Abstract: The invention is a watertight joint seal for precast concrete box modules used to form underground enclosures to control the discharge of water runoff from roads and parking areas. The modules become sections of a tunnel structure, and the joint seal of the invention is constructed by forming the end of the walls of each module with mating offset inside and outside edge surfaces that are joined by an intermediate surface, applying sealing strips to the inside and outside edge surfaces of one end wall, compressing the modules against each other, and injecting an expansive grout into the cavity formed by the sealing strips and the modules' end surfaces. After the grout cures under the pressure resulting from its own expansion, the joint is watertight and does not suffer from leakage through cracks caused by the creep and relaxation characteristics which generally occur in joints formed with conventional grout or only rubber gaskets.

Abstract: The apparatus is an underground reservoir to capture and slowly release stormwater runoff from impervious surfaces such as roads, rooftops, and parking areas. The structure is assembled from one or more modules comprising at least two side by side precast fiber reinforced concrete vaulted shaped chambers, each with side walls and an arch top. The side by side chambers have common walls with openings in the walls. Modules placed end to end are mated at reinforced concrete end walls that include lifting pins for moving the module. Ends of the chambers are closed, but the end walls have openings for feeding stormwater in and venting air out.