Hi Friends! This drain is right in front of the entrance to our basement-level garage, at the bottom of a ramp leading down to it. Heavy rain makes it overflow, even with the grate off (I know it needs to be cleaned).
There's about six inches of loose silt in the bottom, but I think maybe that pipe is a siphon that drains off the water? I put a probe in there and it's clear, and I can't feel anything else digging with a shovel.
Any suggestions for improving the flow?
Depends on the box, it could be gravel underneath but it I would bet is a solid concrete box with pipes coming in at the top and a drain pipe below that is supposed to take all the water away. Once you clear it out you will see what you are dealing with. The similar setup at my house has 3 perimeter drain lines coming in, and one drain line that goes to the street sewer. Every house is difficult. Take a picture when you have it cleaned out so you can refer back to it next time.