The near-historic rainfall this week that left cars stranded and roads closed across Metro Detroit also will likely make Lake Erie’s algae-fouled beaches worse for neighbors to the south.

About 30,000 Michigan and 400,000 Ohio residents along Lake Erie’s western basin had just shrugged off last week’s algae contamination in their water supply when Mother Nature dumped up to six inches or more of rain in a few hours Monday on parts of Metro Detroit. And when it rains here, the region’s fertilizers, chemicals and wastewater head toward Lake Erie.

For a decade, nutrients like phosphorus that washed into the lake from both states increasingly have been turned into algae that spoils local beaches and interferes with fishing. During the last two summers, it also has led to water consumption advisories.

On Thursday, Michigan Department of Environmental Quality Director Dan Wyant introduced a slate of initiatives aimed at reducing the amount of phosphorus Michigan contributes to Lake Erie. Among those was a plan to improve “ phosphorus removal at five key wastewater treatment plants in the watershed.” All of the treatment plants are in Metro Detroit.

While the fertilizer and animal waste that runs off from large-scale farming operations correctly gets its share of the attention, human waste — mostly in the form of combined sewer overflows — is a major contributor to the algae problem. The cost of separating combined water-sewer lines in municipalities is so expensive — in the case of one large Michigan city, hundreds of millions of dollars — many have opted for other measures that are cheaper, but often less effective.

Combined sewer overflows occur in areas where sanitary sewer lines are connected with storm water lines. During heavy rains like Monday’s, the amount of water in the system overwhelms what treatment plants can handle, and untreated sewage can be discharged into local streams and rivers. Thirty-seven communities in the four-county area that includes St. Clair County have combined or partially combined systems, according to the Department of Environmental Quality.

“Normally, the Detroit River looks blue,” said Bob Burns, the Detroit Riverkeeper, on Wednesday. “Now it looks brown because of the runoff and the sewage discharges.”

The discharge amounts from this week’s rainfall that closed highways still are being reported to the DEQ. They already are massive: There were 38 known sewage overflows from Metro Detroit; so far, with about half reporting, more than 800 million gallons have flowed into area waterways.

Sewage discharged during these events adds to the phosphorus that produces algae.

“Somewhere between 5 and 7 percent of the phosphorus that reaches Lake Erie, up to 11,000 metric tons, comes from the Detroit River ... ,” said Sandy Bihn, executive director of Western Lake Erie Waterkeeper Association, a Toledo-based nonprofit dedicated to protecting the lake.

“In 2011, the worst year for algae on Lake Erie, there were 45 billion gallons of sewage overflows from the Detroit Wastewater Treatment Plant.”

In recent years, the Department of Environmental Quality has forced several communities to address their phosphorus and discharge issues through National Pollutant Discharge Elimination System permits that reduce phosphorus. Detroit’s main treatment plant has been one of the program’s success stories.

“We’re glad to say they’re meeting those standards and they’ve made great progress in reducing the amount of phosphorus that comes out of that plant,” Wyant said Thursday.

Prohibitive costs

Despite those efforts, several communities in the region continue to operate with combined sewage and storm water lines. Others operate with systems that are partially separated.

“There are basically two options — one is to separate your systems and the other is to put in other things like retention treatment basins,” said Amy Mangus, manager of plan implementation with the Southeast Michigan Council of Governments. “A lot of the communities went with retention basins.”

Even those are not foolproof, as Monday’s rain showed. Wyandotte’s Pump Station No. 5 reported a discharge of more than 184 million gallons Monday into the Detroit River’s Trenton channel.

The main reason combined systems continue to be unaddressed is cost. Grand Rapids began separating its lines in the 1990s. By January 2011, nearly all of the city’s combined sewer system was addressed to the tune of $360 million.

“Grand Rapids went through that process because they could make it economically feasible,” said Melissa Demaschke, Great Lakes program director for the Sierra Club. “For a city the size of Detroit, it’s a bit different. You’re talking about taking up streets to lay down new pipe. ”

Human waste isn’t only a concern in Michigan. In Toledo, the handling of city sludge on part of an island in Maumee Bay has raised concerns. Mayor D. Michael Collins has claimed it is a likely contributor to the area’s algae bloom problem.

U.S. Environmental Protection Agency officials in Ohio said the amount of runoff from the island is minuscule.

But Thursday, Michigan DEQ’s Wyant urged an end to the open-water disposal of dredged sediments that contain nutrients from Toledo’s harbor.

Ohio Gov. John Kasich and three agencies also released a Lake Erie water quality plan Thursday that in part makes available $150 million in no-interest loans to communities to improve their drinking water and wastewater treatment plants.

Less expensive options

In the absence of pricier fixes, communities can adopt other practices to reduce the amount of storm water that reaches the system and leads to discharges. Those include:

■ Constructing new parking lots with bioswales — shallow depressions filled with vegetation — to help soak up water.

■ Urging residents to redirect downspouts from paved driveways onto grass or gardens.

■ Encouraging businesses to utilize cisterns or green roofs to capture rainwater.

■ In areas such as Detroit, where demolition projects are underway, encouraging municipalities to turn over the soil at the time the buildings are taken down to make the ground more receptive to water.

Without the separation of all the region’s storm water and sewer lines, conservationists hope implementation of smaller steps might offset heavy rain and greatly reduce the discharges.

But most realize events like the Monday’s rainfall could overwhelm even the most modern sewer systems.

“This should be a wake-up call,” Damaschke said of the rainfall that paralyzed the region. “These extreme weather events are happening, and we need to address them.”

Separating combined water lines

Why environmental officials prefer to separate sanitary sewer lines that are connected with storm water lines:

■ In heavy rains, the amount of water overwhelms what treatment plants can handle and leads to untreated sewage being discharged into local streams and rivers.

■ Separating the lines greatly reduces the chance of untreated human waste getting into rivers and other waterways.

■ 37 communities in the Macomb, Oakland, Wayne and St. Clair counties have combined or partially combined systems. They include Berkley, Clawson, Ferndale, Grosse Pointe Woods, Harper Woods, Huntington Woods, Port Huron, Royal Oak and Wyandotte.

Source: Michigan Department of Environmental Quality

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