SITE CHARACTERIZATION OF THE CONTAMINATED SEDIMENT IN THE BANKS OF THE MAHONING RIVER, OHIO

The Mahoning River is designated as one of the five most contaminated rivers in the U.S.A. Major sources of contaminants in the river are the steel industry, which was active for about 75 years (1900-1975), and partially treated human waste discharged by the local cities and towns. The contaminants are mainly PAHs, PCBs, and heavy metals (mostly zinc, iron, cadmium, chromium, copper, nickel, and lead).

The Mahoning River is 108 miles long. It rises in Columbiana County, Ohio, flows to Warren, Ohio, and then to Pennsylvania. This study investigates the most contaminated section of the river, which is located in northeastern Ohio. This section is 31 miles long, and extends from Leavittsburg, Ohio to the Ohio-Pennsylvania border near Lowellville, Ohio. The investigated section of the river flows through industrial, residential, and undeveloped areas, and passes through 9 cities and towns: Leavittsburg, Warren, Niles, McDonald, Girard, Youngstown, Campbell, Struthers, and Lowellville.

Thirty-two monitoring wells were installed in the banks of the most contaminated section of the river. The wells were drilled by a hand-auger and cased with 3-inch diameter slotted or perforated PVC pipes. Most of the wells were finished in the bedrock. The wells were installed on both banks of the river at five sites: Leavittsburg, Warren-Lovers Lane, Warren-Packard Park, Girard, and Lowellville.

The wells revealed the following characteristics of the contaminated banks. At Lowellville, the sediments consist mainly of sand and clayey sand with moderate to high permeability, depending on the amount of clay present. At the other sites, the sediments consist of clay, sandy clay and silt with low permeability. At the five sites, depth to the contaminated sediment below the ground surface varies from 1 to 5 feet, with an average of 3 feet, and the thickness of the contaminated sediment varies from 1 to 8 feet, with an average of 4 feet. The thickness of the contaminated sediment is controlled by the depth to the impermeable bedrock, which ranges from 3.5 to about 10 feet. At the five sites, depth to groundwater below the ground surface ranges from 1 to 6 feet, with an average of 3 feet. The heaviest contamination (black, dense and viscous petroleum products) is observed at Lowellville and Warren-Packard Park. Light contamination is observed at the other sites.