After speaking with Dirk at the Oxford base, we need to head to the water bottling plant. This is indicated with the objective marker. When you arrive, walk up to the indicated valve and turn it to lower the water level slightly.

Now we need to grind up the newly revealed pipe, melee attacking the three valves along the way. When you reach the end of the pipe, use the fan to launch up to the next area, and then use one of the vents up here to perform a ground slam on a button in the centre of the roof for a scene.

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Interact with the valve (left) and then grind up the passage (right) and smack all the red valves as you go.

This will lower the water level further and reveal another emergency stop valve below. Make your way down to this and interact with it to reveal a second route along pipes leading to another rooftop button. Again, follow the path shown in the brief scene, hit the three valves as you go past and then ground pound the button on the roof to once again lower the water level.

Hop down to the newly revealed third valve and approach it. As you do, the objective marker on it will disappear and instead you’ll have to fight some OD. Run over to the buildings where they are attacking from to meet a new enemy type – the Spawner. These guys are heavily armoured and will continuously spawn regular OD enemies until defeated. You will want to use the buildings here and the wires strung up between them to keep moving whilst focusing your fire on the Spawner. Once the Spawner goes down, the rest will quickly follow.

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Repeat the valve interaction and grind process a second time (left). Destroy the Spawner that appears (right) during the third valve sequence.

Return to the third valve and interact with it and for the final time grind up the path shown, knock out the three valves along the way and hit the pressure pad on the roof.

This will drain the water completely. Drop down to the ground, interact with the highlighted panel and grab the water from inside the nearby shutter. Run the water back to the Oxford Base to complete the mission.