By Alex Gregg and Rick Griggs
Published Wednesday, April 30, 2008
| From the May 2008 Issue of FireRescue
Last summer, the California Department of Forestry and Fire Protection (CAL FIRE) and the Riverside County Fire Department (RCFD), of which we are members, faced a challenging and complex trench rescue operation. In this article, we’ll review the incident and some of the lessons learned.
On June 23, 2007, at 1311 hrs, units from CAL FIRE and the RCFD were dispatched to a trench rescue in the city of Desert Hot Springs, approximately 5 miles north of the city of Palm Springs.
Upon the arrival of Medic Engine 37 (ME37), the company officer found the victim trapped in an excavation that was approximately 25 feet in diameter and approximately 25 feet deep—not a typical trench. The excavation was in the driveway of a duplex under construction located at the end of a cul-de-sac in a residential neighborhood. This location made it very difficult to operate due to the limited space. In addition, the backhoe was still in place and could not be moved due to concerns of secondary collapse.
The victim was trapped inside a 30"-diameter concrete ring. He was under the backhoe bucket, buried up to his mid-chest with one arm trapped below the surface. The captain of ME37 notified the Perris Emergency Command Center of the situation, isolated the scene to prevent additional collapse and established verbal contact with the victim.
En route, Battalion 3117 made requests for additional resources. Upon arrival, he assumed command of the incident and placed the captain from ME37 into the operations role. As resources arrived additional Incident Command System (ICS) positions were filled. Additional resources included vacuum trucks, as well as hardware and shoring materials obtained from a local Home Depot. A representative from Cal/OSHA’s San Bernardino Field Office was requested to respond due to the serious nature of the incident.
At the time of the dispatch, the temperature was 103 degrees F; it would eventually rise to 109 degrees F during the incident. The relative humidity was 9 percent, and the wind speed was 10 mph with gusts to 14 mph.
Recognizing the weather would play a large role in the incident, we set up a rehab area under a tree just down the street from the incident. However, we soon determined cooler facilities were needed and ordered an air-conditioned transit bus to serve as the rehab center. Personnel were allowed to cool and hydrate between work cycles.
An engineer/paramedic and one crew from American Medical Response, monitored personnel for early signs of heat-related illness and fatigue. The incident safety officer (ISO) worked with the incident commander (IC) and the operations section to establish 30-minute rotation and rehab cycles for incident personnel.
The victim was operating a backhoe (locked out by responders and left in place) in the driveway to the residence. He was working to install a septic system when the concrete ring he’d lowered into the excavation on a chain failed to release from the clamp system. The victim climbed into the unshored excavation to free the clamp system from the concrete ring when he lost his balance and fell into the stack of concrete rings. He then became entrapped when sand collapsed around him.
The sides of the 25' x 25' excavation were extremely steep, an estimated 65- to 70-degree angle. The bottom of the pit was about 4–5 feet in diameter.
The soil consisted predominantly of sand (Type C soil), which complicated the rescue because as it dried, it began to slough off, covering the victim more. Each time this occurred, the victim became more stressed and quite verbal about his predicament. We kept in constant communication with the victim, reassuring him that we were working to get him out.
The spoil pile of material removed from the excavation was very close to the edge of the excavation. Crews elected to move the spoil pile for two reasons. First, the weight (surcharge load) was resting on the edge (lip) of the excavation, placing additional stress on the walls of the excavation. Soil weighs an average of 100 lbs. per cubic foot (3,800 lbs. per cubic yard). Second, the spoil pile was tall enough to prevent the proper positioning of the aerial ladder. Two fire crews (inmates trained in wildland firefighting) were used to remove the spoil pile using hand tools.
The shoring group placed several sheets of plywood around the lip of the excavation to provide edge protection. Personnel lined the walls of the excavation’s opening with salvage covers to reduce the amount of sand falling onto the victim. Based on the nearly circular shape and size of the excavation, it was going to be difficult to stabilize the trench with struts and panels. Doing so would have created a bicycle-spoke effect in the excavation, which would have severely limited our access to the victim.
Accordingly, we decided to construct a box to place over the victim and rescuers for protection. The box was comprised of three 4' x 8' x 3?4" prefabricated trench panels with 2" x 12" uprights attached. Panels were secured together with 4 x 4s at the corners. Leaving the fourth side of the box open so the shoring could fit around the bucket of the backhoe, crews secured two pipe-jack struts to the uprights inside of the shoring box to prevent the open end from closing in the event of a secondary collapse.
They then lowered the box into place over the patient using the aerial ladder. Once the box was in place, a vacuum truck began removing soil.
To retrieve the victim, we set up a short-haul rope rescue system from the ladder truck. The secondary hauling system was set up inside the garage using a Z-Rig with a two-point anchor set off of a concrete-filled metal post embedded in the garage floor and a 4-x-4 wood structural member of the house. To keep the rope from scraping the walls of the excavation and to get a more vertical pull if necessary, we ran the system over a cantilevered straight ladder laid flat on the garage floor anchored by fire personnel and extended over the excavation.
