HAZARD MITIGATION

HAZARD MITIGATION

BY DAVID J. HAMMOND, S.E.

The Humberto Vidal Building explosion in Puerto Rico occurred on Thursday, November 21, 1996. On that same day, task force leaders from four states, a representative of the California Office of Emergency Services, and I were at the National Association of Search and Rescue in Fairfax, Virginia, participating in the first planning meeting for developing a course for FEMA Urban Search and Rescue National Response System task force leaders. It was early afternoon when we learned that officials in Puerto Rico had requested additional assistance and resources to deal with the extensive destruction that had occurred and that the Florida Task Force 1 (Metro Dade) was being activated to respond to San Juan. We were asked to respond as part of the Incident Support Team (IST), which would be comprised of 24 members from Florida, New York, California, and Colorado–many of whom spoke Spanish.

Five of us and FEMA`s Urban Search and Rescue`s Steve Presgraves left for Puerto Rico on the next available aircraft. Presgraves was to serve as ESF-9 (Emergency Support Function) leader, responsible for the IST and the task forces that would be dispatched to the scene. Metro Dade Assistant Chief of Operations Carlos Castillo was to be IST leader, and I was assigned as operations chief, a duty I performed for 16 days in Oklahoma City. The other members were assigned various functions within the IST organization system–that is, logistics, safety, and planning for 24 IST members.

ARRIVAL IN PUERTO RICO

Later that day, we arrived at the FEMA command center in Puerto Rico. Castillo had arrived before us and had met with the incident commander, Pedro Toledo, the Puerto Rico Police superintendent and president of the Security Commission in Puerto Rico.

At the initial briefing, IST Leader Castillo reported that there had been a gas explosion.

INCIDENT SITE

The Humberto Vidal Building, the most severely damaged structure, had undergone an interior collapse. The six-story commercial building was located in Paseo de Diego, a heavy-traffic commercial area in downtown Rio Piedras, San Juan, Puerto Rico. The explosion had occurred at approximately 8:30 a.m. (Puerto Rico time). At the time of our arrival, 19 people were dead and more than 85 injured. Unconfirmed reports had up to 20 people missing–a figure that would change as the days went on. Work at the incident site had ceased while the stability of the building was being evaluated.

My first impressions on arriving at the site immediately brought me back to the night of my arrival in Oklahoma City (the bombing of the Alfred P. Murrah Building). TV transmissions do not do justice to actual on-site, close-up eye views of these types of disasters. An eerie feeling came over us as we discussed the similarities between this disaster and the Oklahoma City Bombing. Although smaller in size, it presented many of the same challenges. Floors and walls were gone. Debris was everywhere. The basement was filled with the remains of the upper floors. Hazards were all around us. And, certainly, the potential for a secondary collapse was evident. Before putting the task forces to work, a number of steps had to be taken.

FEMA teams work under the jurisdiction of the local incident commander. We met with the officials of the Commonwealth of Puerto Rico to explain the resources and capabilities of the task forces. Each member of the IST had to know his counterpart. The ESF-9 leader would deal with the FEMA division director. The IST leader would deal with the incident commander. The operations chief would deal with the civil defense director. The civil defense agency was in charge of search, rescue, and recovery. The task forces had to be briefed and instructed on proper protocols and procedures. The fact that many team members spoke Spanish was very helpful.

At a meeting prior to commencing a team (task forces and Puerto Rico Civil Defense) operation, we were given the following update: The explosion had occurred in a street gas pipeline directly in front of the Humberto Vidal Building. Nineteen people were killed as a result of the explosion–four were removed from inside the building and 15 from outside the building, in the street and on the sidewalk. Reportedly, an odor of gas had been in the area for a couple of days prior to the explosion. There wasn`t any gas line into the building. It was suggested that since propane is heavier than air, the gas may have seeped into the basement area and been ignited by an unknown source. The local utility company shut down the service in this area after the explosion by isolating this area. The National Transportation Safety Board was investigating the cause of the explosion. Surface searches were conducted; the Puerto Rico Police canine units were used extensively with superior results.

OPERATION PLANS

We planned our operations. Searches would begin again at 0700 on Friday. The task forces would be teamed with the Puerto Rico Civil Defense rescuers. After briefing the Metro Dade Task Force and finalizing our operational plan, I met with Carlos Acevedo, the Puerto Rico Civil Defense Regional Director for Zone 1 (the San Juan area). We would work together until the initial rescue efforts concluded..

The guidelines were clear: The IST and task forces would be working with the Civil Defense rescuers, who were in charge of the operation. The teams would work together in two shifts. The day shift would begin work at 0700 hours; the evening shift would relieve the day shift at 1900 hours (7 p.m.). The leader of the retiring shift would transfer information to the leader of the incoming shift. It is imperative that incoming shifts be briefed on what the previous shift had accomplished and the incident action plan (IAP) for the commencing shift. The IAPs are developed for each operational period and contain all necessary information regarding planned objectives, medical considerations, communications, weather reports, an organizational chart, and building/site plans, when available.

