Puzzle:Underground Water Treatment Plant

Fixing the plant will give you another Achievement ("Reserve : Supply the city with fresh water")

After escaping the fire, you will enter the plant and on the monitor you can see its initial state:

Turn off the 4 big flocculation pool pumps:

While the alarm still sounds, open all orange card doors (one will not open):

In the locker room you will find a green access card:

On the first floor, in the men's toilet, is a yellow access card. Do not flush the toilet, or you'll have to restart the map:

Stop the alarm.

Go to the second floor, to the control room and access it:

On the desk, yo will find the correct water flow and the water plant key:

Find this place and go to the hidden valve room using this path:

Open the valve of SEWER PIPE 03:

Find and unlock the raw water pool door:

And open RAW WATER to COAGULATION valve:

So far the screen must look like this:

Find the Flocculation start button and push it to start:

And the screen must look like this now:

On the floor, where are the 4 pumps there is a grey door to raw water. Unlock it and exit through it:

There are two red handles, one is in the sedimentation room, the other is at the end of the tunnel. Find one of them and grab it:

Find "sewer pipes 01 and 02" shed and enter it:

Mount the handle and open the valve:

Turn around and activate the pump:

Find Sewer pipe 02 and open the valve:

Go to the Sedimentation room and open valve 3 (all must be open):

Locate the hatch (near the shed entrance) and enter it:

Inside, open the Flocculation -> Sedimentation valve:

If you done everything correct, the screen will look like this:

Finally, exit with the minitrain:

Enjoy :)