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Environmentally progressive utility uses copper naphthenate treated poles exclusively.
Nisus Corporation

Seattle City Light, a utility owned by the city of Seattle, has been in operation since 1905 and is considered the nation’s greenest utility.  We interviewed Larry Garcia, Senior Environmental Analyst at Seattle City Light, on their use of copper naphthenate treated utility poles.


Q: How large is the service area of Seattle City Light?

A: We serve over 775,000 people in Seattle and the surrounding area.

Q: What were the factors that impacted your decision to start using copper naphthenate? 

A: First of all we look at products that work. The products must be AWPA (American Wood Protection Association) standardized for inground use in our climate zone.

The city of Seattle has a policy on persistent, bioaccumulative toxins (PBTs) that calls out pentachlorophenol specifically. Penta has chlorinated dioxins as a contaminant and they are clearly PBTs.  CCA also qualifies as a PBT. The policy is to avoid PBTs if there is any alternative. 

Larry Garcia

Senior Environmental Analyst

Creosote is an option, but it is very unpleasant for line workers to climb. This leaves ACQ, CA, and CuNap as potential pole treatment chemicals.  Water-based coatings result in a very hard pole. Our workers seem to prefer an oily pole to a pole that is physically hard and more difficult/hazardous to climb. The azoles in CA are problematic.  The EU has them listed as potential endocrine disruptors, and some are regulated.

CuNap is not a restricted use pesticide. From an environmental perspective, ACQ and CuNap are the preferred options.  CuNap with an oil carrier was selected due to pole hardness issues like climbability and gaff penetration.

Q: What % of the poles you are currently purchasing is treated with copper naphthenate? 

A: 100%

Q: What % of the total poles in service for Seattle City Light is treated with copper naphthenate? 

A: It is certainly less than 50%, but I don’t know for sure.  We still have penta and creosote poles dating back to the 1920s. 

Q: How long has Seattle City Light been using CuNap poles and how would you classify their performance?

A: We have been using them for 20 years.  The performance of the CuNap-treated poles seems to be comparable to penta treated poles.

Q: Have you ever had a premature failure of a copper naphthenate treated pole? 

A:  Not any due to treatment issues or premature decay. We have had to replace CuNap poles due to car accidents and landslides.

Q: Do customers or the general public ever question utility pole treatment methods?

A: Most of our customers have no idea how a pole is treated. Occasionally people will inquire and they are happy to hear we are using copper naphthenate.

Q: What message regarding copper naphthenate poles would you give to the rest of the utility industry? 

A: It is a reliable treatment method.  I think it is clearly the best choice for us.

Nisus Preservation News

Nisus Corporation

Ken Laughlin

Divisional Vice President, Wood Preservation