Prior to our first working shift, we knew that the Puerto Rico rescuers had removed 19 victims, searched all the areas that could be searched safely, and evaluated the status of damaged structures involved in the initial explosion. The first day of searches would be limited to exposures on both sides of the building; commercial contractors began shoring the most severely damaged columns in the Humberto Vidal Building, using 14-inch steel H-piles to brace them.

We began searching a toy store located directly behind the Humberto Vidal Building when looking from the front of the building. It was reported that some children may have been in the store at the time of the explosion. During these types of incidents, it is extremely important to gather information and follow up thoroughly to ensure that all victims are accounted for, regardless of the source of the information. Canines from the Puerto Rico Police Department were used to search the store. The Metro Dade Task Force canines were used in a secondary search. Both searches were negative.

All the debris from the store was to be removed so that structure specialists could evaluate the store`s stability and the task force and the rescuers from Puerto Rico could work together while the shoring was being erected in the original building. This took most of the morning.

WORK STOPPAGES

Early in the afternoon, as rescuers were about to begin searching other exposed buildings, an extremely heavy rainstorm caused the operation to be stopped. Weather plays an extremely important role during any type of incident. Stoppages must always be considered when planning; they may be due to weather, hazard mitigation, questionable structure stability, and other factors.

As soon as the weather cleared, the searches resumed in another of the exposed buildings, a drugstore called the La California; a few feet of covered alleyway separated its west wall from the east wall of the Humberto Vidal Building. The Puerto Rico Police canines again began the initial search. This produced immediate results. The canines alerted (which indicated that a victim may be present) in the center of the store; a female victim was recovered from that area. After completing the required documentation, Puerto Rico Civil Defense rescuers removed her body to a temporary morgue. This recovery was unusual in that the building`s owner, who was in the building at the time of the explosion, had reported that all personnel in his building had been accounted for. He closed the building after the explosion and opened it only after being asked to that day so that a search could be conducted. Investigators believed that the force of the explosion blew the victim from the Humberto Vidal Building into the exposure, which seemed possible given the fact that both walls were missing.

During the evening shift, rescuers were able to start searching the upper floors and basement area after the shoring of the columns had been completed. An odor of gas in the basement area caused the work to be halted during the shift.

Sections of broken concrete hanging from reinforcement rods and dangling over the heads of workers below (“widow makers”–a term coined in Oklahoma City) were also present in Puerto Rico. Rescuer safety was a major concern. To decrease the risk of severe injury for rescuers, contractors at the scene built protective platforms–aluminum scaffold beams covered with plywood–to catch the sections of concrete and other debris that came loose and fell over the work areas. The majority of debris was located in the basement area. Members working in these areas did so under these platforms. Fans were required to improve the quality of the air in the area.

Workers were rotated and relieved frequently. The high temperatures, dust and debris, and presence of decaying bodies created an extremely intense and rough working environment. The work was very labor-intensive. In addition, there were the hazards posed by the potential for gas to become trapped in pockets, a broken water main leaking into the basement, and working within the confined space below the protective platforms. Heavy equipment could not be used because of limited access from the street. All of the work was done by hand. Some power tools–such as pavement breakers, drills, and saws–were used to reduce the size of the debris. This work was being done while the stability of the building was being reinforced. Certain stabilization procedures required work stoppages.

Electronic transits constantly monitored the severely damaged columns and beams. Air-operated horns were used as safety signaling devices whenever the work area had to be evacuated. Safety officers were assigned to all work locations. Safety was the number-one concern. Rescuers should never become victims.

SECOND TASK FORCE ACTIVATED

The amount of debris and the extremely labor-intensive workload necessitated the activation of a second task force (Florida TF-2, Miami), whose members arrived on Sunday morning. They were briefed and incorporated into the operational plan. Working a 12-hour-on/12-hour-off schedule, we now had one full task force of 62 members (half from Metro Dade and half from Miami) working around the clock.

Priority work areas were identified after canine teams were used to search the basement area. David Hammond, S.E., IST lead structure specialist, estimated that 1,000 cubic yards of debris were in the basement. As the teams worked together, work progressed at an expected pace. From our experience in Oklahoma City, we knew that this would be an extended operation and that additional task forces might be needed.

Each day, rescuers located and removed additional victims. By Monday (the fourth day of operations), nine victims had been removed. As the days wore on, concern for the safety of the team members grew due to the nature of the work, the long hours, and the strenuous labor involved. There were also concerns about the stability of the building. On Tuesday, a 10th victim was located and removed.

That evening, the structure specialists and engineers found additional damaged columns and beams, forcing a work stoppage. After a thorough evaluation of the building conditions, additional damage was found. The Acting Governor ordered that all work in the building be stopped. Work would recommence on December 18.

LESSONS REINFORCED

Incidents of this scale generally require additional resources and personnel.

Information gathering is an important part of the action plan.

The incident command system is a must for managing incidents of this nature.

Rescuer safety must be the first priority for those managing these incidents–the risk vs. gain factor must be considered.

Develop an incident action plan for each work period.

Work stoppages will be necessary (i.e., weather-related, hazard mitigation, and so on).

Use electronic transits operated by qualified personnel to monitor the structure.

