Go to (718, 1860). There is a large rock with a dirt path just to the right of it. Run around the rock and follow the path past the back through the rocks, past the "Aging Bormu", to the Datacron.

The entrance to the sewer maintenance tunnel is located at -17, 228 on the surface next to Gedron Hix. After entering the tunnels, turn right at every turn available and you will see it on the ground ...