Water Supply Preplanning is more than just knowing general hydrant locations and putting the “wet stuff on the red stuff.” There are many considerations that need to be investigated to mitigate those major fire incidents when you realize the basic supply is not doing the job.
As firefighters, we are all familiar with the importance and concept of pre-incident management, commonly known as preplanning. As NFPA Standard 1620, “Standard for Pre-incident Planning” shows, there are many considerations that need to be factored into this process. One of the most important is knowing that the establishment of a capable and sustainable water supply for effective fire extinguishment exists. Knowledge of basic water supply sources as well as sources to augment the basic water supply cannot be overemphasized for major fires in commercial and residential structures. High-rise buildings, large industrial manufacturing and storage buildings, and large multi-building apartment complexes have the potential for fires to develop rapidly and grow exponentially beyond the capability of the fire department in a short amount of time if not being met with an adequate volume of water. When determining adequacy of water supply for firefighting, the rate of flow, the residual pressure required at the rate of flow, the duration of flow and the total quantity of water must all be considered. Just knowing the location of the nearest hydrant at the time of the fire is not enough.
Important considerations when preplanning water supply are knowledge of specific target occupancies within your jurisdiction (“Target” occupancy indicates an occupancy where a greater than average complexity of firefighting operations can be expected), required fire flow requirements, the nature of the municipal water system and/or the availability of alternative water sources to meet those requirements, and fire department resources and capabilities. Understanding a fire department’s water supply capabilities also can assist municipalities in improving their water supply credit for insurance grading purposes, leading to better tax rates.
Specific Target Occupancies
The first step in considering water supply adequacy is identifying specific target occupancies in a jurisdiction and determining their required fire flows. Several building characteristics contribute to this determination such as construction and occupancy type, the presence of automatic sprinklers, and exposures. Secondary characteristics such as building size and percentage of involvement also are considered when specific fire flow methodologies are used. It is important for the fire service operations side to communicate and coordinate with the office of fire prevention whenever new construction or a change of occupancy or use occurs with an existing building so changes in water supply can be made accordingly.
Information on the number and type of sprinkler systems on-site, underground fire protection system and hydrant piping arrangement, fire department connection locations and the most recent flow test data closest to the property should be obtained. When supplementing the fire sprinkler system during a fire, the fire department may be taking supply out of the same underground piping that is supplying the sprinkler system. Outside hose allowances are considered in sprinkler system design; however, high-volume master stream appliances cannot be supplied from the common piping feeding the sprinkler system so an alternative supply point for this purpose should be identified.
Required Fire Flows
The American Water Works Association (AWWA) defines required fire flow as “the rate of water flow, at a residual pressure of 1,4 bar and for a specified duration that is necessary to control a major fire in a specific structure.” Several methodologies exist in the United States for the calculation of this flow requirement; some are intended for pre-incident assessment, which are more detailed, versus those intended for use as a quick fireground calculation for the incident commander of a fire event. The Insurance Services Office Needed Fire Flow method and the International Fire Code method are examples of pre-incident methodologies, while the Iowa State method and the National Fire Academy methods are designed for quick assessment use by the Incident Commander. These calculations typically determine a flow rate for either a percentage of or total fire involvement in a non-sprinklered building and can serve as a basis for determining the adequacy of available water supplies.
However, if a building is sprinklered, usually the required fire flow is determined to be the demand of the fire sprinkler system for the specific hazard. This holds true only if the sprinkler system has been properly designed, installed and maintained. For specific target occupancies, it is recommended that water supplies for firefighting operations be contingent on the possibility of the sprinkler system not controlling or suppressing the fire. Often, a fire has started or extended above the sprinkler system in a storage occupancy, causing a major, uncontrolled fire to develop. First arriving fire pumping apparatus usually connect to the closest hydrants which usually are located on the same distribution system. With too many engines taking suction out of the same piping system within close proximity of each other, the piping size and configuration may not be able to provide the necessary volume (and subsequently, the pressure) needed to keep up with the exponential growth of the fire. This usually creates a water operations plateau until mutual aid arrives to establish a large diameter hose supply pipeline from a separate hydrant system or alternative water supplies are established to help deliver the volume of water needed.
Municipal Water Supply Infrastructure and Alternative Water Supplies
In a jurisdiction, it is important to know where hydrants are available and where they are not. Where hydrants exist, it needs to be determined whether they are “good” hydrants or “weak” hydrants. Good hydrants are typically those connected to larger pipes located on a gridded piping system where adequate volume and pressure exists. Weak hydrants systems are typically inadequate due to physical location on the distribution system, smaller pipe sizes, aged piping with decreased diameters due to tuberculation or connected to “dead end” mains, a single pipe that allows water flow in only one direction. Fire departments can work with water purveyors, insurance rating organizations and their fire prevention bureaus to obtain water flow information. From this data, the need to augment water supplies for specific target occupancies can be determined, making effective use of time and resources during a fire indicent.
Where municipal hydrant systems do not exist, the fire department must be equipped to use alternative water supply systems to provide the required fire flow at the scene of a fire. Alternative water supply systems utilizing open water sources include dry hydrants, available and accessible suction points, large diameter hose relays, and water shuttle operations using tankers and portable drop tanks. These are highly logistical operations and require much planning and resources. NFPA 1142 “Standard on Water Supplies for Suburban and Rural Firefighting”, addresses water supplies in areas where water systems are not readily available and is useful in such planning.
A new pumping technology recently made available for the municipal fire service is the composite floating submersible pump system. These systems use a compact, ultra-lightweight, centrifugal pump that provides a positive pressure water supply source, eliminating the need for drafting operations and capable of delivering over 7571 lpm. Briefly, it is a “floating hydrant” and makes more open water sources available and accessible. These systems offer fire departments another “tool for the toolbox” for more tactical and flexible options in water supply preplanning.
Fire Department Resources and Capabilities
When considering water supplies, not only must there be an availability of water, but the ability of delivering that water at the required fireground flows and pressures. Adequate personnel and equipment is necessary to perform this task. Fire pumper apparatus with the appropriate pump capacities and personnel must be available to deliver the required flows necessary. If limitations exist, or department capabilities exceeded, the appropriate resources must be evaluated and considered from neighboring jurisdictions. Given the type of emergency, automatic mutual aid or the ability to dispatch the needed mutual aid must exist for successful mitigation of major fire incidents. These agreements need to be negotiated and operational expectations planned, as well as ensuring compatibility between operations, i.e., hose appliance adapters provided should departments use different hose connections, jurisdictional preplans for specific target occupancies, compatible communication frequencies and designations, etc.
Water supply preplanning is a necessary part of fire operations before the fire incident. It is much more than just “putting the wet stuff on the red stuff.” Proper water supply preplanning takes into account both the adequacy of the water supply and the fire department’s water flow capability to deliver the required fire flows. To this end, fire departments that perform their due diligence in this area of preplanning will be more effective in their firefighting operations and efficient in their resource management.
There is much information available for those willing to take the time to look for it. Fire operations personnel should use all available informational resources, such as their fire marshal/fire prevention offices, insurance underwriters, building facility personnel, etc. for determining required fire flow needs and establishing contingency plans for augmenting water supplies. For new buildings, getting involved in the early stages of planning is as important as keeping up with occupancy changes, property renovations and fire protection system issues. Establishing lines of communication within departments helps keep the operations side on top of water supply issues and requirements within their jurisdictions.
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