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Building a legacy – your legacy. 701 Xenia Avenue South Suite 300 Minneapolis, MN 55416 Tel: 763‐541‐4800 Fax: 763‐541‐1700 Equal Opportunity Employer wsbeng.com K:\02029‐790\Admin\Docs\FEASIBILITY STUDY\OPTIONS CONSIDERED\Memo_MGrochala_051316.docx Memorandum To: Michael Grochala, City of Lino Lakes From: Katy Thompson, PE Date: May 19, 2016 Re: Lino Lakes Northeast Drainage Area – Options Considered WSB Project No. 02029‐790 Below is a summary of the design options that have been considered to alleviate the drainage issues in the Northeast Drainage Area of Lino Lakes. SUMMARY OF OPTIONS CONSIDERED OPTION 1: USE EXISTING DRAINAGE SYSTEMS This option is further broken down into three alternatives, utilizing the existing Anoka County Ditches within the drainage area, Anoka County Ditch 55 (ACD55) and Anoka County Ditch 72 (ACD72). The existing ditches have a 33‐foot easement, on center. Option 1A: Existing System to Remain In Place The existing system (Figure 1) is in need of maintenance, with RCWD having completed a study in 2014 outlining system improvements. The capacity of the system is not sufficient to develop the area as established in the City of Lino Lakes Comprehensive Plan. For property owners to make improvements in this drainage area, per RCWD rules, they may need to dedicate up to 40% of their developable land for stormwater management, including ponding of back‐to‐back 100‐year flood events and infiltration requirements. This area has tight soils and infiltration options are costly and limited. Spray irrigation is temporarily being used to meet the requirements at the McDonald’s site until a regional BMP is constructed. The existing system does not provide treatment upstream of Peltier Lake which is classified as an impaired waterbody. Any proposed project must not impair water quality or flood storage within or downstream of Peltier Lake. This option was not considered for further analysis. Option 1B: Outlet to Clearwater Creek This option considered the lands drained by ACD 55 to the east of I‐35E and proposed to reroute this drainage area south, via storm pipe, along the proposed Otter Lake Road extension, to Clearwater Creek (Figure 2). This option benefits 710 acres, of which 495 are in Lino Lakes. This option was not considered for further analysis in the feasibility study due to adverse impacts to Clearwater Creek, including increased discharge and potential bank erosion concerns.