GENERAL ORDER No. 95

This is an excerpt from the document involving tree trimming and line  maintenance. The full text is at: http://www.cpuc.ca.gov/divisions/CSD/USB/gos.html

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35) Tree Trimming

Where overhead wires pass through trees, safety and reliability of service demand that tree trimming be done in order that the wires may clear branches and foliage by a reasonable distance. The minimum clearances established in Table 1, Case 13, measured between line conductors and vegetation under normal conditions, shall be maintained. (Also see Appendix E for tree trimming guidelines.)

When a utility has actual knowledge, obtained either through normal operating practices or notification to the utility, dead, rotten and diseased trees or portions thereof, that overhang or lean toward and may fall into a span, should be removed.

Communication and electric supply circuits, energized at 750 volts or less, including their service drops, should be kept clear of limbs and foliage, in new construction and when circuits are reconstructed or repaired, whenever practicable. When a utility has actual knowledge, obtained either through normal operating practices or notification to the utility, that any circuit energized at 750 volts or less shows strain or evidences abrasion from tree contact, the condition shall be corrected by slacking or rearranging the line, trimming the tree or placing mechanical protection on the conductor(s).

 EXCEPTIONS:

1. Rule 35 requirements do not apply to conductors, or aerial cable that complies with Rule 57.4-C, energized at less than 60,000 volts, where trimming or removal is not practicable and the conductor is separated from the tree with suitable materials or devices to avoid conductor damage by abrasion and grounding of the circuit through the tree.

2. Rule 35 requirements do not apply where the utility has made a "good faith" effort to obtain permission to trim or remove vegetation but permission was refused or unobtainable. A "good faith" effort shall consist of current documentation of a minimum of an attempted personal contact and a written communication, including documentation of mailing or delivery. However, this does not preclude other action or actions from demonstrating "good faith". If permission to trim or remove vegetation is unobtainable and requirements of exception 2 are met, the utility is not compelled to comply with the requirements of exception 1.

3. The Commission recognizes that unusual circumstances beyond the control of the utility may result in nonconformance with the rules. In such cases, the utility may be directed by the Commission to take prompt remedial action to come into conformance, whether or not the nonconformance gives rise to penalties or is alleged to fall within permitted exceptions or phase-in requirements.

Note: Revised November 6,1992 by Resolution No. SU-15, September 20, 1996 by Decision No. 96-09-097 and January 23, 1997 by Decision No.  97-01-044.

4. Mature trees whose trunks and major limbs are located more than six inches,  but less than 18 inches, from primary distribution conductors are exempt from the 18-inch minimum clearance requirement under this rule. The trunks and limbs to  which this exemption applies shall only be those of sufficient strength and rigidity to prevent the trunk or limb from encroaching upon the six-inch minimum clearance under reasonably foreseeable local wind and weather conditions. The utility shall bear the risk of determining whether this exemption applies, and the Commission shall have final authority to determine whether the exemption applies in any specific instance, and to order that corrective action be taken in accordance with this rule, if it determines that the exemption does not apply.

Note: Added October 22, 1997 by Decision No. 97-10-056.

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Table 1, Case 13 establishes the minimum clearances measured between line conductors and vegetation under normal conditions. Looking up in Table 1, Case 13, footnote (ccc) provides the relevant information: "For 22.5 kV to 105 kV, minimum clearance shall be 18 inches." Appendix E excerpt covers the trimming guidelines to Rule 35. Here is the relevant excerpt:

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Appendix E Guidelines to Rule 35

The following are guidelines to Rule 35. The radial clearances shown below are minimum clearances that should be established, at time of trimming, between the vegetation and the energized conductors and associated live parts where practicable.  Vegetation management practices may make it advantageous to obtain greater clearances than those listed below:

A. Radial clearances for any conductor of a line operating at 2,400 or more volts, but less than 72,000 volts 4 feet

B. Radial clearances for any conductor of a line operating at 72,000 or more volts, but less than 110,000 volts 6 feet

C. Radial clearances for any conductor of a line operating at 110,000 or more volts, but less than 300,000 volts 10 feet

D. Radial clearances for any conductor of a line operating at 300,000 or more volts 15 feet

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Rule 35 was modified as indicated mentioned above: January 23, 1997 by Decision No. 97-01-044. The document describing that decision is located at: http://www.cpuc.ca.gov/divisions/energy/site/documents/d9701044.htm

The discussion portion of that document is reproduced here. The discussion section of this document is as follows:

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4.0 Discussion

The degree of tree trimming appropriate around utility lines can become a highly technical determination. It requires us to set minimum clearance standards which depend upon the degree of hazard in relation to the voltage level carried by the line and the consequent potential for arcing, and the possibility of abrasion of wires from direct contact.  We do not need to determine what the appropriate maximum clearances should be, but we do have to determine the minimum safe clearances and a reasonable level of expense for the utility to maintain such clearances.  Ratepayers should not be required to pay unreasonably high rates because the utility trims trees on a cycle that cannot be justified. This means that, to the extent that we promulgate any guidelines that may later be claimed to be a standard for reasonableness, we must act with a restrained hand. We must also temper our determination with aesthetic and environmental considerations to discourage ham- handed trimming by utilities. In short, we must make a cost/benefit analysis to obtain the proper result.

