ansi a300 part 9 - isatexas.com · reality bites puget sound energy, 1998 – 2007 34,000+...
TRANSCRIPT
Michael Sultan Davey Resource Group
in a utility world…
ANSI A300 Part 9:
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2012
Reality Bites
Puget Sound Energy, 1998 – 2007
34,000+ tree-caused outages
Trees were primary cause of unplanned
service interruptions
95% due to tree failure
From Arboriculture & Urban Forestry July 2011. 37(4): 147 - 151
Key Points
What is ANSI A300 (Part 9)?
How does it relate to IVM?
How does it apply to utilities?
ANSI Standard A300 Tree Risk
Assessment - Part 9
a. Tree Structure Assessment
Tree Structure
Tree Risk
Residual Risk
ANSI Standard A300 Tree Risk
Assessment - Best Management Practices
What about Tree Structure?
Defects
+
Architecture
+
Loads
Failure occurs when load exceeds strength
Types of Failures:
Entire tree failure (uprooting)
Trunk failure
Branch failure
Loads on Trees:
Gravity
Self weight
Rain, snow, ice
Other (e.g. climbers, rigging)
Wind
Force (dynamic)
Direction
Forces affecting trees…
M D
F
Tension Shear
Compression Torsion
What is RISK?
Probability + Consequences
Likelihood of Failure and Impacting a Target
Very Low Low Medium High
Imminent UnlikelySomewhat
LikelyLikely Very Likely
Probably Unlikely UnlikelySomewhat
LikelyLikely
Possible Unlikely Unlikely UnlikelySomewhat
Likely
Improbable Unlikely Unlikely Unlikely Unlikely
Likelihood of Impacting TargetLikelihood
of
Failure
- Table 1 -
Risk Rating Matrix (utilizing results of table 1)
Negligible Minor Significant Severe
Very Likely Low Moderate High Extreme
Likely Low Moderate High High
Somewhat
LikelyLow Low Moderate Moderate
Unlikely Low Low Low Low
Consequences of Failure
Likelihood
of
Failure and
Impact
- Table 2 -
ANSI Standard A300 Integrated Vegetation
Management - Part 7
a. Electric Utility Rights-of-way
Danger Tree
Hazard Tree
Tree Pruning and Removal
Trees and tree branches with the
potential to affect utility facilities should
be monitored for risk, and pruned or
removed as appropriate (refer to ANSI
A300 Part 9, Tree Risk Assessment).
Can we predict what will happen?
Species Specific Failure Data
+
Wind and Storm Data
+
Site and Forest Conditions
What does it all mean?
Management v Maintenance
Management
Maintenance
Time
Cost
C O M M U N I C A T E
E D U C A T E
+
What we’ve covered…
ANSI A300 (Part 9)
How it relates to IVM?
How it applies to utilities?
