Laserfiche WebLink
<br />I <br />I <br />~I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Runoff quantity is then 5" x 0.39% X <br />I' <br />12" x 6.45 acres = 1.05 acre feet + 0.90 <br /> <br />= 1. 95 acre feet to imply that the new <br />pond level will be 938.4. <br /> <br />However, if the 15 inch storm drain pipe in the <br />southeast corner drains the water off at 4 cfs, it <br />will never get as high as 938.4 and the pond will <br />return to elevation 937.5 within a very short time <br />after the rain stops. This, of course, assumes <br />that the berms are lowered to elevation 937.5 so <br />the storm drain can function. If the berms are <br />not lowered to the 937.5 elevation, the ponds will <br />be at elevation 939! (3.0 acre feet in storage) <br />when the 12 hour storm begins and the pond eleva- <br />tion will rise to 939.5:. <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Subsurface water - Since the project area consists <br />primarily of till of relatively low permeability, <br />a real ground water table does not exist in the <br />area. The water table is a reflection of surface <br />water level in the ponded areas on the site. The <br />water table, therefore, fluctuates with precipita- <br />tion, surface runoff, and evaporation. The glacial <br />deposits within this area contain essentially no <br />ground water which can be released and pumped from <br />wells. However, there are sand lenses contained <br />within the till which are water bearing. <br /> <br />The major ground water aquifer underlying New <br />Brighton and the project site is the Prairie du <br />Chien-Jordan Aquifer. At the present time the City <br />of New Brighton pumps water from wells within the <br />prairie du Chien-Jordan aquifer which underlies the <br /> <br />I <br />I <br /> <br />III-12 <br />