MILWAUKEE CITY HALL FOUNDATION RESTORATION. Project Update November 12, 2014

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1 MILWAUKEE CITY HALL FOUNDATION RESTORATION Project Update November 12, 2014

2 Milwaukee City Hall Building History/Fast Facts - City Hall is a masonry and iron superstructure - Originally constructed from ,000 Square Feet - Achieved National Historic Landmark Status (2005) - Multiple interior renovations and exterior restorations have been conducted over the years - City Hall is a free-standing structure presently connected to the Zeidler Municipal Building by a pedestrian and utility/infrastructure tunnel at basement level - City Hall s utility services presently enter at the basement level and perimeter hollow walk areas and run up the interior core of the building to serve the occupied levels.

3 ORIGINAL WOOD PILE PLAN APPROX. 2,500 PILES

4 Milwaukee City Hall Foundation System- Background/Fast Facts City Hall is supported by over 2,500 untreated wood piles consisting of both hard and soft wood species Pile lengths are estimated between 23ft and 27ft Two layers of oak grillage layers are placed horizontally in alternating directions directly on top of the wood piles The oak grillage supports limestone pile caps which in turn support the exterior walls and interior columns/piers of the building The building has experienced differential settlement over the years as a result of fungal rot/decay of the grillage and pilings, a process that is difficult to predict The differential settlement is monitored through a series of survey points around the building

5 AREA BUILDING FOUNDATIONS / GEOTECHNICAL PROFILES

6 Milwaukee City Hall Water Recharge System- Background/Fast Facts Water recharge system installed in 1950 s to aid in submergence of foundation system wood piles and grillage The system is a network of perforated pipes run in trenches adjacent to the wood piles Wood piles when left exposed are subject to faster fungal rot/decay as oxygen becomes available to accelerate the process The system is float-controlled and fed from two water sources with a total typical discharge rate of water of 2.5 gallons per minute ( gallons per day) Several monitoring wells are located throughout the basement/sub basement to monitor water levels Water levels vary across the building and also fluctuate seasonally with groundwater changes The system is currently aged but functional, nearing the end of its useful life.

7 Milwaukee City Hall Hollow Walk System- Background/Fast Facts City Hall was originally constructed with a hollow access corridor located around the perimeter of the building beneath the streetlevel sidewalk extending along the east, north, and west sides. The north hollow walk area was previously abandoned/filled-in. The structural steel, reinforced concrete and structural masonry that support the sidewalk slabs are deteriorating Moisture intrusion has been an ongoing problem in the hollow walk areas The hollow walk areas currently serve as hallways, utility corridors, or back-of-house/storage areas HOLLOW WALK AREAS (HIGHLIGHTED)

8 Milwaukee City Hall Foundation Restoration Project- Goals Repair, restore, or upgrade the Foundation System, inclusive of the Wood Piling, Water Recharge, and Hollow Walk components Provide 100-year Service Life criteria for wood pile repairs or any new foundation supplementation efforts Task 1- Conduct a thorough investigation of the past efforts, examine current conditions, excavate test pits, make recommendations for implementation. Determine areas of critical/immediate need, suggested need, and areas that can be continuously monitored for now and repaired at a later date Task 2/3- Design and execute repair strategies

9 INVESTIGATIONS PERFORMED TO-DATE

10 CURRENT PERIMETER SURVEY, MONITORING AND DATA COLLECTION POINTS 66 MAJOR SURVEY POINTS; 50 ADDITIONAL CONTINUOUS MONITORING POINTS BEING ADDED IN DEC 2014

11 Milwaukee City Hall Foundation Restoration Project- Repair Areas The North main body of City Hall requires the most immediate attention due to settlement observations and current trends Project phasing is currently envisioned starting in the NW quadrant followed by the NE quadrant with a new supplemental foundation strategy The SW and SE quadrants of the main body of the building as well as the South Tower are currently being evaluated for future phasing for repairs and continuous monitoring

12 CURRENT SETTLEMENT DATA TRENDS AND ANALYSIS GREEN = LEAST SETTLEMENT < 1 YELLOW = MODERATE SETTLEMENT RED = GREATEST SETTLEMENT VALUES ARE APPROXIMATE TOTAL SETTLEMENT SINCE 1986 (28 YEARS)

13 SEQUENCE 1 REPAIR AREA- NW QUADRANT TIMEFRAME: 2016 REPAIR FOUNDATIONS; CONSTRUCT NEW MECHANICAL AND ELECTRICAL SERVICE AND EQUIPMENT ROOMS SEQUENCE 1

