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A <br />WSB <br />477 Temperance Street I St. Paul, MN 55101 1 (651) 286-8450 <br />April 20, 2017 <br />Ms. Rachel Juba <br />City Planner <br />City of Hugo <br />14669 Fitzgerald Avenue North <br />Hugo, MN 55038 <br />Re: Stormwater Management Plan Review <br />Western Spring Manufacturing <br />WSB Project No. 3288-170 <br />Dear Ms. Juba: <br />We have completed our review for the Western Spring Manufacturing site for stormwater management. <br />The following information was received for review: <br />■ Preliminary Plans, prepared by Campion Engineering Services, Inc., dated April 6, 2017 <br />■ Storm Water Management Plan, dated April 6, 2017 <br />■ Storm Sewer Design, dated February 23, 2017 <br />■ Geotechnical Report, prepared by Braun Intertec, dated January 23, 2017 <br />Based on the review of the plans, we offer the following comments: <br />General <br />1. The soil boring report shows evidence of groundwater near the site of the infiltration basin. The <br />boring closest to the basin reported the groundwater elevation to be approximately 924.5. The <br />bottom of the basin is proposed to be 927.0, leaving only 2.5' of separation. The requirement is 3' <br />of separation between the bottom of the infiltration basin and the high-water table. This will need <br />to be addressed. <br />2. The onsite infiltration basin is designed to accommodate 2.83 acres of impervious area. Proposed <br />impervious for construction is approximately 1.93 acres. This allows up to 0.9 acres of impervious <br />to be constructed in future expansions. <br />3. The regional basin has additional capacity for rate control. Rate control for each site is limited to <br />the 10 -year event using TP -40 values for full development. See attachment for the available <br />parcels that the basin was designed to accommodate. New developments are still required to <br />provide onsite volume control to meet RCWD requirements. <br />Thank you for the opportunity to provide comments on this project. If you have any questions, please do <br />not hesitate to contact me at 651-286-8463. <br />Sincerely, <br />WSB & Associates, Inc. <br />Mark Erichson, PE <br />City Engineer <br />Building a legacy —your legacy. <br />Equal Opportunity Employer I wsbeng.com <br />K: 03288-170�AdminWocs�3288-170 COM LTR-rjuba-042017- Western Spring Manufacturing. docx <br />