PRC 4292: the ten-foot firebreak around a pole, and what counts

PRC 4292 requires a firebreak of not less than 10 feet in each direction from the outer circumference of any pole or tower supporting a switch, fuse, transformer, lightning arrester, line junction, or dead end or corner pole, on brush, grass or forest covered land. 14 CCR 1254 makes it a cylinder rising to the highest conductor attachment.

A 12 kV tap pole on brush covered land in Tuolumne County carries a fused cutout, and that single piece of hardware converts the ground around it into a regulated space with a radius, a height, and three separate treatment standards by elevation.

The clearance figure everyone quotes for that circuit is measured outward from the conductor. This one is measured outward from the pole, it does not change with voltage, and a crew that clears the span and leaves the pole base alone has done half the job the Public Resources Code asks for.

What the statute actually requires

PRC 4292 sits in Chapter 3 of Part 2 of Division 4, headed "Mountainous, Forest-, Brush- and Grass-Covered Lands," and it is one paragraph:

Except as otherwise provided in Section 4296, any person that owns, controls, operates, or maintains any electrical transmission or distribution line upon any mountainous land, or forest-covered land, brush-covered land, or grass-covered land shall, during such times and in such areas as are determined to be necessary by the director or the agency which has primary responsibility for fire protection of such areas, maintain around and adjacent to any pole or tower which supports a switch, fuse, transformer, lightning arrester, line junction, or dead end or corner pole, a firebreak which consists of a clearing of not less than 10 feet in each direction from the outer circumference of such pole or tower.

Two sentences follow. The first removes any line "used exclusively as telephone, telegraph, telephone or telegraph messenger call, fire or alarm line, or other line which is classed as a communication circuit by the Public Utilities Commission." The second lets the Director, or the agency with primary fire protection responsibility, "permit exceptions from the requirements of this section which are based upon the specific circumstances involved." The section has been in this form since it was amended by Stats. 1976, Ch. 1300.

One number, then, and no voltage bands. PRC 4293 gives three distances on three voltage bands; 4292 gives ten feet to a 4 kV lateral and ten feet to a 230 kV line. The only voltage that matters is the floor in PRC 4296, which reads in full: "Sections 4292 and 4293 do not apply if the transmission or distribution line voltage is 750 volts or less."

A volume, not a circle on the ground

The statute says "a clearing," which reads like ground work. 14 CCR 1254, Minimum Clearance Provisions-PRC 4292, says otherwise, and it is the section that decides what a crew is actually being asked to do:

The firebreak clearances required by PRC 4292 are applicable within an imaginary cylindroidal space surrounding each pole or tower on which a switch, fuse, transformer or lightning arrester is attached and surrounding each dead end or corner pole unless such pole or tower is exempt from minimum clearance requirements by provisions of 14 CCR 1255 or PRC 4296. The radius of the cylindroid is 3.1 m (10 feet) measured horizontally from the outer circumference of the specified pole or tower with height equal to the distance from the intersection of the imaginary vertical exterior surface of the cylindroid with the ground to an intersection with a horizontal plane passing through the highest point at which a conductor is attached to such pole or tower.

Inside that cylinder the regulation sets three standards, one per layer. At ground level, remove "flammable materials, including but not limited to, ground litter, duff and dead or desiccated vegetation that will allow fire to spread."

From 0 to 8 feet, remove "flammable trash, debris or other materials, grass, herbacious and brush vegetation," and "all limbs and foliage of living trees shall be removed up to a height of 2.4 m (8 feet)." From 8 feet to the horizontal plane of the highest conductor attachment, remove "dead, diseased or dying limbs and foliage from living sound trees and any dead, diseased or dying trees in their entirety."

Take a 45 foot Class 4 distribution pole with a fused cutout, framed so the highest conductor attachment sits at 38 feet. The regulated space is a cylinder 38 feet tall and a little over 21 feet across. A healthy blue oak standing 9 feet off the pole face, with its lowest limbs at 5 feet, is inside it.

Those limbs come off up to 8 feet under 1254(b), even though the tree is sound, even though nothing about it is close to a conductor, and even though it would raise nothing at all under Rule 35's overhang paragraph. Above 8 feet the same tree is judged on condition rather than position, and only its dead, diseased or dying wood comes out.

The regulation's metric conversions are looser than its English ones and the two do not agree. 2.4 m is 7 feet 10 inches, not 8 feet; 3.1 m is 10 feet 2 inches, not 10. The statute's own figure is ten feet, so the English numbers are the ones to work to and the ones to write down.

Where the ten feet starts

Not from the center of the pole. 14 CCR 1251 defines the term the statute uses: "Outer Circumference" means "the exterior surface of a pole or tree at ground level or a series of straight lines tangent to the exterior of the legs of a tower at ground level."

