Analyses of native water and dredged material from southern Louisiana waterways, 1975-76

From June 1975 to July 1976 the U.S. Geological Survey conducted nine dredging and seven postdredging studies related to water quality in selected reaches of major navigable waterways of southern Louisiana. Samples were collected from the Mississippi River-Gulf Outlet, Mississippi River at Southwest Pass, Mississippi River at New Orleans, Bayou Rigaud near Grand Isle, Barataria Bay and Waterway, Bayou La Carpe near Houma, Atchafalaya Bay (Ship Channel), Lower Atchafalaya River area, Intracoastal Waterway near Calumet, Intracoastal Waterway (Port Allen to Morgan City), Petite Anse area, and Calcasieu River and Ship Channel. These studies were conductd to determine potential environmental effects of dredging activities in the waterways. The Geological survey collected, treated, and analyzed 383 water and water-sediment mixture samples from 85 dredging sites and 142 postdredging samples (72 sites). Water samples were collected 100 yards upstream and downstream from the dredge effluent, from the disposal area, and from the effluent outfall during the dredge phase of the study; samples were collected at former dredge sites during the postdredging phase. Samples were analyzed for selected metals, pesticides, nutrients, and organic constituents. The analytical data are presented in tables. Sampling sites are shown on maps. (Woodard-USGS)