. First, it creates a large pulse of rainwater surging into rivers, carrying pollutants from the surfaces it runs over, such as spilled motor oil or antifreeze from a parking lot. The second negative effect is that it interferes with the natural process of recharging groundwater supplies. In a natural system, Pickering said, some rain runs off the surface into streams and other bodies of water, but some also soaks into the ground. This system replenishes groundwater, which makes its way into rivers and streams more slowly, getting filtered naturally along the way and providing a water source during the dry summer months.

"The urban water cycle is radically different from the natural water cycle because there are so many impervious surfaces," Pickering said. "These types of systems help try to reverse that and restore natural flow."

The project captures half the rainwater that falls on the 5,000-square-foot roof of the maintenance garage at 155 North Harvard St. in Allston by diverting one of the roof's two main downspouts into a 1,200 gallon holding tank. The water is filtered before it enters the tank and is used in the lot next to the building to wash vehicles. Rather than flowing into storm drains and into the Charles River, the water used to wash vehicles flows into sewer drains that take it to sewage treatment plants, where the water is cleaned before being released.

Phil Reidy of Rainwater Recovery Systems LLC, which installed the tank, said 1 inch of rain will provide enough runoff from the building's roof to fill the tank. Excess water is diverted into a 2,500-gallon underground dry well buried under the lawn in front of the building that releases the water into the ground.

David Harris Jr., manager of passenger transport and fleet management services, said they use as much as 300 to 400 gallons of water per day, much of which is now saved by using rainwater. The University tries to wash each vehicle at least once per week in the warm months and as often as weather permits in the cold months as part of a routine maintenance plan that removes salt and grime, reduces corrosion, and makes maintenance work easier.

"There's plenty of water and the quality of water is excellent," Harris said.