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<br />CASE # J.." <br /> <br />NEED FOR TOPOGRAPHIC MAPPING <br />By: Steven Jankowski, City Engineer <br /> <br />Background: <br /> <br />Topography has a significant impact on the development of a community infrastructure, <br />including storm and sanitary sewer, water systems, roads, subdivisions and public parks. <br />At the present time, the best topographic information, which is available for the entire City, <br />consists of the U.S.G.S. quadrangle maps which provide 10 foot contour intervals on a <br />scale of one inch equaling 2,000 feet. While these maps are useful in addressing regional <br />issues, they are not usually adequate for even general subdivision planning. <br /> <br />This spring, Anoka County had the entire County aerial photographed as it does every four <br />years. These aerial photographs, which are at a scale of one inch equals 200 feet, provide <br />excellent information relative to horizontal spacial relation. (i.e., the distance of a house <br />from the road, etc.). Most communities have enhanced the capabilities of these aerial <br />photographs by adding topographic information which includes two foot contours. This <br />level of detail would enable the following: <br /> <br />· Definition of drainage basins to adequately plan storm sewer routes and pipe sizing. <br /> <br />· Determine route locations for extending the sanitary sewer system and identify <br />where lift stations will be necessary. <br /> <br />· More accurate prediction of water system pressures and fire flows which are <br />elevation dependent. <br /> <br />$ Assist in layout and design of City parks. <br /> <br />· Identify the scope of highway modifications for sight distances. Improvement on <br />reroutings and provide sufficient infOlmation for the planning of new roadways. <br /> <br />· Accurate identification of areas contributing runoff to problem drainage areas. <br /> <br />In addition, the topographic information would be extremely useful to developers for the <br />design of their plats. Other communities which have undenaken similar topographic <br />mapping have recovered part or all of the costs by charging the developer a fee based upon <br />acreage at the time of plat recording. This should not be objectionable to developers as they <br />now must contract for this same information. <br /> <br />Since the cost of mapping the entire City would be a significant expense, I would propose a <br />phased approach to the mapping. At the present time, the southeast quadrangle of the City <br />is undergoing rapid urbanized development. This is the area having the most critical need <br />for topographic mapping. I have discussed the cost of obtaining a reproducible, two foot <br />contour mapping over approximately eight areas with afmn specializing in the work. The <br />cost is estimated to be $30,000. If a charge of $10 to $15 per platted acre were charged to <br />undeveloped land in the mapped area, the total cost could eventually be recovered. <br /> <br />Recommendation: <br /> <br />I believe the mapping described above is an essential element of the information which <br />should be maintained by the City's Engineering Department. I, therefore, would <br /> <br />q <br />