Have a standard evacuation signal and an accountability system. FEMA task forces use the following:

–Evacuate the area–three short blasts (one second each).

–Cease operations/All quiet–one long blast (three seconds).

— Resume operations–one long and one short blast.

Relieve and rotate rescuers frequently enough to ensure their safety.

Good communications and coordination are musts for successful operations.

Interagency cooperation and understanding of agencies` responsibilities and duties by all parties involved are required to achieve successful results.

The FEMA task forces have 19 different specialists in their organizational structure. This operation required the services of all of them. The canines, technical search, rescue specialists, medical specialist, structure specialist, haz-mat specialist, heavy rigging specialist, and logistics specialist all played extremely important roles in the around-the-clock operation. n

I arrived in Puerto Rico at 2400 on Friday, November 22, along with John O`Connell, a member of Rescue 3 in the City of New York (NY) Fire Department and the leader of the Building Collapse & Trench Rescue Development Group for the state of New York. At 0600 on Saturday, I arrived at the explosion site with the IST day shift. At the morning briefing, I met Jack Erdozian, IST structural specialist, and was briefed on the building`s damage and current mitigation status.

Erdozian and I visited the site to observe what had been done and to make an independent assessment. Four large steel H-piles had been installed as raker shores, two each at Columns C-2 and C-3. The C-2 insertion point was at the fourth floor; the insertion point for C-3 was at the third floor. John Pepper, structural specialist FL TF-l, had suggested the shores, which were installed by local contractors.

I reviewed the raker shores and agreed that they were somewhat helpful as a first step but that they had the disadvantage of applying a horizontal load into the building while providing the desirable vertical support.

After some discussion, it was agreed that a second and better vertical support for the heavily damaged column could be provided by bringing a large mobile crane to the site and rigging Column C-2 so that it could be supported from above. I aggressively supported this idea. The column was prepared to have four one-inch-diameter cables extended down through the roof and the fifth floor and then looped around the column in choker fashion just below the fifth-floor beam. The crane arrived at the site; it was rigged with four cables, which were lowered through the previously cut holes. The loops were fabricated in place under the direction of Paul Gurdak, FL TF-1, rigging specialist.

The building and the prescribed collapse zone were cleared; the cables were carefully pulled snug without lifting the column off the previously installed raker shores. A theodolite, operated by Department of Transportation personnel and installed by public works personnel to monitor the movement in Column C-2, was used to verify the movement (or lack of movement) when the cables were snugged tight. The entire tightening went smoothly and was completed by 1800 hours.

THE DAMAGE

In the basement, where the explosion appeared to have occurred, the exterior retaining walls were badly cracked, especially on the west side (Camella Soto Street), and offset outward near the first floor. The concrete walls at the stair/elevator were very badly cracked and bent out of plumb in the same locations. Above the first floor, these walls and their corner columns had few cracks, except at their joints with the second- and third-floor beams. The concrete stair was fragmented and collapsed in the basement story and badly cracked and impassable on the first floor but undamaged and usable above the third floor.

The light slab/bar joist system had been blown completely off the concrete floor beams and had collapsed in the basement. The floor beams were in relatively good condition. The joist system appeared to have been blown cleanly away without the presence of any rebar dowels at other connections between joist and beam.

On the second floor (called the mezzanine), which had been constructed with a very large opening, all of the floor slabs had been blown away, leaving a 21-inch steel beam twisted and bare at line B and cracked and displaced concrete beams on Lines C, D, and E.

All of the third-floor slabs and joists were missing except for a portion just south of the elevator core (Lines E to F, 2 to 3). All of the third-floor steel beams remained, but all of the shorter, smaller concrete interior beams were damaged or missing. Columns C-2 and C-3 were severely damaged at the third floor, and the steel beam on Line D had pulled partly out of the Column D-1. At Column C-2, the steel beam/column joint had offset at the top to form about a 15-degree angle off vertical from top to bottom (very near collapse). Column C-3 was out of plumb more than eight inches at the third floor, and its south spandrel beam had partly separated (also near collapse). It was also later discovered that Column E-1 had split and offset just above the third floor (very near collapse).

Part of the fourth floor slab and joist had collapsed north of the elevator core, but all beams remained. Large sheets of corrugated metal deck hung nearly vertical from near Line 1 between Lines C and E, with parts of their concrete fill slabs remaining, unsupported, near the original floor line.

The interior stair from the third to fourth floors was badly distorted; it had collapsed and was suspended on the third-floor beams.

The fifth floor, the sixth floor, the low roof, and the high roof over the sixth floor were not structurally damaged.

At the north wall (facing De Diego Street), the infill in the third story was partly missing, and two small piers between the original three window openings had been blown away. The remaining infill appeared to be still anchored to the concrete frame. The infill in the fourth and fifth stories had most of its windows missing but otherwise appeared to be undamaged.

The south wall masonry infill fared somewhat more poorly than that at the north wall. The small piers were also missing at the third story. Also, parts of this infill were disconnected from the fourth-floor beam and were leaning out about one foot. The fourth-, fifth-, and sixth-story infill panels appeared to have suffered little structural damage.

