Field hazard tree assessment: the level, the trigger, and the call

A field hazard tree call is worth what the assessment level behind it was. ANSI A300 (Part 9) clause 93.4.1 requires that the level and detail of tree risk assessment be specified, and clause 93.3.3 says the assessor owes only the level the scope of work bought. Level 3 is scheduled by the owner.

An 84 foot gray pine stands 61 feet from the nearest primary phase of a 12 kV span. The inspector is on a Routine annual patrol, working the road, and the tree is behind a fence on the uphill side.

From the truck the crown looks full and the bole looks straight, and the entry that goes into the tablet says nothing found. A Level 1 finding of nothing is not a finding about the tree. It is a finding about the side of the tree that faced the road, made from a perspective somebody chose before the inspector got there.

That choice has a name and a clause number, and it is the first thing a hazard tree record should carry.

The level is specified before anybody walks up to the tree

ANSI A300 (Part 9) is the tree risk assessment part of the A300 family. PG&E posts the full text of the 2011 edition, approved by ANSI on February 17, 2011 with the Tree Care Industry Association as secretariat. TCIA sells the 2017 revision, whose published contents still list "Levels of tree risk assessment" and "Risk analysis and reporting- Owner determination." Which edition the contract named is its own question and it is worth settling before a scope of work is written.

The part that decides what a field call is worth sits in two clauses:

93.4.1 The level and detail of tree risk assessment shall be specified. 93.4.2 One or more of the following inspection levels shall be specified:

Shall, in this standard, "denotes a mandatory requirement" at 92.21. The assignment carries the level and the assessor inherits it. The standard closes the loop from the other direction at 93.3.3:

The arborist shall not be required to perform a higher level of assessment than specified by the scope of work.

That clause is protection for the inspector and exposure for the program. An inspector who performed the level the scope of work bought has conformed, even where a higher level would have found the decay. The gap between the level bought and the level the tree needed belongs to whoever wrote the scope.

Level 1, Level 2, Level 3, in the standard's own words

Level 1 is the one that names utility corridors:

93.4.2.1.1 Level 1 assessments shall be a limited visual assessment of an individual tree or a population of trees near specified targets, such as along roadways or utility rights-of-way, to identify specified conditions or obvious defects. 93.4.2.1.2 Level 1 assessments shall be from a specified perspective such as foot, vehicle, or aerial patrol. 93.4.2.1.3 Level 1 assessment methodology shall be specified.

Three sentences, three uses of the word specified. A stated perspective is part of what makes the look a Level 1 at all.

Level 2 is the look that gets somebody out of the truck:

93.4.2.2.1 Level 2 assessments shall include a 360-degree, ground-based visual inspection of the tree crown, trunk, trunk flare, above-ground roots, and site conditions around the tree in relation to targets.

Level 3 adds everything else, and the standard makes it advisory rather than mandatory:

93.4.2.3.2 A level 3 assessment employing advanced methodologies should be used when the extent and severity of conditions or defect cannot be determined by a Level 2 assessment.

Level	Clause	What the standard fixes	What the specification still has to supply
1	93.4.2.1	Limited visual, individual tree or population, near specified targets	The perspective, the methodology, and the conditions being looked for
2	93.4.2.2	360 degree, ground-based, crown through above-ground roots, in relation to targets	Whether sounding is performed, and which tools
3	93.4.2.3	All Level 2 requirements, plus one or more of thirteen named advanced methods	Which method, who schedules it, and who pays

A Level 2 on the page still has blanks in it

The word Level 2 in a contract settles the walk around the tree. It settles very little else. Sounding is conditional:

93.4.2.2.1.1 When sounding is specified, a mallet or equivalent tool should be used to detect large hollows and loose bark in the trunk, root collar, and above ground buttress roots.

Tools are permitted rather than required, at 93.4.2.2.2: "Use of hand tools, trowels, binoculars, or probes, shall not be precluded from a Level 2 assessment." And the output is open too, at 93.6.2: "The type of report (oral, written) required shall be specified in the scope of work." A Level 2 performed with eyes only and reported verbally to a supervisor conforms to the standard.

Which is why 93.3.2 is the clause a program manager writes against rather than reads past:

The scope of work specification should include, but is not limited to: 1) Tree location, selection criteria; 2) Level and details of risk assessment; 3) Type of report (e.g. oral, written) to be developed; 4) The time frame for reporting; 5) To whom the report should be presented; and, 6) Mitigation.

