Agenda - Public Works Committee - 09/21/2004

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CASE # / CONSIDER JUNIPER RIDGE DRIVE/151sT AVENUE STORM WATER MODIFICATIONS By Steven J. Jankowski, City Engineer Background: In 2000 modifications were made to the storm sewer system along a portion of Juniper Ridge Drive which included the s%wnent from 151st Avenue south to the cul-de-sac. A part of these improvements included the construction of an emergency outfall to the Rum River, which would be utilized during extreme precipitation events. A part of the normal operation Of the storm water system calls for the ponding of water within a fifty foot drainage and utility easement located along the northerly side of the lot located at 15000 Juniper Ridge Drive. This ponding area also has as its primary discharge point another outlet which flows into the pond located between Tonto and Ute Streets in the adjacent Juniper Woods subdivision. Subsequent to the 2000 project, a garage was constructed on this lot just beyond the easement. During a recent storm event, storm water ponded beyond the easement and came within' a couple of feet of the newly constructed garage. Staff performed some survey work and determined that the outlet weir was set at an elevation which would cause water to pond beyond the drainage and utility easement prior to discharging through the emergency outfall to the river. In view of the above, staff has requested the desig-n engineer do a review of the design ct/terra to detemnine the extent to which the weir on the emergency outlet should be lowered. It is also anticipated that additional ponding volume will be required within the drainage and utility easement to ensure the peak elevation of the 100 year flood will be contained within the easement. It is anticipated that the corrective work will include; lowering the weir elevation, increasing the pond areas volume, and filling and resodding a portion of the yard at 15000 Juniper Ridge Drive. It is anticipated that all work, excepting the landscaping will be performed by the Public Works department. The cost of the landscaping work should be less than $1,000. Recolnnlendation: Staff recommends that an analysis of the drainage basin be conducted and that necessary con'ective actions be taken to ensure that the 1 O0 year precipitation event is contained within the drainage and utility easement at a contracted construction cost not to exceed $1,000 which shall come fi-om the stom~ water utility. Action: Motion to recommend to City Council that an analysis of the drainage basin be conducted and that necessary corrective action are taken to ensure that the 100 year precipitation event is contained within the drainage and utility easement at a contracted construction cost not to exceed $1,000 which shall come from the storm water utility. Reviewed By: Puhlic Works DirectoffFire Chief Assistant Public Works Director Street Maintenance S upe~wisor PW: 09/21/04