The C# driver opens and closes a connection every 10 seconds to ping the health of the server(s) it is connected to. It does this so that pinging the server is not dependent on a connection being available in the connection pool. The bad thing is that it causes lots of noise in the server logs about connections opening and closing.

A better solution would be to open a connection and keep reusing it. This would be a dedicated connection for pinging and would never be put in the connection pool.