Unfortunately, the record in this proceeding does not provide the tools to make an intricate analysis, and we must instead rely upon the compliance filings of the utilities, which contain relatively scanty information; a meager workshop report; the Settlement, which contains little factual material upon which to base a standard; and the comments received in response to D.96-09-097, which consist in large measure of opinion and argument, rather than hard data. Given this state of affairs, we must resort to an approach which does not rely upon an extensive administrative record and a rigorous cost/benefit analysis, but relies instead upon everyday experience to reach a rational result.

We are guided by a few basic principles. First, the existence of a reliable electric transmission and distribution system is assumed to be essential to our way of life. We simply cannot do without it, and this State’s experience with recent power outages underscores how much we need to insure that it operates without interruption. Next, safety—of utility workers, others who work around the lines, property owners whose lives and property are vulnerable to fire hazards, and the general public who may come into contact with power lines—is of the first importance in operating that system: if we accept the reality that we must have a reliable system, it must also be safe for all who live, work, or play near it. Finally, we must be certain that our efforts to insure safe and reliable service cause as little disruption to the natural environment and the aesthetics of affected property as possible, to the extent that we offer guidance about trimming beyond specified minimum clearances.

Although some of the comments request that we conduct evidentiary hearings concerning the adoption of these standards, we decline to do so. The process to date approximates that for a rulemaking under our Rules, and interested persons have had an adequate opportunity to comment upon the proposed standards.(5) We must act now to insure that adequate tree trimming standards are in place, because efforts by the utilities are already underway to ameliorate the rising incidence of fires and outages due to contacts between tree limbs and electric lines. We therefore address these comments and issue our final standards at this juncture, rather than going through another procedural step before doing so.

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Exemption 4 above was added October 22, 1997 by Decision No. 97-10-056. That document is available at: http://www.cpuc.ca.gov/divisions/energy/site/documents/d9710056.htm

This document discusses the rule change which exempts mature trees in  some cases. Here is an excerpt from that discussion:

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"Clearances for Major Trunks and Limbs

PG&E seeks to modify Rule 35 to the extent of exempting old established trees whose trunks are more than six, but less than eighteen inches, from an overhead line from the literal application of its clearance requirements. PG&E says that there are numerous examples of such trees throughout its service territory, and it appears that many of them are located in aesthetically sensitive communities such as Carmel, and in parks or rural areas where large species such as redwood, pine, and mature eucalyptus trees are growing in proximity to power lines. PG&E argues that these trees have safely coexisted with overhead lines for decades, and that their removal (as would arguably be required under Rule 35) would be expensive and destructive. PG&E also seeks exemption of so-called "directionally pruned" trees whose major branches have historically been trimmed to grow away from the conductor, but are less than 18 inches from it, yet allegedly pose no safety problem."

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Clearly there is some consideration of "aesthetically sensitive communities such as Carmel". One could certainly argue that Bonny Doon is similarly "aesthetically sensitive".

 From the State Law: Public Resources Code, section 4292-4296.

[ The full PRC code is located at http://www.leginfo.ca.gov/calaw.html Check the box titled "Public Resources Code" on that page. To find this section, search for '4293'. ]

4292.  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.  This section does not, however, apply to any line which is 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 director or the agency which has primary fire protection responsibility for the protection of such areas may permit exceptions from the requirements of this section which are based upon the specific circumstances involved.

4293.  Except as otherwise provided in Sections 4294 to 4296, inclusive, any person that owns, controls, operates, or maintains any electrical transmission or distribution line upon any mountainous land, or in 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 the fire protection of such areas, maintain a clearance of the respective distances which are specified in this section in all directions between all vegetation and all conductors which are carrying electric current:

(a) For any line which is operating at 2,400 or more volts, but less than 72,000 volts, four feet.

(b) For any line which is operating at 72,000 or more volts, but less than 110,000 volts, six feet.

(c) For any line which is operating at 110,000 or more volts, 10 feet.

In every case, such distance shall be sufficiently great to furnish the required clearance at any position of the wire, or conductor when the adjacent air temperature is 120 degrees Fahrenheit, or less.  Dead trees, old decadent or rotten trees, trees weakened by decay or disease and trees or portions thereof that are leaning toward the line which may contact the line from the side or may fall on the line shall be felled, cut, or trimmed so as to remove such hazard.  The director or the agency which has primary responsibility for the fire protection of such areas may permit exceptions from the requirements of this section which are based upon the specific circumstances involved.

4294.  A clearing to obtain line clearance is not required if self-supporting aerial cable is used.  Forked trees, leaning trees, and any other growth which may fall across the line and break it shall, however, be removed.

4295.  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, nor do such sections require any person to enter upon or to damage property which is owned by any other person without the consent of the owner of the property.

4296.  Sections 4292 and 4293 do not apply if the transmission or distribution line voltage is 750 volts or less.