Trash Racks for Principal Spillway Intakes
-Improving the design for efficient delivery of flood discharge
A trash rack is a component of the principal spillway intake tower. The purpose of the trash rack is to provide protection against debris (i.e. tree limbs, logs, etc.) entering and clogging the intake tower and/or spillway. Early principal spillway intake towers were designed with an open top concept, meaning flow from the reservoir would enter the principal spillway intake tower from the top. This design created inefficiencies in the flood flow delivery from the reservoir, through the dam, and to the downstream channel as the trash rack became plugged with debris; thus, lowering the discharge capacity of the principal spillway. USDA-ARS Hydraulic Engineering Research Unit scientists with the recommendation from USDA-Natural Resources Conservation Service (NRCS) field engineer, M. M. Culp, created a research program to address the issues observed in the field with the open top trash rack design concept. The outcome of the research was the adoption of a standard design, USDA-NRCS Technical Release 70, for a closed-top stepped baffle trash rack that minimize the debris collected in the principal spillway intake tower. Ultimately, the new design concept allowed for the full design capacity of the principal spillway during flood flow events, and it reduced the risk of activating the auxiliary vegetated spillway and/or overtopping the dam. To learn more about the trash rack research, visit our publication index and request a publication.
Optimization of trash rack design features to improve dam safety led to the adoption of standard design criteria by the USDA-NRCS.