There’s a tree growing out of a drain behind the biomedical sciences building. This peculiar contraption is just one way that UCSC has found to deal with the pollutants picked up by storm water runoff.
Named the Treepod Biofilter, this tree is a storm water filtration system. It cleanses storm water runoff of pollutants before it enters the larger drainage system. Its installation, which took place during the construction of the new biomedical sciences building at UC Santa Cruz throughout 2011–12, is part of a larger campus effort called the Storm Water Management Plan (SWMP).
“In all of our projects that we do on campus, there’s a big push to do low impact development and manage our storm water as if it were the natural environment as opposed to a built-in environment,” said SWMP’s manager Courtney Trask.
Prior to 2009, storm water runoff had been managed by a combination of efforts made by the Physical Planning and Construction Office, the Environmental Health and Safety Office and other campus offices. In 2009, SWMP became possible when the California Water Resources Control Board granted UCSC a “permit for the Discharge of Storm Water from Small Municipal Separate Storm Sewer Systems.” This permit allowed UCSC to independently maintain its storm water.
A system for water management is required under the federal Environmental Protection Agency because UCSC’s storm water runoff drains into local watersheds. The Treepod Biofilter is a more desirable alternative to traditional drains, according to some.
“The Treepod is a natural landscape based treatment device that’s also nice to look at because it has a tree in it,” said Sue Lillo, a representative for Kristar, the company that manufactured the Treepod.
Kristar regional sales engineer Chris Demarest said the Treepod treats storm water as it seeps through the three feet of soil within the filter. Composed of 80 percent sand and 20 percent compost, the soil’s medium is designed to foster sufficient vegetation to absorb pollutants. Microorganisms and vegetation as well as the roots of the tree itself uptake pollutants from the water before they make it to the natural sediment beneath the filter or are discharged into the underlying drainage pipe.
According to UCSC’s Clean Water website, pollutants include oil, grease, pesticides, herbicides, fertilizers, soapy water from domestic cleaning products, sediment from construction projects and various loose trash.
The quantities of pollutants taken up by the tree or shrub in the biofiltration system are small enough that the tree or shrub is not harmed.
“The roots will uptake heavy metals and we’ve done studies to show that the tree or shrub that’s inside the bioretention system will actually take heavy metals up, and they’ll be shown in their leaves when the leaves drop,” Demarest said.
To avoid having the tree grow too large for the filter, Kristar recommends that a small tree or shrub with shallow root zones is used for the Treepod.
While many filters are designed to purify stormwater of these pollutants, the Treepod has the allure of having a small environmental impact.
“Some people look at this as being more desirable,” Lillo said. “You’re planting a tree.”
SWMP has implemented other sustainable drainage systems aside from the Treepod that can be seen around campus. A patch of pervious pavement, a porous type of cement located next to the Treepod, absorbs water rather than letting it run off into drains that lead to watersheds. Rock swales, the white stone paved stream beds that occur frequently across cmapus, slow down stormwater runoff, allowing more of it to be absorbed by the underlying soil. In other areas, detention basins pool stormwater allowing it to be absorbed rather than pick up pollutants and drain into a watershed.
This Treepod is an example of how SWMP is still experimenting with ways to improve managing stormwater at UCSC. It is the only one of its kind on campus today, but Trask hopes to change that.
“Obviously every location is different, we need to make sure it can handle the amount of water we’re sending its way and that the maintenance is reasonable,” Trask said. “[This Treepod is the] first one for now, but the hope is that it won’t be the last one.”
