The Chicago Park District will try a new strategy next summer to keep out bacteria from the chronically infected 63rd Street Beach.
On trial will be a $385,000 "Gunderboom'' fabric filter system. The system is basically a curtain hanging down from a floating rod (the boom) out in the lake. Water is allowed to pass through the filter into the swimming area but it screens out unwelcome microbes.
"This is actually getting at the problem,'' said parks Supt. David Doig. "It is exciting because it attempts to address how we keep the bacteria out of the beach area.''
Richard Whitman of the U.S. Geological Survey welcomes the experiment.
"If it works, it'll be a ground-breaking model,'' he said.
The project still must be approved by the park board.
For years, 63rd Street Beach has been closed to swimmers a frustrating number of days each summer. It consistently shows the highest daily counts of E. coli among all the lakefront beaches during the swimming season, park officials say.
The source of the bacteria is a mystery. Possible culprits include seagulls and pets. A leaky sewage pipe was thought to be a big source and patched. However, other suspects are the very shallow water level and the curved shoreline that creates a cove.
The Gunderboom system was developed by engineers in Anchorage, Alaska, who were on hand in 1989 when oil from the Exxon Valdez threatened the shore. The system is named for engineer Bill Gunderson.
Next spring, 30 days before Memorial Day when beaches open, the Gunderboom patented filter will be dropped into Lake Michigan--hanging it from an 1,800-foot C-shaped rubberized boom filled with Styrofoam to keep it afloat. It will protect a 1,000-foot stretch of beach.
"We guarantee a minimum of 50 percent reduction in bacteria and/or . . . safe swimming levels,'' said Jim Miner, executive vice president of Gunderson's company, PN&D Engineering. "It should be safe every day for swimming.''
The fabric is made of polypropylene and polyester, and looks a bit like tough black felt. The curtain will be sealed to the lake floor by a nonpermeable skirt. Each end is fastened down on land, and several points are anchored under water.
Bathers on the beach will be able to see the boom in the water, 10 inches to a foot above the surface and 600 feet out at the farthest point.
A pump will be installed, ready to move water from inside the boom area to outside, if, say, a storm sends waves over the top and inside the swimming area and the bacteria count rises.