Tuesday, July 1, 2014

Managing Silt Runoff and Sewer Overflows

Many governmental or quasi-governmental entities are responsible for water quality in southeast Michigan.  The U.S. Environmental Protection Agency (EPA) and the Michigan Department of Environmental Quality (MDEQ) oversee most of them.

In addition to regulating the Great Lakes Water Authority (GLWA) in metropolitan Detroit, EPA and MDEQ supervise overlapping responsibilities of agencies and organizations tasked with restoring degraded watersheds like those of the Clinton and Rouge rivers. [Updated January 29, 2016.]

Several decades ago, a legacy of severe and persistent pollution along the U.S.-Canadian border (including the Detroit River) led to a bi-national agreement and the designation of a number of locations as Areas of Concern (AOC), requiring extraordinary efforts to clean them up.  The Clinton River and Rouge River watersheds were among them.

Beneficial uses in these two watersheds were found to be impaired by pollution.  Organized attempts to address these concerns are called Remedial Action Plans (RAP).

Unfortunately, some of the causes of those impairments continue to this day.  For example, “Historical point source discharges and ongoing nonpoint sources are responsible for sediment contamination in the mainstream Clinton River.”

The following excerpts are from the Oakland County (MI) Water Resources Commission’s website, apparently quoting the Michigan Department of Environmental Quality (MDEQ);

“Why is erosion and sediment control important?”

“Sediment is the greatest pollutant by volume entering our lakes and streams. Sediment is the product of uncontrolled erosion. Everyone in Michigan is affected by erosion and off-site sedimentation. Erosion and sedimentation result in: loss of fertile topsoil, filling of lakes and streams, increased flooding, damage to plant and animal life, and structural damage to buildings and roads.”

“Construction is one of the major causes of erosion in Michigan. Without proper planning and management, over 100 tons of sediment per acre per year can be generated on some construction sites." 

After heavy or prolonged rainfall, silt runs off of ground that has been disturbed, i.e. loosened or dug up, as occurs at construction sites.  The regulation of silt runoff in Michigan leaves a lot to be desired.

The silt runs into lakes and streams or into combined (stormwater and human waste) sewer systems which lead to wastewater treatment facilities.  Silt causes turbidity in natural bodies of water, clogs sewers and imposes an added burden in treatment processes.  

During the heaviest rains, when the deluge threatens to overwhelm treatment plants, untreated or partially treated wastewater, laden by degrees with toxins, pathogens and sediment, is diverted into lakes and streams.  In our region, that means the Detroit River and Lake Erie.

For decades, water quality agencies in the region have been unable to manage such combined sewer overflows, which occur in the billions of gallons each year.  

Earlier schemes (e.g., immense storage tunnels) having been determined too expensive, new methods of controlling polluted overflows (principally, a number of relatively small retention-treatment basins) have been devised in the past two or three years and are being implemented.

Citizens, taxpayers and water services ratepayers would be well advised to learn about the new plans and watch to see how well they work.

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