Law enforcement and search and rescue personnel are frequently required to search for drowning victims, as well as missing objects, underwater. Typically these searches have been conducted using divers, underwater cameras, and water-trained search dogs. Underwater searching by divers is time consuming and can be very dangerous, depending upon water depth, visibility, current, and underwater obstructions.
The lack of good “point last seen” information can extend the search area to hundreds of acres. Often the search area is large because there are no eyewitnesses or the eyewitnesses cannot accurately identify the place where the drowning victim or object was last seen. Large areas are often impossible to effectively search with traditional techniques and consequently, searches are terminated after several days and recovery is left to chance.
Gene Ralston, is a retired environmental consultant who specialized in water related environmental issues. He and his wife, Sandy, have frequently volunteered their equipment and time to assist the Idaho Mountain Search and Rescue Unit, in addition to local and national authorities, in searching for drowning victims. Gene recovered his first victim in 1983. In early 1999, Gene had the opportunity to experience the successful use of side scan sonar to search for a drowning victim. After seeing the benefit of using side scan sonar, Gene and Sandy decided to purchase a system of their own to assist with underwater searches.
The side scan sonar system's transducer is housed in a towfish, which is towed through the water a few feet above the bottom. The reflected acoustic returns are processed into images similar to aerial photographs, which are viewed in real-time on a computer monitor in the towing vessel.
Typically, the side scan sonar searches a swath 66 to 164 feet wide at about 2 miles per hour, although other ranges can be used depending upon the size of the object being sought.
Location information from a differentially corrected global positioning system (DGPS) is used to guide the towing vessel along predetermined search lines as well as to identify the location of any point on the side scan image. When differential corrections are available, position accuracy is generally sub-meter. The stored GPS location information allows the searchers to return to any point in the image for further investigation or recovery.
Gene recognized not only that the new side scan technology would be useful to his clients, but also that it would be of great assistance in search and rescue activities. He had a special towfish and variable-speed hoist custom manufactured for deep water operation. The side scan sonar he uses was custom manufactured. The custom stainless steel towfish has been used to search as deep as 850 feet. The hoist drum has more than 900 feet of electromechanical cable for deploying the towfish in deep water. A second, lighter weight aluminum towfish can be hand deployed, if necessary, in shallower water.
Two weeks after getting their side scan sonar in operation, Gene & Sandy were requested by Rich County, Utah, Search and Rescue, to conduct a search for a drowning victim in Bear Lake. The victim had drowned more than six weeks earlier and local authorities had called off the official search. Within a few hours of beginning the search, the victim was located in 148 feet of water in an area just outside of the area searched by an underwater remote operated vehicle (ROV) and camera. The ROV was later used to recover the 24 year old man.
During the first year of operation, the Ralstons participated in 16 search missions from California to Maryland. Search activities have included assisting NASA in the search for space shuttle Columbia debris in Toledo Bend Reservoir on the Texas Louisiana border. The Ralstons have also assisted the FBI and other law enforcement agencies with the search and recovery of multiple, high-profile homicide victims.
The National Park Service has requested Gene and his crew on several occasions to assist in the search for drowning victims on Lake Powell and Lake Mead. Water depth and very irregular underwater terrain complicate the Lake Powell and Lake Mead searches. During one search on Lake Powell, the victim was found in 286 feet of water on the morning of the second day of searching. The National Park Service's ROV was used to recover his body. Other drowning victims have been found in Lake Powell as deep as 400 feet. Four drowning victims were recovered from Lake Mead in 2002.
Recent underwater searches of note include the successful recovery of a man who had been missing for more than fifteen years and the discovery of a 1927 Chevrolet sedan that disappeared in Lake Crescent, Washington, in 1929. The discovery of a person who had been missing for twenty-nine years in over six-hundred feet of water in British Columbia, was a surprise to everyone. Gene and Sandy have located the remains of 128 people during the last twenty-three years.
The Ralstons purchased a remote operated vehicle (ROV) to assist with the recovery of drowning victims. Once the side scan identifies an object of interest, the ROV can be used to inspect and recover the object. The OUTLAND 1000 has 500 feet of umbilical cable and is outfitted with a high resolution color, and black and white, video camera. Two weeks after they had received the ROV, they used it to recover a drowning victim in Lake Pend Oreille, in northern Idaho. The man was in 160 feet of water.
The benefits of using side scan sonar to search for drowning victims and other Items underwater, include being able to search a large area quickly and safely. Divers are not placed at risk during the search operation and are only deployed for the recovery once the object is found. The side scan sonar images are also useful to evaluate any hazards to divers before they enter the water.
The Ralstons offer the use of their time equipment to anyone in need of their service throughout the USA and Canada. If your need is immediate, please call (208) 362-1303. If you have a general question which may not need answering for a while, use the contact link above.
Side scan sonar image review is provided as a free service to anyone who would like assistance in sonar image interpretation. Gene has found five drowning victims in images made by other agencies.
