The following is a list of pipeline accidents in the United States in the 21st century. It is one of several lists of U…en.wikipedia.org
I think this list is a good start. I don’t know how you would determine “frequently”, either as a function of miles of pipe or time.
For more periods of time:
This List of pipeline accidents in the United States provides access to links for various timeframes, which are…en.wikipedia.org
This link below also provides some useful information, although it’s an old post and some of the links are broken:
Forgive me for wondering , but if there is going to be Fracking which is known to cause earthquakes and all the other…www.foreffectivegov.org
One of the key points is the number of pipeline inspectors for every mile of pipeline.
Even though older pipes are more likely to break/leak, it’s the potential for disaster that makes any pipeline dangerous.