Marcia McNutt reflects on the role of the US Geological Survey (USGS) team following the Deepwater Horizon oil spill. Secretary Salazar asked Marcia McNutt to lead the Flow Rate Technical Group, a team charged by National Incident Commander Adm. Thad Allen with improving estimates of the oil discharge rate from the Macondo well as quickly as possible. Given the unprecedented nature of this spill, the team moved rapidly to deploy every reasonable approach. The team estimated the plume velocity from deep-sea video and from Woods Hole Oceanographic Institution's acoustic Doppler current profiler. The team calculated the total volume of the spill using aircraft remote sensing. After the unsuccessful top kill attempt in late May, during which large volumes of mud were pumped down the flowing well, an important part of understanding the failure of the procedure was answering the question.