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Southeastern District
Metal and Nonmetal Mine Safety and Health

Accident Investigation Report
Surface Nonmetal Mine

Fatal Falling/Sliding Material Accident

Mine I.D. No. 54-00120
Cantera Espinosa
San Juan Cement Company, Incorporated
Espinosa Ward, Dorado, Puerto Rico

September 16, 1996


Juan A. Perez
Supervisory Mine Inspector


Jose J. Figueroa
Mine Safety and Health Inspector

Originating Office
Mine Safety and Health Administration
135 Gemini Circle, Suite 212
Birmingham, Alabama 35209

Martin Rosta
District Manager


Two employees were fatally injured and three other employees received burn injuries when hot, raw material inundated the kiln and clinker cooler area of the mill at approximately 9:45 a.m. on September 16, 1996.

Manuel A. Lopez, plumber, age 54, was fatally injured on the day of the accident when he was covered with hot dust after falling from a temporary work platform. The victim had a total of 25 years mining experience, all with this company.

Andres Mojica, plumber helper, age 41, was injured on the day of the accident when he attempted to escape the hot material. He received third degree burns over ninety percent of his body and died as a result of his injuries on October 2, 1996. He had 21 years mining experience, all with this company.

Luis Camacho and Feliz Baez, maintenance technicians, and Miguel A. Diaz, maintenance supervisor, received burns when they came in contact with the hot material.

Training records for the five employees involved in the accident were not made available.

Rolando Melendez, human resources director for San Juan Cement Company, notified the MSHA San Juan field office of the accident at 10:45 a.m. on September 16, 1996. An investigation was started the same day.

Cantera Espinosa, a portland cement mill, owned and operated by San Juan Cement Company, Incorporated, was located at P.R. Road 2, Km 26.7, Espinosa Ward, Dorado, Puerto Rico. The principal operating official was Robert Rayner, president. The plant normally operated three shifts, 8 hours a day, seven days a week. One hundred and ninety-two persons were employed.

Limestone to produce cement was mined from a nearby quarry, transported by haulage trucks to the plant where the material was crushed, stockpiled, and conveyed by belts to a raw mill, kiln and finish mills. The final product was shipped in bags and bulk to customers on the island of Puerto Rico.

The last regular inspection of this operation was conducted on August 5-8, 1996.


Raw material was transported in an enclosed system from a storage silo to a preheater tower and continuously flowed to a kiln and then to a clinker cooler. There were four cyclones installed between the preheater tower and the kiln. At various stages, air cannons were installed to shoot a blast of air into the system to assist a continuous flow of material and prevent blockages. All four cyclones had been provided with systems to monitor the flow of material; however, the monitoring systems for the No. 3 and No. 4 cyclones had been disengaged because false signals were given when the air cannons were shot. Because the monitors had been disconnected, the control room operator could not determine the flow of material by use of the control board.

Apparently, on previous occasions, hot material had been released into the atmosphere when blockages occurred and a manually-operated warning system was installed at the control room to warn persons in the area if an obstruction was detected in the cyclones. The alarm system consisted of a switch which activated sirens and strobe lights. The area had been posted with a warning sign instructing employees to leave the area if the alarm was activated.

About four months before the accident occurred, a platform had been constructed on the south side of the clinker cooler to install new air cannons. The platform was built as a temporary work station but had never been removed. The platform was 8-1/2 feet long, 6 feet wide, and constructed approximately 7 feet above a permanent walkway. However, the protrusion of the air cannons made the actual work area somewhat smaller. It was not provided with permanent access or handrails and the right side of the platform had an unobstructed drop to floor level, 25 feet below. Both of the fatally-injured employees were on this platform when the accident occurred.


On the day of the accident, employees reported to work at 7:00 a.m., their normal starting time. A blockage of raw material had occurred at the silo's air slide conveyor and dust collector which impeded the flow of material into the kiln. At approximately 8:30 a.m. the problem appeared to be corrected and Angel A. Robles, process coordinator, instructed the control room operator to start the material flow to feed the kiln.

