Chapter Corner

Safety in Marinas

Posted in: July 2014

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.

The Hazards

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 translate into smaller resistance values. The above mentioned reference gave the following guidance.

Water Type

Conductivity (umhos/cm)

Distilled water

0.5 - 3.0

Melted snow]

Potable Water in U.S.

Freshwater streams

2 - 42



The more impurities you put in water, the more conductive it becomes. Saltwater offers a good conductive solution. Seawater for example can be upwards of 55,000 umhos/cm. When the resistance of a fluid around an object is less than the resistance of the object itself, current will take the path of least resistance; not through the object. When a human body is in fresh water that is energized, because the fresh water has a high resistance and the human body offers a lower resistance, electrocution is likely. This is why a boy like Lucas was electrocuted even though he was suspended in water not touching any energized piece of equipment or structure. This does not mean that there is no electrical hazard for salt water applications.

Hazards exist in any location where water and electricity are in close proximity to each other from a pond on a golf course that may have employed pumps for fountain-like attractions to the private boat dock.

Codes and Standards

There are two key documents, from an electrical perspective, that command your attention when addressing marinas and boatyards. NFPA 70, the National Electrical Code and NFPA 303, “Fire Protection Standard for Marinas and Boatyards.”

Let’s begin with NFPA 303 ( as this document is the standard for marinas and boatyards and “. . .applies to the construction and operation of marinas, boatyards, yacht clubs, boat condominiums, docking facilities associated with residential condominiums, multiple-docking facilities at multiple-family residences, and all associated piers, docks, and floats.” This document addresses management, electrical wiring and equipment, fire protection, berthing and storage, and operational hazards. Reading through NFPA 303 brings to light that there are many types of hazards that demand attention at these types of locations. The need for routine inspections at marinas is very important to sustaining safety in these locations. Chapter 5 addresses “Electrical Wiring and Equipment.” It offers additional requirements to the NEC and specifically calls out Article 555 which is titled “Marinas and Boatyards.” If you are involved with marinas and boatyards or anything similar, NFPA 303 is a must for your library.

When it comes to the National Electrical Code, chapters 1–4 apply generally and chapters 5, 6, and 7 apply to special occupancies supplementing chapters 1 through 4. Chapter 5 is where we find Article 555 for “Marinas and Boatyards.” Remember, a marina may have fueling stations so hazardous location requirements should be consulted as well. Article 555 was first introduced in NEC 1968 as “Boat Harbor Wiring” and consisted of Sections 555-1 through 555-6taking up just about a half of a page. This Article has seen attention since then and NEC 2011 didn’t disappoint. It was during the 2011 code cycle that Section 555.3,“Ground-Fault Protection” was added.

This new section of the NEC began with ROP 19-252 as a requirement for GFCI protection on the main or feeder circuits in a marina. ROP 19-252proposed the GFCI protection language but was rejected by Code Making Panel 19 with the following panel statement: “Although the recommendation has merit, additional technical substantiation and product development is needed. The use of GFCI for personnel protection is not prohibited by the current code. The proposed requirement for GFCI personnel protection (6 mA leakage) is not practical for all marina environments.” The main concern was the realization that many boatyards have a considerable amount of leakage current, and it all adds up in the main and/or feeder circuits.

To address the concerns of the panel, equipment level ground fault protection with an upper limit of 100mA was established. It was a decent compromise because even equipment level ground fault protection will at a minimum detect a problem in the wiring infrastructure that can lead to an electrocution. This language is not perfect but is a step in the right direction and stimulated discussions that need to happen for progress in safety to occur.

Ground Fault Protection

To get electrocuted three things are important: The amount of current, the path it takes through the body, and the amount of time the current is permitted to flow. A ground fault circuit interrupter (GFCI) device does not know the path that current takes when it leaves the circuit, it simply detects the amount of current that is not returning over the neutral conductor and opens the circuit. UL 943 governs the response of a GFCI device. A GFCI device is designed to not trip for currents less than 4mA and always trip for currents above 6mA.

To understand what this means to a person, it is around 1 milliampere that you will feel a faint tingle and above 6 milliamperes that life threatening symptoms begin. It won’t take much current to paralyze a person, especially a child, and cause drowning when suspended in water.

The language of Section 555.3, “Ground- Fault Protection” permits the use of a GFCI where product is available. On feeder circuits or at the main, any ground fault device that trips on current less than or equal to 100mA would be permissible.

Moving Forward

The Fire Protection Research Foundation ( has initiated a project to begin an effort to address the problem in and around marinas and boatyards and more. The title of this project is “Assessment of Hazardous Voltage/Current in Marinas, Boatyards and Floating Buildings.” The goal of the project is “. . . to identify and summarize available information that clarifies the problem of hazardous voltage/current in marinas, boatyards, and floating buildings, and to develop a mitigation strategy to address identified hazards.” It is this type of attention that can save lives. It’s efforts like this that will make a difference.

As always, keep safety at the top of your list and ensure you and those around you live to see another day.

Thomas Domitrovich, P.E., is a National Application Engineer with IEC Platinum Industry Partner Eaton Corporation in Pittsburgh, Pennsylvania. He has more than 20 years of experience as an electrical engineer and is a LEED Accredited Professional. He is active in various trade organizations on various levels with IEC, the International Association of Electrical Inspectors, the Institute of Electrical and Electronic Engineers (IEEE), the National Electrical Manufacturer’s Association (NEMA), and the National Fire Protection Association (NFPA). Domitrovich is involved with and chairs various committees for NEMA and IEEE and is an alternate member on NFPA 73. He is very active in the state-by-state adoption process of NFPA 70, working closely with review committees and other key organizations in this effort.