Later in the operation, we transitioned to a rated tripod set up in the garage at the edge of the concrete floor due to the stresses being placed on the ladder and to achieve a higher change of direction angle. Note: In this situation an Arizona Vortex system may have been a better option, but one was not available.
At approximately 1600 hrs, a firefighter was lowered into the excavation box and began using buckets to remove the dirt from the patient, then transitioned to using the hose from the vacuum truck. Direct visual communications and hand signals were established between the vacuum truck operator, rescue (continued on p. 52) group supervisor and the rescuer. Upon removal from the excavation, each rescuer would pass down critical information with the next entrant.
More firefighters followed in rotations and were able to free the victim to just below the waist, assess him for injuries, place him on oxygen and begin IV fluid administration as part of the treatment for possible crush syndrome. Rescuers then placed a victim harness around the victim’s waist.
Tension was applied to the victim’s harness from the highpoint anchor in the garage area while the vacuum hose was used near his lower legs in the hopes that it would assist in his release. The victim was instructed to remain as still as possible while this was attempted. However, after several attempts it became painful for him and he started to struggle and struck the edge of the excavation, causing additional materials to fall back into the excavation on top of him and covering him back up to the waist again. The victim was again freed down to the knees and again tension was placed on the harness. This time the victim reached up to try to pull himself free and pulled additional soil back into the excavation and buried himself to the thighs again.
After more firefighters working in rotation were able to again uncover the victim, commanders elected to make a tactical change. The next rescuer sent into the excavation, a member of the County Trench and Confined Space Rescue Training Cadre, was set up so that he could invert, if necessary, into a position with his head down, suspended by his feet, if he needed to get deeper into the pre-cast rings that surrounded the victim. This rescuer was initially lowered into the excavation feet first and was able to free the victim to just below the knees. He then asked to be pulled up slightly and inverted so that he could go headfirst into the rings and free the victim’s feet. After a few minutes of working inverted, he was able to completely free the victim from the rings and remove him to the edge of the rings.
He then righted himself and used a pick-off strap on the victim and both were extricated out of the excavation approximately 7 hours after the incident began. Care of the victim was transferred to the crew of Mercy Air 2 and AMR for transport to the local trauma center for evaluation and treatment of his injuries.
This incident provides several lessons that can be applied to any trench rescue:
- Understand that weather conditions play a big part in your plan. The conditions we faced required that we rotate our personnel in shorter intervals. This included not only those working in the “hole” but also those working in support functions outside of the hole. Example: As one hand crew worked moving the spoil pile, the other crew would be on standby or rehab. Using a mass transit bus as a rehab center is also a very efficient way to handle a large number of personnel at one time.
- Don’t underestimate the power of a vacuum truck, but be prepared to troubleshoot. Using the vacuum truck from the water district was key to extricating the victim. This piece of equipment can remove large amounts of soil, including rocks. However, large rocks got lodged in the suction hose during the operation. This required pulling the hose from the excavation several times and disassembling it to clear the jam. We found that a long-handled tool, such as a pike pole, worked well to dislodge the rocks from long sections of suction hose. Without this vehicle we would have been there much longer. Keep in mind most water districts have at least one of these vehicles.
- Preplan where you’ll obtain lumber and additional materials for a trench rescue. Many departments lack the ability to carry everything on their rigs needed for a trench rescue. Having access to additional lumber and building materials is crucial. The RCFD has agreements in place at several lumber and hardware stores throughout the county; with one phone call, store personnel can pull an established materials list on file, load a truck and be en route to the incident in short order.
- Train with your water district regularly. As part of your preplanning for these types of incidents, set up a joint training session with your water district to familiarize your personnel with the capabilities and limitations of their vacuum truck and orient the water district staff to your SOPs. Note: Keep contact numbers for the water district and lumber supply centers available in your dispatch/command centers, including after-hours and weekend numbers.
- Order staff early to allow for reflex time of your resources to arrive on scene. Trench rescues require a lot of staffing; this incident had 80 personnel assigned to it.
- Use a trench rescue tactical worksheet. This will prompt you on what must be done as well as provide organization and guidance to keep you within OSHA guidelines.
Although it took nearly 7 hours to rescue the victim from the excavation, it was done without injury to responding personnel. The round shape of the excavation made it nearly impossible to use established shoring techniques; improvisation was necessary to ensure the safest possible work environment. A well coordinated, multi-agency response greatly contributed to the outcome of the incident. Although few of the personnel on scene had ever worked together in a situation like this before, effective command and control of resources and closely following the incident command system were key to the successful outcome.
Comment Now: Post Your Thoughts & Comments on This Story