# Presentation: 313545

## HAZARD TREE SAFETY ASSESSMENT

**       ****Version 03-20-2006**

##         A HAZARD TREE

**...is any tree (regardless of its size) that is hazardous to people or property because of:**
**• ****location or lean **
**• ****physical damage**
**• ****overhead hazards**
**• ****deterioration of limbs, stem or root system**
**• ****a combination of above.**

**Notes:**

Exposure is not limited to the active work area, but also includes the perimeter of the work (within 1 tree length or greater depending on site factors such as slope), as well as other locations such as rest areas and staging areas.

## Tree Class ComparisonLive Dead Conifers 1 2 3 4 5 6 7 8 9 

**Notes:**
TREE Class Comparison for Conifers And Hardwood Trees
The following tree decay class diagrams illustrate the general breakage and decay patterns seen in coniferous and deciduous trees. The six step hardwood classification system (broad-leaved deciduous trees) is parallel to the coniferous scheme, but is more accelerated in the middle and latter classes. Both systems are used in this workbook to provide information for rating trees for defect failure potential

##       TREE Class Comparison                     Hardwoods 2 3 4 5 6

##   RISK = HAZARD x EXPOSURE

**The procedures for determining whether a tree is dangerous to workers under various levels of disturbance, and the appropriate steps and safety procedures for mitigating the hazard.**

**Notes:**
Consider the following simple equation which illustrates the relationship between risk, tree haz­ard or condition and exposure (i.e. work activity or location)
RISK = HAZARD X EXPOSURE
The procedures for determining whether a tree is dangerous to workers under various levels of disturbance, and the appropriate steps and safety procedures for mitigating the hazard, are de­scribed in the following sections. 
When To Conduct  Visual  tree inspections (also refer to Steps 1–5 on the following pages)
• at the time of the initial on-the-ground fire assessment
• prior to any workers entering the area to commence on-the-ground fire suppression
• if, since the previous assessment, BUI values are above thresholds AND there is continuous burning within the area of work
• if more than three days with continuous burning have passed since the previous assessment
• if work activity in the area creates more disturbance than what the area was originally assessed for 
• conduct tree inspections to the highest disturbance level (i.e., work activity) you expect to attain on site
• tree inspections need only be conducted on trees which are visually “suspect” (i.e., they are damaged or potentially dangerous).
Determining tree danger rating
There are five steps required to determine tree danger rating:
Step 1 Determine level of ground or tree disturbance [1, 2 , 3, 4] and type of work Activity. See Table 1.
Step 2 Conduct site assessment overview. Look for site factors which suggest tree decline or potential tree failure. Refer to Table 2.
Step 3 Conduct visual tree inspection. Assess the tree(s) for visual hazard indicators (see ta­bles 3, 3A and 3B). If the root condition is suspect (i.e., the roots have been burned into, severed or uplifted), a shallow root excavation with a Pulaski may be necessary.
Step 4 Make the appropriate safety decision (either Safe or Dangerous), and implement necessary actions. 
Step 5 Provide Documentation of assessed trees and assessed areas (includes date, location, level of disturbance, marking procedures and how danger trees have been managed). 

## Generalized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree Failure

**Notes:**
Visual Tree Inspection
The determination of tree safety/danger is generally a visual process. Only trees which are consid­ered by a certified assessor to be “suspect” or potentially dangerous after conducting “the site as­sessment overview” need a visual tree inspection. Where visual inspection identifies questionable root stability, the tree would usually be rated as “high defect failure potential,” and be considered dangerous, unless further probing with a hand tool indicates that the roots are sound. Careful observation of potential tree defects and hazards is required (see below for discussion).
Tree Hazards
A tree can be potentially dangerous if it has defects in its top, branches, stem or root system. The degree of hazard will vary with the size of the tree, type and location of the defect, the severity of any damage, the tree species, and nature of the work activity or target. 
The danger tree assessment process requires that assessors identify tree hazards and know how to recognize, evaluate and manage for all types of hazards.

