Algae Crisis Pt. II: The Urban Factor
SCHAEFER: This summer’s drought has kept Lake Erie largely free from toxic algae blooms. With less rain came less runoff from row crops along the Maumee and other rivers that feed into the lake. That farmland runoff carries phosphorus contained in manure and fertilizer. It’s phosphorous that feeds the growth of algae. The lack of rain and storms also meant no big overflows of sewage – that’s the other major source of Lake Erie phosphorus.
In fact, a study last year by scientists at the U.S. Geological Survey concluded that sewage from municipal plants in Detroit, Toledo and other cities along Lake Erie contribute almost as much phosphorus to the lake as farms. Dale Robertson is the lead author of that study.
DALE ROBERTSON: I think my study is showing that they're both important. They might, on an individual day, individual season, they could vary. But, when you're looking at this, there's a lot of nutrients coming in from both of those sources.
SCHAEFER: The USGS study has sparked some controversy. Ohio-based scientists, who for years have looked at the lake’s algae/phosphorus problem, believe the study is flawed when it comes to determining the source of the algae blooms. Pete Richards is a water quality scientist from Heidelberg University in Tiffin. He says you have to look at the concentrations of phosphorous, not just the amounts.
RICHARDS: Because the concentrations of phosphorous in the Detroit River plume are so much lower, you just can't grow much algae in a given volume of water without running out of nutrients. You can grow ten to twenty times – and maybe even more – in the same volume of water in a typical Maumee River plume.
SCHAEFER: Richards also says satellite images make it clear that it's the mouth of the Maumee – not the Detroit River – where algae blooms form.
To some, the degree of responsibility that’s pinned on farms or the cities doesn’t matter. They just want to make sure we don’t have a repeat of the kind of algae outbreak we did in 2011.
SCHAEFER: Last fall, the floating mat of toxic algae blanketing large parts of Lake Erie was so thick it slowed down boats as they carved their way through, leaving behind brilliant green wakes. Steve Connor says it was the worst he's ever seen. Connor is a charter boat captain in who's been fishing on Lake Erie for more than forty years.
CONNOR: When you take a body of water that, because of this algae problem, turns into a slimy, green-looking body of water, nobody really wants to come out here and say, well, that's really attractive to go fishing in.
SCHAEFER: The sport fishing industry, beach resorts, amusement parks – all took a hit from the 2011 algae outbreak. Connor says cities …not just farms…have to do more to stay on top of it. Overflows from sewage systems that collect storm water and waste water are a fairly regular occurrence in Cleveland, Toledo, Detroit and other communities around the lake. And it's a huge cost to fix it.
ROBINSON: I feel very saddened for the Detroit area, because of the financial hardships that they are suffering. Cleveland, they're suffering. Toledo, fortunately, was under that billion dollar mark.
SCHAEFER: That's George Robinson, who’s directing Toledo’s 20-year project to separate the city's storms sewers from its sanitary sewers. He's grateful that its only costing a half billion dollars. But he's also concerned about Detroit's sewage treatment plant – the largest in the Great Lakes – which last year dumped 7-billion gallons of sewage and storm water into the lake. Officials there are still struggling over how to finance sewer upgrades without overburdening residents. In Cleveland, sewer rates are going up as much as 75-percent. That's one reason cities are also now eying lower-cost green infrastructure projects to keep storm water and sewage out of Lake Erie.
ANDY LANGENDERFER: At the low end of the project, there's only one set of catch basins, whereas normally we'd have maybe six catch basins along here.
SCHAEFER: In the flood-prone neighborhood of Maywood, the city of Toledo has turned one street into a test of green infrastructure. Engineer Andy Langenderfer says the city spent 7-hundred thousand dollars to disconnect storm sewers, build permeable sidewalks, and turn tree lawns into water collectors, called bioswales. Langenderfer is standing on the once grassy strip between sidewalk and street that now dips to a shallow trench filled with blooming plants.
LANGENDERFER: You're seeing the top if the bioswale. But actually the trench is down a good five feet. So it's a mix of gravel and different types of soil mixtures, trying to slow down that runoff to the actual storm sewers.
SCHAEFER: So far, Langenderfer says bioswales are reducing runoff by up to 70-percent in the one neighborhood where they’ve been tried. The city is looking to replicate similar green infrastructure projects, but cautions they won't replace the need for more expensive hard infrastructure solutions. Still, scientists say every little bit helps in the fight to curb the phosphorus that's feeding Lake Erie's harmful algae blooms. For ideastream, I'm Karen Schaefer.
Editor's note: Be sure to tune in next week as we report on other Lake Erie challenges, like the threat of Asian carp, during the Great Lakes Week conference in Cleveland.