introduction concrete pipe Frame and Grate – A catch basin frame refers to a steel frame the sits atop the manhole structure and holds a catch basin grate; a slotted piece of steel that allows water to infiltrate the catch basin. CB Collars – Sometimes called “grade adjusters”, a catch basin collar sits directly beneath the frame and directly above the concrete top slab. The collars range in height and are used to make the unit sit as close to the final grade as possible. CB Top Slab – A catch basin top is essentially a transition slab that brings the catch basin barrels from its standard diameter to an opening of another shape and/or size for access. Risers/Barrels – Catch basin barrels, sometimes called “risers” make up the majority of most catch basin structures, acting as the intermediate pieces between the catch basin base and top. Inlet and Outlet Connections– An inlet (or inlets) refers to the pipe connections entering the manhole. The invert elevation of the inlet pipes refers to the elevation at which the bottom of the inside diameter of the pipe sits within the manhole, which will always be higher than the outlet. An outlet refers to the pipe connection exiting the manhole. stormwater treatment technologies box sections manhole and catch basin material LAFARGE PIPE eMANUAL PAGE 7