## Generalized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree FailureASSESSING TREE LEAN

**Notes:**
Tree lean may be recent or long-standing. Dead trees and dangerous live trees that are leaning must be assessed for severe root and basal rot. Long-standing lean trees have often subsequently grown a vertical top in the time since the lean occurred. Live lean trees develop tension and compression wood at stress points, to aid in support. They also develop a reinforced root system, where disturbed, to compensate for prior damage. Unless the roots are disturbed further or decay is present, the potential for failure of long-standing leaning trees is low, and such trees need not be considered a hazard. 
Recently-leaning trees are tilted over their entire length. Since there is no evidence of subsequent reinforcement of the root system or bole wood, assessors must as­sume hazard potential.
Assessors should also identify other rooting problems which can compound the ef­fects of high tree lean. These include shallow roots or substrate, burned, damaged or decayed roots and/or lifted roots, burned or disturbed anchoring soil layers, or adjacent history of windthrow.
Leaning trees which are securely lodged in a large sound tree with no chance of breaking free, have negligible lean hazard. Leaning trees in this condition must be evaluated on an individual basis.
Sweep is defined as the curvature or distortion of the stem, and is often associated with competition for sunlight, snowpack and steep slope conditions. Sweep should not be confused with lean. 
Slope is an important determinant of the direction of falling, and how far and with what force a tree will roll or slide after falling. Danger trees falling on slopes may travel farther than the length of the tree.

## Generalized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree FailureASSESSING ROOT CONDITION

**Notes:**
Root condition should be assessed at the root collar (as close to the ground as possible). If visual inspection indicates questionable root stability, then a shallow root excavation and cautious chopping or probing into the roots with a Pulaski or other suitable hand tool should be done to expose the condition of the roots and to determine if the type of scheduled work activity will destabilize the tree.
Trees with >50% of lateral roots damaged, burned or decayed have a HIGH failure potential rating. This condition should not be confused with roots where the soil duff layer has been scraped or burned away—merely exposing the roots, not damaging them.
Watch for root systems which have been severely burned along with the supporting/anchoring soil layer. These “propped” roots can be very unstable.• Trees on shallow soils over bedrock or hardpan, or with high water tables, will have shallow root systems. Also look for root pull and cracked or lifting soil mats. They will become more hazardous over time and should be examined carefully before work commences.• Trees growing in or near areas where root disease is seen to be present are likely to be diseased as well. Watch for stand openings associated with uprooted trees, standing trees with thin or discolored crown foliage (chlorosis), and fruiting bodies of root disease-causing fungi near the base

## Generalized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree Failure4 Significant Hazard Indicators

| 
D =
Dangerous | D if tree has one or more of the following significant tree hazards: 
Insecurely lodged tree 
Hung-up limbs or tops (consider size and height above ground) 
Highly decadent or unstable: i) >50% of tree cross-sectional area damaged, burned, scarred, decayed or fractured; ii) class 4-8 trees with heart rot conks along the majority of the length of the stem; or iii) >50% lateral roots damaged or with advanced decay 
Recent high lean (>15% toward work area) AND damaged root system/anchoring soil layer |
| --- | --- |
| S = Safe | All other trees |

**Notes:**
The qualified person must be sufficiently experienced and/or trained to be able to recognize and ensure workers avoid exposure to the above significant hazards. Crews should be instructed to keep a “heads-up” for any of the 4 significant hazards and to stay away (generally greater than .5 defect lengths) from any trees showing these hazards. However, any trees that the qualified person determines or suspects to be dangerous must be dealt with as follows BEFORE any workers enter that area: 
• have tree's) or hazardous parts removed 
• flag a no-work zone of appropriate size and shape around tree's) and instruct workers to stay out of this area (generally .5 defect lengths in size). 
NOTE: Work crews must also observe wind speed conditions. If wind conditions become strong enough (i.e., winds set whole trees in motion), workers should consider leaving the work area and go to a safe refuge. 

## Generalized Tree Defects or Indicators Which Influence Tree FailureGeneralized Tree Defects or Indicators Which Influence Tree Failure            No-Work Zone (NWZ)

**The size of NWZs is 1.5 times the defect length. This length can be modified (larger or smaller) depending on the site-specific conditions, such as slope or surrounding tree size and condition. The NWZ must be big enough to accommodate the hazard.**

##     No-Work Zone (NWZ) Sound tree, no lean, hazardous top, flat ground 

**Notes:**
Sound tree, no lean, hazardous top, flat ground1. Determine the length of top that might dislodge.2. Add 1⁄2 of this length, to get a 11⁄2 top length distance. This distance is the radius of the no-work zone 
Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.
The size of NWZs is 1.5 times the defect length. This length can be modified (larger or smaller) depending on the site-specific conditions, such as slope or surrounding tree size and condition. The NWZ must be big enough to accommodate the hazard.

