Milwaukee Mile Gets Caution Flag over Erosion
[excerpted from the Journal-Sentinel]
A race is on - 15 feet beneath the Milwaukee Mile track - to prevent the collapse of leaking metal pipes carrying the entire flow of Honey Creek under State Fair Park in West Allis.
Should the pipes fail, sinkholes could form on the infield of the historic oval and swallow a section of a road course used by sports car clubs, officials said.
Though a NASCAR race is not scheduled this year at the Milwaukee Mile, the track and road course will be open to car clubs and driving schools.
The ground surface already has subsided 2 feet at three spots adjacent to the infield course, said facility engineer Jeff Jacobson. The pipes are not much deeper, just 15 feet or so below ground.
Fair Park crews have dumped gravel on the depressions, first observed in the summer of 2008, as they monitor the stability of the soil, Jacobson said. The area is fenced off from parking during the annual State Fair.
The Milwaukee Metropolitan Sewerage District's commission on Monday will discuss hiring a contractor to line the bottom of each of four metal pipes with concrete to stop leaks and prevent further corrosion of bolts holding the pipes together. During construction in late 1964 and early 1965, corrugated steel plates were bolted together to form 9-foot by 13-foot oval culverts.
Water from the creek has been leaking out cracks in the bottoms of the aging pipes, eroding soil around them, said David Fowler, MMSD senior project manager.
Soil above the pipes drops down, filling voids but causing depressions on the surface, he said.
Nearly 2.14 miles of north-flowing Honey Creek was forced underground in the mid-1960s, according to Fowler.
The creek drops into two 10-foot by 15-foot concrete box culverts at the north end of McCarty Park in West Allis. It does not return to the surface until it flows out of three 10-foot by 15-foot concrete culverts immediately north of I-94, near 84th St. in Milwaukee.
Beneath State Fair Park, the creek's flow is split between four oval steel culverts.
Engineers in the 1960s decided to confine the creek in culverts to quickly move water downstream in storms and eliminate flooding in the dense neighborhoods through which it flowed.
Photos from the time show the creek in channels next to garages and backyards of small urban lots. Some of those backyards now have manhole covers marking the creek's underground presence, Fowler said.
At State Fair Park, MMSD staff has recommended spending $212,000 to repair 50-foot sections of each of the four pipes below the Milwaukee Mile.
Water will be diverted from one pipe at a time to provide a dry surface, said Urbain Boudjou, MMSD project manager. Then a layer of concrete will be poured on the bottom of each pipe. Grout will be pumped around the pipes to fill voids and stop soil from slumping, Boudjou said.
Trucks will be parked on the infield of the Milwaukee Mile, pumping concrete and grout through lines dropped into manholes at access shafts.
Construction is scheduled to start in February and be completed before heavy spring rains of late April and May.
The contract also will include removing part of a vehicle found in one of the pipes, according to Fowler.
The abandoned, rusted chassis likely was driven or pushed up the pipe by people entering the culvert north of I-94. That opening also will be used to remove it from the pipe since the vehicle is too big to lift out of a manhole, he said.
Honey Creek flows north more than 8.8 miles from its origin near S. 43rd St. in Greenfield, through West Allis, Milwaukee and Wauwatosa, where it joins the Menomonee River.