I've created a Nintex workflow on a list and it is triggered whenever a new item is created.  Once the workflow reaches a state machine action item, it then applies a schedule to a site workflow and that site workflow is only meant to run once.  The site workflow is used to delegate the list workflow task if the approver doesn't respond to the task after 24 hours.  I didn't use the built-in delegation feature of the Flexi-task because the Flexi-task is being shared (variables are used to assign the task) and only one person in the workflow will have his task delegated.  This is just a background explanation so that you understand why I'm using a site workflow for delegation purposes.  

As a result of this design, I would imagine that the site workflow scheduling page will get rather full and to clean it up manually will be time consuming.

Is there any PowerShell script that can be used to delete schedules where "Next Run" is equal to "Schedule finished" and "Repeat Sequence" is equal to "Run once"?  My searches for this haven't been successful.  Can the workflow schedules be accessed using PowerShell?  Any help would be much appreciated!