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96" Sewer Main Inspection and Core Sample

PROJECT TITLE: 96″ Sewer Main Inspection and Core Sample


CLIENT: Municipal Utility


A local municipal utility was performing assessments on their sanitary collection system. They were trying to establish realistic goals, budgets and schedules for their CMOM program. In order to do so, they needed to know the actual physical condition of a 96-inch concrete sewer main, so they wouldn’t come upon any surprises when it was time to perform any scheduled work.

The job was a difficult one. It involved a visual inspection, which required safely accessing and lowering a technician into the sewer main through a manhole entry way that ranged from 0’ to 14’ high. Then they had to drill core samples from the 96” line. The work took long enough that it required enclosed operating helmets (positive air masks) with fresh air supply for the technicians, because H2S gas was present inside the pipe.

Bulldog Diving’s diversely trained crews are vastly experienced and certified in all facets of confined space entry. Specs required a 6-inch core sample, which proved to be a challenge due to the structural rebar in the sewer line.


To produce clean core samples it is necessary to stabilize the core drill.  Bulldog was able to fabricate a mobil stabilizer arm in house, allowing entry team to easily move to each site and retrieve core samples.

With the entrants sub level and having to wear a positive pressure air mask, 2-way communications utilizing hand held radios proved difficult.  despite difficulties we were able to demonstrate our ability to safely perform all required testing and retrieve required core samples.


Our Bulldog crew was able to complete the job on schedule, allowing the client to accurately assess the condition of their sewer main in a timely manner. Using this empirical data, they were able to develop a realistic maintenance and repair schedule and budget for current and future use. This was also one of the jobs that inspired us to develop a lightweight, positive air flow helmet with built-in, two-way comms to allow our crews to work comfortably and safely in topside environments that may involve the presence of hazardous or toxic gases.