For a wood pole the practical effect is small and real. A 15 inch butt diameter puts the cleared circle at 21 feet 3 inches across, not 20. For a lattice tower it is not small at all. The ten feet runs outward from the tangent lines drawn around the legs, so a tower with a 20 foot leg spread produces a rounded rectangle roughly 40 feet across. Measuring from the tower centerline instead would leave the far corners short by most of the required distance.

The definition also says "pole or tree," which is deliberate. 14 CCR 1258 provides that where conductors and subordinate elements are fastened to living, sound trees, "commonly referred to as tree lines, the requirements of PRC 4292 and 4293 shall apply the same as to a pole or tower line." A living tree carrying a switch takes a ten foot firebreak measured from its own trunk at ground level. Which conductors may be attached to a tree in the first place is a different question with its own answer.

Slope is the other thing the ten feet is not. The California Power Line Fire Prevention Field Guide, 2021 edition, at page 21, is direct about it: "The distances for clearance requirements must be measured horizontally, not along the surface of the sloping ground."

On a 30 percent side slope, ten horizontal feet is about ten feet five inches of ground surface on the downhill side. A crew running a tape along the hill is under-clearing by roughly five inches on every pole, which is invisible in a photograph and obvious in a follow-up inspection.

Which poles are subject poles

The statute's trigger list and the regulation's are not identical, and the difference is the whole determination.

PRC 4292 names a pole or tower supporting "a switch, fuse, transformer, lightning arrester, line junction, or dead end or corner pole." 14 CCR 1254 names a pole or tower "on which a switch, fuse, transformer or lightning arrester is attached" plus "each dead end or corner pole." Line junction is absent from the regulation's list, because 14 CCR 1255 handles it from the other side. The exemptions read:

The minimum clearance provisions of PRC 4292 are not required around poles and towers, including line junction, corner and dead end poles and towers: (a) Where all conductors are continuous over or through a pole or tower; or (b) Where all conductors are not continuous over or through a pole or tower, provided, all conductors and subordinate equipment are of the types listed below and are properly installed and used for the purpose for which they were designed and manufactured

Ten connector types follow:

• Compression connectors.

• Automatic connectors.

• Parallel groove connectors.

• Hot line tap or clamp connectors designed to absorb expansion and contraction by spring tension.

• Fargo GA 300 series piercing connectors made for tree wire.

• Flat plate connectors "installed with not less than two bolts."

• Tapered C-shaped member and wedge connectors.

• Solid blade single phase bypass and disconnect switches associated with circuit reclosers, sectionalizers and line regulators.

• Completely sealed liquid-filled equipment.

• Current limiting non-expulsion fuses.

So the question a field determination actually answers is not what kind of pole this is. It is whether every conductor runs continuous through the pole, and if any does not, whether the thing joining it appears on that list of ten and was installed the way its manufacturer intended. A flat plate connector carrying one bolt is not the connector 1255(b)(6) describes. An expulsion fuse is not the fuse in 1255(b)(10).

The 2021 Field Guide uses the working vocabulary for the outcome, "non-exempt or subject poles and towers," and notes at page 18 that some utilities carry Subject Pole identification in their pole numbering rather than numbering every pole. That flag in the asset record is the determination, and it is only as current as the last time somebody changed hardware on the pole.

The hardware exemption is a test result

PRC 4292's second escape hatch, the Director's power to permit exceptions "based upon the specific circumstances involved," has a published procedure behind it for equipment. The 2021 Field Guide sets it out at pages 23 and 24.

A utility or hardware vendor submits the request to CAL FIRE's Wildfire Planning and Engineering Division, Utility Fire Mitigation Program. The request carries:

• A written request and pre-meeting invitation.

• A sample product.

• Engineered product drawings and installation instructions.

• Test results.

• Video of the tests recorded in 1080p high resolution color and infrared.

• Photographs and descriptions of the equipment tested.

• A description of the test procedures.

• A third-party electrical engineer's conclusions.

CAL FIRE is to notify the requesting utility in writing within 60 days, approving or denying a temporary 36-month exemption and giving the justification.

The test conditions are the part worth knowing before anyone budgets for this. Tests are conducted under the direction of a third-party electrical engineer, using equipment capable of making and breaking preset loads, with current, voltage and start and end times graphically recorded and kept as part of the request. The fuel bed is "representative of flammable vegetation (dead, dried grass or equivalent) with a fine fuel moisture of 5% at a minimum temperature of 80 degrees Fahrenheit and an accompanying wind speed of 10 MPH or more."

Enclosed devices must generate no external arcs, sparks or expelled hot particles in operation. Open and fixed devices must interrupt line and short-circuit current within their design range without creating arcs, sparks or hot particles capable of igniting flammable vegetation. And the pass condition is absolute: "Igniting any portion of the test bed will disqualify the device."

