01-05-2015 Council Packet - Laserfiche WebLink

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WS — Item 2 WORK SESSION STAFF REPORT Work Session Item 2 Date: January 5, 2015 To: City Council From: Michael Grochala Re: NE 35E Area Drainage Study Background The City Council authorized preparation of the NE 35E Area Drainage Study in November of 2012. The purpose of the study was to evaluate options to address drainage for a 700 acre area lying NE of the 35E interchange. The study was expanded in July of 2014 to include an additional 700 acres on the west side of Interstate 35E and provide a new surface water outlet to Peltier Lake. The majority of this area currently drains into either County Ditch 55 or 72. Land within this area is poorly drained with clay soils that have minimal infiltration capacity. The ditches, which are tile lines that convey water from this area, were constructed in the early 1900's for agricultural purposes. The size of the tile ranges from 10 to 15 inches and does not have the capacity to carry new runoff from developing properties. Staff has worked with WSB & Associates, the Rice Creek Watershed District, and neighboring property owner to evaluate options. Over the past 6 months WSB has worked on detailed stormwater modeling to verify that water quality and quantity requirements can be satisfied by the establishment of a new system. As a result of the modeling effort and associated preliminary wetland review a preferred alternative alignment is being proposed. While still conceptual the proposed location of the new conveyance system appears to minimize wetland impacts while efficiently serving adjacent future development. Pete Willenbring of WSB and Associates will be at the work session to provide an overview of the work completed to date. Requested Council Direction Staff is requesting council interest in pursuing this alternative. Attachments 1. Preferred Outlet Alternative