Metro DetroitAugust 26, 2014
Runoff from storm could cause algae blooms
By Kevin Bunch
C & G Staff Writer
METRO DETROIT — The storm event that swept through metro Detroit Aug. 11 overwhelmed the sewer and drainage systems throughout the region, causing wastewater to flow out to the surface and mix with the stormwater.
That water, in turn, has inevitably found its way into lakes, streams and rivers. Depending on whom you ask, the negative impact of all that water could be miniscule, or it could be profound.
Wayne State University Professor D. Carl Freeman said the amount of sewage overflow could contribute to algae blooms in Lake Erie or Lake St. Clair, as the contents of the wastewater — along with any nutrients it may have picked up from the surface soil — are effectively fertilizer.
Depending on the species of algae, they could produce a toxic side effect that renders the water undrinkable and kills the local wildlife, similar to the bloom that occurred on Lake Erie in July.
“We had a lot of sewage overflows, and so what this is going to do is supply a lot of nutrients to the receiving water bodies,” Freeman said. “And that can lead to outbreaks of various kinds of algae, not unlike what we saw in Toledo.”
Part of the problem there is due to Lake Erie being shallow, though Lake St. Clair is even shallower than Erie, he said. Whether or not an algae bloom forms in Lake St. Clair is dependent on whether or not the wastewater gets trapped in the lake itself or is pushed into the Detroit River and down into Lake Erie.
Freeman said it also depends on the temperature over the next few weeks. The hotter it is, the quicker the algae can bloom. If it stays closer to the 70-degree range, then the polluted water will find its way down to Lake Erie before blooming.
Researcher Donna Kashian, visiting scientist at the Great Lakes Environmental Research Laboratory and Wayne State University professor, was more optimistic that any problems would be minimal. She said the massive amount of rainfall that hit the region probably diluted the amount of contaminants to some extent.
She said there were two major components to any pollution that she is concerned about, though: runoff from farmland getting into river systems and out into the lakes, and runoff from industrial sites pushing petroleum products and chemicals out into the water. She thinks we would already be seeing the effects of the latter, however.
“In this area, those are the two that would be my biggest concern,” Kashian said. “In terms of the oils, the petroleum products (and chemicals), those have already entered the system, and there has been no measurable effect on the environment.”
She said runoff from farms traveling down waterways like the Maumee River could contribute to algae blooms. As the problem is already a big one, she does not think it needs any additional runoff contributions but does not know how big an impact they may have. Wind could also help break up a bloom and keep it from getting too large.
Brad Wurfel, spokesman for the Michigan Department of Environmental Quality, was optimistic that the impact would be minimal due to the sheer amount of stormwater in the system, as well. He said that it should have diluted the wastewater enough to limit the impact on the ground.
Wurfel said if the area had gotten just enough water to overwhelm the sewer system, it would have been much more potent as it drained out. He thinks the fact that the rainfall seemed to go beyond that stage would help on that front, even though it was very unfortunate in other ways.
“It’s difficult to quantify the impact on the environment and public health just because it’s so much water,” Wurfel said. “It’s a massive volume of water, and the dilution factor, I think in a lot of cases, offsets the toxicity.”
Wurfel said Aug. 15 he had someone on staff researching it and that the department should have results within a week or two, though those were not available at press time.
Additionally, he said it would take some time to see how erosion from the water impacts the area, as the water itself settles.
Freeman said it’s possible that eroded runoff containing bacteria such as E. coli will get into the water system, requiring beaches to be closed. Additionally, with construction being done throughout the region, he is sure erosion was a problem.