Construction crews work in darkness--when energy demand is lowest--on a stretch of American River levee near the California State University-Sacramento campus Sept. 12, 2012 to close a 900-foot-long gap in a seepage cutoff wall underneath high power lines. The Corps has built more than 20 miles of seepage walls into American River levees since 2000. Areas where construction was complicated by utilities, bridges or power lines were set aside for later construction. The project is part of the American River Common Features project, a joint flood risk reduction effort between the Corps, the state’s Central Valley Flood Protection Board/Department of Water Resources and the Sacramento Area Flood Control Agency.