Agenda - Council - 12/17/1985 - Laserfiche WebLink

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I i I I I I I I I I I I I I I I I I I IV. PROPOSED IMPROVEMENTS TO alleviate the flooding, west of Ramsey Boulevard and north of U.S. Highway No. 10, it is proposed to construct a 36 inch trunk storm sewer from the Mississippi River to the north side of the Burlington Northern railroad right-of-way. The Portion of the 36 inch trunk between U.S. Highway 10 and the railroad is proposed to be perforated to allow groundwater to enter the storm sewer. It is also proposed to extend this 36 inch perforated pipe 400 feet west on the north side of the railroad. The location of~the proposed pipe is shown on Exhibit B. This line would provide drainage to subdistricts W-3A, W3, W4, W5, W6, W7 and W8 of the West Drainage District and approximately 1,310 acres surrounding Lake Itasca. The size of the pipe is based on providing the storage ponds as shown in Table 1. The proposed trunk would be capable of draining a 100-year frequency storm in a period of 10 days. In addition, it is proposed to construct subdrains consisting of 12-inch perforated pipe along the north side of U.S. Highway 10 as shown on Exhibit B. This would help to lower the watertable in the immediate area approximately six feet and provide inlets for surface water. In the long-term, it is estimated that the subdrains and perforated pipe would have some impact on the water table throughout most of the drainage district. The amount of impact cannot be determined without an extensive hydrologic .study. However, to maintain maximum highwater elevations on existing and ..proposed ponding areas, either ditches or storm sewer outlets will be required, as shown in the Comprehensive Storm Drainage Plan. 4