Protecting Residences From Wildfires

Property Develpment

Only the developer of a property can provide some of the vital means of fire protection, such as access and water supply. It is the developer's responsibility to know about them, and to design them into the project before any structures are erected. But others have related responsibilities. Planning departments should develop and legislative bodies should adopt minimum standards. Planning departments, with advice and assistance from operating departments (e.g., fire, public works, sanitation), should enforce the standards even if they must deny approval of nonconforming proposals. People with financial interests (e.g., bankers, insurers) should satisfy themselves that firesafe features are incorporated in the project before committing their resources. All development plans should employ the master planning concept in order to properly assess the interactions between various elements (e.g., public safety, transportation, sanitation, water, schools). 3d,4

Access

One of the most important aspects of land development from the fire protection viewpoint is access. It involves a great deal of engineering and expense and is almost impossible to improve or alter after development is complete. If inadequate, access becomes critical during a conflagration both from a firefighting standpoint and with regard to life safety
3e (Alger 1971, Los Angeles County Fire Dep. 1970, Los Angeles City-County Fire Bd. Inquiry 1971, Oreg. St. Dep. For. 1978a, County Sup. Assoc. Calif. 1966, Colo. St. For. Serv. 1977).

Adequate ingress and egress are necessary to allow safe and rapid passage of both fire equipment and private vehicles in opposite directions simultaneously. But they can be costly not only in the expense of road construction but also in the resulting reduction of saleable lots because they require space. This is particularly true in lot-splitting situations where the original parcel can be divided only into four or less new parcels, thereby reducing the opportunity to spread costs. Adequate access is a cost that must be borne, however, if past disasters are not to be repeated time and again (Alger 1971, Los Angeles County Fire Dep. 1970, Orange County Bd. Sup. 1976, Oreg. St. Dep. For. 1978b, County Sup. Assoc. Calif. 1966, San Bernardino County Bd. Sup. 1974).

Proposed Standards: Meet all of the following standards; deny any variances that do not show positively that they will not adversely affect firefighting and evacuation capabilities:

  1. Provide two or more routes of access to a public road, preferably on opposite sides of the development (loop roads with single entry do not meet this standard).
  2. Dedicate streets and roads to public use and maintenance. If they are allowed to remain private, provide for their maintenance in perpetuity.
  3. Set minimum dedicated right-of-way at 60 feet to provide two 12-foot hard surface traffic lanes, two 8-foot parking lanes, and two 10-foot roadside strips wherein fire hazards shall be abated.
  4. Base minimum centerline radius of curvature of streets and roads on fire hazard severity classification: moderate-50 feet, high-75 feet, extreme100 feet. Allow no variance to less than 50-foot radius.
  5. Establish road grade based on fire hazard severity classification: moderate- 12 percent, high-10 percent, extreme-8 percent. Allow no variance to exceed 200 feet in length or 2 percent above standard, and only on straight line portions of the road.
  6. Do not permit any dead-end streets. Allow culdesacs provided they do not exceed these lengths based on fire hazard severity classification: moderate-800 feet, high-700 feet, extreme-600 feet. Require cul-de-sacs to have a turning area at the end of not less than 90-foot diameter.
  7. Require bridges to have a minimum load limit of 36,000 Ibs. (18 tons), and to not be narrower than the driving portion of the road serving each end.
  8. Stipulate that each lot or parcel must have direct access to a road meeting the above standards, such access to be traversable by a modern structural fire engine.
  9. Design road and street intersections to be as close to 90 degrees as terrain will permit, for at least 80 feet from intersection centerlines, and in no case allow the angle of such road intersections be less than 45 degrees.
  10. Clear the area within 200 feet on each side of the centerline of all roads and maintain it to fuelbreak standards-except for structures.

Water Supply

Water is still the most effective tool for fighting wildland fire when and where it can be obtained in sufficient quantity. It is really the only effective tool for fighting home and most other structural fires. Therefore, a large, dependable source of water above that required for normal daily domestic purposes must be provided for at the time a subdivision (including mobile home park), shopping center, recreation area, or individual homesite is planned and developed
3f (Alger 1971, County Sup. Assoc. Calif. 1966, Nat]. Fire Prot. Assoc. 1974).

