02-07-2022 Council Work Session Packet

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wsb Memorandum To: Katie Larsen, City Planner, City of Lino Lakes From: Diane Hankee, City Engineer, City of Lino Lakes Date: January 5, 2022 Re: Robinson Property Concept Plan WSB has reviewed the Robinson Property Concept Plan for a 710 unit PUD prepared by Integrate Properties, LLC and submitted on December 13, 2021. The site is located south of Main Street (CSAH 14), east of Sunset Avenue (CSAH 53), and north of Robinson Drive and Carl Street. An Environmental Assessment Worksheet was not provided and should be completed for this site. Engineering • Erosion Control & Grading The proposed Robinson Property project would require mass site grading, appurtenant erosion control, and a SWPPP. Stormwater Management The Robinson Property is drained by a series of private ditches and roadway ditches west of Sunset Avenue (CSAH 53) and south of Main Street (CSAH 14) that tie into Anoka County public ditch 10- 22-32 (ACD 10-22-32). ACD 10-22-32 flows south through the Robinson Property to Carl Street. ACD 10-22-32 continues south under Carl Street and ultimately discharges to Marshan Lake. Anoka County should review the preliminary drainage design and site access concurrent to the City's preliminary plat reviews. Most of the site is within the City's General Floodplain District (FEMA Zone A) and, according to the Geotechnical Evaluation Report cited in the Concept Plan Submittal, groundwater levels range from 4-feet to 9-feet in depth. The applicant will be required to meet all City of Lino Lakes ordinances and RCWD rules for surface water management. The Robinson Property is in the Marshan Resource Management Unit (RMU) according to the City of Lino Lakes 2018 Local Water Management Plan (WMP). The WMP noted several issues within the Marshan RMU, including the following issue pertinent to the Robinson Property: "ACD 10-22-32 is ineffective for future urban runoff volumes." (Appendix B). A strategy for mitigating this issue specific to the Robinson Property noted in the WMP was: "Proposed master community plan for sod fields" (Appendix B). In addition, the WMP identified existing and future flooding and pollutant loading concerns within the RMU, including Marshan Lake and adjacent wetlands and ACD 10-22-32 (Table 2-21). WMP Goal 4.1 is to "Provide adequate storage and conveyance of runoff to protect public safety and minimize property damage." To address the City's flooding concerns in accordance with this goal, implementing stormwater rate and volume control practices where feasible throughout the Robinson Property will be critical. Sufficient freeboard must be provided for proposed structures above the seasonal high groundwater levels and floodplain elevations in compliance with City Ordinance Chapter 1102 (Stormwater, Erosion and Sediment Control) and RCWD Rule C (Stormwater Management). Ditch conveyance capacity along Sunset Avenue (CSAH 53) and Main Street (CSAH