Canadian Occupational Safety

12 www.cos-mag.com Canadian Occupational Safety L uke Seabrook was a 39-year- old commercial diver from Dartmouth, N.S. On July 15, 2015, he was inspect- ing a gate at a Nova Scotia Power tidal plant in Annapolis Royal. The gate was locked out by the power company and the controls indicated the gate was closed. However, the gate was not completely sealed — it was ajar about 12 to 18 inches. Due to a difference in pressure from the water levels on either side of the gate, a vacuum effect was created. Seabrook was pulled into the gate where he became trapped and drowned. "He didn't have a hope in hell; nobody would," said Angela Seabrook, Luke's mother, to the CBC. Seabrook's employer, Paul's Diving Ser vice, pleaded guilty and was required to pay a total of $34,000, a mix of fines and a donation to a safety education fund. The company was also required to conduct 15 safety presentations. Additionally, Seabrook is suing Nova Scotia Power, claiming damages under the provincial Fatal Injuries Act. Commercial divers work for a variety of different industries, including aquaculture, fish farming, construction, offshore oil and gas, law enforcement and utilities. They may be undertaking inspections, mainte- nance or construction work. On any given day, a commercial diver can be found breaking up rock with a hydrau- lic jackhammer, pouring concrete under water and rigging up cars to be hoisted out of a lake. Regardless of the job, occupational health and safety needs to be the first thing that commercial divers think about before they dive in. "There is pretty well zero margin for error. It's not very often that divers are injured. They usually just end up dead," says Aaron Griffin, program co- ordinator, underwater skills, Seneca College in Toronto. DELTA P The phenomenon t hat took Seabrook's life is known as Delta P — the number 1 killer of divers. Differential pressure (Delta P) refers to an underwater hazard on or near a water control structure (such as a dam) where a difference in pres- sure exists because of a hole, gap or crack in the structure, according to the Canadian Association of Diving Contractors (CADC). Delta P also occurs at the intake of suction pipes or at any location where there is an unequal pressure difference. "If you imagine a drain for a hot tub, you're sitting in there but you can feel the water pulling into the drain. Now imagine you're a diver — we can get sucked into those places and either trapped or pulled right through," says Kelly Korol, director of training and operations at DiveSafe International in Campbell River, B.C . "Delta P is very unforgiving. It's basically you're in front of a pipe that's got flow and you're sucked right into it, and it's usu- ally fatal. It's our biggest worry." To prevent Delta P, a simple bag test can be conducted — something Paul's Diving Service failed to do. A bag is filled with a bit of sand (about 5 pounds worth) and is tied to a rope. The bag is raised and lowered slowly across the entire structure where the diver will be working. A severe draw on the bag and rope or anytime where the bag is trapped and cannot be pulled free are indicators of a serious Delta P hazard, according to the CADC. "It can have devastating conse- quences if you don't do it. I'd much rather have a sandbag stuck on the wall that I never have to worry about than a diver, because you'll never get a diver off of there," says Griffin. After a successful bag test, a recog- nition dive should be conducted to establish a safety zone. This dive is performed in order to identify any signs of a potential Delta P hazard, such as structural damage, accumula- tion of debris, cracks, holes and gaps, according to the CADC. Once the safe zone is established, a restraint should be placed on the diver's cord (called the umbilical) so they cannot swim outside of this zone during work. Lockout is another very important component in mitigating this hazard. Valves and machinery must be locked out — but indicators can't be trusted, says Griffin. "The normal procedure is yes, the indicator shows it's down, but you actually physically need to check to make sure that all flow hazards have been stopped — visually confirm," he says. DECOMPRESSION ILLNESS Divers are very familiar with decom- pression illness (DCI), a disease caused by the improper or incomplete elimination of inert gas from body tis- sues. The gas is absorbed by the body while breathing in a high-pressure environment. "This forms bubbles much like opening a bottle of soda water too quickly. Bubbles get stuck in blood vessels, joints and possibly the spine and brain, causing tissue damage, pain, nerve and brain damage and possibly death," says Griffin. Almost all the provincial occupa- tional health and safety authorities require commercial divers to use decompression tables to prevent DCI. The tables outline how divers should return to the surface so the pressure is not reduced too quickly. "Your bottom time is limited the deeper you go," says Griffin. "If you exceed your no decompression limit — your bottom time — you would have to do decompression stops on the way out. Instead of just coming right up to the surface and going about your day, you might have to stop at 20 feet for 10 minutes and then 10 feet for another 10." Symptoms of decompression illness include fatigue, skin itch, joint pain, dizziness, vertigo, numbness, tingling and shortness of breath. "You will rarely ever hear of a diver dying from decompression sickness. If we do, it's usually a diver who wasn't following the dive tables," Korol says. "Some of them are just old-time divers who are uneducated, and they just think that they know better." If a diver does have a decompression illness, a physician must be alerted and the worker needs to be taken to the nearest hyperbaric chamber for treatment. The treatment involves breathing pure oxygen at elevated pressures for a specified length of time. Hyperbaric chambers are required to be on site whenever planned dives exceed the no-decompression limit or a depth of 130 feet is exceeded, accord- ing to the CADC in its guideline for the CSA Z275.2-15 Occupational Safety Code for Diving Operations standard. SurDO2 (surface decompression using oxygen) is a method that dive companies can use to reduce the amount of decompression time in the water. The diver does some short in-water decompression stops and then comes to the surface and fulfills the remainder of his decompression requirements in a hyperbaric chamber, breathing 100 per cent oxygen. COLD STRESS Cold stress is something that divers need to be prepared for if they are DEEP DIVE Delta-P, an underwater vacuum effect, is the number 1 killer of commercial divers and demonstrates why pre-dive checks are necessary before every job By Amanda Silliker PHOTO: MAXWEL HOHN

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