Safety Considerations and Fire Department Operations at Construction Sites

The building environments that form and shape our respective response districts pose unique challenges to the day-to-day responses of fire departments and their subsequent operations at structural alarms. With the variety of occupancies and building characteristics present, there are definable degrees of risk potential with recognizable measures that must be taken.

Although each occupancy type presents variables that dictate how a particular incident is handled, most company operations evolve from basic strategic and tactical principles rooted in past performance and operations at similar structures. With any structure, regardless of its construction type, materials, occupancy classification, age or size, the majority of incidents requiring actual operation time occur when the structure is in use or vacant.

But what about the early stages of the life cycle of a building - when a company is called to respond to an incident at a building under construction or at a construction site? Fire department responses and operations at building and construction sites present unique circumstances and considerations that are not part of that day-to-day alarm response procedure.

During the construction process, building and construction sites represent the highest potential for fire, injuries and large-scale operations than at any other time within the life cycle of a structure. When completed, the building may have state-of-the-art detection and suppression equipment present, it may be compartmentalized and use the best fire resistive materials available. However, during the construction process the building represents a high-risk target hazard with the potential to stretch to the limit the capabilities and resources of any fire service agency.

Buildings can be classified within five fundamental construction types:

  • Fire-Resistive
  • Non-Combustible
  • Ordinary (exterior protected)
  • Heavy Timber
  • Wood Frame

These are represented in various forms and sub-classifications within the NFPA 220 Standard on Types of Building Construction, as well as within each of the Model Codes Standardization Council (MCSC) Recommended Types of Construction, and the three (3) Model Building Codes, UBC, BNBC and SBC.

Regardless of construction classification, during the construction process each building can be affected adversely by flame and heat impingement due to fires, weather and environmental conditions, improper or inadequate construction techniques and methods as well as substandard or inappropriate construction materials and system assemblies.

When referring to the broad range of building and construction sites, there are five general classifications for most projects:

  • Renovations
  • Rehabilitations
  • Conversions
  • Expansions
  • New construction

Although there are some overlaps, each project presents hazards that affect life safety, structural integrity and exposures. Projects within the renovation and rehabilitation areas may include vacant or abandoned structures that are transformed into new occupancy/use buildings, or can include older structures that are brought back to their original state.

Current development trends are those in which older structures of brick-and-joist construction typically are renovated into commercial shopping centers, apartments and mixed-use occupancies. In many instances, the building interiors are altered extensively to accommodate the design criteria and, in doing so, may alter the integrity of the structures.

Conversions usually involve change from one occupancy use to another. For example, a factory used for manufacturing is converted into arts and crafts shops or into a multiple-occupancy facility. Most sought after structures of this kind include the heavy timber building (New England Mill Type) as well as old, reinforced concrete frame or steel-framed factory or manufacturing structures.

Expansions, on the other hand, constitute existing buildings that broaden their building layouts and floor areas to accommodate the owners' needs. Many times the buildings will stay in operation while the expansion construction is undertaken, creating myriad life safety, suppression and control concerns.

New construction involves site preparation, mobilization of materials and manpower and the evolution of a new structure. Each project category, when coupled with a specific construction type, presents specific hazards and conditions that must be identified, assessed and acted upon correctly. The potential that exists in any construction area during fire department response can include, but not be limited to:

  • Fire
  • Explosions
  • Collapse
  • Excavation &Trench Cave-In
  • Compromised Structural Conditions
  • Hazardous Materials Situations
  • Accidents
  • Failures

The ability for a fire department to intervene in the progression of an incident will be related directly to the magnitude of the incident, its complexity and its demands on resources, manpower and technical based competencies, familiarity with the site and construction methods used, the stage of construction, as well as the effectiveness of SOP's/ SOG's, communications and the incident command management structure of the involved agency.

The most critical aspect to any operation in a building or on a construction site is the effect the incident will have upon the surrounding area or construction. The hazards present on a building and/or construction site pose threats to workers on the site, firefighters, civilians and exposures. Any one of these categories can strain an operation and response.

But add two, three or all four concerns and the situation, however small initially, can escalate into a complex operation involving multiple agencies and resources. All with variable risks for significant challenge to firefighter survivability and injuries.

