Diesel Drain is a shrinker - that is, a drain that gets smaller and smaller as you head upstream from the outfall, with no infall or anything else to signify the "end". Shrinkers are usually less fun to explore because of this, unless they are very long or have lots of cool features.

Diesel Drain is LONG for a Virginia drain! It covers a large part of Roanoke, running for it's whole length underneath a major roadway (the drain got its name from the diesel exhaust drifting in from above). I covered roughly two miles underground, stopping only when the tunnel height dropped below 6'.

The outfall is a trio of 7'x7' box-section concrete tunnel. The water is knee deep here, but this is just backwater from the creek, so most of the drain is pretty dry. Soon after the water gets shallow, there is a large junction room where you can switch from one tunnel to another. Soon after this, there is a second junction room. The second junction room is odd, in that the left-most tunnel (facing upstream) is inaccessible due to a 6' wall. From this room, the right tunnel separates from the other two, eventually transitioning to (very dry) round concrete pipe.

Back at the second junction room, a walk down the middle tunnel eventually leads to a transition to 8'x6' box tunnel, where the left tunnel joins back in. This tunnel soon curves to the right, and the transitions to the rarest of storm drain features... a pair of over/under pipes! I'd never seen stacked pipes like this before, and (although this is where my exploration came to an end) these pipes seem to run for a long ways like this. Very cool.

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