14 SEQUENCE 2 REPAIR AREA- NE QUADRANT TIMEFRAME: 2017 REPAIR FOUNDATIONS; DECOMMISSION OLD MECHANICAL AND ELECTRICAL SERVICE AND EQUIPMENT ROOMS COMPLETE SEQUENCE 2

15 SEQUENCE 3 REPAIR AREA- SE QUADRANT TIMEFRAME: FUTURE- TBD REPAIR FOUNDATIONS RECONFIGURE ZEIDLER ACCESS TUNNEL COMPLETE SEQUENCE 3 COMPLETE

16 SEQUENCE 4 REPAIR AREA- SW QUADRANT TIMEFRAME: FUTURE- TBD REPAIR FOUNDATIONS RECONFIGURE ELEVATOR LOBBY COMPLETE SEQUENCE 4 COMPLETE COMPLETE

17 SEQUENCE 5 REPAIR AREA- SOUTH TOWER TIMEFRAME: FUTURE- TBD REPAIR FOUNDATIONS COMPLETE COMPLETE SEQUENCE 5 COMPLETE COMPLETE

18 Milwaukee City Hall Foundation Restoration Project-Repair Strategies and Sequencing Allow existing wood piles and grillage to remain in place Install supplemental micro-pile deep foundations and reinforced concrete pile caps adjacent to existing stone pile caps Drill, install, post-tension and grout steel rods to passively transfer building loads to the new foundation elements over time Abandon water recharge system in areas where wood piles and grillage are no longer relied upon for structural capacity Abandon hollow walk area by backfilling it and replacing structural sidewalk slabs around the building with lower-maintenance slab on grade sidewalk slabs

19 REPAIR STRATEGY PLAN

20 TEST PIT EXCAVATION PHOTOS (Dec 2013 Jan 2014)

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22 REPAIR STRATEGY ISOMETRIC

23 REPAIR STRATEGY PLAN AND ELEVATION: MICRO-PILES WITH POST-TENSIONED PILE CAP Typical Repair Occurs on (2) Sides of Existing Pile Cap

24 REPAIR STRATEGY ISOMETRIC

25 REPAIR STRATEGY ISOMETRIC

26 REPAIR STRATEGY ISOMETRIC

27 REPAIR STRATEGY ISOMETRIC

28 HOLLOW-WALK BACKFILLING / ABANDONMENT WITH FOUNDATION REPAIR PERSPECTIVE

29 Milwaukee City Hall Foundation Restoration Project- Challenges Overall logistics and access to the work areas are the greatest challenges The project will need to be implemented in multiple phases over multiple years Use of the basement level for any purpose other than construction and maintenance of utility services will be limited in the phased construction areas To minimize disruption and construction noise levels to occupants on upper floors, any disruptive work will be conducted on second shift (after 5pm) In order to access foundations, interior walls/finishes, crawlspace framing, slab on grade and mechanical, electrical and plumbing infrastructure and distributions networks will need to be removed and/or relocated Maintaining City Hall as a fully operational civic and public building throughout construction; maintaining all utility/infrastructure services Relocating City services/personnel presently located in the basement level of City Hall to coincide with phases of construction

30 PRESENT DAY BASEMENT LEVEL SPACE UTILIZATION PLAN

31 PRESENT DAY BASEMENT LEVEL SPACE UTILIZATION PLAN Relocation of Historic Preservation Dept. from B4 to B12 (2015)

32 PRESENT DAY BASEMENT LEVEL SPACE UTILIZATION PLAN Relocation of DER Training from B6 to other City facilities (2015)

33 PRESENT DAY BASEMENT LEVEL SPACE UTILIZATION PLAN Relocation of Treasury Dept. from B5 to First Floor (2015)

34 Milwaukee City Hall Foundation Restoration Project- Next Steps Pilot study has been completed that validates the feasibility of repair method / drilling through existing stone pile caps. Design Development and Construction Document Preparation Budget and Scope Refinements Programming and Design for Relocations of Basement Occupants and Functional Uses Implement Continuous Monitoring Program for Foundation System to Increase the Reliability of Settlement Observations and Trend Information in December 2014

35 Milwaukee City Hall Foundation Restoration Project: Schedule

36 Milwaukee City Hall Foundation Restoration Project- Next Steps Cash Flow Timeframe Expenditure 2015 $2.1 Million Includes: Phase 1 Foundation Design B5 Treasurer Office Relocation to First Floor B4 Historic Preservation Relocation to B12 B6 DER Training Relocation to Other Areas

37 Milwaukee City Hall Foundation Restoration Project- Questions