Now finished in 25 minutes, without secret areas.
I found two places where the player can get stuck. You can walk along the wire to the light poles, then you can land on the open gate, then you can fall between the alarm guard station (small, red and white) and the gate.
Second place you can get stuck is on the rail line, all the way at the end, by the house where there is a guard inside. Jump on the bumper (buffer stop) and you get stuck between it and the flatbed rail car.
I suggest you add clip brushes in these two places to stop the player from falling in and getting stuck.