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K:\015144-000\Admin\Docs\AUAR - Update 2020\Stormwater\MEMO - 040920 - Stormwater AP.docx 701 XENIA AVENUE S | SUITE 300 | MINNEAPOLIS, MN | 55416 | 763.541.4800 | WSBENG.COM Final Technical Memorandum To: Michael Grochala, City of Lino Lakes From: Madison Rogers, WSB Andi Moffatt, WSB Date: April 8, 2020 Re: Stormwater Management – I-35 Corridor AUAR City of Lino Lake, Minnesota WSB Project No. R-015144-000 INTRODUCTION The original Alternative Urban Areawide Review (AUAR) was completed and approved in September 2005. The AUAR analyzed the stormwater impacts of the three development scenarios. Based on the analysis, a Mitigation Plan was developed. AUAR updates are required every five years from the original date of the approved AUAR. Updates were prepared in 2010 and 2015. Each assumed no change in the proposed development land use scenarios and included discussion of mitigation improvements that had been completed at the time. Since the 2015 AUAR update was prepared, the City has completed an updated Comprehensive Plan. This AUAR Update includes review of three revised scenarios. The information and analysis outlined within this memo is intended to complete a portion of the AUAR Update related to Item # 11.ii – Water Resources – Stormwater related to revising of the three revised scenarios. This memo is intended to update the stormwater analysis provided in the original AUAR where applicable. WATER RESOURCES – STORMWATER ii. Stormwater - Describe the quantity and quality of stormwater runoff at the site prior to and post construction. Include the routes and receiving water bodies for runoff from the site (major downstream water bodies as well as the immediate receiving waters). Discuss any environmental effects from stormwater discharges. Describe stormwater pollution prevention plans including temporary and permanent runoff controls and potential BMP site locations to manage or treat stormwater runoff. Identify specific erosion control, sedimentation control or stabilization measures to address soil limitations during and after project construction. Procedures and Methods Followed The procedures and methods used to estimate the runoff volumes and pollutants loads within the AUAR were based on the Natural Resource Conservation Service (NRCS) runoff curve number method and event mean concentration pollutant values from the Minnesota Stormwater Manual. Any development within the study area will be required to meet the stormwater standards of the City of Lino Lakes and Rice Creek Watershed District (RCWD). These standards include: • Promote volume control and groundwater recharge. • Protect water quality from nutrients, heavy metals, and other urban pollutants.