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Messrs. Kent Lokkesmoe and Pete Willenbring <br />Page 2 <br />March 31, 1982 <br />course of the excavation work, it became obvious that organic soil areas <br />near to the underwater excavation would tend to move laterally to the <br />lower areas. This resulted in additional quantities of excavation par- <br />ticularly in the north central and south portions of the site. The <br />excavation contractor expressed concern that any excavation near to the <br />Scottland Green apartment complex property line could result in similar <br />soil movement and settlement in improved areas on that site (such as <br />parking lots, lawns, etc.). The contractor recommended that no excava- <br />tion work be done adjacent to the property lines. <br />The area in question is presently heavily vegetated with marsh grass, <br />willows, and other wetland vegetation. The second consideration in <br />leaving this area rather than performing excavation work is that such <br />inplace vegetation would be conserved. <br />If the described area is not excavated, the storage available at <br />the ponding area is changed. We have recalculated the hydrologic and <br />hydraulic requirements for the ponding area based on full development <br />of the tributary drainage area and the 100 year runoff event.. Our cal- <br />culations are enclosed. The results indicate that the ponding area will <br />adequately accomodate the design storm event and that discharge from the <br />area can be slightly reduced. The following table summarizes previous <br />and proposed ponding area design values. <br />Approved <br />Revised <br />' <br />Plans <br />Plans <br />1. <br />Tributary Drainage Area <br />266 A <br />203 A <br />2. <br />Normal Pond Level <br />893.0 <br />893.0 <br />3. <br />100 Year Pond Level <br />895.7 <br />895.7 <br />4. <br />Available Storage (100 yr.) <br />51.6 AF <br />40.5 AF <br />5. <br />Pond 100 Year Discharge <br />15.0 cfs <br />12.5 cfs <br />Revised grading and outlet detail plans are also enclosed. <br />We request your early consideration of this request to modify the <br />existing permits for work in Oak Lake Park pond. Please contact me if <br />you have any questions or 'require further information. <br />Yours very truly, <br />A._�W4(ft� <br />Gerald M. Sunde <br />GMS:skw <br />cc: Fred Haas, Mary Anderson Const. <br />Dale Cremers, KA <br />