Follow the road until you come to a Combine checkpoint. Head back to your car and carry on along the grass until you can rejoin the road. Alternatively, you can avoid all of the mines if you use the gravity gun to pick up the supply from a distance. On your way down, a few more will drop out of inaccessible areas of the upper floors, so just get rid of them in the same way.

Knock out some of the sea-facing windows and use the gravity gun to fire them into the ocean to destroy them. Work your way up, but be careful when you reach the prize of some suit batteries and crossbow ammo by the corpse on the top level you will be ambushed by two rollermines that fall through a hole in the ceiling. Kill the two soldiers, and go around the back to enter the house via a large hole in the back wall. When you get to the overturned truck and boxes just ignore it and drive off onto the grass on the right, and follow this along to the house at the end.