The west wall, the long side facing Camella Soto Street, was completely open below the third floor. The second-floor wall beam was badly damaged at Line C and missing between Lines E and F. This beam was still hanging from the column at Line E and extended down into the basement. In the third story, most of the masonry infill was missing. The one panel that remained (between Lines C and D) was badly cracked, disconnected at its top, and leaning out about six inches. Above the fourth floor, there was no observed structural damage to the infill except for the solid panel that faced the stair and elevator. This six-inch concrete unit masonry wall was also disconnected at the top and leaning out. Much of the metal screen was still in place.

The east wall, which faced a covered alleyway, had no missing beams, but the masonry infill was damaged in several bays in the third story. At least two sections of the wall between windows was disconnected at the fourth floor and leaning out about a foot. The wall above the fourth floor had little significant structural damage.

PRIMARY HAZARDS

The Humberto Vidal Building contained many falling and significant collapse hazards involving the remaining, damaged, and poorly braced columns. The postblast structure had no continuous floor plane for the first, second, third, or fourth floors. The remaining beams provided some column lateral bracing, especially in the exterior wall frames and at Lines D and E, where the beams connected to the stair/elevator core.

The worst collapse hazards were Columns C-2, C-3, and E-1, which had badly broken joints at the third floor. Column D-2 was out of plumb at the third floor. Several other columns had cracked joints at that level.

The basement walls presented an additional collapse hazard, in that the first-floor slab that had held back the soil pressure was missing, as was the concrete beam on Line C that had extended from Line 2 to 3.

The falling hazards included the leaning wall panels at exterior walls and many items hanging from the fourth floor; they varied from light metal straps and ducts to heavy pieces of disconnected concrete slab.

MITIGATION METHODS

Mitigation methods used during the rescue phase were as follows:

Columns C-2 and C-3 were braced with 14-inch steel H-piles at and above their broken joints.

A large crane was used to suspend C-2 and C-3 from above.

Horizontal cable ties were used to restrain the offset in Column C-2.

Aluminum scaffold beams with plywood covering provided falling hazard shields.

The movement of the critical areas of the structure was monitored at four different locations with electronic transits (theodolites). Each station was equipped with an alarm horn. The transits also were used to monitor the application of the suspension cable load to the critical columns to ensure that no significant lifting was done.

In many locations, pipe shores were used as vertical shores, and a bundle of four 4 3 4s was used as a thrust beam against the basement wall at Column C-3.

Many falling hazards were removed, including walls, plaster ceilings, remaining pieces of floors, and so on. n

The explosion in the Humberto Vidal Building caused the first, second, and third floors to collapse into the basement. The basement, which had been full of stock, became filled with 11- to 12-foot-high debris and rubble. The type of concrete used to construct the structure and the force of the explosion created minimal void areas. The structure was of various types of tile block, gypsum, and poured concrete. The concrete, however, did not have any larger-size stone in it. The majority of the stone was small gravel and was easily pulverized in the explosion, creating the minimal void possibilities. Some of the concrete floor sections had steel reinforcing bars with Q-decking; others had only concrete poured over wire lath. The structure had been renovated several times.

CABLE TIE-BACK SYSTEMS

Since the explosion had blown out several of the lower floors, which were missing, and heavily damaged the beams and columns above, the damaged structural columns and beams had to be tied to the upper parts of the structure.

Three main tie-back systems were used. The first was a 34-inch section of cable placed around the heavily damaged, cracked, and out-of-plumb Column C-2 on the second floor. This column was a priority, since it was still supporting three floors above it. Since the column was set in approximately 15 feet from the face of the structure, it would take some time to raker shore it from the outside.

To relieve some of the pressure on that damaged column, wire rope cables were used to tie the column back to the rest of the structure to secure it and prevent it from further shifting. The cable was wrapped around the column and then around the elevator shaft and then fed around Columns E-2 and E-3. Eyes–two on each end and one in line in back of the E-2 column–were placed in the cable. The eyes were made from 434-inch wire rope clips, which were spaced approximately six times the cable`s diameter from each other. The clips were installed with the solid bend of the clip over the dead end of the line (the tail), to ensure that they would hold. If the clips were put in any other way, they might slip and become loose. An eye put in line on one end of the cable made it possible to use a come-a-long to tighten the cable. The come-a-long was tightened until all the slack around the elevator shaft was taken up. Caution was taken not to move the column during the tightening process. Just enough strain to give the column some additional support was placed on it. The cable clamps were then tightened to secure the cable; the come-a-long was left in the system in case the cable had to be readjusted.

The second cable tie-back system was more elaborate and time-consuming. It was installed to support a heavily damaged main bearing beam on the third floor. At the fourth floor, the column above the damaged support members was strapped with four separate cables. Four separate holes were drilled through the roof, the top floor, and the fourth floor. The holes were aligned with each other so that the proper strain could be placed on the cables and the load could be uniformly distributed through the system. n

Following the shutdown of rescue operations on November 26, 1996, the Puerto Rican government hired the firm of Felipe Nazario & Assoc. Engineers to design mitigating measures that would allow the four remaining victims to be removed. The approach of the Nazario firm was to inspect all existing damaged joints in the concrete columns and strengthen the most vulnerable ones using epoxy grout bandages that would surround the joints and fill the voids. In addition, the sixth-story roof, floor, and walls were to be removed to reduce the load on all of the columns. Falling hazards hanging from the fourth and third floors were also to be removed.

