Paula Wallis, TunnelTalk

United States safety inspectors are investigating the August 18, 2009 death of a construction worker inside a small diameter tunnel in Conroe, 40 miles north of Houston, Texas.

According to local authorities, the worker, from Boring and Tunneling Company of America (BorTunCo), died inside a 24in diameter pipe when a sudden influx of water flooded the excavation trench, and tunnel.

Construction site rescue

“Three construction workers were in the trench shortly before 3pm,” said Trey Spikes, Justice of the Peace Precinct 2 in Conroe. “One worker entered the tunnel to free a drill bit that was stuck. While inside the tunnel, a tremendous amount of water started pouring into the job site filling the (15ft long x 8ft wide x 12ft deep) trench within 8 to 10 minutes.”

Two of the workers in the trench escaped to safety with the assistance of the foreman. The third worker could not back out of the 140ft tunnel in time. His remains were recovered about 50ft into the tunnel more than three hours after the initial call for help.

“We got the call at 3:15pm,” said Assistant Fire Chief Paul Sims. "By the time we arrived the trench was full of water. We had to pump out the water, stabilize the area and set up equipment, before sending someone in to recover the body."

Initial reports stated that a sudden and unexpected rainstorm caused the flooding. "A freak flood event occurred and somehow or another, the rainwater penetrated through the ground into our excavation," said Dale Kornegay, President of BorTunCo, during a local television interview.

“It was a very heavy downpour,” said Sims, who responded to the emergency call. After many, many days without rain, the skies just opened up. It was hard to drive to the scene, visibility was so bad”.

Hourly observations by wunderground.com, a weather tracking service, show how quickly the storm moved through the area that day (Fig 1). However, Fire Chief Ken Kreger said the flood was more likely caused by a broken water main, burst sewer pipe or groundwater.

Emergency responders say the construction site didn’t appear to be unsafe. “There was a trench box with railing around the edges and ladders, fresh air being pumped into the tunnel and sump pumps," said Sims. Best I could tell things were right, but I’m not an inspector.”

Trench drained of water

The 39-year-old worker was a Mexican national who had worked for the company for nine years. Sims said the man was not wearing a safety harness and lifeline when his body was recovered. John Rekus, a work-place safety expert in Maryland said, while it would have been a prudent practice, harnesses are not require for workers in tunnel excavation.

“There are federal regulations that pertain to workers in confined spaces, which do require harnesses, but OSHA (Occupational Health and Safety Administration) has a separated set of regulations for tunneling,” said Rekus. “ However, the construction company in this case could still be cited under OSHA’s “general duty clause” which is not a specific standard, but a catchall regulation that requires employers to provide workplaces that are free of recognized hazards."

OSHA will be applying the regulations in its investigation of the Conroe tunnel flooding. Investigators were on the scene shortly after the incident. Elizabeth Todd, spokesperson for the Administration's Houston office said the investigation could take six months to complete and until then, OSHA would not comment on the case. OSHA records show the company has had 12 safety violations in the past 10 years, but nothing since 2003.

Fig 1. Weather log

The Houston company specializes in trenchless technology. It was founded in 1948 by Gilbert Turner who is credited with inventing and patenting the Turner Method of boring, now called slurry boring, to handle Houston’s dense clay.

The company was drilling a drainage pipe under Interstate 45, which is undergoing a major expansion from four lanes to eight, when the tragedy occurred.

BorTunCo President, Dale Kornegay, said the company is still looking for answers into what went wrong. "Having gone through 24 hours of self-flagellation of what did we do wrong, what did we do different, how do we make sure it doesn't happen again, we are going to find something, but we haven't found it yet," said Konegay.