Demolishing Conners Creek
June 26, 2025
This article originally appeared in the September 1996 issue of DEMOLITION magazine, then called Demolition Age.
Michigan power giant Detroit Edison will save nearly $14 million over the next 20 years by eliminating the heating, maintenance and insurance expenses associated with its 81-year-old Conners Creek Power Plant.
“While the plant will always have an important place in company history, the demolition will allow us to reduce expenses and improve our competitive position,” said Frank E. Agosti, senior vice president for power supply.
The Detroit landmark, always known as the “Seven Sisters,” for its seven 350-foot-high stacks, was officially retired in 1983. It has been a beacon for area boaters since being erected in 1915.
A separate “high-pressure” side of the power plant has not generated electricity since 1987 but will not be demolished. The high-pressure side of the plant and its two stacks will remain as a standby power source for the company. The plant’s low-pressure turbine/generators were sold in 1984.
The nine-story plant was imploded at 9 a.m. on Saturday, Aug. 10, 1996, by NDA member Engineered Demolition of Minneapolis, which completed the implosion of nearby Carmel Hall in Detroit last March. They were working for Chicago-based NDA member U.S. Dismantlement Corp. (USDC), a subsidiary of NDA member Integrated Waste Special Services (IWSS) of Buffalo, New York, which has overall turnkey responsibility for the plant’s demolition.
USDC formed a strategic alliance with Detroit Edison, which focused on three areas of investment: recovery, hazardous materials removal and protection isolation. The protection isolation was critical because the low and high pressure turbine generators at the facility may be returned to service at some future time.
The Detroit Edison station was originally built in 1915, with a major equipment upgrade in 1935, and the high-pressure building, known as “Two Brothers,” was added in 1952. The low-pressure building contained seven turbine generator units driven by steam from 11 Sterling boilers. Above the 130-foot-high boiler house roof, the 17-foot-diameter stacks rose another 225 feet, topping out at 355 feet above the ground.
Total demolition of the surrounding buildings that included the turbine room, electrical switch rooms, administration, shops and maintenance buildings began in April this year.
After the surrounding buildings were cleared, the challenge was to safely fell the stacks without danger to persons, harm to the environment or damage to nearby property. Adjacent structures at potential risk were the active Essex Substation that distributed the electricity to a large area of industry and homes, the 300 megawatt high-pressure generating plant and its accompanying water treatment and coal-handling facilities.
After 14 months of environmental preparation, Detroit Edison and USDC agreed that implosion would provide greater safety and the least amount of environmental impact to the surrounding area.
The use of precisely timed linear shape charges was the method chosen to safely bring down the structure at one time, in order to reduce the personnel hazard, the long-term environmental impact and to minimize the fall zone radius.
Once the decision to shoot the building was approved, additional preparations were then necessary. The basement and mezzanine levels were cleared of boiler equipment, walls, stairways and cross-bracing, providing a 30-foot drop zone in which the boilers could rotate, gain momentum and compress under their own weight. The exterior brick was removed from its steel frame and a complete physical separation from top to bottom was also necessary between the Seven Sisters and the HP power plant to remain.
The weight of the seven stacks alone was 9,000,000 pounds of brick, steel and concrete. Even the weight of the air (over 200 tons) contained in the cavernous boiler room was a quantity to be calculated for displacement.
Engineered Demolition’s explosives team spent three weeks pre-weakening the building by selectively cutting the structural steel support columns at nine elevations. During the final week, approximately 1,500 pounds of high explosives were positioned at 480 critical points. The six-second, oblique cascade timing sequence was designed to provide for felling of the structure to the southwest, away from the remaining power plant. The actual implosion was accomplished in 10 seconds.
The project involved a variety of government agencies and authorities. An aeronautical study was required by the Federal Aviation Administration because the stacks had long served as a visual identification point for aircraft landing at the Detroit City Airport some 3.7 miles away. The Army Corps of Engineers and the Michigan Department of Natural Resources reviewed the closure of the plant’s underground circulating water system.
The U.S. Coast Guard established a marine safety zone on the Detroit River, north of Belle Isle, to temporarily restrict boaters from entering the danger zone on the day of the blast. The Detroit Police Department maintained an exclusion zone perimeter that allowed neighboring companies to conduct their normal business operations by preventing traffic congestion while protecting spectators.
A number of area activities grew out of the implosion. Detroit television stations broke regular programming to broadcast the event live on the air. Dick Purtan of WOMC, the city’s oldies station, broadcast his special morning radio program, billed as “A Blast From the Past,” live from the Roostertail Club, a nearby harbor and banquet facility.
Proceeds from admissions were donated to charity. Entrepreneurial tour boats, serving brunch on board, offered charters to view the plant demolition from the waterway, alongside several hundred recreational boats that had come out for the occasion. An estimated 30,000 spectators viewed the implosion from parks and riverbanks along the U.S. and Canadian borders.
In a little over 10 seconds, part of Detroit’s long industrial history was brought spectacularly to earth.