To instantaneously close a hole to prevent a water way even when the incursion of foreign matters from an upper side or a lower side of a gutter sheet as an impervious sheet laid on specially a refuse filled ground or the like to make the hole, have an excellent waterproof function and, at the same time, to prevent the damage in the impervious sheet by the front end or the like of a rock.

A seepage control method of an impervious sheet laid on the final disposal plant or the like of solid wastes is so constituted that a waterproof sheet layer 2 is laid on a substrate 5 and that two component reaction hardening type urethane coated film material reacted with prepolymer having isocyanate group and compound containing polyol is sprayed and spread on the end in a state of waterproof sheet layer 2 to form a seal layer 4. A protection layer 3 is laminated on the seal layer 4.