The amount of water reserved for firefighting purposes and the size and type of delivery system provided depend on (a) the degree of wildfire hazard involved (fire hazard severity classification); and (b) the type and location of the occupancy (home or mobile home in a subdivision; farm or other individually developed homesite; multiple such as commercial, recreational, industrial, apartments, etc.). The water requirements for multiple occupancies are usually stipulated by the insurance carrier or local fire department or both. Although normally based on requirements for fighting an interior fire, they are usually adequate for protecting the building from an encroaching wildland fire as well, because usually these requirements are set quite high to reflect both the financial property risk and the multiple life risk.

Adequate water for firefighting purposes, either by a fire department or by the occupant, has been unavailable and unreliable on many occasions where homes were involved. In some cases, adequate water was available but not developed, as the potential fire problem was not recognized. In other situations the problem was recognized but considered a remote possibility. Sometimes the cost was considered too high. Sometimes a sufficient water supply was not available at any price-and in such a situation, the structure should not have been built. A common cause of water deficiency is the practice of extending or adding on to a subdivision where the water system was adequate for the original development and is adequate for domestic service to the addition but is insufficient to provide fire flows both to the original and to the additional developments. 3g (Alger 1971, Los Angeles County Fire Dep. 1970, Orange County Bd. Sup. 1976, County Sup. Assoc. Calif. 1966).

In contrast to normal daily use, consumption of water for firefighting purposes is of relatively short duration but of high volume. Water is also used during emergency conditions when electric power service may well be interrupted. Different engineering, therefore, is required than would be needed for a purely domestic water system. Water supplies for firefighting involve large storage facilities, high-volume mains, and dependable delivery (either gravity or pumps with alternate standby power sources). These facilities should be provided during the development phase as their price skyrockets if they must be added after development and occupancy (Orange County Bd. Sup. 1976, Oreg. St. Dep. For. 1978b, County Sup. Assoc. Calif. 1966, Nat]. Fire Prot. Assoc. 1974).

Proposed Standards: Adhere to the following standards as they apply to individual projects, and do not permit variances because they would expose both life and property to unacceptable risks:

  1. All structural developments regardless of type or location to have a dependable supply of water adequate for both normal daily consumption and emergency fire needs.
  2. Where homes or other small buildings are supplied by their own independent water systems, they are to have a minimum storage capacity of 2500 gallons, supply mains of at least 1 I/z-inch diameter, one 11/2inch standpipe conveniently located for fire engine filling, and at least two hose outlets 50 or more feet from the building in addition to outlets on the exterior of the building.
  3. The water systems of commercial, industrial, recreational, and multiple-dwelling (apartment or condominium) developments are to be engineered to meet Standard 1 above and approved by the fire agency having jurisdiction.
  4. Subdivisions and mobile home parks are to be provided with 6-inch or larger circulating (loop) mains and storage capacity sufficient to provide the minimum fire flow indicated below for at least 2 hours with a residual pressure of 30 lb/sq.in., and have fire hydrants of at least 6-inch diameter with these maximum spacings:
    Hazard class:  Hydrant spacing   Minimum flow 
                      (ft)            (gal/min) 
    Moderate          700                500 
    High              500                750 
    Extreme           300               1000 
    
  5. Any area large enough for helicopter landing and take-off (e. g., school yard, parking lot) is to have at least one hydrant.

Perimeter Protection and Fire Access

The point or line at which the urban/wildland interface is most critical is the edge of the undisturbed native vegetation nearest to the structure. For a farm or other wildland home, this is the edge of the clearing made for that building. How thorough and extensive the clearing must be is the subject of various State and county laws. The same laws apply to clearing around buildings in subdivisions and mobile home parks, but are seldom adequate to meet the 1ife and property threats involved in these more densely developed areas. What is needed in these developments is some sort of perimeter clearance or treatment of the native vegetation to a greater distance from the structures than that required by existing statutes and ordinances (Orange County Bd. Sup. 1976, Oreg. St. Dept. For. 1978b, County Sup. Assoc. Calif. 1966, Task Force on California's Wildland Fire Probl. 1972).

