a hollow housing defining an interior chamber and configured for positioning in the ground in fluid communication with the trench, said housing comprising an inlet conduit allowing trench water to enter into an interior of the housing until the level of liquid substantially equalizes in the trench and in the housing, said inlet conduit extending from an opening in a sidewall of the housing, and wherein a mesh screen is positioned in said opening to prevent debris from entering into the housing;

a vertical separating wall mounted in the housing and dividing the housing into an inlet chamber and an outlet chamber;

a water passage channel formed below the separating wall;

a screen extending across the interior of the housing, the screen dividing the inlet chamber and the outlet chamber into respective bottom parts and upper parts; and

an outlet conduit having an inlet opening located above the screen in the upper part of the outlet chamber and an outlet opening directed outside of the housing; and

oil-absorbing members removably positioned in the housing.