(Portland, OR)  --  Officials are warning residents to avoid the water in the Columbia Slough following a sewage spill.  City officials say a broke sewer pipe at a pump station on Northeast Alderwood Road caused ten-and-a-half-thousand gallons of sewage to flow into the slough yesterday afternoon.  Residents are urged to avoid contact with the water for the next 48 hours.  Officials are still working to determine how the pipe broke.