Every year, rescue professionals are tasked with rescue and recovery efforts in aquatic environments. If the victim presents on the surface, a large part of the rescue/recovery effort is directed through visual sight. When the victim submerges, the rescue/recovery effort uses an entirely different approach. Most rescuers who work in the aquatic environment are well aware that visibility underwater is often limited. The diver must be methodical in the search effort. One step forward on the line tender’s part or one bent arm from the diver during the sweep can lead to a “miss” of the object. Those simple alterations in a search pattern will miss the target, which then will give false confirmation to the area being searched. The question at the end of a dive should be, “Can we be 100 percent confident that the area we searched is clear of the object?” All too often, we can’t be 100 percent confident in saying that we are 100 percent confident, simply because we really are not as divers. This article will talk about how to incorporate sonar operations during water rescue and recovery incidents. We will also discuss a few of the more common types of sonar units in my area.
|(1) This is an image of a recovery operation conducted in Northern
Illinois by MABAS Division 4/5 Sonar Team. A “marker cage” has
been placed next to the body for reference as the Marine Sonics side-
scan sonar unit is towed in a parallel pattern, later to be cross
referenced by a perpendicular pattern. The image’s detailed definition
allows for easier object identification.
(Photos by author.)
Using sonar technology in water rescue and recovery is not a new idea. In fact, for many years, some type of sonar device has been instrumental in high-profile drowning cases. Many of us have seen wrecks, underwater formations, and other objects on sonar images. Many of us have improvised and used a “fish finder,” a drop single-beam sonar type of unit that has been around for years, as a recovery tool.
Some may ask, what is sonar? Sonar stands for sound navigation and ranging. There are two types of sonar technology-passive and active. Passive sonar is essentially listening for the sound made by vessels. Active sonar is emitting pulses of sounds and listening for echoes. Sonar is not new; it has been around since the 1490s, when Leonardo da Vinci placed a tube in water and could detect the sound of a passing vessel. From then on, the use of underwater detecting devices sprung forth, leading to the technology we have today. Worldwide use of sonar technology takes place in everyday activities such as oil drilling, environmental exploration, archeological detailing, and public safety.
For the purpose of this article, I will cover three devices used in my area and their implementation across the state of Illinois in the mutual aid box alarm system (MABAS) allocation and distribution system. I will highlight some of the success stories, evaluate the challenges, and look toward the future.
|(2) This image is from the Kongsberg Sector Scan Sonar unit. The search
was for a missing ice fisherman who fell through on a large lake the night
before. On the day the sonar team responded, it set up in an airboat and
traveled out to the last seen point. On the second drop of the sonar head
(no tripod was used, we secured the cable to the side of the airboat), we
located the victim. Significant artifact was present at larger sector lengths
because of the reflection off of the ice shelf. This forced the team to tighten
up the search pattern distance. Still, with the shortened distance, it quickly
located the victim. Drop camera confirmation took place as we were able to
measure from the sonar head location to the victim. The drop camera crew
literally placed the camera on the victim’s leg.
Locally, many police and fire agencies have used a drop single-beam type of fish finder for years. Although it was successful at attempting to locate underwater objects, the time spent was great because of the limited field of view. Today, local teams in my area use the following three sonar units in conjunction with one another to bring closure to the incident at hand.
The Hummingbird series of side-imaging, and now down-imaging, sonar units are step one. Many of the first-response fire and police agencies will own a side-imaging unit and allocate the resource on front-line response watercraft. Once the specialists are called out, the Marine Sonics side-scan tow fish unit will be deployed as the first line of defense from the side-scan sonar team. That, in conjunction with the Kongsberg MS 1000 sector scan, will determine object validity and provide direction to divers to make the recovery. Those three devices have led to many successful rescues/recovery missions in our area.
|(3) Shown here is the display image of an underwater object seen from
a Hummingbird side-imaging sonar unit. This unit provides much
detail and also provides water depth, miles per hour, course heading,
date, and time.
Why So Many?
Why three different units? They all work together, and each has its own place. Cost is a big factor; the other is each unit’s specific capabilities. The price range is from a few thousand dollars for a well-equipped Hummingbird unit up to $50,000 for well-equipped sector-scan units. The lower-end units have limitations but can function in many different environments. The higher-end units offer clarity, diver direction ability, and greater “tool” varieties.
As previously noted, many front line police, fire, and EMS agencies, as well as the Department of Natural Resources (DNR) and a few private individuals, have invested in some or all of these devices. Recently the MABAS has invested a great deal of funding to purchase side-scan sonar units and sector-scan units with all the bells and whistles. These units have been strategically distributed across the state of Illinois to provide type A water rescue teams with technology to aid in water rescue and recovery.
|(4) Shown is the diver who was able to drop down on top of a victim
to make the recovery. The diver was in the water for less than a few
minutes to make a safe and effective recovery.
Safe and Effective
The use of sonar technology in our rescue and recovery efforts in the aquatic environment allows us to be safer, more effective public safety divers. More importantly, sonar technology reduces our risk, confirms our search areas, and rules out areas that divers would otherwise need to search. This may just prevent placing our divers in a high-risk environment for no reason. In the long run, we can reduce costs by reducing the number of divers we would need to search an area. We will always need our divers, but we can now focus on keeping our divers topside until they are needed to bring the victims home.
TODD RISHLING has more than 20 years of experience in the water rescue and recovery field, primarily in fire rescue. He is the sonar liaison for the State of Illinois MABAS Water Committee, helping with the organization of 15 level A dive teams who operate sonar units in the state. He is also the dive team leader for MABAS divisions 1 and 5 as well as the dive team leader for the Elk Grove Village (IL) Fire Department, where he serves as a career fire lieutenant. He has also served as a flight paramedic for Flight For Life Helicopter in McHenry, Illinois, for 16 years.