In Arknights: Endfield, the subquest “Go to the second site to gather soil samples” is part of the Outpost: Reconstruction HQ quest. Your goal is to go to the conveyer belt, wait for the harmful gasses to stop before making your way through them, and reach the soil samples to gather them. Here’s how to go about it.
Location
The location for this quest is near Old Dorms, Originium Power Plant, Power Plateau.

How to go to the second site and gather soil samples
Step 1
Go to the conveyer belt.

Step 2
Here, you’ll have gasses jetting out. Wait for them to stop for a while.

Step 3
Then go through the gap.

Step 4
Get off the belt and go to the small opening on the right.

Step 5
Then hop on the second belt and go up.

Step 6
Again, wait for the gasses to stop before moving ahead. Go to your right.

Step 7
Straight ahead, you’ll find the heap of soil.

Step 8
Interact with it to gather the soil samples.

Step 9
Once done, you’ll be able to move ahead to the next marked subquest.
Rewards
The rewards for the main mission – Outpost: Reconstruction HQ quest – are as follows:
- Oroberyl – x50
- Operational EXP – x200
And that is how you can get to the second site and gather soil samples for the Outpost: Reconstruction HQ quest in Arknights: Endfield. Until next time!