03-08-2004 Council Packet - Laserfiche WebLink

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»04-2971 3220-3240 Watertown Road January 14,2004 Pages ///. OHWL and Floodplain Impacts The Zoning Code defines the OHWL for watercourses as “the elevation of the top of the bank of the channel”. It also establishes the “Regulatory Flood Protection Elevation" (RFPE) as an elevation no less than 1.0 foot above the ‘regional flood’, i.e. 1' above the lOO-year floo(4)lain elevation. The Surface Water Management Plan indicates that the Normal Water Level for the large wetland basin just to the north of the property is elevation 963 .S', with the High Water Level (1 00-year flood level) at elevation 970.4'. Ihe top of the bank of the channel at the constriction area in Lot I is at ^proxinute elevation 968.0', and closely matches the delineated wetland botmdary. In recent dUscussiocs with the City Engineer, staff has concluded that the OHWL for setback and lot area calculation purposes for this property should be established at the wetland boundary elevation of 968'. The RFPE, i.e. the minimum floor elevation for any building, should be established at elevation 971.4'. In proposed Lot 1, it spears that neither the buildable area nor the septic sites will be impacted by floodplain and OHWL elevations. However, the creek driveway crossing will likely require filling within floodplain as well as wetland. ly. Front Lot/Baek Lot Impacts The original subdivision was created prior to the 1994 adoption of “fi*ont lot/back lot” standards (Sections 78-1370 and 82-2S6). The existing lots aren’t subject to these special setback and area requirements, but because new lots are being created, the subdivision will be subject to those standards. The impacts include: • Lot 1 as a back lot must meet a 3 acre minimum (it does); - Lot 1 is subject to 150% of the standard setbacks (See staff sketch, Exhibit C2). - Access to Lot 1 must be via a 30* driveway outlet (as proposed) - Lot 2 is subject to a 50' side street setback firom the driveway outlot, rather than a 30' side setback. Summary of Regulatory Impacts 1.The 968' OHWL along the creek is the contour firom which setbacks should be measured for this property. The key OHWL setbacks that affect development of the site are: - 100'structure setback from OHWL - 75' septic setback from OHWl. - no ha^cover allowed within V 5' of OHWL Areas below the OHWL wiU not count toward lot area calculations. The lot dry/wet areas and the OHWL setbacks as shown by the surveyor appear to be acceptable.