Erosion of construction areas represents the largest source of sediments in urban runoff. Reported unit loads of sediment from urban construction sites ranged from 12 to 500 tons/half-yr (Novotny and Chesters 1981). Furthermore, building activities generate other pollutants such as chemicals from fertilizers and pesticides, petroleum products, construction chemicals (cleaning solvents, paints, acids and salts), and various solids. Grading exposes subsoil, increasing surface erosion due to stormwater runoff.
Erosion of urban lawns and park surfaces is usually low. Exceptions are open, unused lands, and construction sites.
Soil is a source of suspended solids, organics, and pesticide pollution. Despite the SCS's active promotion of erosion control, the U.S. Department of Agricultural estimates 57-76 million acres (21-31 Mha), about 15-25% of the nation's agricultural land, is in need of sediment control measures.
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