03/08/2000 P&Z Packet - Laserfiche WebLink

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• • • 5.3. PUBLIC INFRASTRUCTURE Stormwater & Urban Runoff Comprehensive Management Plan. The City shall develop a comprehensive stormwater manage- ment plan. The management plan shall delineate requirements on private lands and detail public improvements. The following principles should guide the development of the plan. Decentralize Retention. Stormwater retained "close to the source" reduces the need for large -scale improvements that are expensive and inconsistent with the project's emphasis on ecology. Utilize landscaped swales, wetlands, park and plaza features, or other site amenities to minimize piped drainage and facilitate percolation. Naturalize Retention. Generally, retention areas should have a natural profile and wetland plants to filter pollutants (e.g. motor oil and fertilizers) and slow run -off. Naturalized solutions are espe- cially critical along the edge of natural areas to protect sensitive habitats. Permeable Paving. Permeable ground surfaces allow the exchange of water and air to occur, re- charging aquifers and aerating soils. Such surfaces should be required ... or gain a density or FAR bonus. Large areas of paving such as parking lots should use combinations of materials according to the need for durability: areas of lower use call for grasscrete or gravel, while areas of high use should have permeable concrete or asphalt. Plazas should be paved with sand- packed pavers, particularly in low -lying areas. Grading. Site designers should consider ways to minimize grading when locating streets and build- ings. When areas with slopes must be graded, " landform" grading techniques should be used and slopes exceeding 1:3 should be avoided. Rounded forms that use concave and convex shapes also help conceal cuts by presenting a more "natural" look. Varied slopes disperse drainage flows, al- lowing more percolation and reducing the potential for erosion. Water, Wastewater, Police, Fire, Etc.** TO BE DEVELOPED BY CITY Linear Drainage (conventional slope) Flow Concentrated at Toe of Slope Radial Drainage ( landform slope) Flow Concentrated in Valleys e:�� Kph vf: i11 ej rop of '140A•!�� / �.Nairli � ail a l0'140,441w, ;,' �=� �otawcd eLl�i� VIIIS.110# Grading. A "naturalized" landform (right) is preferred over straight, linear slopes (left). Naturalized landforms also reduce the likelihood of erosion. 74