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I believe it is proper to start with a disclosure: I am not an environmental engineer. I am a retired fire code official, fire protection engineer and firefighter who has had to deal with some of these issues. Over the years, I have become more aware of what is or may be in fire protection water. These opinions are my own and are not associated with any of the organizations I am involved with.
It is safe to say that the era of discharging fire protection water without considering the other “stuff” that may be in it is changing. Even the discharge of potable water back to the environment may be regulated and require testing and possibly treatment.
This is not a surprise to the people who work in the water treatment and wastewater industries. The discharge of water to the environment may be regulated by federal, state or local governing regulations; a National Pollutant Discharge Elimination System permit; waste discharge requirements established by the jurisdictional water quality control board; sewer pretreatment requirements for publicly or privately owned treatment works; and possibly others.
From a fire protection standpoint, the most public and concerning example of this is the findings of perfluorooctanoic acid and perfluorooctyl sulfonate in local drinking water wells.
These chemicals have been widely used by industry, but specific to fire protection and fire safety, they have been used to manufacture aqueous film-forming foam concentrates used in firefighting and in the process of producing fire retardant materials (see August 2020 Plumbing Engineer (https://bit.ly/3suGCit) and Fall 2022 NFPA Journal (https://bit.ly/3DBU4Y2)).
Other chemicals having a long history of use in fire protection systems include anti-freeze solutions. These are provided to prevent freezing in sprinkler system piping located in areas of buildings, or external to buildings, where the piping is subject to temperatures less than
40 F. Other chemicals routinely used in water treatment, such as chlorine, may have long-term effects on sprinkler piping, particularly increasing internal corrosion and, thus, changing the character of the water in the system.
These chemicals typically cannot or should not be discharged into the environment without a review by the governing environmental regulators, who may require some method of treatment to mitigate their presence.
It is not always chemical substances in the water or in the piping that may be cause for treatment. For example, in New York, a site’s State Pollutant Discharge Elimination System permit may regulate many issues, including the temperature and turbidity at the point of discharge into a body of water.
More recently, questions about the environmental impact of all the substances entrained in fire protection water during and after a fire have been raised (LinkedIn article, https://bit.ly/3sQDtK2). Of course, some fire protection standards — such as NFPA 30, Flammable and Combustible Liquids, and NFPA 400, Hazardous Materials — have had requirements for the containment of fire water from fires in storage occupancies for quite a while.
What Do We Need To Know?
This is the start of a process to understand what regulations apply to the various ways that fire protection water gets discharged to the environment. These concerns and possible actions to address them will vary depending on the location of the facility.
Knowing and understanding the requirements can be challenging, as the discharge of water with anything in it but water may be regulated by federal, state and local requirements either generally or specifically due to the nature of individual facilities. The purpose of the following questions is to help work through the process of knowing and understanding the requirements:
• Who is responsible for answering these questions? As facility owners, operators, engineers, designers and regulators, we have an obligation to know the requirements applying to the discharge of water (or water solutions), and ensure that the design, construction, operation and maintenance of the fire protection systems for which we are responsible complies with those requirements.
• What is the water supply providing fire protection? Water for fire protection can be taken from many different sources. It can be raw water from open sources (streams, rivers, ponds, lakes or oceans), it can be raw water from closed sources (wells), and it can be treated water (potable or greywater) from public or private sources.
Where the fire protection water is coming from and what is in it coming into a facility may influence when, where and how it may be discharged back into the environment.
• How will it be modified prior to use? Required modifications may depend on the source or its intended use. Modifications may include filtering or treatment before storage. They could include the need to provide primary backflow prevention between a potable water source and the nonpotable water found in fire protection systems after it has entered a nonflowing portion of the system.
This could also include the installation of secondary backflow prevention between the nonpotable water in the fire protection system and other portions of the system containing chemical treatments, such as an anti-freeze solution.
• How will it be modified during use? This question is intended to capture changes such as education or injection of firewater modifiers. For example, the addition of foam concentrate used in expansion foam systems (see NFPA 11, Standard for Low-, Medium- and High-Expansion Foam).
• When and how will it be discharged? This question relates to the system’s purpose and design. The answer will determine many of the design aspects for handling the fire water, including what, if any, infrastructure needs to be added to the facility to ensure environmental compliance is maintained.
Examples of these would be consideration of the discharges due to flushing of supply piping during installation, and system discharges required when performing inspection, testing and maintenance (ITM). It may also include discharges due to system operation during a fire and the use of hose streams during manual firefighting operations.
• How will the firewater be modified during or after it is discharged? This question would include how the water would be changed once discharged. For example, during installation, flushing of the mains would be expected to pick up dirt, small rocks and debris that the flushing is intended to move out of the pipe, as noted in NFPA 24, Standard for the Installation of Private Fire Service Mains and Their Appurtenances. (See May 2022 Plumbing Engineer (https://bit.ly/3f3OLHC); and September 2022 Plumbing Engineer (https://bit.ly/3fabKk8).)
