Hey everyone.

I have been considering for years to enter a drain. In fact it is a small stream starting from the nearby mountain (right), continuing between houses with some open spaces for a while (circles), and goes underground for about 1 km (line). Then it is open again. In the summer the water is too little and I consider going in then.

I have some safety concerns:

1) In the completely underground part, could the air be hazardous? The water may not come only from the mountain, but also from buildings, as in the summer, the open part after the underground smells somewhat off. Could the oxygen decrease dangerously? Could these and other things I might not have thought of, be very dangerous for just 1 km?

2) At open spaces between houses I am afraid I will end up in someones property.

Do you have any advice?

How large is the tunnel?

Are there any curtains or other structures blocking airflow or is it all open-air and free-flowing?

You might be best off scouting the length off the tunnel from aboveground; maybe sharing some photos of what you see will help assess any risks.

I came back with some photos. There are 3 openings next to each other. In the past there was only one. I believe and I have indications that the route I need to follow is that in the middle, but I cannot be sure. It is as wide as it seems. I captured only the one end, but the other end is similarly big. The length is 1km (=0,62 miles).

It's hard to tell how big the drain is, but you said "big" so I would think the air would be fine.

Just make sure the weather is fine for the whole catchment, not just where the actual drain is. Most drain deaths happen in summer where it started off sunny - when it rains, no drains.

Regarding the private property - can you just walk through the property along the waterway? Maybe just walk back if it seems too dodgy?

These are just suggestions - there are no guarantees when going places that aren't made for people.

Good luck.

Thank you,
I found out that last year an event about walking through this had happened (leaded by an expert) , so I have one more indication that it will be fine.

I stick to tunnels with airflow. This gives a good indication of airflow.

Storm drains usually lie on property lines. Usually. Go during the day, don't lurk near people's stuff, and you're usually fine.

Also watch for homeless people.

That's an awesome drain picture you have here! I would say that tunnel is a 11 foot or 12 foot arch. It looks very similar to some of the drains we have in MSP. Nice job! Keep it the great work!