Lift Station Diving and the Confined Space Trap
By Ray Whitfield, ADCI-certified commercial dive supervisor. Reviewed by Dana Whitcombe, technical reviewer.
Commercial Diving Contractors Alabama | Commercial Diving Contractors Alaska Last spring I was 22 feet down in a lift station wet well outside Joplin, Missouri, with a 25,000-lumen underwater light and still couldn't see my hand on the glove. That's typical. The pumps were tagged out, but the smell of old sewage rides the surface anyway. Every guy who does this work knows that smell. It's hydrogen sulfide, and it's the first reason you treat a lift station as a permit-required confined space. That's the trap. A lift station looks like a concrete box with a ladder and a couple of pumps. Maybe ten feet across. But it's an enclosed space with a hazardous atmosphere and a liquid medium that can change in seconds. We don't just put on a dive suit and jump in. There's a protocol, and if you skip it, you're the next recovery story. Call it the everything-at-once job. You need a confined space entry permit, atmospheric monitoring, ventilation, a standby rescue team, a descent system, and dive gear. And the water is the wild card. This article is my field guide to doing it right.
Know your enemy: the wet well
A lift station is a buried concrete shaft, usually 8 to 12 feet in diameter, with one or two pumps at the bottom. The water coming in is raw sewage from a sewer line, and it's moving. In a typical 24-hour operation, the pumps cycle on and off automatically, which means the water level rises and falls. It also means the atmosphere can flush with foul air that has nowhere to go. We've seen H2S readings climb from 2 ppm to 50 ppm in the space of ten minutes, just because a pump kicked in and disturbed the water. The bottom is a silt and grease cake, with a thin layer of water above it that's usually about 70 degrees and roughly the color of weak coffee. Visibilities are typically zero. The diver works by touch. There are float cables, a pump intake suction bell, a discharge line, and a chain ladder that you'd better not trust too much. The whole thing is greasy enough to make the ladder, the rails, and every handhold feel like a vinyl car seat in July. One digression: I've seen more bent push-button controls than I can count because somebody didn't physically lock out the pump breaker. The remote telemetry can start a pump at 3 a.m. While the diver is inside. If you don't place a padlock on the breaker or valve handle, you're relying on a software command. That's not a lockout. We always test the lockout by ringing the pump out at the motor, then jogging the contactor with the breaker open. It's boring, but it stops you from becoming a statistic.
Permits and paperwork that keep you alive
OSHA's permit-required confined space standard, 29 CFR 1910.146, is the baseline. It requires a written permit that lists every hazard, the isolation procedures, the entry team roles, and the rescue plan. As a contractor, we need our own permit system, and the host employer — usually a city or a wastewater district — has to authorize it. We also follow the consensus standards for commercial diving, like the ADCI's Code of Practice, and the U.S. Navy Dive Manual for depth exposure and decompression. That means the dive side has a dive supervisor, a diver, a standby diver, and an attendant. The confined space side has an entry supervisor and an attendant. In practice, we cross-train, but the roles are distinct. The entry supervisor signs the permit and makes the final call on whether to abort. The attendant is never allowed to enter the space for any reason. His job is to monitor the diver, keep the radio clear, and start the rescue if the line goes slack. You also have to consider the biological side. Raw sewage is a potential source of bloodborne pathogens, so OSHA 1910.1030 applies. That means protective equipment, decon procedures, and hepatitis B vaccinations for the crew. The laundry we use for our coveralls and towels is a commercial operation certified under TRSA Hygienically Clean, not a washer at the end of a shed. We don't cut corners there, because the next dive depends on that gear coming back clean.
Atmosphere, ventilation, and the gas detector
Before anyone goes near the hatch, the gas detector goes in. I carry an MSA ALTAIR 4XR, but the RKI Eagle 2 and Honeywell BW GasAlertQuattro are just as common. The detector reads oxygen, hydrogen sulfide, carbon monoxide, and lower explosive limit. We take a baseline at the top, then lower it down the midpoint, then to just above the waterline. On a lift station, the numbers aren't the same at every level. Hydrogen sulfide is heavier than air, so it pools near the surface. H2S at 10 ppm is the OSHA permissible exposure limit. At 50 ppm — that's an immediately dangerous to life or health concentration. I've seen 150 ppm at the water line in a station that looked fine at the top. We ventilate with a duct fan, usually a 16-inch model that moves about 10,000 cubic feet per minute. The fan sits on the edge of the hatch with a 20-foot flexible duct going down. We let it run for at least 15 minutes, then we recheck the atmosphere. But ventilation isn't a one-and-done. The water itself is a reservoir of dissolved gas, and the slightest turbulence will release it. So the gas monitor is on a tether inside the space, reading continuously. It's connected to a transmitter that alarms on the surface if the H2S spikes. A real operator doesn't rely on a single reading. He watches the trend. The other trick is to test the ventilation flow. Hold a smoke tube at the duct exhaust, then feel the current at the bottom. If you're not moving the air, the fan pitch or duct length isn't right. And don't forget: the exhaust end has to discharge well away from the intake side, or you're just recirculating the same gas.
The dive itself: rigging, comms, and bailout
We set up over the hatch with a portable davit or a tripod. The main point is a positive anchor for the diver's safety line and a fall protection rail for the entry attendant. The diver's rig is a heavy-duty dive suit, a full-face mask with two-way communications, and a steel tank. We use bailout cylinders — the only place in my career where I don't argue about spending, because it's the diver's own life on his back. You could get away with a 13 cubic foot pony bottle to get you out of the water, but I prefer at least 30. It's heavy, but it's also a few extra minutes if the main air fails. The diver enters through the access hatch, which is often only 24 to 30 inches wide. A typical lift station has a 30-inch manway, and you're wearing a harness and a backpack cylinder. Getting through that opening is a yoga pose the first time you do it. The standby diver is suited and ready on the surface, with his own bailout and a complete second rig. He doesn't go in unless the attendant calls for him, and he stays tethered. The diver's bottom time is usually 20 minutes, thirty if everything is calm. That's not about air; it's about fatigue and the cold. We log every minute and follow dive tables for repetitive exposures. Decon starts as soon as the diver is up. The suit gets rinsed inside and out with a municipal water hose, then wiped down with a disinfectant that's safe for neoprene. The tanks get a soap-and-water scrub. And the crew strips down to clean clothes before they leave the site. Everything contaminated goes into a closed bag and into a dedicated commercial wash. The same place we use for the coveralls. It's a process, and it's the part you never see on a work order.
Frequently Asked Questions
Is lift station diving just like any other commercial dive? No. It's a confined space entry first and a dive second. The hazards of hydrogen sulfide, lockout/tagout, and flow control make it a unique mix. What certifications does a lift station diver need? Commercial diver certification from an ADCI school, plus confined space entry training. Many clients also require OSHA 1910.146 compliance and often require a drug and alcohol test for the crew. How often should a lift station be inspected by a diver? Depends on the flow, the plant, and the pump service history. Some stations go years; others need a check every quarter. A good video inspection from above the waterline can tell you if a dive is necessary. Can you see anything in zero visibility? In a typical lift station, you're working blind. We use magnetic touch plates to identify the pump intake and discharge pipe, and we feel for debris. That's why comms and a reliable tender are so important.