02-12-2015 Planning Comm. Agenda

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Planning Commission February 5, 2015 Page Two and we would recommend that a maintenance agreement be executed to ensure future maintenance is completed and a mechanism is in place for a recovery of any City costs necessary to ensure compliance. 2. All storm water runoff from this site currently drains south onto private property and the development plan as submitted does not change this condition. The new development will result in more impervious surface and discharge rates are maintained or lowered for the proposed conditions for a 2 -yr, 10 -yr, and 100 -yr event. During the smaller rain events the overall volume of water discharged from the site will be lowered, which will benefit the property to the south. However during large rain events the discharge volume will increase, which could adversely affect the property owner to the south. Based on the topography on the plan and that shown on the County's GIS map it appears the storm water discharge from 716 Labore Road is directed towards the house at 715 Keller Parkway. We have concerns that while the overall discharge rate of storm water off the site is being maintained or reduced up to the 100 year storm event, the volume of water discharged will increase for the larger storm events. We had discussed this concern with the Applicant's Engineer prior to the submittal and recommended that they work with the neighbor to ensure runoff water is directed across the property or through a in a manner that will not negatively affect the neighbor. Based on the plans it does not appear that any measures are being taken to address the conveyance of the water across the 715 Keller Parkway property. Summary The storm water calculations should be revised and resubmitted based on the comments listed including the use of the new Atlas 14 rainfall events. We have concerns relative to the discharge of storm water onto the private property to the south without an improved means of conveyance to a public right-of-way or easement. We would recommend the Planning Commission direct the applicant to work with the adjacent Property Owner to ensure storm water conveyance does not negatively impact 715 Keller Parkway. Please contact me if you have any questions regarding the above information at (763) 780-0450 ext. 3. Sincerely, ELFERING & ASSOCIATES Lee Elfering, P.E. City Engineer cc: Bill Dircks, Public Works Director Ltr-020515-PC 10062 Flanders Court NE, Blaine, MN 55449 - Phone: (763) 780-0450 - Fax: (763) 780-0452 9