Windows Workflow Runtime leaks a ton of memory-Collection of common programming errors

Here’s a overview of my workflow implementation:

• GUI thread starts worker thread
• worker thread analyzes some data
• worker thread starts several other worker threads to work on subsets of data
• each of these last worker threads creates a workflow runtime and executes a sequential workflow

Up until now, I’ve been creating a new WorkflowRuntime object in each thread like this:

  using( WorkflowRuntime workflow_runtime = new WorkflowRuntime()) {
      AutoResetEvent waitHandle = new AutoResetEvent(false);
      workflow_runtime.WorkflowCompleted += delegate(object sender, WorkflowCompletedEventArgs e) {waitHandle.Set();};
      workflow_runtime.WorkflowTerminated += delegate(object sender, WorkflowTerminatedEventArgs e)
      {
          Console.WriteLine(e.Exception.Message);
          waitHandle.Set();
      };

      WorkflowInstance instance = workflow_runtime.CreateWorkflow(typeof(MyWorkflow), parameters);
      instance.Start();
      waitHandle.WaitOne();
}

The reason for doing it this way is that I need to know when a specific workflow instance has been terminated or errored. The problem is that it causes a huge memory leak in my application, as mentioned here on SO.

If I use the using keyword, or even if I call Dispose and set the workflow_runtime reference to null, I get a massive memory leak. However, if I implement the workflow runtime as a Singleton, as described in this post, memory usage is very low and consistent. I can see when workflows are launched and completed by blips in the graph.

The problem is, if I use the Singleton pattern for the WF runtime, how will I know when a specific workflow has an error? If I just register the event handlers, won’t all of them get called when any of the workflows get terminated or completed?

EDIT: should I just use another handle on the stack for errors, and then wait for either to be set, and then check which one was set? I should have considered that before.