PCB's to be Cleared from Mitchell Park

[excerpted from the Journal-Sentinel]

Workers in protective suits equipped with hoses for fresh air will enter a 120-year-old brick sewer beneath Mitchell Park on Monday to begin removing a thick, jelly-like layer of soil and debris contaminated with toxic chemicals, Milwaukee Metropolitan Sewerage District officials said.

Federal environmental officials have agreed to a partial cleanup of polychlorinated biphenyls in the old brick line so work can proceed on a wet-weather relief sewer to be built beneath the aged wastewater conduit.

The new 7-foot-diameter pipe will take storm-swollen flows from south side street sewers directly to Jones Island, freeing up space in the deep tunnel storage system for flows from other areas, said Bob Plecash, project manager for MMSD.

The $35 million relief sewer must be completed in 2010 as part of a court-ordered list of projects aimed at reducing sewage overflows into Milwaukee's rivers and Lake Michigan.

A tunnel boring machine has completed about 75% of its 2 1/2 -mile route from a shaft at the inner harbor west, generally beneath Virginia and Pierce streets, to a rail yard north of Mitchell Park.

The machine is boring the segment beneath Mitchell Park, and the final destination is W. Canal and S. 25th streets.

To get there, the machine will dig through dirt just inches below the brick sewer. The old line, about 30 feet below ground, is still in use. MMSD engineers fear it could collapse when the machine passes by unless the bricks are reinforced.

But the work of shoring up the bricks cannot be done until the PCBs are removed, said Tom Zimmerman, MMSD engineering design and construction manager.

You can read the full article at JSOnline.com.