Laserfiche WebLink
<br />k lot z 4~~ ass 0 cia t e s <br /> <br />this planning study, but the City should pursue more detailed sewerage drainage studies <br />for the various subdivisions where sewer system improvements are apparently the <br />necessary drainage problem remedy to confirm the problems with the sewerage systems <br />(if a system exists already) and design sewerage system improvements. <br /> <br />4.2.4 Local Ponding Relief Using Sheet Flow Paths <br /> <br />Excess surface ponding in localizes areas can arise because of the interaction of two <br />effects: lack of adequate sewer capacity (as discussed above) and the lack of a pathway <br />that allows excess accumulated waters to drain away from the area of accumulation. The <br />accumulation of runoff water will occur in a low spot. If the sewer system capacity (for <br />whatever reason) is insufficient to receive and convey away the accumulating water, the <br />water accumulates in the low spot. Similar remarks hold for drainage systems which use <br />surface ditches rather than underground sewers. When improvement of the sewer system <br />is not considered appropriate or feasible (because of, for example, high cost; long term <br />delay before sewer improvements can be made, or, as is commonly the case, the rate of <br />accumulation exceeds the properly determined-design capacity of the sewer system), then <br />relief of the accumulated waters using either a sheet flow relief swale or an underground <br />relief storm sewer (i.e., another sewer to increase sewer system capacity) can be <br />considered. <br /> <br />Letter Report No. 1 described certain situations where new sheet flow paths were <br />proposed to relieve excessive ponding. Because of the localize nature and consequent <br />relatively small drainage areas in question, proposed construction of sheet flow pathways <br />was considered as an option to alleviate drainage problems for areas drained by non- <br />FEMA-modeled tributaries when topographic and other conditions suggested that lack of <br />sheet flow paths was a significant contributor to drainage or flooding during large storm <br />events. Underground relief sewers could be considered as an alternative to the surface <br />sheet flow path, but for planning purposes all ponding relief was assumed to be provided <br /> <br />4-8 <br /> <br />Klotz Associates Project No. 0127.008.000 <br />January 2009 <br /> <br />La Porte Citywide Drainage Study <br />City ofLa Porte <br />