12-17-1998 Council Agenda - Laserfiche WebLink

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The Honorable Mayor and City Council December 11, 1998 Page Two 3. The grading plan shows all four houses to be a walk out style. Through a slight raising of the house pads and a slight lowering of the proposed road grade, all driveways are now shown to drain from the garage to the street. This we believe is a significant improvement over the previous grading plan which showed low points in the middle of the driveways. 4. Our previous memo, dated October 23, 1998, indicated that there were missing contours on lot 4. This situation has been rectified. The missing contours have now been shown on what is now called lot 3. The previous grading plan showed an extensive retaining wall, up to 12 feet high, required on lot 2. This has been eliminated from the plan by grading the side lot area. The contours shown on lot 2 however represent a slope that is steeper than 3:1. This kind of slope will be very difficult to maintain. It may be advisable to install a small terraced retaining wall to achieve a flatter slope on the north side of the house pad on lot 2. 5. No new drainage calculations were submitted, therefore we assume that the previous drainage calculations are still valid. Any change made to the drainage calculations would show a slight reduction in the post - development run off, given the reduction of one lot in the preliminary plat. The storm drainage calculations previously submitted showed the existing area draining to the northwest corner at approximately 1.76 acres. After grading and development of the lots, the total area draining to the northwest corner will be reduced to slightly less than one acre. By doing this, the storm drainage calculations show the post - development run off to be less than the pre - development run off at the northwest corner. The situation at the southwest corner is just the opposite. The pre - development area shown is 0.6 acres draining to this area. After development there will be approximately 1.37 acres draining to this area. Therefore, a pond is required and shown on the preliminary plat and grading plan. The pond falls entirely within an easement provided on the preliminary plat. The grading plan however does not accurately reflect the grading of this pond area, and lacks some of the detail required for the outlet of the pond. We assume that the outlet will be directly to the south, to the Trunk Highway 36 drainage system, and will not impact the property to the west. We also assume that emergency overflow will be provided, although one is not shown on the grading plan at approximately this same location. A MnDOT permit will likely be required for the pond outlet. The new grading plan has been revised in the northwest corner to reflect some minor cutting and filling to provide for positive outlet of the storm run off. This will eliminate any ponding of water on the neighboring property to the west. However, there is no easement shown giving permission to the developer of the Gilanderi Addition for accomplishing this grading operation on the neighbors property. It will be necessary for the developer to provide proof of this easement, or permission before final approval of the plat. 0: \Prof \803660) \0240 \660- 1102.dec Howarc R. Green Company CONSULTING ENGINEERS Page 4