3.0. SR 12-13-1993 - Laserfiche WebLink

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1 r j I j I I . I 1 1 ! j ;. 1 . ! j f 15 2-090 l.d~c 4. Analyze the portion of the site that flows to the south down Freeport A venue. This will require modeling of the entire drainage system that flows all the way to the Mississippi River. Comment on the effect on the intersection of Main and Evans or any other critical point. Watershed Modeling Developing Elk Park Center will effect storm water discharges in a large drainage basin within the City of Elk River south and southwest of the proposed development extending from Proctor A venue on the west to TH 169 on the east and north of the railroad tracks extending through the City. Water flows generally in a north to south direction, to the basin outlet under the railroad tracks, and then through a 60" RCP storm sewer pipe to the Mississippi River. Storm sewer routes in the basin include storm sewer along Freeport Avenue, Gates A venue, Main Street, School Street, and an outlet from the pond within Lion's Park. Three sub-areas of the larger drainage basin have ponds with no local outlets. These ponds may in the future be connected to the Elk River storm sewer system. The three sub-areas are all located west of Jackson A venue and north of School Street. Much of the storm sewer system modelled was constructed during the early- 1980' s. Since this time, the City of Elk River has experienced considerable growth, especially along the TH 169 corridor. The entire drainage basin system was modelled with the TR-20 Project Formulation-Hydrology program for a lO-year and 100-year event. Close attention was directed toward junctions in the storm sewer system where surcharging would occur for a given storm event. Surcharging occurs where a manhole fills with water and may even overtop and flow out onto a street if the head forcing the water is high enough upstream of the manhole. Three critical points currently exist on the system; the intersection of Freeport A venue and Gates A venue, Gates A venue between Main Street and 3rd Street, and also the intersection of Main Street and Evans Avenue. These three locations experience surcharging; however, the Main Street and Evans A venue location is the only location experiencing a flooded intersection for storms as frequent as a 10-year event. For large storm events such as a 100-year event, much of the flow of water in the drainage basin is overland. But in the case of the Main and Evans intersection, this intersection is a low area, so the problem is compounded by overland flow flooding the intersection, along with the surcharged condition of the storm sewer system. -11- 230-152-10