Back to the gray pine. Somebody walks the 360 and the butt sounds hollow on the uphill face. Whether the mallet came out of the truck at all is a contract question, answered months earlier by item 2 on that list. An audit finding that reads "Level 2 not performed to standard" has to point at the clause of the scope of work that said what a Level 2 was on that circuit. Most distribution contracts stop at the words Level 2.

One utility's trigger, written as an if-then

PG&E's TD-7102P-01, Revision 4, effective November 15, 2025, is a worked example of a utility filling those blanks in. It sorts distribution inspection into two work categories. Table 2 gives the Standard category an assessment type of "Level 1 leading to Level 2 Inspections, as needed." Step 3.4 supplies the as needed:

For the Standard work category, the VMI must PERFORM a Level 1 Inspection. 1. IF the VMI sees or suspects vegetation with defects or site conditions as stated in the Hazard Trees/Vegetation Clearance section of the "California Power Line Fire Prevention Field Guide" (SEE Appendix A, Overview of Tree Defects and Site Conditions), THEN the VMI must also PERFORM a Level 2 Inspection of the vegetation.

Sees or suspects is a deliberately low bar, and the trigger points outward at CAL FIRE's field guide, whose Hazard Trees section is a defect list with no thresholds in it. The procedure reprints that list as its own Appendix A, nineteen bullets deep, and its additions include root defects such as stem-girdling roots, fruiting bodies of known wood decay fungus, and narrow attachment with included bark. Any one of the nineteen turns a drive-by into a walk-around.

The Elevated work category removes the trigger and buys the Level 2 outright. Table 2:

Assessment Type: Includes the components of the Standard work category AND Level 2 Inspections of all Strike Trees Focus: Include the components of the Standard work category AND DOCUMENT all Strike Trees into the system of record AND USE a Tree Risk Assessment (TRA) form for all Strike Trees prescribed for work to mitigate fall-in risk. Minimum Qualifications: Certified Arborist-Tree Risk Assessment Qualification (TRAQ)

The procedure's own glossary defines a Strike Tree as "a tree or tree part which has the potential to impact PG&E facilities upon failure." Height, lean and balance are the named factors. A tree that leans or balances away from the facilities sits expressly outside the definition. The gray pine at 84 feet and 61 feet out is inside that definition on height alone. On an Elevated circuit it gets the walk-around whether or not anything showed from the road.

The interval the judgment is made against comes from the patrol type rather than the level. Table 1 gives a Routine patrol an assessment timeframe of the next Routine annual inspection cycle, and a Hazard patrol "Next Routine annual inspection cycle (approximately 6 months)," because hazard patrols land mid-cycle.

The same codominant union on the same pine is being rated against a twelve month window on one visit and a six month window on the next. The rating is only readable next to the window it was made against, and the cycle assumption behind the window sits in a different document again.

Where that procedure disagrees with itself

Two places in Revision 4 say when the Tree Risk Assessment form is required, and they do not say the same thing. Table 2 and step 3.5 both scope it to Strike Trees "prescribed for work to mitigate fall-in risk." Table 4, the prescriptions table, drops the qualifier:

Elevated work category: COMPLETE a TRA form of all Strike Trees prescribed for work.

Read narrowly, the form is owed only where the prescription mitigates fall-in. Read as Table 4 has it, every Strike Tree with any prescription on it needs one. The difference is most of the population on a foothill circuit, because most Strike Trees are pruned for distance rather than mitigated for fall-in.

The procedure leaves the reading open, and the person who settles it is the utility's vegetation program. Get the answer in writing before a QA sample turns it into a finding, and record which reading the crew's units were built under. The audit that reads those units afterward is somebody else's document and it will not ask the question kindly.

The qualification the contract names, and the seven years behind it

A300 names no credential anywhere in Part 9. Clause 93.2.1 is the whole of it: "Arborists assessing tree structure and failure potential shall have appropriate training and experience." PG&E's procedure is more specific, and lists Certified Arborist with Tree Risk Assessment Qualification as the minimum for the Elevated category. That is two credentials stacked, because TRAQ eligibility itself runs through a prior credential such as ISA Certified Arborist, ISA Board Certified Master Arborist or ISA Certified Arborist Utility Specialist, or through a degree or a state license.

