Quiet the Cannons (Horde)

Objectives
Destroy 8 Holdfast Cannons.
 * s destroyed x8

Description
Now it's time to do something about those darn cannons up on the bluffs to the east!

If you'd be so kind, hop into your boat and cruise on over to the Southsea Holdfast. Up top you'll see a bunch of cannons firing down on us.

Those pirates don't know squat about engineering. It shouldn't be too difficult for you to clog 'em up and make them explode.

Rewards
You will receive:

Progress
Oh, I don't know, you might want to destroy a few more of those cannons at the pirate holdfast.

What do you think?

Completion
They're still shooting, but not nearly as much! Yeeeeeeeeeaaaaaaaaah!