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WS — Item 2 WORK SESSION STAFF REPORT Work Session Item 2 Date: July 7, 2014 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 majority of this area drains to County Ditch 55, under 35E and ultimately to Clearwater Creek. Land within this area is poorly drained with clay soils that have minimal infiltration capacity. Additionally, the tile line (Ditch 55) that conveys water from this area was 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. Given the constraints of the system and need to balance agricultural, development and public infrastructure needs, a comprehensive management plan is needed for this area. Addressing both water quality and volume requirements within this area will have an impact on the developability of property within the corridor. Since this is an area of high importance from an economic development perspective, it appears to be in the best interest of the city and land owners to develop a plan that identifies the best options for stormwater treatment and storage, preservation of natural areas and establishment of a preferred conveyance system and routing for stormwater. The initial conceptual plan submitted to the Rice Creek Watershed District (RCWD) proposed the construction of a new storm sewer line running south to Clearwater Creek. However, after further review a 2nd alternative has been developed that would 1) address a surface water management over a larger drainage area, and 2) avoid issues related to possible increased flow volumes to Clearwater Creek. The "Peltier Lake Ponds and Greenway Corridor" would provide a new outlet directly to Peltier Lake. The new concept provides the opportunity to provide an improved drainage outlet for nearly 1,400 acres while creating a high value greenway system, as proposed in the Comprehensive Plan, and improving water quality entering Peltier Lake. Pete Willenbring of WSB and Associates will be at the work session to provide an overview of the proposal. Our next step would be to complete a detailed study including approval of a Comprehensive Stormwater Management Plan through the RCWD. Requested Council Direction Staff is requesting council interest in pursuing this alternative. Attachments 1. NE Drainage Area Map.