Exposure threat to site workers creates life safety concerns that require determination of their work area assignments, numbers present and actual location for accountability. Information detailing the magnitude of the life safety concerns can be derived from on-site field offices and contractors' trailers. The ability to relocate personnel from areas of immediate danger to an area of safe refuge may prove to be a major strategic undertaking. Limited access points, passenger elevator cranes and hoist ways present life safety concerns.

Incident commanders and company officers also must consider firefighter life safety and have the ability to judge operational areas and surrounding construction exposures. Ventures into areas of recent concrete pours ("green" concrete) or suppression operations involving wood shoring, formwork or unprotected steel components could be fatal if decisions are based on faulty operations and decision-making parameters.

Civilian dangers include situations involving equipment failures, material drops and toxic products of combustion. Recent incidents involving crane collapses, exterior scaffolding assembly failures resulted in injuries and rescues at protected walkway areas. Materials falling or blowing off job sites onto streets and walkways, as well as mechanical and other equipment failures resulting in the collapse of building components onto vehicles and roadways, create situations requiring special attention for the incident stabilization and rescue.

Unique challenges to fire control are presented by exposure concerns and hazards at building construction sites. Depending on the construction stage and area(s) of fire involvement, materials present and construction type, the exposure concerns could be negligible to major. A job site consisting of three-story, wood-frame apartment units could create serious exposure concerns due to flying brands, rapid flame spread and fire intensity toward surrounding exposures, which include additional framed units under construction, construction equipment and fire apparatus, as well as adjacent structures and occupancies.

When such exposure concerns become evident, rapid deployment of additional response companies and resources should be communicated as quickly as possible. Often when the problem becomes evident, it may be too late to gain offensive fire control. Based on incident considerations, areas should be written off defensively, with protective measures deployed effectively to get ahead of the situation.

The complexities and hazards and assessment factors present at building and construction sites become the focus when a company is dispatched to an on-site incident. Each construction stage represents a milestone in the process that, when coupled with respective safety considerations, can give an incident commander or company officer insight into the risk potential present at the job site. The stages are represented by percent of completion of the project or structure. The stages overlap, as do some of the safety conditions and hazards.

Start up/mobilization to 15 percent Stage

Initial project start up is underway. At a jobsite involving new construction, site work is taking place and excavation, trench and subsurface work is in progress. Temporary roadways, usually consisting of exposed earth with gravel topping, are compacted. Adjacent utilities are tapped into with temporary on-site services.

Construction equipment is mobilized or brought on site. Materials, components and equipment are stockpiled and stored. Temporary storage buildings are constructed and makeshift offices and rest areas for workers are built. Construction work includes laying the foundation, formwork placement and support structuring.

Risk potential is greatest when dealing with the stored/stockpiled equipment and materials and site considerations that affect emergency access and response and construction worker safety. Site accessibility may be hindered by excavation areas, site trenches and pits, construction worker vehicles and construction equipment, as well as temporary fencing and barricades.

Weather conditions may play a critical role in response access with temporary roadways and site areas affected by rain, snow, thawing and mud. Companies should determine, through site inspection and preplanning, designated entry gates to site areas, alternate access roads or areas to project locations and use of heavy construction equipment for accessibility. Many times, response maps may not have information available for effective and accurate response. Coordination between local building officials and fire department commanders is a must.

Incomplete connections, closed valves and inadequate water pressure can create water supply problems with on-site systems. Unknown or nonexistent hydrant locations may make it necessary to preplan alternate water sources. Additionally, during initial size up and incident assessment , take into account possible time delays for long and multiple hoselays.

Trench cave-ins, excavation collapses, shoring and framework failures present challenges to even the largest agency. Undertake pre-incident training to ensure safe and effective rescue operations. In response districts or divisions where extensive, ongoing construction is present, consider securing adequate trench/cave-in rescue equipment, material and tools and develop a company with trained personnel.

In the rehabilitation, renovation or conversion stages, interior and exterior finishes and materials may be in the process of removal or alteration. Interior partitions may be partially removed, with materials stockpiled and staged at various areas. This stockpiling, with its high fire loading, presents a potential hazard. A fire in a 52-story office building gutted the entire fourteenth floor of the structure, where building materials had been stocked for a renovation project. Interior floor and wall partition removal creates serious deficiencies in the compartmentalization capabilities of the areas, as well as allowing for avenues of fire travel both vertically and horizontally.

