Russ Madsen discovered, while helping with 96F-14, that the finest sand gathered around the joints in this storm drain pipe. Since then I've learned that this is rare; most of the time the sand is uniform. Still, it pays to check and sometimes I find very good sand in a deep deposit around the joints.

The image above shows the storm drain pipe leading southwest to the breakwater. You can see the Madsen Point annuli, with my delvings below them.

The image below shows details. The concrete annulus covers a joint in the cast concrete pipe. The partial ring at the bottom of the image is the imprint of a bucket that has been loaded and hauled off.