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Letter from Plowe Engineering 1-29-09 Lino Lakes, Minnesota 55014 Office (651) 361-8210 Fox (651) 361-8701 January 29, 2009 Robert Generous City of Chanhassen 7700 Market Blvd Chanhassen, MN 55317 Oi' CHi-\i\!HASSE'I' r:)[::Cf:IVED - ..IAN 3 0 2009 ':r-iM\/H^""I'-I\J " ''''''0 ~ , PLANNING DEP"; RE: Apple Tree Estates (proj. 08-1227) Dear Mr. Generous: We have received your letter dated January 21,2009 and offer the following responses: 1. The development review applicationfee is $1,570, not $700. Subdivisionfee is $720 ($600 plus $15 per lot). Variancefee is $200. Notification signfee is $200. Escrow for attorney costs is $450. The developer will provide the additional fees as required with this re-submittal. 2. Tree preservation and removal calculations must be submitted. Provide tree removal calculations based on existing conditions and preliminary grading plan. The calculations should include the estimated tree removal for the house and drive on Lots 1 of 2. (Section 18-61 of the Chanhassen City Code.) The boundary and topographic survey shows existing tree information. Sheet C5 (landscape) has been added which shows both existing and proposed tree canopy coverage and indicates those trees which are to be removed. (Trees anticipated to be removed for house construction on Lot 2 and driveway construction for Lots 1 and 2 are shown.) 3. A landscape plan must be submitted with the application. (Section 18-61 of the Chanhassen City Code.) Sheet C5 (landscape) is included with this submittal. 4. Lot calculationsfor each lot. (Section 18-40 of the Chanhassen City Code.) Verify the upland area of Lot 2, Block 2 meets the minimum lot area, exclusive of the wetland. Lot information is included on Sheet Cl. Note that the calculation for Lot 2 Block 2 excludes the wetland area for computation of total lot area. 5. Lot 2, Block 2, does not meet the minimum wetland setback, which is 46.5 feet (30-foot wetland buffer setback and 16.5-foot buffer). (Section 20-411 of the Chanhassen City Code.) Lots 1 and 2, Block 2, should be combined as one lot. The wetland should be included in a separate outlot. The configuration of Lot 2 Block 2 has been adjusted to meet the 46.5-foot wetland setback requirements. The developer will work with City staff to provide measures necessary to clearly mark buffer area as "off limits" (e.g. landscaping, signage, etc.) 6. Hard surface coverage calculations shall be provided for each lot. (Section 18-60 of the Chanhassen City Code.) Hard surface calculations are included on the lot information table on Sheet C 1. Hard surface calculations include a 3600 square foot building and the driveway areas as shown on the plan. 7. Lot and Block numbers shall be consistent across plan sheets. Lot and Block information has been updated to match the preliminary plat. 8. There is inadequate separation between the HWL and the lowest floor elevations of Lots 3,4 and 5 (See Section 19-144 (2), minimum 3feet separation required). The pre-treatment basin has been removed and replaced with a Hydro International "First Defense" vortex separator. 9. The proposed design includes sediment and bioretention basins that are perched above the home to the west. Staffis concerned about property damage to the home if the slopes of either basin were to fail during a large event. As noted above, the pre-treatment basin has been removed. The bioretention facility has not been moved north in order to preserve the line of existing pines trees. In the unlikely event that the basin slopes should fail, it appears from the topography that there is natural draw that should direct drainage north past and around the existing house. 10. The piped outlet from the bioretention basin should be extended to the OHWL of Lake Susan. To minimize tree impacts and avoid disturbing the bluff, the bioretention outlet now connects to the existing storm sewer manhole west of Lot 4. We will work with City staff to verify that the existing pipe has adequate capacity to handle the additional run- off. 11. The EOF of the bioretention basin should be moved so that it will not directly discharge onto the neighbor's property. The bio-retention basin EOF has been moved to the north portion of the basin (where the draintile outlet is proposed) so that drainage is not directed directly onto the neighbor's property . 12. The wetland boundary as identified in the Kjohaug report needs to be verified This will be done when conditions are suitable. It is understood that the wetland boundary will not be verified until site conditions are suitable. 13. A significant portion of the contributing watershed to the wetland is being redirected to Lake Susan. Secondary impacts must be mitigated under WCA as well. For your review, included is a comparison of volumes to the wetland for existing and proposed conditions. 14. It is unclear where the wetland discharges to. This will need to be clarified and it must be shown that this will not result in downstream impacts. Developer will work with City staff to verify that wetland outlet/overflow does not cause negative downstream impacts. Please feel free to contact me with any additional questions. Sincerely, a-~ Adam Ginkel, P .E. Plowe Engineering, Inc.