As the heroes prepare to bolt into the access door leading into the control room, Wheeler's voice comes over their communicators, " Circe, Gun Monkey! Another emergency has cropped up. Report back to headquarters immediately." "Damn Him!", exclaims Gun Monkey, and then, just as soon as the arrived, they depart. The remaining heroes blink, and then enter the control room. Inside they see all the apparatus for operating the dam, but not no signs of anyone, least of all Dr. Null!
OOC: We'll run this with just the three characters from here. The control room is atop the dam itself. The tank bots are below on the ground. In the attached image, the two grey rectangles appear to be powerhouses to the heroes. The "antennae" extending from the dam into the reservoir are intake towers connected by access bridges to the dam. The bots are climbing towards them via an access ramp on the west side of the dam. Let me know if you have any other questions about the layout.