Abstract: A storm drain inlet for a below-grade collection box including front, rear and side walls and a top. The inlet includes a pair of side columns, which connect to the collection box side walls. An upper crosspiece extends between the side columns and is attached to the collection box top. A lower crosspiece comprising a back plate extends between the side walls and provides a form for the rear edge of a concrete apron poured in front of the collection box. The side columns, upper crosspiece and concrete apron define an inlet throat open to the collection box interior. A roadway or parking lot structure can include curbs, which can be poured adjacent to the collection box into proximity with the inlet side columns. The curbs are preferably not rigidly connected to the inlet in order to accommodate relative movement therebetween. The inlet can be adapted for both poured-in-place and precast collection boxes. It can be scaled to accommodate various widths and heights.