The U.S.G.S. reported last year's Tropical Storm Lee contributed 39 percent of the sediment, 22 percent of the phosphorus and 5 percent of the nitrogen flowing through the Conowingo Dam between Oct. 1, 2002 and Sept. 30, 2011. The report also states that there has been a 55 percent increase in phosphorus loading and 97 percent increase in sediment loading over the last 15 years. Historically, the Conowingo Dam has prevented nutrients and sediment from entering the Bay. Now, the Dam's reservoir has dangerously diminished capacity to trap sediment and nutrients. Major storms exacerbate the problem by delivering heavy volumes of water which scour the reservoirs floor, lifting previously deposited sediment and nutrients and carrying it through the dam's spillways and into the Chesapeake Bay.