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� Jesse Struve From: Jesse Struve Sent: Thursday, September 12, 2013 1:35 PM To: Melanie Curtis Cc: Christine Mattson Subject: 20130912 3227 Casco Cir#13-00728 Melanie, I have reviewed the proposed survey for the new house at 3227 Casco Circle and have the following concerns: 1. From our conversation,the applicant is not doing any of the work shown in the 0-75' zone with the exception of installing the proposed drainage pipes. All other work not being proposed with this application needs to be removed from the survey. This includes removing the existing retaining wall and all work associated with the boathouse. 2. The survey shows a piped outfall from the low spot which discharges partially down the slope. This discharge does not show any erosion control measures to prevent erosion of the slope to the lake. Something will need to be installed down the slope probably all the way to the lake to prevent erosion. This may also need to be shielded from the lake. 3. There should be treatment of the runoff prior to entering the pipe. I would recommend a rain garden be installed which can handle the volume of runoff associated with at least a 10 yr event prior to water being directed into the pipe. 4. The engineer should provide modeling results of this low area which shows if back to back 100 yr rain events or a 100 yr snowmelt occurs,that the pipes can handle the volume of water without impacting the proposed house. 5. The installation of the pipe may very well disturb more than 10 CY of material within the 0-75' area which would trigger the CUP. If you look at the invert of the pipe at the 75' setback it will be approximately at 944.00 elevation and the existing topo point is at 951.3'. This is a 7' deep trench and when you have an OSHA approved trench it will be at least 1:1 slopes if the soil are acceptable. That means there will be a 14' wide trench and will disturb more than 10 CY and a CUP will be triggered. 6. The grading along the west side of the property may be directing water onto the neighboring property. This runoff could affect the neighboring garage. The drainage should be directed to the east more to maintain the drainage on the property. Additionally,the applicant may want to consider installing some measures to slow or reduce the amount of water being directed down the property lines. By channelizing the runoff there is a potential of additional erosion on the slope. Jesse Struve, PE Director of Public Works/City Engineer City of Orono (952) 249-4661- Direct (952) 249-4616- Fax www.ci.orono.mn.us i