Confined Space Fatality at a Wastewater Treatment Plant in Indiana
The National Institute for Occupational Safety and Health (NIOSH), Division of Safety Research (DSR) is currently conducting the Fatal Accident Circumstances and Epidemiology (FACE) Project, which is focusing primarily upon selected electrical-related and confined space-related fatalities. The purpose of the FACE program is to identify and rank factors that influence the risk of fatal injuries for selected employees.
On June 6, 1987, a maintenance worker for a city's wastewater treatment plant entered the plant's "wet well" to clean the bar screen which filters the raw sewage prior to its entry into the plant. The employee performed this duty without a co-worker or a safety harness. The event was not witnessed. The body was discovered at 12:38 PM, approximately one hour after the victim was last seen. The victim's body was removed from the "wet well" by the local fire department and pronounced dead at the site by the county coroner.
Officials of the Occupational Safety and Health Program for the State of Indiana (IOSHA) notified the Division of Safety Research of this fatality and requested technical assistance. This case has been included in the FACE Project. On June 23, 1987, the DSR research team (two research industrial hygienists and a physician) met with the compliance officer for IOSHA, the personnel and safety director for the municipality, and the superintendent of the city's wastewater treatment plant. NIOSH personnel toured the plant's facilities, reviewed the sequence of events leading to the fatality, interviewed co-workers, and took photographs of the site.
Overview of Employer's Safety Program:
The employer in this incident is a small municipality in Indiana with a population of approximately 23,000. The wastewater treatment plant employs 17 persons: seven certified operators (five working at the plant and two working the city's sewers), five maintenance laborers, two laboratory technicians, one process control technician, one maintenance foreman, and one plant superintendent. The plant operates three shifts providing around the clock coverage. Safety issues involving confined space entry were informally communicated to the employees during personnel meetings, occurring every four to six months. These meetings discussed the importance of:
1. Using a gas detection meter to determine the air's quality. 2. Using a safety harness and rope around the employee entering the space. 3. Positioning a co-worker at the entrance of the space.
Although the meetings reviewed these safety procedures, the procedures were rarely practiced. The only gas detection meter and harness owned by the plant was kept on the sewer maintenance truck and was unavailable for use while the truck was away from the facility. Employees frequently entered the "wet well" alone.
Synopsis of Events:
On June 6, 1987, three employees were scheduled to work: a laboratory technician, an operator, and a laborer (the victim). The victim and the operator arrived at work at the usual starting time for the day shift (8:00 a.m.); the laboratory technician, who was planning to leave his shift early, arrived at 6:00 a.m. Shortly after 8:00 a.m. it was determined that the east primary aeration tank had shut down. In response to this problem an extra laborer and the maintenance foreman were called into work. In order to repair the problem associated with the aeration tank the 14-foot-deep aeration tank had to be drained. This was accomplished by re-routing the sludge from the east aeration tank back to the "wet well" at the entrance of the plant. The "wet well" is the entry point for all industrial, commercial, and residential sewage and is 27 feet long by 18 feet wide by 26 feet deep. Access to the bottom of the well is provided by a permanent ladder which terminates on a concrete walkway at the bottom of the well. The raw sewage enters the well at the flow gate, travels through a trough (24 inches deep), and drains via gravity into a "comminuter." The "comminuter" pulverizes large debris, such as bricks, large rocks, or tree branches that find their way into the sewer lines. The "comminuter", which required approximately five major repairs since its installation in 1970, had been shutdown since 1984.
Thus, the primary means of preventing large objects from entering the plant was a "bar screen" which needed to be cleaned approximately three times per shift. A metal rake was used to scrape off debris collecting on the screen and deposited that debris into a bucket. Upon completion of the job, employees would climb to the top of the ladder, hoist the bucket of debris to the surface, and discard. Re-routing the sludge from the east aeration tank to the "wet well" increased the volume of water flowing into the "wet well" and caused a more pronounced odor (described as "rotten eggs"). Additionally, the "bar screen" clogged more often requiring more frequent cleaning. The victim had cleaned the screen four times during the first three hours of his shift. Each time this was performed without sampling the air, without a safety harness attached, and without a co-worker positioned at the entrance. The victim was also to mow the lawn that morning. A co-worker, who was also mowing the lawn, went to lunch at 11:37 a.m. and last saw the victim cutting grass.
