Agenda - Planning Commission - 02/01/2007

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Preliminary Plat: Pine Prairie January 26, 2007 Page 2 of6 Building Coverage/Open Space Requirements: Maximum building coverage is 35% within townhome developments. Also, the City requires a minimum of 40% open space, or non- impervious areas. Of this 40%, 10% must be identifiable community space, or active open space. Please submit revised plans breaking down the percentage of building coverage, total pervious/impervious percentages, and identify an area of at least 3,100 square feet as community space. This can be accomplished through a picnic area, gazebo, or other community amenities. As proposed, the total green space coverage on the property is 53%, which meets the open space requirements. Please submit a revised plan indicating an area for identifiable community open space. Grading & Drainage: A grading and drainage plan has been prepared by Mr. Tim Eggerich PE. which proposes conveying runoff to a detention pond to be located in the northwestern corner of the plat. Once this pond is full, additional runoff will backup and discharge into the county highway ditch and flow northward sheeting onto the adjacent property. Topographic contours should be extended 100 feet beyond the boundaries of the plat. The type, size, invert, and rim elevati<?ns of all storm sewers should be added to the grading plan. This information,is available, but is shown on a separate utility plan sheet. A table specifying house type, garage elevation, lowest opening elevation, street centerline grade, 100year flood elevation, and front and back yard slopes must be added to the plan. The grading plan should also contain emergency overflow elevations. The proposed storm sewer which provides both inflow and outflow from this pond is proposed to be constructed below the normal water surface elevation. This could result in a frozen pipe condition particularly during the winter/spring runoff months. This could subsequently result in flooding of the street and surcharging of the detention pond above its design standards. In addition it appears that the overflow of the pond onto the adjacent property to the north may not be confined to areas covered with drainage and utility easements. The drainage swale along the rear of Lots 4 through 9 is proposed at a grade flatter than 2%. A certificate of grading will be required prior to occupancy to ensure that a minimum grade of 1 % has been achieved. Staff is recommending consideration of an alternative discharge through The Ponds subdivision drainage system or through the CSAH 5 road ditch to the south. A permit needs to be obtained from the Lower Rum River Water Management Organization. Utilities: This plat will be served by municipal sanitary sewer and water. The City will require installation of public sewer and water mains under proposed Helium Street. This will remove future maintenance out of the County right of way and will reduce significantly the length of lateral sewer and water services required. Please revise the submitted utility plan to reflect this. Fire Department Considerations: The proposed six-unit building meets the threshold for sprinkling requirements, and will be required to provide a sprinkler system for fire protection. The proposed water pipes should be sized to accommodate additional water demand for this system. Please revise your utility plan to indicate this. The Fire Department reserves the right to require fire lanes, where deemed appropriate on narrow public or private streets. It is not anticipated that fire lanes will be required on Helium Street. 26