Don't Get Zapped By Cable Clearance Over Water

Feb 1, 1999 12:00 PM, By Donald C. Thorn, Ph.D., P.E.

After a sailboat comes in contact with a low utility power line, attorneys look to forensic engineering for answers to the fatal accident.

When three teenaged boys set out for a day of fun on the river one lazy afternoon, they didn't have a care in the world. One of them had his family's new catamaran sailboat the group couldn't wait to try out. Things couldn't have been better for the three young friends:until their carefree outing turned to tragedy.

Until they decided to come back up river, they really didn't even need to put up the sail. The boat was small, but quite comfortable for the three of them. One leaned against the aluminum mast facing the stern, the second sat further to the stern with his hand on the aluminum tiller, while the third sat in the bow watching the scenery.

Then suddenly, the cruise took an unfortunate turn. As the mast of the small vessel made contact with a low overhead 12.5kV utility power line, a surge of current shot through the mast and the boy touching it:killing him instantly. The boy at the tiller survived, but with serious injury. The boy at the bow luckily sustained no injury. Although never proven, it appeared the deck was wet. If so, this would offer a path for the current to travel from the boy at the mast to the boy at the tiller to the river.

The investigation. Shortly after the family of the deceased boy filed suit against the power company and manufacturer of the catamaran, attorneys asked me to join the case and offer a forensic analysis of the accident. What was my first reaction? It seemed to me a river was not a good place to have a sailboat, and I couldn't help but wonder if the boys hadn't brought the incident on themselves. However, the attorney quickly pointed out the location in question was near the mouth of the river (as to approximate a lake).

At the time of this case, I had ample experience with power line clearance problems over land and buildings. However, I never had an opportunity to look at clearance over water, nor had I any familiarity with sailboats. I knew I had a lot to learn.

Fortunately, I had a friend who was an avid boating enthusiast. Although his primary interest was power boats, he guided me to several sources who filled me with information. In fact, in the course of my investigation, I learned more than I had ever dreamed about the design of pleasure boats. These sources assured me a sailboat of this sort should have had the mast grounded by a plate in the hull in contact below the water line, primarily as a lightning-protective measure. If this grounding plate had been in place, the injuries were still likely to occur. However, there's a good chance they may have been less severe.

While examining the facts, the height and location of the power line became of great interest to the attorneys. The power company responded to the suit by stating the river was not a body of water suitable for a sailboat. They further argued they were not really subject to the National Electrical Safety Code (NESC) insofar as the line over the river was concerned. Frankly, we never completely resolved the question of NESC applicability. Certainly, the NESC stated rather clearly a line of that voltage over a body of water suitable for sailboats should be no lower than some stated value, which was higher than the lines were actually placed. In fact, the power company's own diagrams made this very clear. However, we soon turned our attention away from the NESC.

It wasn't long before we determined the site was within the jurisdiction of the U.S. Army Corps of Engineers. We found the utility did not request permission from this agency to install the line, nor did it officially notify the agency of the construction of the line upon installation. This appeared to relieve the Corps of Engineers of any responsibility for the line. This is especially important because if the Corps had inspected the line, as constructed, it should have rejected it (as it did not meet standards).

From my standpoint, the actual violation of clearance requirements was not >nearly as significant as the way the clearances are defined in such a >situation. With my experience limited to land problems, I had to do adjust >my thinking to become used to phrases like "ordinary high water," "design >high water," "normal flood level," etc.

Based on the evidence, I advised the attorney that both defendants were in the wrong. The manufacturer of the boat had failed to provide the grounding plate. (Of course, the power company's expert was quick to concur with this finding.) The power company was wrong in a legal sense in having failed to acquire proper licensing and inspection of their line. The utility was also wrong from an engineering viewpoint by virtue of having constructed the line so that it was in violation of either of the two authorities to whom they should have turned:the NESC and the Corps of Engineers.

Interestingly enough, although the power company made a strong effort to deny any responsibility in this accident, they furnished diagrams of the line both before and after the wires were raised to a height to bring them into conformity with requirements. Also interesting is the fact that some individuals raised objections on environmental grounds to the permit for the reconstruction of the line. One cannot help but wonder what it would have cost the power company if it could not have modified the line to meet the requirements because of the environmental objections.

The resolution. The power company offered an adequate settlement to the plaintiff. Because the parties settled out of court, I never learned whether the boat manufacturer contributed to the settlement.

In terms of forensic work, this case was both interesting and successful. All the pieces fell into place, and the questions of engineering error were fairly obvious. But one important lesson to learn in this case comes back to the utility. Electrical utilities must exercise great care to make sure they're not only within the standards of the governing authority, but also which authority that is.