When the co-worker returned from lunch at 12:38 p.m., he noticed that the rope and bucket were in the well. The co-worker walked to the "wet well" and noticed the intake gate was closed, the cleaning rake lying on the cement platform, and the bucket empty. He called the victim's name several times without response and then noticed the victim's left leg protruding from the surface of the sewage. The rest of the victim's body was submerged in the trough.
The co-worker ran to the office where the laboratory technician was working and told him to call the emergency squad and fire department. The co-worker then returned to the "wet well" with the maintenance laborer and they both descended into the well. While trying to retrieve the body, they became nauseated and faint and exited via the ladder. Upon ascending the ladder one of the workers stated he almost slipped and fell into the well. The ambulance arrived, followed by firefighters. Using self-contained breathing apparatus (SCBA), two firemen descended into the well. The firemen retrieved the victim and laid him on the cement platform. One of the firemen descended into the well without a breathing apparatus to take pictures. He experienced some lightheaddedness and eye irritation. The victim was hoisted to the surface and pronounced dead at 1:00 p.m. by the coroner. The five firemen involved in the incident were all taken to the local emergency room for evaluation of nausea and dizziness. No one required hospitalization; however, three of the five received tetanus shots.
Cause of Death:
An autopsy was performed by the county coroner. The official report is pending a blood toxicology screen and serum levels of anti-epileptic medication. A noncompounded fracture of the victim's left knee at autopsy suggested a fall of at least five feet. The death certificate lists the cause of death to be "aspiration of foreign material".
Recommendation #1: Employers should maintain equipment in proper operating condition.
Discussion: This facility recognized the need for an automated procedure to prevent large debris from entering the plant and installed a crushing device called a "comminuter" in 1976. This device, when working, adequately performed the task. Its use eliminated the need for operators and maintenance laborers to enter the "wet well", thus eliminating this hazardous exposure. Eliminating the need to enter a confined space completely abates any hazards associated with the confined space. The "comminuter" should be maintained and repaired in operating condition.
Recommendation #2: The employer should initiate comprehensive policies and procedures for confined space entry.
Discussion: Although the employer had outlined informal procedures for confined space entry prior to the incident, these should be expanded and formalized into a written policy. This policy should include the following points:
1. Is entry necessary? Can the task be completed from the outside?
2. Has a permit been issued for entry?
3. Has the air quality in the confined space been tested?
oxygen supply at least 19.5%
Flammable range less than 10% of the lower flammable limit
Absence of toxic air contaminants
4. Has the confined space been isolated/locked out from other systems?
5. Have employees and supervisors been trained in selection and use of personal protective equipment and clothing?
6. Have employees been trained for confined space entry?
7. Is ventilation equipment available and/or used?
8. Is the air quality tested when the ventilation system is operating?
Recommendation #3: Employers should enforce safety procedures.
Discussion: Employees of this facility did not routinely follow the established confined space entry procedures. Employers must enforce established procedures and supervisory personnel must continuously monitor work practices.
Recommendation #4: Employees who are required to enter confined spaces should receive pre-placement and periodic physical examinations to determine that they are physically capable of performing these duties.
Discussion: During the course of employment the physical condition of an employee can change and the employee can become inadequately suited to the job's responsibilities. Employees required to enter confined spaces should receive pre-placement and periodic physical examinations to determine that they are physically capable of performing these duties. The victim had a history of epilepsy dating back to his childhood. The victim's last known seizure occurred in 1978 and his last known evaluation was done on February 29, 1984. His seizures were controlled with medication and a physician's note dated January, 1984 stated the victim's seizures were under control and he could "resume normal activities". The victim was hired by the wastewater treatment plant in 1976 at the age of sixteen. At that time he was 5'11" and weighed 210 pounds. He listed his history of epilepsy and stated that he was on medication. At the time of the victim's death co-workers estimated his weight to be 230 pounds.