When you get closer the soldiers will attack you again. Kill them all.
Then walk up the hill and get inside the building. The one with a red barrel next to it.
Alyx will notice that there is a shield generator inside. Turn right and walk to the wall. To the left you will see a control panel.
Alyx will be able to shut off the shield. However, when you walk to the main room, there will be some kind of malfunction and the shield will turn on again. You will have to figure something out to get rid of it.
Get to the ride side of the room. Remove a padlock that blocks the ladder. Then, climb up.
When you're there, head left. Watch out for headcrabs. You will get to a pipe. Use it to get to the other side.
Jump in to a room with guns and replenish your supplies if you have to.
Turn around. To the right there will be an entrance to the room with shield generator. Crawl in.
Stand next to the door and shoot at the generator with the gravity gun. The beam will turn into a ball. Shoot at it so it doesn't have a chance to transform again. After a while it will disappear and the shield will be turned off. Open the door and get back to the car with Alyx.
Drive straight. You will get to a roadblock. Turn left on a slope. Use the break to control the speed.
Then turn left and drive under a fallen tree. Keep going until you get to a tunnel.
When you drive out of the tunnel you will hear a stider. Luckily it won't be there. Get to a sign and turn left.
You will drive into the river. Head towards a dam. When you're there, get out of the car and go up the stairs to the left.
A strider will show up.
You won't have to fight with it because Dog will take it down.
Dog will open the gate for you. Get back to the car and race with Dog to the base. If you're first, you will achieve one of the goals.
When your in the base, get out of the car and follow Alyx.