The 30 to 60 percent Stage.

This is the phase in which the structure begins to evolve into its designed form. The framing systems used rise up with materials being bolted, cast or framed in place. Skeletal steel frames are built up and the structure is fastened together temporarily to allow for the positioning of additional members. Inadequate or incomplete connection points could be affected by weather and environmental conditions, causing the structure to fail and collapse. The dead load of the material itself may shear connecting bolts. Unprotected steel columns and beams are affected by fire and heat exposure from even a small rubbish fire which, in turn, may cause the member to buckle, expand and collapse. Some steel framing may rely on cold-drawn steel cables to provide tension on the frame elements until the exterior skin is applied. These cables can fail at temperatures as low as 500 degrees Fahrenheit, precipitating a collapse.

Exposed cast-in-place, as well as precast concrete construction, also can be affected by fire and heat exposure. The connection points may fail at a faster rate than that of the material itself, due to the smaller mass of the connecting components. Additionally, the outer layers of concrete can break away when exposed to fire and hear. This action, called spalling, occurs when the moisture content within the concrete is drawn out due to extreme heat conditions. There are two types of spalling. The first is an explosive kind that blows the material in large components away from the members, causing the pieces to be propelled outward toward operating companies, often accompanied by a loud noise. The second type of spalling is a dropping off or flaking action in which the spalling falls from the components with little force. Regardless of the action type, the size of the spall material may be such that crushing injuries are sustained.

Since both precast and cast-in-place concrete rely on steel reinforcement for its tensile strength capabilities (the concrete itself provides the compressive strength), spalling actions cause the embedded steel "rebars" to be exposed to the heating and expansion action of heat and fire conditions. This can cause the materials to separate, loosening the bonding action and causing a collapse.

Additionally, concrete when applied in a cast-in-place application - where the concrete relies on formwork that is held in place by adjustable steel column rods, wood shoring and bracing - creates an extremely high fire load factor.

Typically, concrete requires a 28-day cycle to cure to reach its compressive its design strength. Any fire conditions encountered within these formwork and shored floor areas should be treated as conditions in which the concrete is assumed to be "green" or freshly poured. No immediate fire suppression activities should be attempted within these floor areas because of the likelihood of collapse.

In wood -frame structures, again, the main concern can be toward fire suppression capabilities due to the fire loading of the materials present, as well as the surface-to-mass ratio as a result of exposed framing present. Be aware that rapid fire spread within single structures and to adjoining structures can occur.

As the structural framing is completed, the exterior skin or building envelope is applied. Windows and doors are fastened, interior partitions are framed and open floor areas begin to become compartmentalized. The mechanical, electrical and service systems begin to be put in place. During the 30 to 90 percent construction phases, there are still numerous conditions that contribute to fire.

According to NFPA studies as referenced within the NFPA 24 Standard, 60 percent of the fires occurring in buildings undergoing construction, alteration or demolition originates from three specific causes:

  • Salamanders or portable heating equipment (25 percent)
  • Cutting, welding and plumbers' torch operations (20 percent)
  • Matches and smoking (15 percent)

During construction phase operations in adverse and cold climates, the use of portable heating devices and salamanders, along with heavy tarps and reinforced plastic sheeting cover the building to maintain a minimum temperature, is common.

Scaffolding around the perimeter of the building may be covered, allowing no visible indication of building type, materials or alarm response conditions upon the arrival of a company. The heating devices usually fueled by LPG tanks pose dangers because of valve and tank malfunctions, contact with combustible and exposure to fire areas during suppression operations. BLEVEs are common with construction site fires and must be considered when mounting an attack.

The 60 to 90 percent stage.

The conditions and hazards present within the 30 to 90 percent phase can be addressed in similar fashion. During this phase, rooms, floors and other areas are undergoing completion with more finish work done with fewer trade personnel.

During the early 60 to 75 percent stages, conditions still exist requiring full awareness of interior mobility, access and operations. There may be floor areas that still are incomplete or unprotected. Drop-offs and walk-offs may be present at any number of locations. Open shaft-ways, hoist ways, mechanical chase areas and stairwells may exist in uncompleted stages.

