The Milwaukee Department of Public Works estimates it will cost $30 million to $40 million to reinforce the foundation beneath the northeast and northwest corners of City Hall. The northeast corner has settled up to 2 inches since 1986. Credit: Eric Oxendorf

SHARE Click to enlarge

By of the

With Milwaukee's City Hall finally shedding the scaffolding it has been wearing on and off for eight years, city officials on Wednesday released details of a new massive fix to the historic landmark.

With the building ever-so-slowly sinking, restoring a solid foundation will cost an estimated $60 million to $80 million over the next few years, Milwaukee Public Works officials said.

That comes on top the $76 million restoration of the terra cotta exterior — and the subsequent repairs to that project.

That means the combined cost of the two projects would range from $136 million to $156 million.

For comparison, the city will spend a total of $83.6 million next year on maintaining its core infrastructure of sewers, streets, bridges and street lighting. And just for another benchmark, it cost around $150 million to build the new Potawatomi Hotel next to the casino on Canal Street in the Menomonee Valley.

Under a proposal presented to the Common Council's Public Works Committee, in 2016 and 2017, contractors would build a second foundation of pilings around the north perimeter of City Hall as the first steps needed to halt its gradual settling.

The north half of the main building requires immediate attention, Public Works Commissioner Ghassan Korban said.

The northwest quarter of City Hall, at E. Kilbourn Ave. and N. Water St., would be done first in 2016 at an estimated cost of $15 million to $20 million.

The northeast quarter, at E. Kilbourn Ave. and N. Market St., would be shored up in 2017 at the same cost, Korban said. The pace of settling is greatest at this corner. Monitors have measured a drop of 2 inches since 1986 and a few cracks on inside walls can be linked to the settling.

The northwest corner has dropped up to 1.5 inches in that period, a report presented to the committee shows.

Estimates for shoring up the foundation of the southeast and southwest quarters of the building are in the same range of $15 million to $20 million each. The southern half of the building has settled up to 1 inch generally with a few locations dropping up to an additional half-inch.

No estimate for the south tower work was available Wednesday. Monitors have measured the least settlement at the south tower along E. Wells St. — less than 1 inch — and it is the lowest priority for restoration work, Korban said.

The committee approved spending $2.1 million in 2015 for final design of the perimeter foundation and other preliminary work. All cost estimates will be refined and likely will be reduced during the design process, Korban said.

Ald. Joe Davis Sr. was the only one of five committee members to object to the proposal. The full council will be asked to approve the plan on Nov. 25.

Davis questioned why city engineers decided to restore the building's exterior terra cotta before tackling the sinking foundation.

The original renovation of the terra cotta and other exterior walls was completed in 2008 at a cost of $76 million.

In February 2011, a piece of a decorative urn fell off the east side of the building onto Market St. That prompted city officials to build a corridor of metal scaffolding with a plywood cover on sidewalks around the building to protect pedestrians.

A second round of terra cotta repairs began after a July 2013 out-of-court settlement with general contractor J.P. Cullen & Sons Inc.

The risk of falling terra cotta off the exterior "presented more of a clear and present danger to people walking around City Hall," Korban told Davis. Given the slow settling of the foundation, engineers decided the exterior needed more immediate attention, Korban said.

Now that the protective corridor and other scaffolding needed for exterior repairs have been removed this month, additional monitoring sites will be placed around the building next month to allow for more detailed measurements of building elevation during 2015, Korban said.

The 119-year-old building is slowly sinking as its wooden pilings are rotting. A consultant blamed "fungal rot and decay" for the gradual deterioration of the old oak and pine logs.

City Hall, on the National Register of Historic Places, was built between 1893 and 1895. The first step in construction was pounding 2,500 untreated wooden pilings into a filled tamarack swamp. Log lengths varied from 23 feet to 27 feet.

Two layers of thick oak planks were placed atop the pilings. The planks were covered by slabs of limestone. The pilings and limestone caps support the weight of the building.

A system of perforated water pipes was installed in trenches around the pilings in the 1950s to help keep the wood submerged and prevent it from drying out and rotting if exposed to oxygen. The 60-year-old system is at the end of its useful life and could be abandoned if the additional perimeter foundation is built, a consultant said.

New pilings with concrete caps would be built adjacent to existing stone caps, under the foundation restoration proposal. Old pilings and caps would remain in place.

Steel rods connecting new and old pilings would allow the weight of the building to be shifted gradually onto the new foundation and provide support for the next century.