united states mine rescue association Mine Disasters in the United States
Seminole Rock Products, Incorporated Broward Mine and Mill Explosives Detonation
Miramar, Broward County, Florida
September 9, 1971
No. Killed – 3
The Broward Mine and Mill, an open-pit limestone operation, owned and operated by Seminole Rock
Products, Incorporated, was located at 196th Avenue and Hollywood Boulevard, Miramar, Broward County,
The mine and mill were normally operated one 9-hour shift a day, 6 days a week. A total of 20 persons
The company began mining at this location in February 1971. A previously unreported premature explosion occurred at this operation in late June when several charged holes containing explosives and electric blasting caps were detonated by an electrical storm. There were no injuries or damage to equipment.
Reportedly, proper safety precautions had been taken upon approach of the storm.
Overburden, consisting of about 2 feet of topsoil, was removed by bulldozer or dragline. The top of the exposed limerock, which was at or near the water table, was then covered with about 4 feet of loose limerock so that the drill rig would remain out of water. The deposit was then drilled and blasted.
Broken material was recovered from under water by dragline and stockpiled nearby for drying. The mine consisted of two pits. The pit in operation at the time of the accident was about 140 feet wide and 1,500 feet long.
Holes for blasting were drilled 4¾ inches in diameter and about 47 feet in depth with a diesel-powered, rotary drill. The hollow drill steels were 2½ inches inside diameter, 52 feet long, and equipped with an open-end bit. Water under pressure was used to flush the drill cuttings from the boreholes.
Due to the high water table and conglomerate rock formation, the boreholes generally would not remain open when the drill steel was removed. Consequently, after each borehole was drilled and the water pressure shut off, the drill steel was left in the hole to act as a casing while placing the explosive charge. The upper end of the drill steel was opened and explosives and detonators were loaded into the borehole through the hollow drill steel, known locally as a "Kelly Bar."
When the drill steel was removed, the explosives remained in the borehole at the desired level. The inside of the hollow drill steel frequently was blocked by cuttings, cores, or packed sand as a result of insufficient water pressure in the drill steel while drilling or from a "washback" when the water pressure was shut off after the hole was completed. If the
drill steel were blocked it was possible and not uncommon to unknowingly load the explosives on top of the blockage. As a results some or all of the explosives might remain in the drill steel when the steel was removed from the borehole.
Common practices, when a blockage occurred, were to rotate the drill steel or to apply sufficient water pressure to force out the obstruction and permit the explosives to fall down through the drill steel. These attempts were made while the
drill steel was loaded with the primed charge of explosives. Loading explosives into boreholes through a hollow drill steel and the above-described methods of freeing hung charges or clearing blocked drill steels were standard practices in the entire mining area.
Description of Accident
On the day of the accident, Curtiss Smith and McKinley Jones reported for work at their normal starting time of 7:00 a.m. at the company's Medley Quarry, which was located in Dade County, Florida.
After checking in, they traveled to the Broward Mine to perform their regular duties of drilling and blasting. Their arrival time could not be determined, but the normal time would have been about 7:30 a.m.
Smith and Jones loaded the explosives vehicle with about 1,700 pounds of explosives and then drove the loaded vehicle to the drilling and blasting area where they performed their duties without known unusual incident until the accident.
The victims were seen by several persons during the morning and nothing unusual was observed.
William Flateau reported for work at the Curtis Tool Company in Miami shortly before 7:00 a.m. on the day of the accident and soon departed in a pick-up truck to make deliveries in Broward County. He arrived at the Broward Plant at about 10:00 a.m., obtained the signature of the plant manager for the drill bits he was delivering, and then drove to the drilling and blasting site.
David Fryer, plant foreman, followed Flateau to the drill to exchange some drill bits. Upon arrival at the drill, Fryer observed the tool company's truck parked alongside the drill rig, heading in a northerly direction and Flateau was placing bits on the drill rig.
Smith was off the drill standing near the control panel and Jones was standing behind the explosives vehicle parked near the drill. The drive motor of the drill was running, but the rotation and feed gears were not engaged. Fryer took the bits from his truck, placed them on the drill rig, exchanged greetings with the three men, and then proceeded north in his own vehicle. Fryer drove north about 1,000 feet, turned around, and waited for a moment until a dragline operating
across the pit swung in his direction. He waved to the dragline operator and then proceeded south back to the drilling area.
Fryer estimated he was away from the drill for about 1 to 3 minutes. During this time, the tool company's vehicle had been turned around and was parked facing south, blocking Fryer's exit from the area. Fryer noticed the brake light was on and the driver appeared to be writing on a pad.
An explosion occurred before Fryer noted the position of the drill crew, and he recalled blackness, smoke, and debris filling the air before he fell below the dashboard of his vehicle.
Apparently the tool company's truck was located so that it deflected the main force of the explosion from Fryer's truck as Fryer was not injured and his truck received slight damage.
Evidence and data collected indicated that all but about 16 feet of the drill steel had been removed from the ground before the explosion, and about 4 feet of explosives had been in the drill steel above the surface of the ground. In the absence of evidence to the contrary, it was assumed that the explosion originated in the drill steel and flying metal from the bursting steel detonated about 1,200 pounds of explosives remaining on the explosives truck which was located about 20 feet away from the drill rig. The six or seven fully loaded holes drilled earlier in the pattern had also
The explosions produced a crater about 26 feet in diameter and about 5 feet deep at the drill and another about 18 feet in diameter and 5 feet deep where the explosives truck apparently had been parked. The drill rig was severely damaged. The explosives truck was disintegrated and the tool company's truck was demolished.
Smith received multiple fractures, avulsion of the head, and partial dismembering. Flateau suffered multiple fractures and severe lacerations of internal organs. Jones was nearly decapitated and suffered severe puncturing wounds.
Cause of Accident
The direct cause of the accident was loading explosives and detonators through and with a device capable of producing sufficient force or friction to cause detonation of explosives and detonators.
Historical Summary of Mine Disasters in the United States - Volume III