Issue with thread imnplementation in c#

Question

I have a windows service which initaits a thread in every minute and that thread inisiate a 10 pool of threads in a thread pool.  I am sure with in a span of 1 minute all threads in child thread will get over. But memory used by thread is not realesed so after few minutes in task magaer if you see this particular service will be using memory. Is there any of managing memory while using a thread pool or threads. Mainly I will be thankful if you suggest a way to clear memory used by a thread. I have used gccollect gc.WaitForPendingFinalizers etc but as new threads created memory usage all increses. Please suugest a method to deacrease memory usge