The mitigation work was begun under the supervision of Felipe Nazario and monitored by strategically placed theodolites. After strengthening the badly cracked joints at Columns E-1, C-2, C-3, and D-3, the crane was detached from the cables that had been providing tension support for Columns C-2 and C-3. Since no significant movement was observed, the deconstruction and removal work was begun.

After the roof, roof equipment, sixth-story furnishings, and most of the falling hazards had been removed, the Puerto Rican government became impatient with the process and asked Nazario whether the building hadn`t been sufficiently strengthened to allow victim-removal operations to begin. The Puerto Rican government was anxious to have all victims removed prior to the Christmas holidays to bring closure for the victims` families. Although only less than half of the desirable weight-removal work had been accomplished, Nazario agreed that victim removal could be started, although the risk level was higher than he desired.

The Puerto Rican government requested a team of technical advisers from FEMA. Steve Kilby, IST leader; Dennis Mojica, NY TF-1; and I were sent to Puerto Rico on December 18, 1996. The Puerto Rico Civil Defense teams began work on the morning of December 18, 1996. The advisers arrived that evening (after the first of the remaining four victims had been removed).

After initial briefings, I met with Nazario. It had been intended that additional mitigation measures be constructed as long as they didn`t significantly affect the victim-removal activities. However, none of the suggested strengthening was done because of the relatively rapid removal of the remaining victims and the difficulty in contracting for the additional work (The Puerto Rican Civil Defense teams were not prepared to do shoring or other mitigation work). Fortunately, the final victim was removed by 0300 on Friday, December 20. Search and rescue operations were concluded at 0410 without any incidents of a structural nature. n

On my arrival at the hotel, I met with Steve Kilby, who was IST assistant leader during our first mission to Puerto Rico (PR). We were then transported to the building collapse site for a briefing with José Bravo, FEMA`s division director for the Caribbean area. Carlos Acevedo, PR Civil Defense Zone 1 Regional Director; Jaime Rivero, PR Civil Defense search and rescue coordinator; and Felipe Nazario, a civilian structural engineer contracted by PR`s Housing Department to assist the Civil Defense.

Rivero informed us that search and recovery operations had started before we arrived and that two males (a mechanic and a store manager) and two females (a store employee and a customer) were still missing. The search teams had found and removed one male, believed to the mechanic, between the D-1 and E-1 area of the basement.

Nazario informed us that the original plans to demolish the six-story building down to the basement level had been changed after the demolition crews experienced a very difficult time in dismantling the sixth floor due to the structural soundness of the building. On further investigation, the engineers decided to leave the fourth and fifth floors intact, since it was determined that there was no danger of further collapse. All furniture, overhead loose hanging concrete, and unstable debris were removed from the fourth and fifth floors. The safety platforms assembled during the initial operation were kept in place to provide protection for squads working in the basement. The severely damaged support columns were structurally reinforced by erecting a wood form around the columns. A two-part resin was then poured into the form and allowed to dry.

At approximately 10:50 p.m., the third member of the advisory team–David Hammond, a structural engineer and IST lead technical specialist–arrived on-site. Hammond was briefed on our earlier meeting with the officials from the Puerto Rico Civil Defense. After surveying the building, Hammond concurred with Nazario on what had been done to the problem areas. The search for the three remaining victims was continued.

Kilby, the Civil Defense officials, and I split into two teams, to provide 24-hour coverage. The workday was divided into two 12-hour shifts. Each shift had its own organizational chart. The A (Alpha) shift operated from 6 a.m. to 6 p.m. and was supervised by Bravo; Acevedo; Hammond; and Kilby as technical adviser. The B (Bravo) shift operated from 6 p.m. to 6 a.m. and was supervised by Rivero; Nazario; and me, as technical adviser.

Manpower was clearly not a problem, since hundreds of civil defense volunteers–male and female, young and old–came from various counties of Puerto Rico offering their assistance. Each shift had a minimum of 100 people, who operated throughout the entire operation. These people were further divided into six-person squads. Each squad leader maintained a list of their personnel for accountability purposes. One squad per shift was kept on standby to act as a rapid intervention team.

Due to the high temperature and humidity characteristic of Puerto Rico and the inherent dangers of this type of recovery work, a medical team and ambulance were on-site during each shift, and a list of the locations of nearby hospitals (burn, trauma, and so on) was compiled. I recommended that a schedule be established for rotating squads operating in the search area every 30 minutes, to minimize injuries, dehydration, heat exhaustion, and the like. Although all these precautions were taken, a Civil Defense member from the B shift was taken to a medical dispensary for treatment of heat exhaustion.

Rivero and I had a briefing and agreed to operate as we did on the first mission to PR, using FEMA search strategy and tactics. Hourly haz-mat readings were taken to monitor for pockets of gas in the basement. Continuous monitoring for carbon monoxide was conducted anytime gas-powered tools were used. A decontamination area was set up to deal with contamination problems that might arise, such as members` coming in contact with body fluids.

