A frame for retaining a grate over a trench for directing storm water to subterranean basins includes a frame that is embedded in the concrete surrounding the trench. The frame includes a support member, including a vertical support that is sized and dimensioned to abut the wall of the trench, and a horizontal flange that is cantilevered over the trench to receive a grate member. The frame further includes a reinforcement member that runs parallel to the length of the support member, and a plurality of rib members that couple the reinforcement member to the support member. The reinforcement member and rib members are embedded in the pavement adjacent the trench, to provide a back structure for reinforcing the support of the grate.