Early into their shift, Luis Camacho (injured) and Felix Baez (injured) were assigned to use the vacuum truck to clean spillage at the No. 3 kiln area.

At 8:40 a.m., Manuel Lopez and Andres Mojica (victims) were instructed by their supervisor, Miguel A. Diaz, to repair a leak at the air cannons at the No. 3 clinker cooler. Lopez and Mojica went to the area, used the handrail on the lower walkway and part of the structure to gain access to a temporary work platform, and began working on the air cannons. Neither man was wearing a safety belt or line.

At approximately 9:30 a.m., Robles, was making his rounds and noticed that material was not flowing through the kiln. He went to the control room and informed Rafael Rosado, control room operator, that there might be a problem with the raw material feeding into kiln No. 3. Because the monitors had been disengaged and Rosado was not able to follow the flow of the material by use of the control board, he went to the kiln to make a visual check. When he returned and confirmed that there was no material in the kiln, Robles called his foreman on the radio and asked him to go to the preheater to verify the flow of material. Apparently, a major blockage had occurred somewhere between the preheater and the kiln causing a major buildup and restricting the flow to the kiln. It could not be determined if this was part of the blockage that created the problem earlier in the morning or whether this blockage occurred after the material flow was re-started.

Minutes after Robles contacted his foreman, employees in the area heard a loud noise and observed a thick cloud of dust. The material that was released went through the kiln and was expelled into the atmosphere through the end of the kiln. The temperature of the material was approximately 900 degrees centigrade and while it could not be determined how much material had been released, it measured 12 inches in depth on the floor of the kiln and clinker area.

Lopez and Mojica were working on the air leak and were standing on the platform, close to where the material was released. While trying to escape from the hot dust, Lopez either fell or jumped off the end of the platform, about 25 feet to the floor, landing in, and continuing to be covered by, the hot material. Mojica climbed down off the platform by using the duct work and existing walkways. However, after he got to the floor, he became disoriented and walked into the hot dust accumulating in the area. When he was unable to find his way out, he called for help and collapsed onto the floor.

When Camacho and Baez heard the noise created by the release of material, they ran out of the area. Camacho escaped safely and Baez sustained burns to his feet. Upon hearing Mojica's calls for help, Camacho went back into the hot material and pulled Mojica out. Camacho sustained burns to his arms and feet.

Diaz received severe burn injuries to his feet when he attempted to reach Lopez but had to abandoned his rescue efforts because the material was too hot.

A short time later, several employees arrived on the scene and came to the aid of the injured. Lopez (victim) was pronounced dead at the scene by the District Attorney. It was later determined that Lopez was unconscious after the fall, but died as a result of being covered by the hot material. Mojica, who received third degree burns over ninety percent of his body, was airlifted to the medical center where he died of his injuries on October 2, 1996. Camacho, Baez and Diaz were taken to the hospital by ambulance. Camacho and Baez were treated and released. Diaz was hospitalized with third degree burns to his feet.


The direct cause of the accident was the blockage of material that resulted in the sudden release of hot dust into the atmosphere where employees were working. Contributing to the severity of one of the victims was the failure to use safety belts and lines while working in an area where there was danger of falling.


Citation No. 4544914
Issued on October 7, 1996, under the provisions of Section 104(a) of the Mine Act for a violation of 30 CFR 56.15005:

On September 16, 1996, one employee was fatally injured and second employee was seriously burned when hot material was expelled from another area of the kiln on which they were working. The employee were on a work platform at the No. 3 kiln clinker cooler performing repair work. The victim fell approximately 25 feet to a concrete floor. The injured employee was able to climb down from the platform using the structural steel in the area. Subsequently, he died on October 2, 1996, due to complications as a result of the burns sustained during the accident. A safety belt and line was not being worn by either employee. The company had trained and furnished safety belts and lines to some of its employees but had no follow-up program to see that they were worn when there was a danger of falling.

J. A. Perez
Supervisory Mine Inspector

J. J. Figueroa
Mine Safety and Health Inspector

Approved by: Martin Rosta, District Manager

Related Fatal Alert Bulletin:
Fatal Alert Bulletin Icon [FAB96M36]