From SFBC:

The Sewer Ride returns! Join this above-ground, member-led biking tour of the San Francisco sewer system. This year we search for the erased sand dunes and buried creeks of early San Francisco, to better understand just how much our landscape has been altered in the last 160 years.
Tour returns to Workspace for a rousing ArtParty (7-10pm), with music, beverage, popcorn, and a chance to mingle, discuss the sewer issues of our day, and use the bathroom.
SF Bicycle Coalition recreational rides are free for SFBC members (a $5 donation from non-members is appreciated); rain cancels rides.RSVP Questions? miles@milesepstein.com