What Did They Do With the Dirt?

I was wondering: what did Hamas do with all the dirt they dug out of the ground?

A friend sent me to the La Manche Tunnel experience:

On the UK side, of the expected 5 million cubic metres (6.5×10⁶ cu yd) of spoil, approximately 1 million cubic metres (1.3×10⁶ cu yd) was used for fill at the terminal site, and the remainder was deposited at Lower Shakespeare Cliff behind a seawall, reclaiming 74 acres (30 ha) of land. This land was then made into the Samphire Hoe Country Park. 

In Gaza, they could have extended themselves seawards and enabled better living conditions.

Oh, well.

^