This subchapter applies to all sand and gravel washing operations. For the purposes of this subchapter, sand and gravel washing operations means any person, operation, facility, establishment, or enterprise which washes sand and gravel in such a manner as to separate the sand and gravel from other materials present in the mixture in which the sand and gravel were originally taken from the ground. This definition specifically includes any operation which introduces into washwater any material other than material resulting from such washing of sand and gravel.