PR`s police canine unit entered the basement to participate in the search. The dogs gave numerous alerts between the D-1.5 and the E-2 area. This location was then marked using FEMA search assessment procedures. Civil Defense squads concentrated on searching this area.

PROBLEMS ENCOUNTERED

We encountered our share of problems during this phase of the operation. A contract dispute between the Civil Defense and the local waste-removal company stopped all search operations for one hour. The waste company refused to cart away 50 yard containers because their contract had been canceled. Civil Defense officials were able to settle the problem, and operations were resumed.

At approximately 4:20 a.m., all search and recovery operations were stopped again. A large puddle of water was found in the search area. A water main leak was discovered on the exposure 4 side of the building. The concerns were that the water would mix with body fluids and splash on members and that the water could cause undermining. Civil Defense officials had the Water Authority assess the problem with their structural engineers. The water main problem was corrected by closing some section valves. The water puddle was determined to have been an accumulation from a previous rainfall. Recovery operations restarted; the squads were directed to avoid operating in the immediate area until it was dry.

A change-of-shift briefing was held, and Alpha shift squads were instructed to continue to search the C-1.5/E-2 area. The day shift encountered some problems with heavy debris removal. The squads attempted to use a Bobcat(TM) but were unable to get any traction, which rendered the machine useless. However, they successfully used a cherry picker to assist with the heavy debris removal.

On Thursday, December 19, at 1:30 p.m., CD squads recovered one female approximately 15 feet from the wall between the D-1.5/ E-2 area. Officials notified the Forensics Team, which responded for identification purposes and body removal. The canine unit began to alert 10 feet from the location at which the second victim had been found. Squads continued to search the immediate area. At approximately 4:30 p.m., they recovered the third victim–a female–six feet from the second victim (store employee and customer). This left one victim unaccounted for.

The B shift came on-duty, and the squads were instructed to search the D-1/E-1 area. Earlier reports indicated that one of the building owners thought the store manager was in the basement with the mechanic, whose body had been found in this area two days earlier.

After haz-mat readings were taken, the canine team entered the area. The dogs started to alert along the wall, near a partial stairway. CD squads searched the area and at 1 a.m. found the remains of a badly decomposed body.

It took a while to identify the last victim because all that was found on the remains were shoes and a gold chain and pendant. A family member was able to positively identify the pendant as belonging to the store manager.

Having found the final victim, the grim task of search and recovery operations had come to an end. n



The first, second, and third floors of the Humberto Vidal Building were totally destroyed. The top two floors remained intact, causing many problems for rescuers. (Photo by John O`Connell.)



A view of the heavily damaged La California drugstore. One female victim was recovered here. (Photo by John O`Connell.)





(1) Aluminum scaffold beam. The beams used at this incident were about six inches high, 212 inches wide at the top, and four inches wide at the bottom. A 112-inch piece of lumber imbedded into the top of the beam provides a nailing surface. (Photos by John O`Connell.) (2,3) A platform of double thickness was erected in a section of the structure that presented hazards deemed to be larger than those contained in some of the other areas. Here, the first platform is laid in place and anchored in position. (4) The next deck was then laid in position and secured, creating an extremely durable and solid shelter under which rescue personnel could operate.






Contractor-installed raker shores. (1) Local contractors installed four raker shores against Columns C-2 and C-3, which were in danger of collapsing. The H-beams–14 inches square and weighing 60 pounds per foot–were laid up against the columns at an angle. (Photos by John O`Connell.) (2,3) The shores were inserted just under the beams at the corner of the columns; the beams are to stop the rakers from riding up if the columns move. (4) The short leg is there to stop the beam from sliding backward under pressure. The “hold-back leg,” positioned against the basement wall, prevents the back of the bottom of the raker from sliding backward under pressure. (5) Splice plates–welded to the rakers to a cross-beam that was welded to the bottom beam–help to ensure that the raker would not slide backward if it came under pressure.





Wood shoring beams. (6) The “local craftsmen” installed one beam at the base of Columns C-2 and C-3, and the FEMA rescue forces installed another in the same proximity. The beam consisted of four 4 2 4s anchored together. Four sets of plywood gusset plates were then wrapped around the 4 2 4s on all four sides. Care was taken to keep the beams together. The four pieces were locked together as one unit. The 34-inch plywood gussets were nailed to the 4 2 4s with 8 penny common nails. (Photos by John O`Connell.) (7) Both ends of the inside beam were beveled, since the beam was going to be placed in position on an angle. A carpenter framing square was used to determine the proper angles based on the proper predetermined dimensions. Since the angles on both ends were to be different, each end was measured and cut separately. The lower end of the beam was lowered into position first. Wedges were then installed to take up the space from the uneven column and make it possible to adjust the beam. This beam was placed in position at the column at the point at which it would directly bear against the force of the adjoining concrete beam to give it the best possible bearing support. (8) The opposite end of the beam, the outside beam, was placed at the very bottom of the damaged Column C-3, where it would give the most support. The post is cut on a bevel for a better fit. Two thin wedges were placed in position to take up some of the uneven spacing caused by the broken concrete. (9) Wide view of beam. This beam, installed by FL-TF1 just in front of the beam installed by the local contractor, was placed in this position to stop the heavily damaged column on the right from breaking off and falling into the basement. The back end of the beam was braced by the opposite column and beam to replace the section of beam that had broken and fallen into the basement. The broken beam can be seen under the wood beam tied back to the column.