##       No-Work Zone (NWZ) Sound tree with lean, hazardous top, on slope

**Notes:**
Sound tree with lean, hazardous top, flat ground1. Determine the length of top that might dislodge.2. Add 1⁄2 of this length, to get a 11⁄2 top length distance.3. Determine from the lean how far from the base of the tree the top might land.

Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.

The size of NWZs is 1.5 times the defect length. This length can be modified (larger or smaller) depending on the site-specific conditions, such as slope or surrounding tree size and condition. The NWZ must be big enough to accommodate the hazard.

##      No-Work Zone (NWZ) Unsound or hazardous tree, no lean, flat ground 

**Notes:**
Unsound or hazardous tree, no lean, flat ground1. Measure the height of the tree.2. The no-work zone is a circle around the tree, with a radius of up to 11⁄2 times the height 

Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.

##                No-Work Zone (NWZ) Sound tree with lean, hazardous top, on slope

**Notes:**

Sound tree with lean, hazardous top, on slope
1. Determine the length of top that might dislodge.
2. Add 1⁄2 of this length, to get a 11⁄2 top length distance (horizontal distance from tree).
3. From the lean, determine how far from the base of the tree the top might land.
4. On slopes >30%, extend the no-work zone downslope. This distance must be determined on a site-specific basis.
Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.
The size of NWZs is 1.5 times the defect length. This length can be modified (larger or smaller) depending on the site-specific conditions, such as slope or surrounding tree size and condition. The NWZ must be big enough to accommodate the hazard.

##                 No-Work Zone (NWZ) Deciduous, sound tree, no lean, defective branches 

**Notes:**

Deciduous, sound tree, no lean, defective branches
1. Determine the length of defective limbs that might dislodge.
2. Add 1⁄2 of this length to get a 11⁄2 limb length distance.
The 11⁄2 limb length distance must be calculated for all defective limbs on the tree.

Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.
The size of NWZs is 1.5 times the defect length. This length can be modified (larger or smaller) depending on the site-specific conditions, such as slope or surrounding tree size and condition. The NWZ must be big enough to accommodate the hazard.

## Delineating Larger no-Work Zone AREASDelineating Larger no-Work Zone AREASDelineating Larger No-Work Safe Zone Areas

**Notes:**
Established (flag perimeter) NWZ when hazard tree can not be safely or promptly removed.
Indicate located on IAP map.

No-work zones will generally only be installed around trees too dangerous to fell. The assessor (line supervisor/safety officer/felling boss/sawyers) should ensure that all no-work zones are easily identifiable in the field, and their locations communicated to workers who may subsequently be in the area.
Once the no-work zone has been calculated by the assessor, the area should be flagged. 
Flagging should be placed at sufficient intervals so that workers will always be able to see the NWZ boundary from any position along its perimeter. When necessary, flag the inside of the no-work zone with a second color tape to indicate the centre. This will indicate the orientation of the NWZ to workers.
For short duration and exposure fire situations (e.g., initial attack) NWZ boundaries must be clearly identified on site and documented. Flagging may not be necessary in these circumstances. No forest worker is allowed to enter the no-work zone except to remove a specific tree hazard to the work area (e.g., sawyer, blaster, or guarded mechanical feller buncher enters zone to remove a dangerous tree along NWZ edge).

## Delineating Larger no-Work Zone AREASDelineating Larger no-Work Zone AREASHazard Trees Along Roadsides

**Notes:**
Dangerous Trees Along Roadsides
Potentially dangerous trees along and within reach of active roads should be assessed accord­ing to the appropriate level of disturbance (i.e., level 1 for light vehicle use and level 2 for heavy vehicle use).
Other factors to consider are:
• amount of lean toward road
• distance from road
• slope toward road
• rooting condition
• any hazardous tree defects (e.g., large dead top) that can reach the road.

## Delineating Larger no-Work Zone AREASDelineating Larger no-Work Zone AREAS         SWAMPER, LOOKOUTS AND OBSERVERS  

**This section will be updated when staff work is completed by June, 2006**

## Delineating Larger no-Work Zone AREASDelineating Larger no-Work Zone AREASHAZARD TREE SAFETY ASSESSMENT