Laserfiche WebLink
<br />program and suggested pipe sizes were calculated. These pipes <br /> <br /> <br />are shown on the accompanying drainage maps. (Maps 2.1 and 2.2) <br /> <br /> <br />The maps also show intersections were significant lowering will <br /> <br /> <br />be required to allow streets to flow and adjacent properties to <br /> <br /> <br />drain. Additional street lowerings can be expected in areas <br /> <br /> <br />without storm sewer as well, however that has not been included <br /> <br /> <br />with this Preliminary Findings. <br /> <br /> <br />Two conditions of Coal Creek were assumed for the storm <br /> <br /> <br />sewer outfall design. The first assumes the Creek is flowing at <br /> <br /> <br />a depth consistent with a basin wide 2 year storm event. This <br /> <br /> <br />produces a depth greater than the pipe outfall and would result <br /> <br /> <br />in localized ponding in many intersections until Creek flow <br /> <br /> <br />levels recede. The second condition assumes Creek levels remain <br /> <br /> <br />low enough not to cause a significant backwater effect in the <br /> <br /> <br />pipe. This would occur if a storm event was localized around the <br /> <br /> <br />Town or if there was an adequate time lag between the peak <br /> <br /> <br />discharge from the Town and the peak discharge in the Creek. <br /> <br /> <br />Under this set of circumstances PQnding at intersections would be <br /> <br /> <br />unlikely and the Town would drain properly to Coal Creek. <br /> <br /> <br />The low elevation of the storm sewer discharge is dictated <br /> <br /> <br />by the low ground elevation of the east side of Town. To prevent <br /> <br /> <br />flows from entering the storm sewer and backing into the Town <br /> <br /> <br />during periods of elevated creek flows it will be necessary to <br /> <br /> <br />install flapper gates on the outfall. These gates open under <br /> <br /> <br />pressure from flows within the pipe but are forced closed by <br />water pressure from within the channel. <br /> <br />D/2623 <br /> <br />-7- <br />