ansi a300 part 9 - isatexas.com · reality bites puget sound energy, 1998 – 2007 34,000+...

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?

Michael Sultan Davey Resource Group

214 . 605 . 2660

Michael.Sultan@davey.com