Table 2 at page 25 of that guide lists the hardware currently holding a temporary or permanent exemption letter from the CAL FIRE Director. A pole whose exemption rests on a device is only exempt while that device is the one in the letter, installed as the letter contemplates.

The ground cover exemptions, and one phrase

The remaining two subsections of 14 CCR 1255 are about what is growing rather than what is hanging.

Subsection (c) lists eight areas, and it conditions all of them on one clause: the exemption runs "On the following areas if fire will not propagate thereon." The eight are:

• Fields planted to row crops.

• Plowed or cultivated fields.

• Producing vineyards that are plowed or cultivated.

• Fields in nonflammable summer fallow.

• Irrigated pasture land.

• Orchards of fruit, nut or citrus trees that are plowed or cultivated.

• Christmas tree farms that are plowed or cultivated.

• Swamp, marsh or bog land.

The qualifiers inside the list do real work too. An orchard that has stopped being plowed or cultivated has stopped being the thing 1255(c)(6) exempts, which is the same distinction, drawn in different words, that returns an unmaintained orchard to the stricter clearance case under GO 95.

Subsection (d) is the landscaping exemption. It has three conditions joined by "and": the vegetation must be "maintained less than 30.48 cm (12 inches) in height," must be "fire resistant," and must be "planted and maintained for the specific purpose of preventing soil erosion and fire ignition." The 2021 Field Guide, at page 21, says what CAL FIRE does with that language: "This is not intended as a loophole. The key words are 'specific purpose,' and they require a positive demonstration of this purpose to qualify."

Positive demonstration means a document. A planting record naming the species, the date and the erosion or ignition purpose is what carries a 1255(d) claim on a pole with green growth against its base. A photograph of short grass is not that document, because short grass in April and cured grass in September are the same species and 1255(d) asks about purpose and maintenance rather than about appearance on the day.

When it applies, and where

Three limits sit outside the statute's own text, and all three are dated facts rather than judgments.

14 CCR 1252 makes the standing area determination: "The Director will apply PRC 4292-4296 in any mountainous land, forest covered land, brush covered land or grass covered land within State Responsibility Areas unless specifically exempted by 14 CCR 1255 and 1257." That heading and text were filed October 24, 2005 and became operative November 23, 2005.

Outside the State Responsibility Area the statute still binds on its face, but the determination that it is necessary is the local fire protection agency's to make, and 1252 does not make it for them. Which land sits in which responsibility area is therefore a prerequisite to the finding, not a detail of it.

14 CCR 1253 supplies the season: the minimum firebreak and clearance provisions of PRC 4292 through 4296 "are applicable during the declared California Department of Forestry and Fire Protection fire season for a respective county. The Director shall post the declaration on the official Department web site." The same seasonal limit, and what it does to a reading taken outside it, applies to the conductor clearances alongside these.

PRC 4296 supplies the voltage floor at 750 volts, and PRC 4292's own communication exclusion supplies the last one. The 2021 Field Guide, at page 22, marks where that exclusion is narrower than it looks: lines "used largely but not exclusively for communication are not exempt." The example given is railroad circuits, which are primarily communication but also carry more than 750 volts to operate track switches, and are therefore in scope.

What PRC 4295.5 does not reach

PRC 4295 reaches both halves of the obligation. It says a person "is not required by Section 4292 or 4293 to maintain any clearing on any land if such person does not have the legal right to maintain such clearing," and does not require entry onto or damage to another's property without consent. A pole standing on a parcel the utility has no right to clear is inside that relief, on the same terms as a span. Where a refusal ends and the obligation resumes is its own subject.

PRC 4295.5, the right-of-entry section added by AB 2911 in 2018 and amended by SB 272 effective July 23, 2021, does not reach both halves. Its authority to traverse land after notice and an opportunity to be heard runs "to prune trees to maintain clearances pursuant to Section 4293, and to abate, by pruning or removal, any hazardous, dead, rotten, diseased, or structurally defective live trees."

Section 4292 is not named in it. So on a parcel where access is contested, the statutory entry route reaches the conductor clearance and the hazard tree on its own terms, and the ten foot firebreak around the pole is left to the easement, to consent, or to PRC 4295's relief.

What the record has to name

A pole firebreak entry that reads "pole cleared" is not testable by anyone who was not standing there, because the four things that decide the finding are all absent from it.

An entry that survives reads more like this:

What it names	This entry
Pole	1892096E
Circuit	Sonoma 1104, 12 kV
Subject pole	By reason of a fused cutout at the tap
Land	Brush covered, State Responsibility Area
Season	Sonoma County fire season declared
Cleared	July 9 2026, to 10 feet horizontal from the pole face at ground level
Vegetation	Grass and brush removed; one live blue oak at 9 feet limbed to 8 feet; one dead madrone within the cylinder removed in its entirety
Evidence	Photographs from four quadrants; crew and foreman named

Every element of that can be checked back to 1254 and 1255 by someone reading it a year later. The ones that carry the most weight are the subject pole determination and the date. That is because the date is what decides which standard was live and the determination is what decides whether the pole was in scope at all.

