Cobble

Per ASTM D653, a rock fragment, usually rounded or semirounded, with dimensions between 3 and 12 in. (75 and 305 mm).

COD

Chemical Oxygen Demand; a measure of the need for oxygen by chemical processes.

Coefficient

A scientifically based factor that is taken into account during calculations.

Cofferdam

A barrier built in the water so as to form an enclosure from which the water is pumped to permit free access to the area within.