Kingsbury Creek starts at beautiful Mogie Lake, runs through the railyards of Proctor, and then heads downhill into the St. Louis River estuary, passing several other caches along the way. It's the creek that flooded the zoo in 2012, allowing a seal to escape; the seal later made headlines for swimming down Grand Avenue.
The flood proved that storm water is a big deal, everything around here eventually drains to the lake. This particular culvert system is designed to handle larger flows and allow fish passage, a good example of stormwater engineering. And of course, a great place to hide a cache :).