Please follow these instructions for removing a synced calendar from your iCal (Apple Calendar):
1. Open your iCal on your computer
2. On the left side of your calendar window you should see your synced calendars under "Other". If you do not see this please select "Calendars" at the top of your calendar and the side bar with the list of calendars will appear
3. Please right click over the calendar you wish to remove. You can also place your mouse over the name hold down the "control" key on your computer and then click
4. A pop-up window will appear, please select "Unsubscribe"
Please see video for visual instructions: