The Public Work's storm water and drainage crew structurally maintains all improved and unimproved drainage easements within the city. Improved drainage channels include underground culverts and pipes, curb and swale inlets and outfalls, and paved open drainage channels. The crew also maintains unimproved natural and grassed drainage easements, to insure the free flow of storm water and to minimize the probability of structure flooding. Mowing and vegetation control within these areas is provided by The Colony's Parks Department. This section also operates the city's street sweeping program, which began in 2004, and helps to remove dirt, silt, and other pollutants from city streets before they wash into the storm system and area lakes and rivers.