What the second credential proves is narrower than a roster suggests. ISA's own program guide, revised July 2026, says so directly:

By successfully completing the ISA TRAQ program, you have demonstrated knowledge of the ISA TRAQ methodology and process for tree risk assessment, which is considered relevant for the seven-year term of your qualification. No other conclusions may be drawn concerning qualification holders. ISA qualifications do not represent licensure, registration, or other authorization to practice or to conduct business activities for a fee or otherwise.

The mechanics behind it are a two-day instructor-led course, a written exam of 110 multiple-choice questions passed at 75 percent, and a one-hour outdoor performance exam on a tree at the training site. The credential is valid for seven years, and reinstatement after each seven-year period means retraining and retesting.

The guide states that an extension past the expiration date will not be available, so a lapsed TRAQ takes its holder off an Elevated circuit until the course is sat again. The guide also states that qualifications "are not subject to ongoing requirements, such as adherence to a code of ethics or participation in continuing education activities."

So a TRAQ number on a crew roster establishes attendance and a passing score inside a seven-year window. It leaves open whether the holder was trained on the utility's procedure, on the defect list in its Appendix A, or on the form the procedure requires. That training record is a separate document, and it is the one an evaluator asks for second. How a qualification is documented so a prime can verify it is worth having settled before the request arrives.

The Level 3 belongs to the owner

The gray pine sounds hollow. The inspector has the standard's own list of what comes next, at 93.4.2.3.3:

Level 3 assessments shall include, but are not limited to, one or more of the following tree assessment methods: Aerial assessment of branch or stem defects; Drilling; Evaluation of target risk; Increment boring; Investigation of tree or site history related to possible or defined defects; Lean assessment; Probing; Pull testing; Radiation assessment (e.g. radar, x-ray, gamma ray); Resistance drilling; Sonic assessment; Sounding; and, Sub-surface root and/or soil assessment.

Sounding appears twice in the standard, once as a Level 2 step when it is specified and once on this list, so a program that specified the mallet has already bought one of the thirteen. Every one of the thirteen is scheduled by somebody else. Clause 93.6.4.1 puts the decision in one place, and the wording is flat:

It shall be the responsibility of the owner, the owner's agent, or the controlling authority to schedule repeat or advanced assessments, determine actions, and implement follow-up recommendations, monitoring, and/or mitigation.

The inspector's product at that moment is a recommendation and a record of it. That is the whole of the authority, and it is worth being plain about the limit, because a recommendation for a resistance drilling that goes into a free-text comment field with no work type behind it is a recommendation the utility never received.

Where a recommendation has to land to count as received is the practical half of this clause. The other half is the case where the tree cannot wait for a scheduling decision at all, and the authority to act before anyone is notified is narrow and separately sourced.

Residual risk is a sentence somebody has to write

The standard asks for five things in a written report, at 93.6.2.1:

Written reports should include: Identification and location of the specified tree(s); A description of the methods used; Tree risk assessment data; Recommendations for mitigating risk or additional assessments; and, Recommendations for monitoring and follow-up.

A description of the methods used is where the level goes. Then come the two clauses that almost no distribution record carries:

93.6.2.1.1 All recommendations other than removal of the tree should contain an advisory that not all potential structure and stability concerns associated with trees can be eliminated. 93.6.2.1.2 All recommendations should include a statement addressing residual risk following mitigation.

Take the gray pine to the end. The prescription is a crown reduction over the phase rather than a removal, which is a decision with its own criteria and its own approval path. The crew performs it and the unit closes. An entry reading "crown reduced, complete" satisfies the work order and stops there. An entry that addresses residual risk carries four things:

• the weight removed, and the phase it came off;

• the hollow response on the uphill butt face, still unresolved, with a Level 3 recommended;

• the tree's continuing status as a Strike Tree; and

• the next look, which on this circuit is the coming Hazard patrol.

That entry also tells the next inspector, two cycles later, what the last one already knew.

The level does not come from the code

Somebody writing a bid or grading one will want a citation requiring a Level 2. That citation lives in the contract rather than the code. CAL FIRE's field guide gives utilities the option of following the ANSI A300 tree risk assessment standard per their field conditions and needs, and an option is what it says it is.

General Order 165 sets inspection types for facilities, and what separates a patrol from a detailed inspection under it is a question about poles and hardware rather than trees. General Order 95 and the Public Resources Code set clearances and stop.

