This small valve cover sits amidst a small cluster of Catskills manholes and valve access 'chimney' covers on Myrtle Ave at the foot of the hill in Ft Greene Park. This is the point that the Catskills Aqueduct officially ended, and was the distribution point for mains heading north to Queens and South and East to cross the Narrows to Silver Lake Park on Staten Island, as well as local areas in Brooklyn.
By 1915 or so when this part of the aqueduct was completed the small 10" square valve cover was fairly standardized in the city. The Catskill Aqueduct engineers continued there somewhat obsessive identification of the purpose of each node.
Obviously, this access point is for controlling the valves of the bypass....he says with confidence.
This cover is on Myrtle Ave near N. Portland St. in Brooklyn. Others are seen mostly in Brookyn. A larger, manhole size cover is found in Bushwick (see below)