COLUMBIA — Every time precipitation falls over MU’s 1,440-acre main campus, about a third of it can’t soak into the ground. It instead collects over impervious surfaces, such as parking lots, picking up pollutants before making its way to nearby water sources such as Flat Branch or Hinkson Creek.
Rapid development during the past 43 years has rendered 32 percent of the campus impervious, increasing pollution concentration and danger to local water sources, according to the 2013 Stormwater Master Plan, the first of its kind for MU.
"The threat with stormwater runoff is related to development," Jason Hubbart, MU assistant professor of forest hydrology and water quality, wrote in an email. "More people equals more development equals increased stormwater runoff, which leads to multiple effects in receiving waters like Hinkson Creek (erosion, scouring, loss of physical habitat)."
Since 1970, Columbia’s urban land use and population has almost doubled, according to the master plan.
Because impervious surfaces don’t allow liquids to pass through them, they concentrate contaminants — such as heavy metals manganese and cadmium — as stormwater travels over them on their way to nearby water sources.
Stormwater runoff not only threatens the physical landscape, but also the thousands who use the area’s water sources for sport and recreation.
"Diffuse pollution transported by runoff is a leading threat to waters in which we fish and swim," the master plan states.
To combat these hazards, MU rolled out its 2013 strategic stormwater plan in April with three main goals: raising stormwater quality, ensuring regulatory compliance and increasing water retention and reuse.
MU’s current stormwater collection and treatment options aren’t adequate for the need, said Enos Inniss, an assistant professor in MU’s Department of Civil and Environmental Engineering.
"We have more to go, and the campus will be the first to admit that," Inniss said.
Six ways to manage runoff
Because MU lies in the lower Hinkson Creek watershed and intersects 10 additional subwatersheds, ranging in size from 22 to 292 acres, one solution won’t work for every issue.
Thus, MU’s stormwater master plan lays out six strategies, mostly based on topography, to accomplish the university’s goals:
Bioretention cells — Placed primarily in or adjacent to parking lots, these cells feature shallow, depressed trenches that are vegetated and mulched to capture and retain excess stormwater runoff. These features are similar to rain gardens, except the retention cells have drains in them, Inniss said.
"The rain garden typically allows infiltration to happen and then it just goes into the native soil," he said. "There is no drain at the bottom."
Bioretention cells require adequate soils for infiltration and relatively flat land. MU’s 11.4 acres of parking lots face 1.66 million cubic feet of runoff. Coupled with retention cells, these parking lots could annually recoup 80 percent of total runoff.
Vegetated swales — Normally featured in open spaces, parks and roadsides, swales are marshy depressions covered with low-lying vegetation that slowly and uniformly process water throughout a large area. They don’t work well with steep slopes and require more maintenance than curb and gutter approaches.
Planter boxes — Often found next to buildings, planter boxers receive water from downspouts and then filter and drain the water to underground piping. Planter boxes are used heavily because they can remain in close proximity to buildings without compromising foundations.
Cisterns — Usually attached to buildings, cisterns can collect stormwater from building roofs and pavement. They are valued because they can be used on any type of soil, both above and below ground.
Permeable pavement — Placed on low-use roads and pedestrian paths, permeable pavement allows stormwater to filter without collecting and concentrating pollutants. Because it lacks the strength of impermeable pavement, it has to be placed in light-traffic areas and demands higher maintenance than its traditional counterpart.
Constructed wetlands — Slated for large-scale open spaces, golf courses and parks, wetlands are engineered pools that can create additional habitat areas and treat large volumes of water, but require high capital costs.
Graphics by Joey Fening
Current treatment efforts
A larger and more complex retention cell is forming on the campus’s western edge and will join three others when completed in October. Nestled opposite the university’s block-long power facility at the corner of Stewart and Providence roads, this retention cell’s construction costs $64,400, wrote Karlan Seville, campus facilities communications manager, in an email.
"This budget does not include replacing plants over time and maintaining the bioretention, which will come from MU Campus Facilities Landscape Services funds," Seville wrote. "This project is more extensive than others MU has done because it is a larger area and there are many underground utilities in the area."
Inniss said the stormwater treatment features need to be large enough to handle the initial surge of stormwater, which is usually the most contaminated.
"Oftentimes when you first get the runoff to happen, you have rainfall come, and if not enough of the water goes into the ground, it starts to run off the site, and that’s usually when you pick up a lot of your contaminants, pollutants," he said.
"That initial pulse of water is really what you want to capture, because that probably has the higher concentrations of anything you’re concerned about," Inniss continued. "Then as the water continues to come, that water may wind up overflowing into your storm sewer."
Seville highlighted other runoff treatment and conservation features already in place at MU:
- A rain garden at the Rollins Group housing complex
- Two bioretention cells at the Animal Resource Center
- A swale at the intersection of East Stadium Boulevard and South College Avenue, designed to manage runoff from parking lot CG-1
- Pervious pavement outside the MU Student Center, MU Sustainability Office, Rollins Group, west of Stankowski Field and north of the Anheuser-Busch Natural Resource Center
- An underground cistern beneath Tucker Hall, designed to irrigate plants at Tucker Greenhouse
- Green roofs at the University Hospital patient care tower and Bond Life Sciences Center
Additionally, Seville wrote MU plans to install a bioretention at Virginia Avenue South Housing.
Columbia accumulates 40 inches in precipitation each year, on average, according to data collected by the National Oceanic and Atmospheric Administration.
If MU implements its stormwater strategy for its parking lots, roads and roofs, the institution anticipates recapturing 2.5 million cubic feet of runoff per year, about 53 percent of total accumulation, according to the master plan.
Supervising editor is Elizabeth Brixey.