Rick,
I tested and had very high levels (around 38, compared to a recommended limit of no more than 4).
The mitigation system was installed by SWAT Enterprises. The people that did it are from Derry.
Go to swat-radon.com to get more information.
What I found was that almost all of the companies are about the same price but how they install the system depends on where the pipes are in your house.
Brian