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Downtown Milwaukee is sinking. The signs are everywhere. Sidewalks settle unevenly, forcing city crews to “shave” the protruding edges of the slabs. Lateral cracks run for blocks along city streets. Manholes stick up like iron thumbs where streets and alleys have sunk around them. Curbs protrude above receding sidewalks.
Just below the surface, the foundations of scores of old buildings are rotting and shifting as groundwater levels drop, exposing tens of thousands of wooden pilings to decay. Many, such as the Mitchell Building on East Michigan Street, have required extensive repairs. Others, such as the Milwaukee Repertory Theater complex, likely will need future repairs.
“We are in real danger of losing many wonderful historic buildings,” says contractor Dennis Barthenheier, who, for more than 30 years, has made foundation rescue his specialty.
Much of Milwaukee, you see, was built on marshland that bordered its three rivers. The entire Third Ward and nearly three-fourths of Downtown stands on a swamp. Although it was filled in with dirt and garbage and the like, underneath it, water still flowed.
Most of the substantial buildings in old Milwaukee (some erected as late as the 1940s) were constructed on foundations of wooden pilings pounded into the earth, often by Edward E. Gillen Co. The pilings would extend through the filled-in dirt into the ample water table about 10 feet beneath grade and then into the swampy soil found beneath that. The pilings were expected to remain submerged and be sound for centuries. Some buildings – such as City Hall, Northwestern Mutual Life and Boston Store – have underground irrigation systems to ensure that the pilings never dry.
But in recent years, the water table has drained away, exposing the pilings of many buildings to the air. Thus, they decay – the technical term is “pile rot.” As their structural foundation degrades, the buildings could meet with catastrophic failure. That includes the 1895 City Hall, where it will cost $13 million to repair piles that had been sound for at least a century.
And as the water table is depleted, the ground above it starts to sink, causing problems for the Milwaukee Department of Public Works, which spent $40,000 this past summer “scarifying,” or shaving down, protruding sidewalk slabs in the Third Ward.
Where did the groundwater go? Barthenheier and other experts blame the Deep Tunnel: the 28.5-mile sewage and stormwater tunnel that runs 135-300 feet below the city, beneath the marshland that Milwaukee was built upon. The Deep Tunnel is divided into three sections that extend from Downtown, giving this part of the city great exposure to its effect on the groundwater. The tunnel is so porous that huge amounts of water from the old marsh are seeping into it each day, lowering the water table and exposing the old buildings’ supportive timbers to pile rot.
“I don’t know why people hem and haw about it, and why it should be some hush-hush secret,” says Barthenheier. “It’s the Deep Tunnel that’s dewatering Downtown and the Third Ward.”
That’s precisely what lawyers representing the owners of Boston Store claimed in a suit against the Milwaukee Metropolitan Sewerage District, which built the Deep Tunnel. The lawsuit blamed the Deep Tunnel for causing pile rot and damaging the Boston Store building’s foundation.
The tunnel originally was to have been lined with concrete, but MMSD officials decided to line only 45 percent of the structure, says Bill Graffin, the district’s public information manager. The tunnel’s later extensions were lined, but that still leaves 10.7 miles, or nearly 38 percent, of the tunnel unlined. This was a cost-saving decision made during construction as the project went over budget, Barthenheier says. He worked on the tunnel as a laborer during its creation and says the engineers decided to not line the portion of the tunnel that was dug through dolomitic limestone on the theory these stone walls wouldn’t leak. Instead, he says, “We were sealing joints with oakum and lead.” Silty water poured in everywhere, he says.
In the Boston Store suit, MMSD lawyers admitted the sewerage district knew that during construction, 5 to 8 million gallons of water per day had to be pumped from the Deep Tunnel, “primarily from groundwater inflows into the system from the … aquifer surrounding the Deep Tunnel.”
Since the tunnel’s completion in 1993, the inflow has continued, though at a slower rate: U.S. Geological Survey data shows there is groundwater seepage of 2.8 million gallons per day. At that rate, the Deep Tunnel would fill itself twice a year, even without sewer discharges.
During the 1980s, the Southeastern Wisconsin Regional Planning Commission did a key study on the feasibility of the Deep Tunnel, but the issue of water infill never arose. According to Michael G. Hahn, the group’s chief environmental engineer, the group did no “projections of the amount of water that would seep into the unlined portion of the tunnel” and did “no studies of subsidence of surfaces in the Downtown/Third Ward area.”
In essence, the MMSD decided it was cheaper to not line the entire tunnel and simply pump out the millions of gallons of water leaking into it on a daily basis.
