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HomeMy WebLinkAbout2015-01-06 City Engineer Email with DRAFT Stormwater Memo Julie Hultman From: Mlejnek, Cristina <Cristina.Mlejnek @stantec.com> Sent: Tuesday,January 06, 2015 5:18 PM To: Eric Johnson;Andrew Kegley; scott @planningco.com;Julie Hultman Subject: RE: Oak Park Senior Living - Phase 4 Review Attachments: OPH_OakGreenPhaselV_StormwaterMemo_150106_DRAFT.pdf All, Our comments are minimal due to the fact that this is a private site and we are reviewing in the interest of the City and not the Developer. Additionally, we did perform a brief, initial review of the Storm water; and the pond storage appears to be substantial for the proposed increased impervious area. Please see attached for additional, draft Storm water information. Please let me know if further review is desired. Sincerely, Cristina From: Mlejnek, Cristina Sent: Tuesday, January 06, 2015 2:42 PM To: Eric Johnson (eajohnson @icityofoakparkheights.com); akegley©cityofoakparkheights.cam; scott@planningco.com; Julie Hultman (jhultman @cityofoakparkheights.com) Subject: Oak Park Senior Living - Phase 4 Review All, We have minimal comments from an engineering standpoint. All of which were discussed at last week's meeting. They are as follows: 1) Need to resolve the Drainage and Utility Easement issues at the SE corner of the proposed building and the existing storm sewer that runs to the north from CB-5. 2) Placing retaining wall over easement at own risk. 3) Need to see engineering for retaining wall (over 4'). Please let me know if there are any questions/comments. Project Manager Stantec 2335 Highway 36 West St. Paul MN 55113 Phone: (651) 967-4619 cristina.mlejnek @stantec.com nte. The content of this email is the confidential property of Stantec and should not be copied,modified,retransmitted,or used for any purpose except with Stantec's written authorization.If you are not the intended recipient,please delete all copies and notify us immediately. ('lea.e c,onsidt r the e ne o e pr Sire the Creeli. 1 Stantec Memo To: Cristina, Mlejnek From: Nathan Warner Stantec Consulting Services Inc. Stantec Consulting Services Inc. File: Oak Park Heights Private-Oak Date: January 6,2015 Green Phase IV Reference: OakGreen Senior Living Phase IV Stormwater Review This memo summarizes the review of materials provided by Folz,Freeman,Erickson,Inc. The submittal was reviewed for compliance with the policies of the City of Oak Park Heights Local Surface Water Management Plan and the Middle St.Croix Watershed Management Organization. The site will need to comply with the runoff rate,runoff volume,and water quality policies of the LSWMP and MSCWMO. The following materials were reviewed as part of the submittal: • Site Plan • Oak Park Senior Living Phase Four General Plan Narrative • Oak Park Heights SWMP(2007)HydroCAD model Additional materials required for stormwater review: • Drainage Area map • Hydrologic model and/or model inputs • Oak Park Senior Living Master Plan—Drainage Plan Runoff Rate 1. The peak runoff rate for proposed development shall not exceed the existing rate for the 2,10,and ioo- year rainfall events.Not enough information provided to determine existing and proposed rates. 2. Drainage maps should be provided to include contours and land use over the entire drainage area. Runoff Volume 1. Per the City's LSWMP, an infiltration standard(V2"over impervious area plus 1/4"over area with compacted soils)for proposed projects are based on the Middle St.Croix Watershed Management Organization's Watershed Management Plan. The applicant shall work through the review process with the MSCWMO to ensure all standards are being met. 2. Per MPCA NPDES Construction Activity permit,if one or more acres of impervious surface are created, then a water quality volume of 1"over new impervious surfaces must be retained on site(infiltration or other volume reduction method). 3. Not enough information provided to determine the water quality volume or if the site is meeting the volume reduction standards. Water Quality 1. Per the MSCWMO standards,stormwater must be treated prior to discharging into a water body. 2. There are no current requirements regarding TP and TSS removal.Storm water detention ponds should be designed to NURP standards. Design with community in mind ® Stantec January 6,2015 Cristina,Mlejnek Page 2 of 2 Reference: OakGreen Senior Living Phase IV Stormwater Review Stantec Consulting Services Inc. Nathan Warner Phone:651-604-4754 Nathan.Warner@stantec.com Design with)CO MLI tinhg1it116t_il\oak_park_heights_ci_mn\55 private\oakgreen senior living(village&carriage)phases\oak park senior living phase 4\oph_oa kg reen ph aseiv_sformwaf erm e m o_150106_d raf t.d ocx