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Drainage Concerns Page 2 of 4 Long Lake Properties November 4,2009 2687 Wayzata Blvd,Orono,MN Comm#11586 4. After review of the current improvements, drainage documents going back to the early 90's, and with considerable discussion, we came to the following understandings: a. The established (historic) drainage pattern for a portion of the 2687 property is to the south and east onto Morrie's property. b. Morrie previously constructed a storm rip-rap ditch and overflow on the 2687 property to mitigate water issues along the westerly side of his building. The ditch and part of the rock overflow were constructed on the 2687 property. c. Morrie was concerned that the drain tile from the bottom of the rain garden provided a constant flow directly to their storm sewer during recent extended rain events. d. We briefly reviewed our approved plans and drainage calculations to clarify that, with the new infiltration basin in place, the quantity and rate of runoff to Morrie's site has been significantly reduced from historic flows. e. Of additional concern were the pond overflow elevation, outflow characteristics and the construction of the rip-rap overflow. f. We clarified that the drain tile was to provide temporary relief from flooding conditions in the pond while vegetation became established and the surface of the peat layer started providing the required filtering. It also was in place to provide long-term seepage out fall from the pond for"filtered" storm water to protect the vegetation at the bottom of the basin. After further discussion, we proposed the following, which we believe met everyone's approval, and which will resolve this issue: 1. We agreed to survey the completed pond to confirm design volume was met as constructed. We completed the as built survey work and the resulting survey showed the as-built volume to be approximately 15% above the design volume. 2. We also agreed to review the pond outfall, and to construct a concrete weir fixed at the approved design elevation. Our survey showed the current outfall rip-rap weir to be constructed slightly lower than the plan A Service-disabled Veteran Owned Small Business LAND DEVELOPMENT • MUNICIPAL • HIGHWAYS • RAILROADS SURVEYING • WETLANDS 9 ENVIRONMENTAL ASSESSMENTS