So the level arrives from the utility's own procedure and the contract that names it, which has three consequences a prime feels directly.

The same word means two things across two utilities. PG&E defines a Level 2 Inspection as "a detailed visual inspection of a tree and surrounding site that may include the use of simple tools," requiring the assessor to "inspect completely around the tree trunk," and adds that Level 2 inspections are ground-based. Another utility's procedure can define it tighter or looser and stay inside A300, because A300 left the details to the specification. A crew qualification matrix that says Level 2 and stops there travels badly.

The utility's vocabulary can be wider than the guide's. PG&E defines a Hazard Tree as "a tree that has the likelihood of falling and impacting facilities within an inspection timeframe" and then adds "It can also be a tree that may grow into conductors within an inspection timeframe." Grow-in is inside that definition. It is outside the failure-based inquiry the field guide runs. A unit tagged hazard tree under one document and read under the other has changed meaning in transit.

The companion publications move on their own schedule. Revision 4 defines Impact by reference to the ANSI Best Management Practices Tree Risk Assessment, Second Edition, Part 9. ISA now sells the third edition, dated 2025, which its own store page says replaces the second edition from 2017.

Revision 4's reference list also names Best Management Practices Utility Tree Risk Assessment, the 2020 companion by John W. Goodfellow aimed at utility vegetation managers and line clearance contractors. As of September 20, 2026 a field guide quoting the second edition is quoting a superseded book, and nobody issues a notice when that happens.

The tree is indifferent to all of it. What the record has to survive is a reader who was not there, holding a document set that has three editions in it, asking one question: which level was this, and who said so.

Common questions

Further reading

• What a pre-inspection produces: the work order before the crew: The unit the Level 2 look turns into, and the fields that travel with it.

• Hazard trees: what CAL FIRE's field guide actually says: The two part inquiry the escalation trigger points at, and the likelihood scale that has no fixed year in it.

• ANSI standards met: A300 in the audit: Shall against should, and which edition of A300 the contract actually named.

Frequently asked questions

What are the levels of tree risk assessment?

Three, set in clause 93.4.2 of ANSI A300 (Part 9). Level 1 is a limited visual assessment of a tree or a population of trees near specified targets, from a specified perspective such as foot, vehicle or aerial patrol. Level 2 is a 360 degree, ground-based visual inspection of the crown, trunk, trunk flare, above-ground roots and site conditions in relation to targets. Level 3 includes all Level 2 requirements plus advanced methods, and the standard names thirteen of them, including drilling, increment boring, resistance drilling, sonic assessment and pull testing.

Does a Level 2 inspection include sounding the trunk?

Only if the specification says so. Clause 93.4.2.2.1.1 of ANSI A300 (Part 9)-2011 reads 'When sounding is specified, a mallet or equivalent tool should be used to detect large hollows and loose bark in the trunk, root collar, and above ground buttress roots.' Clause 93.4.2.2.2 says hand tools, trowels, binoculars and probes shall not be precluded from a Level 2, which permits them rather than requiring them.

Does any California regulation require a particular level of tree risk assessment?

No. CAL FIRE's Power Line Fire Prevention Field Guide gives utilities the option of following the ANSI A300 tree risk assessment standard per their field conditions and needs. The level therefore comes from the scope of work, which clause 93.4.1 of A300 Part 9 requires to specify it. PG&E's TD-7102P-01, Revision 4, effective November 15, 2025, sets a Level 1 inspection for its Standard work category and a Level 2 on every Strike Tree for its Elevated work category.

What qualification does a utility require for a tree risk assessment?

It varies by utility, because no California rule names one. PG&E's Revision 4 lists 'Certified Arborist-Tree Risk Assessment Qualification (TRAQ)' as the minimum qualification for its Elevated work category. ISA's own program guide states that the TRAQ credential is valid for seven years and that ISA qualifications 'do not represent licensure, registration, or other authorization to practice.'

Who orders a Level 3 assessment?

The owner. Clause 93.6.4.1 puts it plainly: it shall be the responsibility of the owner, the owner's agent, or the controlling authority to schedule repeat or advanced assessments, determine actions, and implement follow-up recommendations, monitoring, or mitigation. The inspector recommends the advanced assessment and records the recommendation. Scheduling it is the utility's move.