Agenda - 11-20-2006-c3 - Laserfiche WebLink

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Watershed Critical Area Mapping Options 3 11/14/2006 Issues Relating to Mapping of the Upper Eno Critical Watershed Areas The original 1994 zoning and watershed maps did not illustrate the associated zoning text, which is typically the operative aspect of regulations. The maps do not reflect the text for the following reasons: 1. Topographic mapping had less elevation refinement leading to more spatial variation when trying to determine distances from existing or future watershed impoundment sites and the associated normal pool elevation (NPE). For example, the Lake Orange NPE is 615', but the Orange County topographic information, at that time, only displayed the 610' and 620' topographic contours. We now have five-foot topographic data available and can better interpolate the map buffer. 2. Some proposed impoundments, such as the West Fork of the Eno River did not have a determined NPE, so a map approximation was made. We now know the proposed Phase 2 NPE is 634'. 3. Some impoundments half -mile buffers were shown on the map but the NPE that established the area buffered was not described or unnamed in the zoning text. For example, the proposed Eno River Impoundment above McGowan Creek was map buffered but not named in the text. We can more accurately establish an area buffer along the Eno River above Corporation Lake to protect the proposed Eno River above McGowan Creek Reservoir at the 580' NPE. 4. Originally, the Lake Orange NPE was 614', but an additional one -foot of freeboard was added. The official NPE is now 615'. 5. Lake Ben Johnson is not presently listed in the zoning text. We can map the impoundment with its 515 " NPE accurately. 6. The original base maps are hand drawn on County cadastral maps. The map's accuracy is not always reliable. The 1984 West Orange Study and 1987 Water Supply Study base maps were hand -drawn on these cadastral maps. While as accurate as possible at the time, the small -scale maps, which resulted, are not accurate for large -scale property maps that developers use for platting. We have digitized these maps and can refine the watershed boundary lines with state -of- the -art watershed mapping provided by the State of North Carolina. G:''(Compreherlsit" i'huuifng l')i `,Ci1.aT'2(Y)6 i'ut lir Ifearings'.\,;, '!0 Q111 H iPjxrfiflo 1'f:xi Anuiis'.hf ,kppintg Ofn:i,�a Cnmparisons.d,;t: