Safety in Marinas
Yet another swimming season has begun, the prime time to talk about marina safety. Whether you are an electrical inspector, installer, manufacturer, or other, we can make marinas a safe place to work and play. Marinas can be quite a dangerous place when it comes to electrical hazards. Let’s break the ice with some thought stimulating information that you can build on during your next marina project.
Marinas in both fresh water and salt water can present challenging locations for the electrical distribution system. These locations present moisture and many other elements that can deteriorate the electrical system over time. In addition, these locations may have fueling stations as well. Much of this equipment is on a structure that rises and sways with the waves. This is a mix that can spell disaster for an electrical system that is not maintained or designed correctly.
This potential for disaster is all too real. Ten-year-old Noah and his 11-year-old friend Nate died in the afternoon back in 2012 while swimming during a July 4th event. Noah died from the initial shock that he received but Nate died the following day after being placed on life support.
Eighteen-year-old Michael jumped into the body of water at the end of a dock and immediately began to struggle due to electric shock. He struggled to swim back and when he grabbed what he thought was safety, a handrail, he was electrocuted. When others tried to save him, they immediately felt the current but luckily no one else succumbed to the electricity that was flowing.
Eight-year-old Lucas was with his parents one day at a boat dock and decided to go swimming with a group of his friends. They entered the water at one end of the dock and let the current carry them downstream to the other end of the dock. As Lucas swam to get out of the water swimming closer to the dock, he turned on his back gasping for air. His life jacket kept his head out of the water. Lucas was not touching anything metal or any structure, he was just floating in water. Still floating downstream, others tried to swim in to help him but they too felt a tingling sensation as they swam closer. Lucas’ mother dove in the water and took ahold of him and she too felt the effects of a strong electrical current that paralyzed her. She was in turned saved by others on the dock who pulled her to an area where she no longer felt the effects of the electrical current. On August 1, 1999, Lucas lost his life.
Unfortunately these are not isolated cases. When a person succumbs to electricity while swimming, it is referred to as Electric Shock Drowning (ESD). These issues are not contained to just large marinas; small private marinas are probably more likely to have issues than the larger facilities.
Fresh Water vs. Salt Water
Water has a resistance usually referred to as “conductivity,” which is measured by applying a voltage between two electrodes and measuring the voltage drop between the probes. The drop in voltage is used to calculate the resistance. The resistance is then converted to conductivity.
Conductivity = 1/Resistance (Mho)
Conductivity is the reciprocal to resistance and is referred to as conductance over a specified distance, Mho/cm. Because the numbers are very small when it comes to the conductivity of water, you will see the terms “mili-“ or “micro-“associated with the measurement of conductivity. The larger the conductivity, the smaller the resistance.
10 Ohms = (1 / 10) Mhos = 0.1 Mhos
0.10 Ohms = (1 / 0.10) Mhos = 10 Mhos
Conductivity of water is quite complex and dependent upon what is in the water that you are addressing. The table below was obtained from the state of California, “The Clean Water Team Guidance Compendium for Watershed Monitoring and Assessment State Water Resources Control Board.” Take into consideration that larger conductivity numbers