Collisions

Biological Factors Environmental Factors Engineering Factors Minimization

Birds can exist near power lines without significant risk of collision Problems occur in specific, localized situations where certain biological, environmental or engineering factors create a higher risk • Collision is:

– Caused by a bird running into a power line or overhead shield wire • Injury or mortality due to impact with the line, or impact with the ground after

striking the line – Collision-electrocution

• Caused by a bird flying into a power line conductor and going phase to phase – Collisions typically occur near the center of the conductor span, but can

occur anywhere along the length of the wires

Collisions

• Avian Vision – Very different between species

• Age and Sex – Less experience or distraction

• Body Size – Large, heavy-bodied birds have

decreased maneuverability

• Behavior – Interactions within or between

species

• Flocking – Reduced ability to see obstacles

• Disease or Injury – Decreased reaction time

Biological Factors

American white pelican

Forster’s tern

• Habitat – Lines bisecting use areas

• Land Use – Management practices

• Flight Altitude – Low daily flights

• Time of Day – Nocturnal movements

• Topography – Navigation

Environmental Factors

• Disturbance – Activity near lines

• Weather – Reduced visibility – Wind

Environmental Factors

Note: transmission line hidden in fog

• Conductor Diameters – Thinner wire = less visible

• Line Configuration – Vertical vs. Horizontal Design

• Structure Design – Shared ROW, Visibility of poles

Engineering Factors

Shield wires

Energized conductors

• Lack evidence of electrocution • Location of carcass

– Physics equation velocity, angle, height

• Specific pattern of injury – Linear indentations in feather and tissue – Linear lacerations – Unilateral broken bones

• Primarily wings, furcula, coracoid, and/or sternum – Deep tissue bruising – Decapitation – Secondary injuries from falling from flight

• Ruptured mesenteries, broken legs, skull fractures • Evidence of scavenging

*MBTA Protections* – Permit or oversight from Law Enforcement Officer needed before handling birds

Evidence of Collision

• Route Selection for New Lines – Co-location with existing lines – Consider habitat, bird use areas, land

use, structure design, etc., when siting new lines to avoid collision risks

– Use vegetation, topography, or man-made structures to shield lines (consult with engineers & foresters to prevent line maintenance and reliability problems due to trees)

Collision Minimization

• Habitat and land use modification for existing lines – Very difficult due to nature of ROW “ownership” – Modify habitats near power lines to reduce attractiveness to birds

• Work with land owners on crop rotations, haying, grazing, etc.

– Modify land use to minimize human activity and disturbance near lines • Decreased access to roads, development of educational materials (company and

public), signage

Collision Minimization

• Marking lines – Purpose is to increase the visibility of the line – Varying effectiveness in different studies – May decrease but not eliminate collision risks

Collision Minimization

• Static Devices – Aviation marker balls – Coils on wire

• Dynamic Devices – Clamp-on – Hanging

• Conductor Diameter – Bundled conductor – Covered conductor

Types of Marking Devices

• Pros – 40-90% Reduction – Low maintenance – Durable – Injectable color – Minimal human visibility

Static Devices

• Cons – Labor intensive to install – Possible wind or ice loading

issues – Minimal human visibility – Cannot be used on voltages

over 230 kV

• Pros – 60-90% Reduction – Hot stick installation – Incorporate movement – Some glow-in-the-dark – High human visibility

Dynamic Devices

• Cons – Moving parts shorten

durability on some products – High human visibility – Cannot be used on voltages

over 230 kV – May void warranty on

OPGW

• Pros – Permanent installation – No added equipment – Increased reliability – Can help with brush-by contact

(trees or mid-span electrocution)

– Useful at higher voltages

Conductor Diameter

• Cons – Unpublished Reduction – Covered conductor may

require re-conductoring – May alter structure type – May not be considered by

regulatory agencies as minimization

• Static or Conductor? – Voltage – Target species

• Spacing – Staggered – In-line

• Accessibility – Conductor height – Site conditions under line

Device Installation Considerations

• Wind and ice loading • Weight

– Stagger products on alternating lines

• Colors may fade – Unknown if this impacts effectiveness

• Vandalism • Durability • Ease of installation • Effectiveness

• View shed concerns • Voltage rating of product

Additional Considerations When Marking Lines

Line markers reduce but do not eliminate collision risk! • Land Uses or Changes

– Work with land owners and agency folks to minimize proposed land uses or changes that are incompatible with existing power lines

• Identified Problematic Lines – Repeat offenders may need to be relocated or reconfigured

• Burying Lines – Cost increases and feasibility decreases as voltages increase – Requires specific polyethylene cables (or oil filled conduits), splice vaults, trenches, specialized backfill, and the ability to rip it all back up to fix any issues – More details in the Construction section

Collision Reduction

• Sage-grouse and Interstate Transmission Line Siting – Avoidance, predation and habitat fragmentation research – Development of interim BMPs

• Whooping Cranes and Interstate Transmission Lines – Collision risk assessments

• Prairie Chickens and Energy Development – Possible listing, avoidance and habitat fragmentation research

• Transmission construction - new – Siting, design, BMPs and avoidance

• Final Eagle Take Permit Rule – Guidance for compensatory mitigation and pole retrofit

Emerging Siting and Collision Issues