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<br />Prelimina~Storm J)rai~c.~.';Le Desicl.!:'.._ <br /> <br />Concept <br />In light of the serious flooding potential from Coal Creek <br />during storms of 10 year frequency and larger, a storm sewer <br /> <br /> <br />conveyance for major storms would be ineffective. The thrust of <br /> <br /> <br />the design therefore is to provide a system that will convey <br /> <br /> <br />flows from minor storms to Coal CreeK.. Two main desiqn problems <br /> <br /> <br />present itself <br /> <br /> <br />1) Design a storm sewer and street improvement program <br /> <br /> <br />that will provide positive drainage for the Town to <br /> <br /> <br />Coal Creek. <br /> <br /> <br />2) Integrate into the storm sewer the necessary <br /> <br /> <br />appurtenances to eliminate the possibility of the pipes <br /> <br /> <br />siphoning water out of the Creek and into Town when <br /> <br /> <br />creek flow levels exceed pipe depths. <br /> <br /> <br />The 2 year storm was selected for the storm sewer design. <br /> <br /> <br />During this size of a storm it is desirable to keep flows within <br /> <br /> <br />the street section and not allowed to overtop curbs. Curb and <br />gutter capacities were determined assuming 6" vertical curb on <br />collector streets and 4" combination curb and gutter on local <br />streets with a minimum slope of O.'i% on all roadways. <br />Preliminary Design <br />Three storm sewers were selected for conveyance of minor <br /> <br /> <br />storm flows to Coal Creek. Inlets were placed where street flows <br /> <br /> <br />would be expected to overtop curbs. The initial hydrologic and <br /> <br /> <br />hydraulic parameters were entered into the UDSEWER modelling <br /> <br />0/2623 <br /> <br />-6- <br />