During inspection and testing, the performance of the most routine tests, such as the alarm flow and main drain tests, might produce some rusty water (see May 2021 Plumbing Engineer, https://bit.ly/3DbMYIq; and NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems). If this water is discharged into the ground, it will create a hole, picking up soil and rocks and sending some of it to places not anticipated unless it has been considered in the planning.
Another ITM case that warrants consideration is if the five-year internal assessment leads to a decision that flushing of the system piping is necessary, then the flushing plan needs to consider what may come out of the pipe and where it can go without violating an environmental regulation (see August 2022 Plumbing Engineer, https://bit.ly/3TGLtcg).
• Where will it be discharged to? This question takes us back to the governing regulations, which ultimately determine what you can do based on what is in the water that is being discharged. How much is being discharged? Where can it be discharged to? Does it need to be collected? Does it need to be treated before final discharge?
Will the fire water be discharged to the ground, pavement, drainage system, sanitary sewer, a holding area or a body of water? Once there, where will it go? Find out what the regulations say about discharging on the ground, to the pavement and so forth. Planning needs to incorporate these requirements.
• Who is the regulating authority? It has already been mentioned that the discharge of water to the environment may be regulated by federal, state or local governing regulations; a National Pollutant Discharge Elimination System permit; waste discharge requirements established by the jurisdictional water quality control board; sewer pretreatment requirements for publicly or privately owned treatment works; and possibly others.
Some of those others may be the jurisdictional code officials. Jurisdictions using either the NFPA building and fire codes or the ICC codes adopt requirements that include containment and drainage restrictions on fire water in certain circumstances. These code authorities (authorities having jurisdiction) need to be engaged early in the design process for new facilities or modifications to existing facilities to ensure the requirements for managing fire water are included.
The Devil Is In the Details
The preceding paragraphs provide a big-picture view of what needs to be known and understood to ensure that environmental considerations for the discharge of fire water are included in the planning. Developing a plan requires concentrating on the details. These details would be expected to influence the type of fire protection systems installed and the means for dealing with the discharge.
Knowing how much fire water will be discharged in each scenario and where the discharge will be directed are the biggest details to be considered. This provides the scale of the need. Knowing what is in, or might be in, the fire water also is important. This knowledge will determine the need for treatment or other options to allow the fire water to be discharged and where the discharge will occur.
Treatment options for fire water are facility- and process-specific and are beyond the scope of this column. However, providing an idea of how much fire water may be involved under what circumstances should be useful to the reader. Quantities will still vary based on the specifics of the facility and need to be validated as a part of the facility design, but the following discussion will provide approximate methodologies for determining discharge amounts.
So, how much water are we talking about? It depends on the situation. Since most fire protection systems never face the challenge of an actual fire, most of the water discharged during the lifetime of a fire protection system is discharged during installation and required ITM. For any particular facility, this will depend on the type of system or systems present.
Discharges from automatic fire sprinkler systems, standpipe systems, special hazard systems (such as foam), underground fire lines, fire pumps and any associated backflow prevention assemblies would be possible sources of water or water-based agent discharge (see January 2021 Plumbing Engineer, https://bit.ly/3THSNo3).
When water-based systems and the infrastructure necessary to support them are installed, the requirements for testing those systems or components will be found in the associated installation standards. The commonly used installation standards for water-based systems are likely to be familiar: NFPA 13, Standard for the Installation of Sprinkler Systems; NFPA 14, Standard for the Installation of Standpipe and Hose Systems; and NFPA 24.
Less commonly used installation standards involving water-based systems include NFPA 11; NFPA 15, Standard for Water Spray Fixed Systems for Fire Protection; NFPA 20, Standard for the Installation of Stationary Pumps for Fire Protection; and NFPA 22, Standard for Water Tanks for Private Fire Protection.
A wide variety of flows are required for the design and acceptance-testing of water-based fire protection systems, depending on the arrangement of the installation. In developing the design of a water-based system, flow testing to determine the adequacy of the available water supply (flow and pressure) will generate one of the larger flows to the environment.
Flushing of the underground fire lines associated with the project will also generate large flows. This will probably be the largest flow for a project as flushing must be conducted at a code-specified flow rate of long enough duration to ensure that all debris moving due to water flow has been removed from the piping (Plumbing Engineer May 2022, https://bit.ly/3f3OLHC).
The larger the piping diameter, the greater the quantity of water that needs to be used to meet the required flow rate and ensure the velocity of the water will scour out debris in the piping. Debris left in the piping that will move when the system operates up to the maximum design flow may clog sprinklers, preventing them from delivering enough water to control or extinguish the fire. The development of an underground flushing plan was discussed in Plumbing Engineer’s September 2022 issue (https://bit.ly/3fabKk8).
If the project involves the installation of a fire pump, several flow tests need to be performed to validate that the pump can provide the flows for which it was designed and constructed. It should not be less than three and may be as many as seven. Higher flow rates are used for flushing the piping supplying fire pumps.
