Although I've only dealt with Cascade Pest Control over yellowjackets in the past, I can say that they seem so very knowledgeable and helpful both in person and in the information they provide on their website (about a variety of pests, including carpenter ants) that they would be the first ones I'd turn to for any sort of infestation.
When we first moved into our home, we had recurring issues with yellowjackets. We hired one exterminator who was good but then when the yellowjackets came back again the following year, I couldn't remember who we'd hired the first time so we brought in Cascade Pest Control.
This guy was also very good and got rid of the wasps very effectively. On top of that, they offered a guarantee that if we had another infestation that season, they'd come back and take care of it for free. What made him great in my mind was that when we had to have him back again the following year, he not only got rid of the infestation but he pointed out all the open spots around the outside of the house where the wasps were finding to get in and nest. He suggested that if we caulked all those up, he wouldn't have to come back out again the next year as well. We did and haven't needed to hire them since.
At every stage, he explained what he was doing and why and what I should look for over the course of the following weeks to ensure that the infestation really had been eradicated. I like someone who will take care of the things that I want or need to have someone else do but will still take the time to keep me informed so that I don't feel left in the dark about the process.
In the case of recurring carpenter ant infestations, it sounds like (from the CPC website) understanding where the REAL nest is located is the key to fully eradicating these pests. If past performance with understanding the nuances of behavior of other sorts of pests is any indicator, I'd say these guys should be pretty good in dealing with any types of unwanted critters they set out to control and are worth a call.
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