You are dropped off by a friendly rescuerer at this location. He can't get closer to the bridge, but he believes that you should be able to reach it from this location.
There are a set of weapons prepared for you as well. You have a choice between a submachine gun (either supressed or regular) or a shotgun. You will also need to collect a medikit as well.
To the street
The first half of the map is strictly linear.
Head up the ramp to the exit of the waterfront, and head to the right. The first road you encounter will have zombies both to the left and right. The exit is the small opening on the opposite side of the street, where you will likely see the first special infected.
The next street has trucks providing cover for the area, as well as a ramp to a second-floor window (where you can collect a new weapon, or a melee weapon). Continue down the street and turn down to the right.
You can optionally run to the end of the street to collect either a magnum or a second pistol.
To the safehouse
From here, you have two paths to the next room; some of which may be unavailable depending on the AI director. The first is mid-way through the street, just after the bar, and the second is near the end of the street before the park's barricade.
In the back yard, go through the door and the kitchen (where you can resupply as well.) Watch your fire as you approach the front of the building; one of the car alarms is still active.
Head to the safehouse to complete the level.