08-17-2015 Planning Commission Packet

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� • PC Exhibit L . BO�.T'�`3C'�J �'�. t`�/1 �;C��J I�� , I f`�J� ; � '� �onsul��tng Er�g�n�er� & S�rvey�ors " 2638 Shadow Lane,Su"ite 200•Chask,a,MN 55318-1172 Phone(952)448-88,38• Fax(952)448-8805 www.bolton�nenk.com August 1 l,2015 City of Orono Attn: Melanie Curtis 2750 Kelley Parkway Qrono,MI�I 55356 RE: Variance Application 15-3733 1185 Ferndale Road West Dear Melanie: As requested,we have completed an engineering r�view of the documents submitted for the above referenced project. We offer the following comments far your consideration: 1. The Certificate of Survey should be revised to indicate perimeter erosion control mea9ures (siltfence, biologs,etc.)down gradient fram proposed work. Measures must be installed by the Contractor and inspected by the City prior to any work. Contractor must provide a minimum 24 hour notice prior to insgaction. 2. Since work is proposed witivn 50' of a wetland,redundant erosion control devices must be installed down gradient from the work adjacent to the wetland to ensure adequate protection. 3. Adjacent property owners have expressed concern regardi.ng seasonal flooding of the wefland on the north side of the pmperty. The proposed improvements will nominally increase the amount of impervious surface in the subwatershed,and the volume of runoff will be increased accor�ingly. However,the minimal amount of new impervious surface will not likely impact the high water levels of the wetland to any significatxt amount. In order to mitigate impact from the new impervious surface,the area between the wedand and proposed driveway could be planted with native vegetation to help reduce runoff volume and improve water quality, 4. Proposed grading detail should be added to the plan to ensure proper dra.inage routes are maintained and runoff is not directed on to adjacent property, Proposed spot elevations and contours should be added as necessary to adequately define grading. 5. The proposed driveway extension may be partially located below the 100 year high water elevation for the wetland,and its constraction would result in alteration to the floodplain. The high water level of the wetland should be indicated on the survey, and grading detail should be provided for the driveway in order to verify any imgacts to the floodplain. Floodplain mitigation may be necessary to offset fill for proposed improvements. 6. Due to the nominal amount af proposed disturbance,the minimum required escrow of$2,50(}for erosion cantrol and engineering oversight should be adequate to provide protection in the event it becomes necessary for the City to install or maintain erosion and sediment contral ar re-establish vegetation within the project area. 7. The apglicant may be required to obtain Minnehaha Creek Watershed District(MCWD) approval and pemutting for their Erosion Control and Floodplain Alteration Rules. A copy of any approvals or permits required should be submitted prior to final approval.