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Storm Water and Wetland Management Plan <br />N,.v.•mher 14, Ins'. <br />Second, The Johnson Plan will work only if the <br />existing low lands (land that h.1: no surface water I <br />discharge point) are not filled. It the low land is <br />filled, the wator Ohm mw ponds in the low land <br />will enter the storm sower and then the storm sewer <br />will he 1.., sn,.,ll I., ...levy Ill.. Il-.w. <br />There are twe reason" for banning fill in low land <br />ar,•as. The first reason is hpcause existing storm <br />vewern du unl IL we a.h •qu..1 .• eapa. fly. 'I'h.• s.....md <br />reason is because the seven county metropolitan area <br />needs to preserve ground water recharge areas. <br />Water in the previously mentioned low lands now <br />infiltrates into the soil. The Johnson Plan assumes <br />that the seepage rate will stay the same. Low land, <br />like wetlands, fill in over time and the seepage <br />rate will be reduced by sedimentation. In other <br />words, less water will percolate into the ground <br />which will cause the water level in the low land to <br />rise and either; a) flood buildings, or h) enter the <br />storm sewer. If this water enters the storm sewer, <br />the storm sewer will he too small to carry the <br />flow. Therefore, from time to time the qrnund <br />surface of low land areas will need to be excavated ' <br />to restore the seepage rate. <br />The low lands may need to he excavated once very ten <br />(10) to fifty (50) years depending on the quantity <br />of fine particles carried into low land with the <br />storm water. Low lands need to he excavated when <br />storm water hacks up and threatens to flood <br />bah'CmPnta, or when low lands uvertlow into the storm <br />sewers too quickly, or when water ponds for long <br />p.•riods of timo- <br />b) Structural Improvements <br />The Johnson Plan includes constructing improvements <br />to the storm sewer sytem. In order to accomplish <br />this, I propose the following program for each <br />drainage basin. <br />1. Survey the drainage basin to determine site <br />specific data such as pipe diameter, pipe <br />length, pipe slope, etc. (the .lohnson Plan used <br />plans which may or may not have been followed <br />during Construction. The plans are certainly <br />sufficient for use in a study, but not <br />sufficient for design work). <br />- 6 - <br />