The greatest distance to which vegetative treatment is required by any existing law is 100 feet from the structure. Perimeter treatment around subdivisions and other high value areas (e.g., mobile home parks, recreation areas, shopping centers) should be at least to fuelbreak standards (200 feet minimum). And it should embody certain additional features for two reasons: (a) Vegetative and structural fuels must be physical] y separated by enough distance to reduce to an acceptable level the danger of ignition of structures by direct flame impingement or radiation-an even greater clearance (usually impractical if not impossible) would be necessary to protect against windborne firebrands; (b) firefighters must have a place in which to fight the fire before it reaches the structures, and so it is necessary to incorporate features which allow access by the firefighters and their equipment to the treated area (Los Angeles County Fire Dep. 1970, Orange County Bd. Sup. 1976, County Sup. Assoc. Calif. 1966, Green 1977).

This dual need can be met in several ways and many combinations thereof. Probably the best means from the firefighter's standpoint is a perimeter street with structures on the inside and a fuelbreak or greenbelt on the outside. Usually this design is economically feasible only if the adjacent area is to be subsequently subdivided. In certain topographic situations, such a design is impossible (Orange County Bd. Sup. 1976). Another way to achieve perimeter protection is to construct a fuelbreak or greenbelt behind the outside structures (fig. 5).

Fuelbreaks are strips of land in which the volume of vegetative fuel is reduced to an acceptable level and maintained in that condition. Greenbelts are similar strips of land wherein not only is the volume of native vegetation greatly reduced but much or all of it is replaced with irrigated introduced species. Strip parks and golf courses, are examples of greenbelts. They perform multiple functions (i.e., fire protection, recreation, esthetic benefits) and can often be made to pay for themselves (Los Angeles County 1973, Green 1977).

Although practical in economic and sometimes physical terms, fuelbreaks or greenbelts present some problems. Access to the treated area by firefighters is denied unless fire access easements are provided and dedicated to such use. These easements should be wide enough and of low enough gradient to allow access by motorized fire equipment as well as by personnel (Orange County Bd. Sup. 1976, County Sup. Assoc. Calif. 1966).

Other developments which can serve the purpose of perimeter fire protection, at least for limited pieces of the perimeter, are recreation areas (particularly waterbased ones), parking lots, school yards, and baseball or other athletic fields. With such developments placed on the perimeter the amount of otherwise unproductive fuelbreak and easements needed would be reduced3h (Alger 1971).

Proposed Standards: Include reduction of native vegetative fuels to at least fuelbreak standards as part of perimeter fire protection for subdivisions and mobile home parks. Provide access lanes to the treated area at least 12 feet wide for firefighting manpower and ground equipment at intervals not to exceed one-quarter mile. Base the minimum width of the treated strip on fire hazard severity classification: moderate-200 feet, high-300 feet, extreme-400 feet. Dedicate such treated areas and access lanes to public use and provide for their maintenance in perpetuity.


Electric Power Distribution

Overhead transmission and distribution of electric power is a major source of ignition for the conflagrations that have destroyed many hundreds of homes in California and elsewhere in recent years. Contrary to popular belief the large high-voltage transmission lines are not the worst offenders. In one study they accounted for less than 8 percent of the fires over 5000 acres in size. They are commonly built of sturdy materials, maintained with adequate vegetative clearances, and inspected frequently and thoroughly (Task Force on California's Wildland Fire Probl. 1972, Moore 1977).

Distribution circuits accounted for nearly 17 percent of the conflagrations studied (Task Force on California's Wildland Fire Probl. 1972). This proportion was exceeded only by arson and was equalled by machine use. All other fire causes were smaller in number. Distribution circuits are of two types: primary and secondary. Primary circuits bring the power from the substation to the user's transformer. Primary electric power distribution circuits are a serious cause of wildland conflagrations. The thousands of miles of these lines present a tremendous exposure and an almost insurmountable problem of inspection and maintenance. Secondary circuits, which convey power from the transformer to the point of use (e.g., home, pump), usually cause fires because of inadequate vegetative clearance which is not now regulated by any State or local law. Secondary circuits cause nearly one fire for every two caused by primary distribution lines (Calif. Div. For. 1972, Moore 1977).

