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lv: ruJ <br /> • From: RJB <br /> Re: Greenfield Estates Plat Review <br /> Date: 2/27/92 <br /> Peter, I have completed my review of the wetland alteration permit <br /> submitted by McCombs, Frank Roos Associates, Inc. My comments are enumerated <br /> below. <br /> 1) Existing and proposed flood storage volumes. <br /> McCombs computations showed that they are replacing flood plain lost due <br /> to home construction with flood plain created as the result of pond <br /> excavation. Therefore, no hydrologic analysis was needed. I am in agreement <br /> with this. <br /> However, I do have a concern regarding the pond outlet configuration and <br /> ground water levels. McCombs states that the current ground water elevation <br /> in the wetland is approximately 898 and their assumption seems to be that <br /> this elevation will be maintained after the wetland is altered. I have <br /> doubts on whether this is an correct assumption. On a earlier permit <br /> submittal by Merila & Associates, the outlet for this wetland is an 24" RCP <br /> culvert at an elevation of 896.33. The Merila plans indicated construction <br /> of a baffle weir in front of the outlet culvert to control water levels in <br /> the wetland. The McCombs plan does not provide for water level control. It <br /> is conceivable that the creation of ponding arcas will provide greatet <br /> discharge area for ground water than the current ditch. This could result in <br /> depression of the ground water levels, which will stabilize at an elevation <br /> near the 896.33 outlet elevation not the 898 assumed by McCombs. This drop <br /> in water level could have negative impacts on the wetland community and <br /> reduce water quality enhancement of the wetland. <br /> 2) Water Quality <br /> I am in general agreement that the proposed configuration of the wetland <br /> • will enhance its water quality function. However, there are several items <br />