10-28-1998 Council Agenda - Laserfiche WebLink

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Ms. Kathy Glanzer October 23, 1998 Page 2 Lots 2 and 3 have the same type of driveway configuration, however, looking at the elevations, it does not work as shown. Lot 3 has a low point driveway elevation of 906.5 and Lot 2 has a low point elevation of 901.6, approximately 5 feet difference in elevation, and less than 25 feet apart. In addition, the side yard line that this drainage is expected to drain down has a 902.0 contour. Obviously, 901.6 cannot drain to 902.0. We would recommend that the grading plan and house layout for these two lots be reanalyzed. In fact, we believe that by adjusting the driveway locations and house pad locations on these two lots, the elevation of the house on Lot 2 could be lowered, minimizing the height of the retaining wall in the rear yard. Currently, there is a retaining wall shown on two sides of the house pad on Lot 2. The highest point is 12 feet. If this retaining wall is left as shown, we would suggest that this overall height of wall be constructed in a stair - step manner with two or possibly three walls of less height. 4. The preliminary grading plan does not show enough information about how the existing road will be removed and the new road connected to the existing road at the south end of Gilanderi Lane. We assume that the drainage pattern that currently exists will not be modified, and after the reconstruction, the same drainage system will exist. 5. It appears that there are a number of contours missing on Lot 4. • 6. The storm drainage calculations show the existing area draining to the northwest corner as approximately 1.76 acres. After grading and development of the lots, the total area draining to this northwest corner will be reduced to slightly less than an acre. By doing this, the storm drainage calculations show the post - development runoff to be less than the pre - development runoff at the northwest corner. The situation at the southwest corner is just the opposite. Pre - development there is 0.6 acres draining to this area. After development, there will be 1.37 acres draining to this area. Therefore, a pond is required and shown on the plat and grading plan. The plat should include an easement to cover the area of the pond inundated by a 100 -year storm. Although there is no pond needed at the northwest corner of this plat, it will not operate correctly as it is currently shown on the grading plan. The grading plan has a note that reads, "Grade ditch to drain water to the north into County Road Ditch." The high point at the northwest plat corner is 873.2. The low point currently in Lot 1 is approximately 866.0. The grading plan is showing filling Lot 1 to approximately 870.0. There is, however, a portion of 868.0 on the neighboring property. No grading is shown on the property to the west. Therefore, water will pond in this area until it is deep enough to flow past the 873.2 contour. It would be a much better approach if the developer got permission to fill on the neighbor's property, creating a swale along the rear lot line of Lot 1, to drain directly to the County Ditch, eliminating any potential for standing water. 7. According to a December 5, 1997 memorandum from Public Works Director, Scott Tangen, sanitary sewer stubs are available for Lots 1 and 2, and water service stubs are available for Lots 1, 2, and 3. Therefore, there will need to be an extension of sanitary sewer and water to serve Lots 4 and 5. Mr. Tangen indicates in his memorandum that the utilities are adequate to serve Lots 4 and 5. However, these extensions are shown an the preliminary plat. As this project moves p�forward, detailed plans should be submitted and reviewed for I -1rPPn ` r t` iany O: \PROJ \603660J \0240 \660 -2301. oct.doc CON; Page 5