Developing Realistic Design Storms for St. Louis - Saving Big $ Thoughout a Long-term Capital Improvement and Replacement Program

摘要

The Metropolitan St. Louis Sewer District (MSD) is in the midst of planning and implementing alarge Capital Improvement and Replacement Program (CIRP), with assistance from a team ofconsultants. An important aspect of the planning process was to develop design storms thatwould realistically reflect local meteorology, and would result in facilities appropriately sized forto meet the District's Cease and Desist agreement with the EPA. Because the meteorology in theSt. Louis County region is dominated by cloudburst-type events that are comprised of fastmovingcells with intense cores, it was necessary to define and separate these high-intensityevents from the longer-duration synoptic-scale events in the long-term record. Statisticalanalyses were then performed on the separated datasets to develop two unique Depth-Duration-Frequency (DDF) curves. In addition, it was necessary to apply Depth-Area-Reduction Factors(DARFs) to the cloudburst-type design storms in order to avoid over-sizing sewer replacementpipes. In general, the cloudburst design storms are being used to size relief sewers within MSDsubsystems, while the synoptic design storms are used for sizing larger-diameter trunk sewersand storage facilities. The MSD design storms will result in a significant CIRP savings over the30-year life of the program.