Where the pole is claimed exempt, the file has to say which subsection carries it and hold the artifact that proves it: the hardware type and its exemption letter for 1255(b), the planting record for 1255(d), the cultivation status for 1255(c). An exemption asserted without its artifact is an unclosed finding wearing a different label. What a working clearance record contains and the retention period each part of it carries are their own subjects.

One practical note on how these get found. The 2021 Field Guide observes at page 16 that aerial inspection is "particularly effective at spotting pole or tower clearances" and the larger hardware that makes a pole subject, while conductor clearances and small hardware are difficult to judge from the air. Pole firebreaks are the part of this statute that an overflight will surface first, which is worth knowing when deciding what a given inspection type is actually able to close.

Where the exposure sits

There is no matching Commission rule to fall back on. GO 95 Rule 35 and Table 1 Cases 13 and 14 measure radially from the conductor, and neither one reaches the ground around a pole butt. At the conductor, two bodies set two numbers on the same span. At the pole base, one body sets one, and it is not the CPUC.

The consequences run through the Public Resources Code. PRC 4021 makes a misdemeanor of the acts and omissions it names:

the willful or negligent commission of any of the acts prohibited or the omission of any of the acts required by Chapter 2 (commencing with Section 4251) to Chapter 6 (commencing with Section 4411), inclusive, of Part 2 of this division

Chapter 3, sections 4291 through 4299, is inside that range. PRC 4171 adds a second lever on the same facts: "Any condition endangering public safety by creating a fire hazard and which exists upon any property which is included within any state responsibility area is a public nuisance." PRC 4119 gives the Director and duly authorized agents the authority to inspect all properties except the interior of dwellings to ascertain compliance.

The finding itself arrives on paper. CAL FIRE records it on the California Fire Safety Inspection Report, form LE-38a, and may also collect it geospatially in the field. The 2021 Field Guide directs at page 16 that a copy go to the utility owning the infrastructure inspected. It also directs that reports be "specific enough for the utility to act on their findings and for the courts to relate them to complaints or other legal actions."

Unlike a conductor clearance, which the same guide instructs fire agency personnel not to measure physically because of the electrocution risk, a ten foot ground radius is something an inspector can put a tape on from a safe position. On this one obligation the agency's number and the utility's number should be the same number, and when they are not, the file is what explains why.

Further reading

• PRC 4293 radial clearance in State Responsibility Areas: The other half of the same statute, measured from the conductor instead of the pole.

• Title 14 CCR sections 1250 to 1258: the implementing rules: The regulations that operate PRC 4292 through 4296, section by section.

• Which agency enforces which vegetation rule: CAL FIRE, the CPUC and NERC, and what each one can do about a finding.

Frequently asked questions

Which poles need a 10 foot firebreak under PRC 4292?

Poles and towers supporting a switch, fuse, transformer, lightning arrester, line junction, or dead end or corner pole, on mountainous, forest covered, brush covered or grass covered land. 14 CCR 1255(a) then exempts any pole where all conductors are continuous over or through it, and 1255(b) exempts poles where the conductors are joined only by one of ten listed connector types, properly installed. In practice the determination is about hardware at the pole, not about the pole.

Is the PRC 4292 firebreak just ground clearing?

No. 14 CCR 1254 defines it as an imaginary cylindroidal space with a 10 foot radius and a height reaching the horizontal plane through the highest conductor attachment. Flammable materials come out at ground level, grass, brush and living tree limbs come out from 0 to 8 feet, and dead, diseased or dying limbs and whole dead, diseased or dying trees come out from 8 feet to the top of that cylinder.

Does PRC 4292 apply all year, and everywhere?

No. 14 CCR 1253 makes the firebreak provisions applicable during the declared CAL FIRE fire season for the respective county, and 14 CCR 1252 applies PRC 4292 through 4296 in mountainous, forest covered, brush covered or grass covered land within State Responsibility Areas. Outside the State Responsibility Area the determination belongs to the agency with primary fire protection responsibility. PRC 4296 removes lines of 750 volts or less entirely.

Does GO 95 require a firebreak around a pole?

Not in the vegetation rule. GO 95 Rule 35 and Table 1 Cases 13 and 14 are radial clearances measured from the conductor, and neither reaches the ground around the pole butt. The pole firebreak is a CAL FIRE side obligation with no twin on the Commission side, which is the reverse of the situation at the conductor, where both bodies set a number.