2 main irrigation shutoff valves?

Hello, I have a 20+ year old house with everything RAINBIRD. I'm having trouble turning on the water after the system was winterized (first time trying this).

I have 3 zones with 3 antisiphon valves (1 foot underground) and a backflow preventer (above ground). It looks like I have 2 main shutoff valves for the irrigation system (both of these valves are 4 feet deep). I opened 1 valve and the other 4 foot deep valve hole filled up and pours out water. How do I dewinterize this system? What is the idea behind having these 2 main shutoff valves? The main line shutoff valve is at the street (which of course is always on).

Thanks

Well looks like the main irrigation shutoff valves are right before the PVB (pressure vacuum breaker) and then right after it. What is the sequence for turning on the water without the water filling and pouring out of the main irrigation shutoff valve after the PVB backflow preventer? Never thought it was going to be this complicated.

LOL, well I figured it out myself. The valve after the PVB (pressure vacuum breaker) was actually a drain valve (hence water filling up tube), so all I had to do was turn it clockwise (shut) and all is working great. GEEZ that took forever to figure out something so simple.

The best person to start up your irrigation system is the person who winterized it. Usually......