Second cable tie-back system. (1) The four one-inch cables tied to the column directly under the intersecting beams take the strain off the lower damaged columns. An eye was spliced into the cable, and the tail was cable-clamped to the main line. Four clamps were used on each eye. (Photos by John O`Connell.) (2) The four cables were brought up to the roof (3) by the block from the 150-ton crane and lowered down through four holes that had been cut in the floors. Personnel from FL TF-1 are operating from the roofs of the penthouse and the main building. (4) The four cables were placed at the four corners of the column to be supported. Here, two cables are being fed through on the fifth floor. Each floor had four holes drilled in it. All the holes were aligned with each other so that the cables could pick up the load evenly. (5) Cable on the other side of column. These lines, on the other side of the column, went directly to the roof and were hooked up to the block on the crane. (6) The four cables are tied up in tension.



(Left) Column C-2. (Right) Column E-1. (Photos by David Hammond, S.E.)






Last cable tie-back. (1) Task force members are tightening a cable around the third-floor beam between Columns C-2 and C-3 so that the beam can be “snugged” in place and some of the pressure can be taken off the C-3 column. Two holes were gently made in the floor slab on the outside edge of both sides of the beam. (Photos by John O`Connell.) (2) The exterior view of the column wrap and the tie-back used to hold it in place. The third vertical cable from the left will be tensioned to hold up the third-floor beam. (3) One-inch cable was wrapped twice and cable-clamped together to ensure that it will not stretch and permit the wrap to shift. Note the angle of the third cable from the left as it passes the column wrap–it passes up past the wrap and goes straight to the fall line of the crane, where the tension will be applied. That`s why the wrap is in place. The wrap is inside the four-leg column pull and tied back so it will not interfere with its operation. (4) Task force personnel assembling another long choker to stretch around three other columns and the outside wall in which they were located. Two eyes were inserted into this cable length and used as a come-a-long to tighten it. Placing it inside the column wrap will stop the wrap from shifting when tension is applied to the cable. (5) Finally, the cable is wrapped around the beam, centered over the beam`s middle, and clamped together.








Cable wrap. (1) A close-up of cable tie-up. The cable is tied to the base of the damaged column. (Photos by John O`Connell.) (2) A direct view of the cable system from the supporting walls and columns. The elevator shaft and this column were used as the bracing system for the damaged column. The cables were wrapped and spliced around them and cable-clamped together. (3) The front of the column-wrap cable system is in tension with the come-a-long. The safety eye on the cable is there in case any part of the system were to let go. (4) A back view of the column wrap. The come-a-long in tension is hooked to the eyes of the cable ends. The hallway and elevator are on the right, and the outside column is on the left. Contractor shoring operations. (5) Three local workmen install a “spot” shore, a mechanical-pipe shore common to the construction trade. (6) The locking pin is the typical locking mechanism for this shoring device. An adjustable pin is placed in any number of holes in the upper part of the shore. A screw thread device is then tightened around the pin to “snug” it into position. In many cases, hammers were used to tighten the screw jacks into position. (7) The two jacks provide additional stability at the cracked area of the column/beam intersections. This system was used throughout the collapsed structure.

PROPANE BY FRANK L. FIRE

Propane is a flammable, colorless, odorless, tasteless, nontoxic hydrocarbon gas. It burns relatively cleanly and is an excellent fuel. Although propane is a flammable gas, it is usually shipped and stored as a liquid. An odorant is added so it can be detected if it leaks from its container. It has an ignition temperature of 8427F and explosive limits of 2.1 percent to 9.5 percent in air. The liquefied gas has a specific gravity of 0.531 and a molecular weight of 44. Its vapor density is 1.517. It boils at 2447F, freezes at 2309.87F, and is not soluble in water. Although gases have no flash points (since they are already in the “right” form to ignite), the liquid often has a flash point of 2248.87F listed in the literature. This “information” is totally unnecessary, since there is no region on earth that has this ambient temperature.

Propane`s CAS (Chemical Abstract Services) number is 74-98-6. Its UN/NA (United Nations/North America) designation is 1978 for the gas and 1075 for the liquefied state, known as LPG (liquefied petroleum gas). LPG may also be a mixture of propane, butane, and some isomers of butane. Propane`s STCC (Standard Transportation Commodity Code) number is 4905781, its RTECS (Registry of Toxic Effects of Chemical Substances) designation is TX2275000, and its NFPA (National Fire Protection Association) 704 hazard rating is 1-4-0. Propane`s molecular formula is C3H8.

n FRANK L. FIRE is the vice president of marketing for Americhem Inc. in Cuyahoga Falls, Ohio. He`s an instructor of hazardous-materials chemistry at the University of Akron as well as an adjunct instructor of haz mats at the National Fire Academy. Fire is the author of The Common Sense Approach to Hazardous Materials and an accompanying study guide, Combustibility of Plastics, and Chemical Data Notebook: A User`s Manual, published by Fire Engineering Books. He is an editorial advisory board member of Fire Engineering.

