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).
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:
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:
- Install all new distribution circuits and extensions of
existing circuits underground in fire hazardous wildland areas, if technologically feasible.
- Place underground, all distribution circuits (new or
existing) carrying less than 20,000 volts in areas of
"extreme" fire hazard severity class.
- 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.
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