J.L. Hudson Department Store - Detroit, Michigan

J.L. Hudson Department Store - Detroit, Michigan

The Loizeaux Group, LLC

With the press of a button at 5:47 PM on October 24, 1998, Detroit's Mayor Dennis Archer dropped the J.L. Hudson Department Store from his city's skyline and into both the history and the record books.

Hudson's was the tallest department store in the country and was second only to Macy's New York anchor store in terms of square footage. Hudson's dominated the retail market in Detroit up through the 1970's before closing its doors in 1983.

The store was built in 12 separate stages: the first in 1911; and, the last in 1946. The complex had 2 retail basements and 23 above-grade retail floors, including mezzanines. Two additional basements and 6 upper stories in the tower portion of the structure provided storage and mechanical support for the 2.2 million square foot building. There were a total of 33 levels in the structure, including: basements; mezzanines; full floors; and, the penthouse.

In the fall of 1997, the Downtown Development Authority of Detroit (DDA), retained a joint venture of Walbridge Aldinger and Jenkins Construction of Detroit to manage the project. Walbridge/Jenkins took bids for asbestos abatement of the structure. The abatement contract was awarded to Loyalty Environmental of Chicago. The contract was completed in 3 months.

The demolition contract went to a joint venture between the Boston-based firm, North American Site Developers, Inc. (NASDI) and the Detroit-based firm, Homrich, Inc. NASDI/Homrich then retained Controlled Demolition, Inc. (CDI) and the Loizeaux Family of Phoenix, Maryland to design and perform the implosion of the Detroit landmark.

No structural drawings of the facility were available, making the structural analysis and implosion design a formidable task for CDI. The interdependency of the 12 different construction stages between 1911 and 1946 (with differing construction, variable column flange directions and varying bay widths) created different "natural failure modes" in each section of the structure. CDI's demolition program had to cope with all of these variables and maintain a homogeneous demolition plan. These factors created an implosion design, preparation and dynamic control challenge for the 2nd and 3rd generations of the Loizeaux Family, recognized as the international founders of the commercial implosion industry.

Hudson's footprint was bordered on all four sides by streets filled with critical infrastructure for downtown Detroit. Additionally, the structure was flanked on 3 sides by turn-of-the-century structures with huge sand-cast glass windows. Many of these original windows had been poorly maintained, and were reported to have occasionally shattered during high winds in the area. Most importantly, Hudson's rose 410 ft. above Detroit's elevated "People Mover" transit rail which ran parallel to the east face.

Mark Loizeaux, President of CDI, called the Hudson's project "the greatest dynamic-structural-control challenge the company had ever faced." CDI had to sever the steel in the columns and create a delay system which could simultaneously control the failure of the building's 12 different structural configurations, while trying to keep the hundreds of thousands of tons of debris within the 420 ft. by 220 ft. footprint of the structure. CDI needed structural data to complete its design. Under CDI direction, NASDI/Homrich's 21 man crew needed 3 months to investigate the structure and 4 months to complete preparations per CDI's implosion design. During that period, the lower 2 basements of the structure were filled with engineered fill material and the perimeter basement walls were bermed to the 1st basement level with soil to support perimeter walls. This was necessary as these perimeter walls would have surely failed under soil and hydrostatic loads once the horizontal support of the Hudson's internal structure was removed during the implosion.

Hudson's extremely stiff "frame" was comprised of double column rows installed in the structure between vertical construction phases, internal brick shear walls, x-bracing, 70 elevator shafts and 10 stairwells. Columns weighing over 500 lb./ft., and having up to 7.25" thick laminated steel flanges and 6" thick webs defied the capabilities of the linear shaped charge explosives available. CDI analyzed each individual column and determined the actual load it carried. Using torches, the appropriate number of steel plates were then scarffed off in order to allow the use of the smaller, commercially available shaped charges to cut the remaining steel. The use of the smaller charges also allowed CDI to keep the air over pressure generated by the implosion to a minimum, thereby lowering the risk of window breakage in adjacent properties.

Under CDI's plan, a jump-bay used to structurally connect the structures built from 1911 through 1916 on the southwest corner to an addition built in 1926 (across an alley) on the southeast corner was pre-removed. This created a vertical plane of weakness CDI could then use to separate the different types of construction in the building.

In 24 days, CDI's 12 person loading crew placed 4,118 separate charges in 1,100 locations on 9 levels of the structure. Over 36,000 ft. of detonating cord and 4,512 non-electric delay devices were installed in CDI's implosion initiation system. As the implosion required the detonation of a total of 2,728 lb. of explosives, CDI implemented 36 “primary delays" and an additional 216 “micro-delays" in the implosion initiation sequence in an attempt to keep detonation overpressure to a minimum.

While the 252 total delays would considerably help to “break up" the detonation pressure to be created, window breakage in adjacent structures remained a concern. Due to the age and poor condition of the vacant structures located to the north, east and west of Hudson's, CDI had 7 glaziers on standby during and after the implosion to immediately handle any glass replacement necessary.

An additional precautionary measure taken was to have NASDI/Homrich place over 2,000 yards of soil over utilities in the 4 adjacent streets. Emergency utility crews were also kept on standby to deal with any problems generated by the implosion.

When the button was pressed at 5:47 PM, assembled officials, contractors and an estimated crowd of 20,000 spectators watched the store begin to fail at its southwest corner. The controlled, progressive collapse moved northeasterly through the structure, literally pulling the perimeter walls inward.

When the dust cleared, a debris pile averaging 35 ft. tall, and as high as 60 ft. tall where the tower had stood, was all that remained of the venerable Detroit department store. Woodward, Farmer and Gratiot Streets were cleared of light debris immediately. It would take an additional couple of days to clear the pile of debris closest to the narrow Grand River Avenue side to ensure vehicular and pedestrian safety.

The intricate delay sequence reduced air overpressure greatly, resulting in far fewer broken windows than originally anticipated. Many of the broken windows appeared to have been those which were documented as being "cracked" during the pre-implosion survey, according to Dave Miller of Schnabel Engineering, the firm hired to perform surveys and record the vibration generated by the implosion. Miller also indicated that the vibration from the fall of the structure was well within allowable limits as recorded at adjacent properties. There were no apparent damages to underground utilities.

Pile-up of debris during the fall of Hudson's pushed 6 steel columns backward, against the post-tensioned concrete People Mover rail near the southeast corner of the structure. A preliminary review by a local structural engineer indicated there was cosmetic, minor structural and control cable/rail damage found. A detailed structural survey will be made to ensure that no serious damage was incurred. As the People Mover was already scheduled for a 2 week shut-down for maintenance of the system immediately following the Hudson's implosion, these repairs will begin as soon as the structural review is completed.

The NASDI/Homrich Joint Venture expects to take 5 months to clear the debris, placing selected material back in the hole as structural fill.

CDI's implosion of Hudson's set 2 new records:

  • At 439 ft. tall, measured from the second basement to the top of penthouse of the tower (the full free-standing structure), Hudson's is the tallest building ever imploded, eclipsing the record also held by CDI since 1975 in their felling of the 361 ft. tall Mendez Caldiera Building in Sao Palo, Brazil. Measured from grade to the top of the tower penthouse, the J.L. Hudson building was 410 ft. tall, topped by a 110 ft. tall flagpole.

  • At 439 ft. tall, Hudson's is the tallest structural steel building ever imploded, eclipsing the record CDI set in 1997 with the felling of the 344 ft. tall, #500 Wood Street Building in Pittsburgh, Pennsylvania.