Agenda Packets - 1984/02/27 - Laserfiche WebLink

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- 2 - requires approval of a conditional use permit. Notification of the proposed conditional use permit has to be sent to the commissioner of the Department of Natural Resources to afford them an opportunity to comment prior to final action by the City. 5. The site in question is positioned at the northerly end of the drainage area which extends generally from County Road I from Long Lake Road and Quincy Street south to the City limits on County Road H. This system is a complex drainage system and currently has several segments that are under flow constraint due to size and slope of existing storm sewer pipe. The site in question is directly drained by a storm sewer pipe that runs parallel with St. Stephen Street approximately one lot depth west of St. Stephen Street. This pipe currently has a capacity of approximately 7.1 to 7.7 cubic feet per second. The proposed plan proposes to release water into this system at a maximum rate of 4.5 cubic feet per second. The balance of the runoff would be stored in a detension facility located at the northern end of the site. The five year, one hour rainfall discharge in the undeveloped state is 6.76 cubic feet per second. Therefore, the developer has met the requirement of Chapter 49A to limit his discharge to the five year, undeveloped state or less. The plan provides for creation of a detension facility at the northern end of the site that will hold approximately 31,500 cubic feet of water that would have to be obtained between the five year discharge rate and the 100C) year rainfall rate. The top of the pond elevation would be approximately 902, which coincides with the flood plain elevation controlled by Chapter 49. The garage building at the northern end of the site would be at or above elevation 903. It should be noted that the existing center line elevation on County Road I northerly of the site is at elevation 905, therefore, water will enter the site from the roadway which is not included in the storage volumes mentioned above. The amount of water is dependent upon the severity of the storm water as to whether drainage improvements might be installed along County Road I. It should be noted that the section of County Road I from Long Lake Road to Quincy Street is currently not served by any storm sewer system catch basins. The water on surface drains to available ditches and/or pipe entrances located off or adjacent to the rights -of -way of County Road I. With the upgrading of County Road I, it is anticipated that at least a portion of the county road will drain through this site. If that is the case, an additional storage will be necessary on the site. The plan, as present,�u, has little allowance, if any, for future ponding needs resulting from the drainage of County Road I. The pond will only provide for approximately 1.8 acre feet of storage or 80,000 cubic feet before garages at the northern end of the site will become flooded. It is recommended that the City 1