“It is obvious that the District was on notice that the Deep Tunnel was severely dewatering the downtown area and causing property owners … harm.” Such was the conclusion of Wisconsin’s 1st District Court of Appeals in its ruling in the Boston Store suit. “The District had identified the Boston Store as a ‘critical structure’ that was at particular risk to dewatering because the timber piles upon which the store was built would begin to rot and shift as the ground was dewatered,” the court noted.
MMSD argued there was another cause to the problem – an old, abandoned well. Doug Cherkauer, emeritus professor of geosciences at UW-Milwaukee, served as an expert witness for the MMSD and says of Boston Store: “They have a well beneath the building that has served as a drain for decades … reducing water levels in the shallow sediments into which the building’s pilings are pushed.” He says the owners had a sprinkling system in place “specifically to keep the pilings wet” that “hasn’t been used in decades.” This was the cause of pile rot in the foundations, he says.
Boston Store’s owners ultimately won an award of just $100,000, partly because they were found 30 percent negligent in causing the damages and partly because of a legal cap on damages paid by municipal governments.
Cherkauer also argues the Deep Tunnel is not the major cause of subsidence Downtown. Rather, he argues, the main reason is “overloading,” meaning the city overbuilt its Downtown, given the swampy land below. The level of groundwater is no lower near the Deep Tunnel than elsewhere, he contends, and any depletion is due more to underground wells and other causes, he adds.
But several experts who testified on behalf of Boston Store disagree. Leland Jan Turk, an expert on groundwater with the University of Texas-Austin, called the tunnel a sink for groundwater, estimating it is now depleted at a rate four times greater than before the Deep Tunnel’s construction.
And Charles Nelson, a consultant in underground engineering, said only a “complete lining” would stop “the groundwater inflow” being caused by the Deep Tunnel.
Despite such recommendations, a 2002 audit of the MMSD by the state’s Legislative Audit Bureau found the District is “unlikely” to do so “because its consulting firm determined that additional grouting would eliminate less than half of the present infiltration and would be more than three times as costly as continuing to pump … the water entering through infiltration.”
That same year, the MMSD did its first-ever inspection of the tunnel. One goal, it said, was to “measure the amount of groundwater infiltration,” yet its report offers no such data, a curious omission. MMSD spokesman Bill Graffin says infiltration is now “about half of what it was when it first went online” – but still some 2.5 to 4 million gallons a day. He also says some of the tunnel’s “seeping joints are healing themselves through calcification,” a response that Barthenheier treats with a derisive laugh.
Barthenheier has built a thriving business, having handled the pile rot and structural problems of a dozen or so old Downtown structures, from the Saddlery Building (233 N. Water St.) to the former Milwaukee Antique Center (341 N. Milwaukee St.) to the Mackie Building (225 E. Michigan St.).
Next door to this is the Mitchell Building, a National Register-listed French Second Empire edifice from 1876. There are 48 columns in the massive stone building, each resting upon a bundle of nine to 12 Douglas fir piles. (If you’re looking for Wisconsin’s virgin forest, it’s underfoot.)
Barthenheier had to devise an innovative way to repair a foundation without removing the building or causing its collapse. The work must be done with hand tools that are considerably more primitive than the steam pile drivers that originally pounded the virgin timbers into the earth some 135 years before. And done in temperatures that could rise to 150 degrees in this steam-heated structure. The building has a dirt-floor basement, and employees dug four feet through the rock-hard soil, working on only one face of a single column at a time, exposing the piles with the care of an archaeologist. Each was rotted and mottled, pockmarked by gaps, resembling the weathered piers of an abandoned dock. Workers would probe to find sound wood and cut off the rotted tip.
The excavated soil had to be carried upstairs in 5-gallon buckets to be dumped. (The rotted stumps were carried up, too, and dozens of them remain in the building’s basement.)
It was slow, backbreaking work, as the ceiling of the basement is low, and most digging and hauling had to be done in a stooped position until the hole got deep enough. Workers would reinforce the pilings horizontally with steel rebar, fill the vertical gap with a new stainless steel shaft, enclose the works in concrete and go on to the next pile.
Also working by hand, workers dug trenches about three feet deep and 30 inches wide in between the restored columns in the basement. The trenches were backfilled with pea gravel. Next, water from the building’s 24 heat pumps will be drained into the basement to help keep the pilings wet. “We’ll divert 6.9 million gallons of coolant water from the sewer system,” Barthenheier says.
Many of these techniques were developed by Barthenheier over the years, starting with his first project in 1981 at what were then the buildings for First Bank at 231 and 211 W. Wisconsin Ave.
“No other contractors have our type of experience in this work,” he says. “By the time we were done with the Mitchell Building, we raised it a sixteenth of an inch.” A narrow victory in Downtown’s ongoing battle to stay afloat. n
