Agenda - Planning Commission - 12/03/2008

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culvert Gl;t this location has the effect of lowering the upstream flood elevation and thereby removes the Ermine Boulevard structirre from the floodway. He further explained the downstream flood elevation is unaffected except for a very minor increase (0.01 ft or l/Sth of an inch) for a short distance (60 feet) downstream of the culvert~ He stated the two downstream property owners within this stretch of Trott Brook have been contacted in writing and staff has met with them to explain the proposed change. He stated the City must undertake several actions in order to facilitate this flood plain change, including the public hearing this evening to adopt flood plain management ordinances incorporating the revised floodway reflecting the post- project conditions; the City's Flood Plain Zoning Ordinance Section 9.22.02, subd. 2, is proposed to be amended by adding the Conditional Letter of Map Revision (CLOMR) outlined in the September 25, 200S FEMA letter as an addition to the City's Official Zo~ng Map. Chairperson Nixt stated it appears this change has a linear effectbut is unable to determine from the calculations the maximum increase in the special flood hazard area; he referenced the sixth full paragraph on page 56 of the agenda (th~ September 25, 2008 letter from Mark Yuan, P.E., Program Specialist with FEMA) which states the maximum increase in SFHA width, approximately 360 feet, will occur just downstream of Ermine Boulevard NW. He asked how this will impact structirres that are already in place downstream. City Engineer Jankowski replied the modeling has shown an increase only in the flood plain. Chairperson Nixt asked if any existing structirresdownstream not currently in the flood plain will end up in the flood"plain if the City updates its map to reflect the changed flood plain that FEMA " says will happen as a result of this. City Engineer Jankowski replied the two adjacent property owners south of Ermine Boulevard, the property to the southeast, the house that is fronting on Eaton Street, has quite a significant drop ih elevation from that house down to the flood plain area. He stated that entire area is prone to flooding. He added the elevation downstream is one eight of an inch higher for a very short distance. The flood plain consists of an area where water is moving and the adjacent area which is inundated. Chairperson Nixt asked how the City will confIrm that what it puts on the amended zoning map is what was communicated with FEMA. City Engineer Jankowski stated the modeling has been reviewed by the DNR and approved by FEMA. Chairperson Nixt stated it appears the City will be improving flow and correcting a culvert that needs repair. He stated it would be helpful to see how the flood plain map is going to change as a result of this, both upstream and downstream, and requested that the City Council be shown a pictorial representation ofthese changes before making its decision on this matter. City Engineer Jankowski agreed to provide a pictorial representation of the proposed changes to the City Council.s Planning CommissionlNovember 6,2008 Page 11 of 18 P11