The City of St. Ignace will focus on one of five options to divert wastewater effluent away from the end of Mackinac County Airport's only runway. Seen as a potential aviation hazard, the warm effluent is piped from sewage treatment lagoons to the bay, where it attracts fish and invertebrates, which in turn attract birds to feed on them.

A 2007 study by the U.S. Fish and Wildlife Service documented the bird problem, and now the city hopes to avoid a potential aviation disaster by redirecting the wastewater outfall.

"The real concern is the birds are right off the end of the runway," said City Manager Eric Dodson at a meeting Wednesday, March 11. "We've seen 500 birds bobbing along right there as you take off to the east, or even on approach from the east."

Seepage beds are relatively inexpensive and could solve the problem, suggested URS Corporation engineers Jan Hauser and Troy Naperala during last Tuesday's meeting at city hall. Also attending were Department of Environmental Quality (DEQ) geologist Randy Conroy and District Supervisor Steve Casey, who participated by telephone. Representing the city were Mr. Dodson, councilman and airport manager Paul Fullerton, and Department of Public Works Director Les Therrian.

URS Corporation, an engineering and planning company based in Grand Rapids, was hired by the city for $7,500 in January to study the problem and develop a solution.

When the lagoons were built in the late 1980s, the wastewater discharge pipe was designed to extend 1,360 feet into the bay, about 25 feet below the surface of Lake Huron, Mr. Casey said, but to save money when lagoon bids came in over budget, the city sought and received Water Resources Commission approval to set the outfall at the edge of the lake. Doing so was estimated to save about $400,000 for a treatment project, according to a St. Ignace News report of a March 2, 1987 city council meeting.

The Michigan Bureau of Aeronautics, Mackinac County, and the airport can find no documents indicating they were notified of the engineering change, said Mr. Fullerton.

"Nobody can find any communication whatsoever," he said, "that we were involved in approving this being dumped on the beach right at the end of the runway."

Now, to extend the pipe out to a depth of 24 feet would cost about $3.5 million, said Mr. Hauser.

"That clearly borders on unaffordable for a town like St. Ignace," he said.

By comparison, said Mr. Therrian, a $1.4 million loan equals about a $90,000 annual payment over 20 years.

The purpose of Wednesday's meeting was to solicit DEQ opinions on the various suggested corrections and discuss their affordability, said Mr. Hauser. Options include doing nothing, extending the outflow pipe into Lake Huron, relocating the pipe further to the north, cooling the effluent, discharging the effluent into a deep injection well, or establishing a surface discharge system.

To do nothing, he said, is not a viable alternative because of safety concerns at the airport.

Extending the pipe out into the Lake Huron would be possible if the length is reduced and the pipe is not set so deep into the lake bed.

The depth is needed to avoid ice scour, said Mr. Casey. Ice can damage the pipe and even break it apart. Mackinac Island has an outfall pipe under the water. In the mid-1980s during sewer system work on the Island, a diver inspected the pipe and found it in pieces that were scattered all over, he said.

A trench would have to be dug under the water and the pipe placed in it for protection against winter ice. Shortening the length of the pipe, he said, would not solve the problem, as the warm discharge still would warm the water and draw birds near the flight area.

Another option would be to move the outfall further north, said Mr. Hauser, although it cannot be moved north far enough to eliminate the bird issue, and moving it closer to homes has the potential to create odor problems for residents.

The effluent could be cooled before it is discharged, which would eliminate having to move or lengthen the pipe. While technically feasible, said Mr. Hauser, the system would be very expensive. Those attending agreed it was not an option to consider.

A groundwater discharge using a deep injection well was discussed as an option. Mr. Casey said he is not aware of any municipality receiving a permit for a deep injection well in the state. Concerns also were for energy costs incurred to operate a pump.

Discussion quickly changed to the consideration of surface discharge on the wetlands north of the airport. The site covers about 30 acres, where the effluent would have some ground seepage and likely travel to Hoban Creek. Mr. Casey advised that permits for that plan may be difficult to get, although he suggested they should apply for consideration.

The DEQ would have to determine the effluent limits of the area, he said.

"We would not allow you to use a wetland as a treatment system," he said. "You can't take a natural wetland and discharge sewage that would in any way impair the existing function" of the wetland.

The idea of constructing seepage beds met with favorable reviews and could be on land north of the wastewater treatment facility, next to the airport. The land is owned by the county and an agreement would be required for the city to use the site.

Getting a groundwater discharge permit probably would be possible, said Mr. Conroy, if a covenant was placed on it restricting groundwater use in the area.

During peak use of the sewer system during a short period in the summer, Mr. Casey said, the city could revert back to the outfall pipe temporarily.

"I don't think you have to solve the problem 365 days a year," he said.

Mr. Hauser said URS now will look at volumes of discharge, the direction of the flow, developing a monitoring well network, and determining the geology of the land.

The cost to construct the seepage beds will be determined after research is complete.

For financing, Mr. Casey suggested the city contact the State Revolving Fund to see if this project could be added to the city's sewer project already in the program.

Mr. Fullerton said the Federal Aviation Administration has indicated to him that it will not help with funding.