You wouldn’t know it by this image, but, yes, this is a wastewater settling pond. The wetlands treatment facility is located in Petaluma near the Petaluma river. Besides providing sanctuary for all kinds of creatures, there are 200+ acres with hiking and biking trails to be enjoyed by the public.
This is a view of the river from the hiking trails.
Lens: Canon EF 24-105mm f/4L.
Canon 5DM3 out for a walk.