In about the lower half of their voltage range (i.e., 2.4 to 17 kilovolts), primary distribution circuits can successfully be installed underground rather than overhead. In the foreseeable future, even higher voltage lines can be installed underground. The subdivision codes of many cities now require such installation in all new subdivisions, although usually for visual esthetic reasons. The same requirement could be imposed in rural and wildland areas for fire protection reasons. Such a requirement would eliminate both primary and secondary circuits as sources of vegetation fires since the transformers would be at ground level or below. From this location the secondary circuit (service drop) is almost always placed underground also (Governor's Study Comm. Conflagrations 1966, Task Force on California's Wildland Fire Probl. 1972, Moore 1977).

If for some reason (e.g., excessive rock, preexisting overhead service) the cost of underground installation cannot be justified in relation to fire safety benefits, the developer should arrange for and the permitting agencies require very high standards of construction, vegetative clearance, inspection and maintenance of overhead power lines (Governor's Study Comm. 1966, Oreg. St. Dep. For. 1978a, County Sup. Assoc. Calif. 1966, Task Force on California's Wildland Fire Probl. 1972, Moore 1977). Proposed Standards:

  1. Install all new distribution circuits and extensions of existing circuits underground in fire hazardous wildland areas, if technologically feasible.
  2. Place underground, all distribution circuits (new or existing) carrying less than 20,000 volts in areas of "extreme" fire hazard severity class.
  3. Maintain the following clearances between vegetation and conductors (wires) for all overhead power lines:
    Fire hazard            Secondary       Primary 
      severity class:     distribution   distribution 
                       0-750 volts   2.4-17KV    18-35KV 
    
    Moderate                 2          4           6   
    High                     4          6           8
    Extreme                  6          8          10
    

Street Names and Numbers

Subdivisions are usually provided with visible street names or numbers and lot or building numbers as a convenience to the buyers and visitors. Often, however, the signs are hard to read, sometimes even difficult to find. Many rural and mountain areas have become essentially urbanized through lot splitting and other sale of individual parcels and subsequent construction, and in these situations there is no developer to assign names and numbers. Roads often get their names from their destinations, names of old-time property owners, etc. Parcels or homes commonly are assigned box numbers by the Postal Service.

Positive identification of location is not merely convenient to a firefighter or other public safety officer responding to a reported emergency or radioing for help; it is an absolute necessity. Developers or others assigning and posting names and numbers can greatly assist in providing adequate fire protection if they will make the signs as permanent as possible and large enough and with enough color contrast and reflective character to be read easily from a moving vehicle at night as well as in the daytime 3i (Oreg. St. Dep. For. 1978a, Oreg. St. Dep. For. 1978b, Task Force on California's Wildland Fire Probl. 1972, Colo. St. For. Serv. 1977).

Proposed Standards: Construct signs of nonflammable materials, with letters at least 3 inches high, halfinch line width, and a reflective color that contrasts sharply with the background of both the sign itself and the surrounding vegetation.


Fire Station Sites

Existing fire stations in wildland areas usually are not located correctly nor are they manned and equipped adequately to provide structural fire protection to subdivisions and other developments. Developers of large subdivisions or mobile home parks or of shopping centers or apartment or condominium complexes should recognize this deficiency and dedicate one or more sites for structural fire stations at the outset. After development is complete, suitable sites will no longer be available (Oreg. St. Dep. For. 1978b, County Sup. Assoc. Calif. 1966, San Bernardino County Bd. Sup. 1974, Colo. St. For. Serv. 1977).

Proposed Standards: Dedicate fire station sites when:

  1. No fire station capable of providing structural fire protection exists within 4 miles of the development.
  2. The development is to encompass more than 640 acres or is to have an occupant density of more than eight dwelling units per acre.
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