In this case, the purpose is to avoid clogging the fire pump impellor, which will reduce the available flow to the fire protection system (Plumbing Engineer March 2022, https://bit.ly/3faN4YQ). The largest of these fire pump flow tests is conducted at 150% of rated capacity. The larger the pump, the larger the quantity of discharged water, so the test must be designed with a plan for where this water can go, and what to do with it during and after testing is complete.
Regular maintenance of water-based fire protection systems is governed by NFPA 25. Maintenance of water-based fire protection systems generally does not require the flowing of water in the quantities required for flushing of fire lines unless the flows and pressures required to be available to supply the system(s) are noted to be deteriorating.
Unless the reason for the deterioration is easily or quickly identified, an investigation, including hydraulic analysis, may require flow tests. Again, the plan for that testing needs to include proper disposal of the water that is used.
The lowest flowing test for an automatic sprinkler system is periodic testing of the water flow alarm. This involves opening the inspector’s test connection or the systems test and drain with the test orifice in place. This test simulates the operation of a single sprinkler on the system to ensure that the water flow alarm will sound and, if provided, send a signal to a monitoring station.
The purpose of this test is to alert someone to initiate a response to the flow. In this case, the amount of water that flows is a function of the sprinkler orifice size and the pressure available to the sprinkler.
Q = k√p
where Q is the flow,
k is the orifice coefficient,
p is the available water pressure.
For the common 1/2-inch orifice sprinkler, a 40- to 50-gallon/minute (gpm) flow could be typical, but it can go higher based on the available pressure. For storage occupancies, fire sprinklers with much larger orifices have been developed, some of which will flow between 300 and 400 gpm on initial (not design) discharge.
The most common flow test for water-based fire protection systems is the main drain test, which is required to be performed as part of regular maintenance testing of the system. More importantly, it is required to be performed after closed system control valves have been reopened. Main drains in the United States are either
1-1/4 inches or 2 inches in diameter and will typically flow between 100 and 450 gpm when fully opened, depending on the available supply pressure.
If the outlet of the main drain is not directed to a hard surface, it will dig a hole. The water will pick up whatever the ground contains and flow to wherever water usually does.
Where backflow prevention assemblies (BPA) are present on the supply to fire protection systems, annual forward-flow testing of water through the BPA is required. The flow required for this test should be greater than or equal to the design flow for the system, and planning for this discharge needs to account for that flow.
The need to contain fire flows and any associated spillage of contents in the fire area is regulated by NFPA 30 and NFPA 400 if adopted as a part of the local code. Similarly, the applicable building and fire codes, such as the International Building Code and International Fire Code, may have provisions for containing hazardous material spills, including water discharged by fire suppression systems.
Should a fire occur that is of sufficient size to cause sprinklers to open or other fire protection systems to be used, the nature of the fire and the design of those systems will determine how much water is discharged. For sprinkler systems, expected flows would be less than or equal to the system design (gpm/ft2 over the design area in which the sprinklers are operating), plus any design hose stream flows assumed.
There is a caveat to this: The sprinkler system design and the water supply available to the sprinkler system must be adequate for the hazard presented to it. It is important to recognize that even if the design was appropriate when the facility was constructed, there are many things that can change over the lifetime of a building that might render the sprinkler system inadequate (Plumbing Engineer October 2020, https://bit.ly/3D3IovK).
In this case, the total amount of water discharged is based on how long the systems and hose lines are in operation during the event.
In the case where sprinklers are not present, the amount of water discharged would be solely based on the water discharged through hose streams (175 to 250 gpm each), other fire appliances such as ladder pipe (up to
1,500 gpm), and the amount of water needed for cleanup after the fire is controlled over the time that each hose or appliance was in operation (gpm will vary depending on the number of hoses and the size of the nozzles used).
The awareness of the need to evaluate the impact of fire flows on the environment in the design of facilities and existing facilities is increasing. These have been more recently brought to light by concerns related to fire retardant chemical additives used in foam-based fire protection systems.
Those of us in fire protection understand that the concern isn’t just limited to foam concentrates. It would be prudent to know what is in the water that is discharged, even if it doesn’t contain additives, so that we can ensure that the fire system and firefighting water will do no harm.
As facility owners, designers and regulators, we need to know and understand how these systems interact, what the regulations are, when mitigation of the consequences of fire water discharge is required, and how to accomplish those mitigations. This requires a plan for fire water containment, drainage and possibly treatment.
We need to know and understand where the water goes because there is a potential for future liabilities associated with its discharge.
Dwight Havens is a retired fire protection engineer and fire code official. His fire safety career started in 1973 as a volunteer firefighter, and he has worked for Grinnell Fire Protection Systems, Cerberus-Pyrotronics, and the Phoenix Fire Marshal’s Office. Havens continues to volunteer with the NFPA’s Flammable and Combustible Liquids Code committees and with the Round Lake (N.Y.) Fire Department.