Pine Heights is the first region you explore after The Meadows. The mission “Restore Pine Heights” involves clearing the region of Noxious Slime. This is a red mucus that is difficult to confuse with anything else.
To remove it, you will need the Irrigation Hose tool. Direct a stream of water at the mucus and it will gradually disappear.
Please note that the water in the tank is limited. You can replenish the water supply using the Vacuum Harvester tool in any body of water.
Once you reach 100% progress, all remaining slime will disappear on its own and the region will be considered restored.