Grouted Sloping Boulder Drop Structures

The District revised the Hydraulic Structures chapter of the Urban Storm Drainage Criteria Manual in 1990 to provide better guidance for the design of drop structures and check structures. One of the new drop structure designs, the Grouted Sloping Boulder (GSB) drop, has become far and away the most popular design.

Unfortunately, we have continued to see design drawings that provide inadequate details for construction. We therefore retained McLaughlin Water Engineers, Ltd. to prepare example design drawings. Last year we published details for a drop structure with a trickle channel. This year we have revised the details for a drop structure with a trickle channel and have prepared an example of a drop structure with a low flow channel. We are encouraging design engineers within the District to refer to these details when preparing construction drawings. Copies of the details, either hard copy or electronic, can be obtained by contacting David Mallory at the District, or by linking to the District's Download Web Page.