Propane has a very wide range of commercial, industrial, and residential uses, estimated to be in the thousands. In some very few applications, it may be mixed with butane.

In residential uses, including motor and mobile homes, it is used as a fuel for heating and cooking and operating hot water heaters, refrigerators, and air-conditioners. It has much the same uses in commercial situations. It is also used as a fuel to power automobiles, light trucks, and buses. (Editor`s note: In the United States, most propane installations into dwellings are piped from the container and must meet specific safety requirements, including those of the Department of Transportation, according to Bruce Swiecicki, vice president of technical services for the National Propane Gas Association in Lisle, Illinois.)

In industrial operations, it is used as a heating fuel; as a fuel for forklifts and other industrial trucks; as a source of energy for fire boilers, kilns, or other furnaces; and to provide heat for various types of drying operations. It is used in industry where precise heating is required, as in annealing, brazing, enamel baking, metal cutting, and soldering. Industrial operations that use another fuel as the primary heating fuel may use propane as a backup. Electric utilities often use propane to supplement the burning of natural gas during peak demand periods. Propane has uses also as an aerosol propellant, a solvent, an extractant (in the liquefied state), an agent in the synthesis of many organic materials, a foaming agent for some foamed plastics, and a refrigerant.

It has many uses in agricultural operations as well, especially where natural gas lines have not been extended. It is used not only to heat and cook but also to dry farm products including tobacco. Propane is often used to power well pumps, small electric generators, and small engines used for a variety of purposes. n

HUMBERTO VIDAL BUILDING DAMAGE

The floor and roof system was a thin (three- to four-inch) concrete slab placed on draped, expanded metal lath over 10-inch steel bar joist spaced 24 inches over center.

In the fourth and fifth floors, the metal lath had been replaced with corrugated metal deck when the building was remodeled 10 years before.

One basement was present. The basement exterior walls were reinforced concrete.

The first floor had concrete beams with the same type of floor covering as the upper floors.

At the exterior, the concrete frame was infilled with partly grouted and reinforced six-inch concrete unit masonry walls above the third floor. The walls had window openings cut in them; a metal security/sun screen covered these openings.

One stair/elevator core was on the west side of the building with a cast-in-place, reinforced concrete stair and nine-inch concrete shear walls. The stair and elevator extended from the basement to the sixth floor.

One additional stairwell, which extended from the third floor to the roof, was near the middle of the building.

A light well, just east of the stair core, also extended from the third floor through the roof.–DAVID J. HAMMOND, S.E.

RAY DOWNEY is a battalion chief, the chief of rescue operations assigned to the Special Operations Command, and a 35-year veteran of the City of New York (NY) Fire Department. The former captain of Rescue Company 2, he is the USAR task force leaders representative to FEMA for all 26 teams. Downey is also the author of the book The Rescue Company, the video Rescue Operational Planning: Factors for Success, and the video series Collapse Rescue for the Fire Service (Fire Engineering Books and Videos). He has lectured around the world on fire service-related subjects.

DAVID J. HAMMOND, S.E., a structural engineer, is lead instructor for the structural specialists and other training courses. He was a member of the FEMA Urban Urban Search & Rescue Advisory Committee, the lead engineer for the FEMA response to the Oklahoma City Bombing, the leader of U. S. Search Dog Team 3 during the Mexico City 1985 Earthquake response, and a support member of the California Rescue Dog Association in numerous other disasters. He served as a director of USAR Inc., an information coordinating nonprofit group and is a former chairman of the Disaster Emergency Services Committee, Structural Engineers Association of Northern California. He was IST lead instructor specialist at this incident.

JOHN O`CONNELL is an 18-year veteran of the City of New York (NY) Fire Department, where he has spent 10 years in Rescue 3. He is FEMA`s lead shoring instructor and was assigned as the IST shoring specialist at this incident. He is group leader of the Building Collapse & Trench Rescue Development Group for the state of New York and has instructed across the country and in Japan.

DAVID J. HAMMOND, S.E., a structural engineer, is lead instructor for the structural specialists and other training courses. He was a member of the FEMA Urban Urban Search & Rescue Advisory Committee, the lead engineer for the FEMA response to the Oklahoma City Bombing, the leader of U. S. Search Dog Team 3 during the Mexico City 1985 Earthquake response, and a support member of the California Rescue Dog Association in numerous other disasters. He served as a director of USAR Inc., an information coordinating nonprofit group and is a former chairman of the Disaster Emergency Services Committee, Structural Engineers Association of Northern California. He was IST lead instructor specialist at this incident.

DENNIS MOJICA is a 23-year veteran of the City of New York (NY) Fire Department, where he is a lieutenant assigned to Rescue Company 1. He is a New York-certified instructor, confined space instructor, and haz-mat technician. He is a member of New York Task Force-1 and served as a FEMA IST assistant operations chief during the Humberto Vidal Building Collapse and as a technical adviser during his return trip on December 18, 1996.

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