02-12-2015 Planning Comm. Agenda

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£LUllG .assoal1r.s February 5, 2015 File: 120183E-0240 Honorable Chair and Planning Commission City of Little Canada 515 Little Canada Road East Little Canada, MN 55117-1633 RE: 716 LABORE ROAD LOT SPLIT CITY OF LITTLE CANADA Dear Planning Commission: We have reviewed the submittal package for the development of 716 Labore Road. The current property is approximately 22,900 square feet in size and the Applicant is proposing to split the property and develop two single family residential homes. A storm water management report was submitted including predevelopment and post development drainage maps, drainage calculations, HydroCAD modeling, soil borings, and a Storm Water Management, Erosion Control & Utility Plan. Based upon our review we would offer the following comments. Drainage Calculations 1. A time of concentration of 6 minutes is referenced in the narrative but that does not match the 10 minute time of concentration used in the HydroCAD calculations. 2. Infiltration should be disregarded in the calculations for rate control to ensure predevelopment discharge rates are maintained if the infiltration aspect of the garden is not functioning. 3. The drainage calculations reference TP -40 rainfall events. The calculations should be run utilizing the Atlas 14 rainfall events. Storm Water Management, Erosion Control & Utility Plan 1. The swale between Labore Road and the westerly proposed house directs drainage towards the west property line but it does not appear the swale continues down the west lot line to the pond. The drainage calculations submitted indicate all storm water from the site is collected in the south pond and based on the grading plan that does not appear to be the case. The grading plan should be revised or the drainage calculations modified to account for this direct offsite flow. Other Comments 1. There is no discussion or mention in the submittal material as to the on-going or future maintenance of the storm water system proposed or the costs associated with it. The system will not receive public water, but the pond serves two private properties so it should be covered by shared easement between the two properties or in a public easement. Whether or not it is in a Public easement the maintenance would not be the responsibility of the City Ltr-020515-PC 10062 Flanders Court NE, Blaine, MN 55449 - Phone: (763) 780-0450 - Fax: (763) 780-0452 8 TRU IIBATJI