Abstract: A method of preventing water leakage through a concrete substrate on the ground into an inner space of an underground structure. Underground structures located adjacent water tables maybe sealed against the intrusion of water as by drilling an opening to the outer side of the concrete substrate. A pipe possessing a valve is then inserted with the valve in a cut-off position to stem the flow of water leaking through the substrate. Cement slurry is then inserted through the pipe into the opening until a portion of the cement is in place along the outer side of the concrete substrate adjacent the ground. An inner end of the pipe is then cut away with the cement slurry being allowed to dry for approximately one day. Unhardened cement is removed from the pipe from which water is still leaking. A cement powder is heaped upon the opening and is compacted into the opening via an impacting hammer.