As in the previous 30 to 60 percent stage, floor obstructions, pipe stubs and capped-off services may exist. Firefighters should use personal lighting to detect whether walkway areas are clear and safe. Extreme care must be taken during the night and in smoky conditions to be certain of floor area integrity.

There are many times that shaftways and chase wells extending through multiple floors are covered temporarily with plywood. Although they may support a worker passing over them, they may not support a fully outfitted firefighter with SCBA and tools.

Inadequate lighting conditions may exist throughout the complex and site, with many exposed electrical lines, conduits and power panels. Exposed wiring coming into contact with exposed steel framing and tools can energize a large area, endangering personnel in the immediate area.

As additional systems are put in place, such as HVAC duct work, plumbing and electrical lines, additional wall areas may be penetrated. Fires originating on one level or area may travel quickly due to convection and conduction. Built-in sprinkler systems may be inoperative due to incomplete pipe runs, closed valves, lines plugged from debris or non-capped branches.

Fire department connections may be blocked by dumpsters or heavy construction equipment. Interior standpipes may not reach to topped-off floor areas or may have open valves, incomplete connections or non-capped branches.

Assign manpower to valve determination if attempts at using the standpipe system prove inadequate. Many times an open valve at a lower level may be the culprit. Again, manpower allocations in these areas must be augmented by multiple-alarm and mutual-aid units early in the incident.

As the finish work nears completion, stockpiles of new materials begin to form. Solvents, adhesives and flammable, combustible and toxic materials used in the finish/completion stages may be present in large quantities. Class A materials from packing, furniture and equipment boxes may be located throughout the structure.

Site accessibility improves as more of the interior building areas are completed. Paved access areas and roadways are completed; trenches, excavations and fill have been removed or backfilled. Exterior scaffolding, begins to be removed and heavy construction equipment and cranes are taken off-site. The final stage, consisting of the move-in, may not necessarily take place when the building is completed. Move-ins, when dealing with large-scale structures or high-rises, may take place on the bottom floors while construction proceeds in upper areas.

It is critical for the safe and effective stabilization and conclusion of any incident within these building sites to assume a greater degree of assessment and subsequent operations. Assessment considerations include:

  • Construction type
  • Stage of construction
  • Site conditions and accessibility
  • Exposures
  • Resources
  • Operating procedures
  • Communications

All operations must assume the risk potential present for the deployment of manpower and equipment, with the full understanding of material, component and site condition integrity during suppression and emergency operations.

The magnitude and complexity of the incident will be directly proportional to the size of the building/construction site and age of the existing building, if under renovation, and degree of construction. Operational conditions must be addressed during strategic and tactical incident management:

  • Degree of exposed construction
  • Degree of incomplete connections
  • Number of exposures
  • Fire loading
  • Flammable/combustible materials
  • Compressed gases and vessels
  • "Green" concrete and shored, supported areas
  • Exposed electrical and utility services
  • Unprotected openings
  • Obstructions
  • Access
  • Lighting
  • Fire protection system integrity

The ability for a response agency to safely handle an emergency incident depends upon a set of specific operational factors that include but are not limited to:

  • Incident type
  • Size-up and Assessment Factors
  • Pre-Planning Awareness & Knowledge
  • Strong Command Presence
  • Effective Modular Incident Command Management System
  • Effective Communications
  • Mobilization/ Reflex Capabilities of Response Companies
  • Anticipated & Immediate Resource Needs
  • Apparatus Deployment
  • Operational Modes
  • Exposure Concerns
  • Incident stabilization, time factors
  • Incident Control

Fire companies should periodically inspect the construction sites in their response districts. They can assess the risk potential present and preplan for potential incidents. Information should be transmitted to second and third-due company units in the event of a large-scale incident.

Serviceability of all existing fire suppression systems on-site must be ascertained. This, alone, may help control situations in a time frame where deployment, application and operation become critical.

Never assume, but be cautious and analytical in any incident that takes you to a building or construction site. The success of any operation will be dependent upon coordination of companies, technical basis of knowledge, skills and training, and the ability to remain highly flexible, based upon the continuum of information processing, cue-based analysis and incident command management.

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