2. AGENDA 09-19-1994 - Laserfiche WebLink

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. Mr. Pat Klaers September 19, 1994 Page Two 2. Given the elevation of the trunk stonn sewer line in Orono Parkway, the pipe is too large and will never flow full; thus, extra monies were spent on pipe capacity which will never be used. Dave Nyberg of MSA, Consulting Engineers, and Jon Bogart of John Oliver and Associates have jointly worked through the design, Dave from the perspective of the overall City concept, and Jon from the perspective of the Tony Emmerich Country Crossings Development. These two have worked through the modeling of the storm sewer system in the Western Area and both have concluded that the pipe will not only provide adequate capacity for the Country Crossings single-family residential developments, but also will have additional capacity for the Sandpiper Estates area and minimal capacity for property lying north of Orono Parkway. They also agreed that the pipe will flow full in the lOO-year storm event. In fact, the actual outlet near Lake Orono will be slightly surcharged in the lOO-year event. 3. Flow from the southeastern portion of the Country Crossings First Addition is directed southerly through the Mississippi Oaks stonn sewer system because the stonn sewer pipe in Orono Parkway is too shallow. . Item #1 has previously discussed the depth of the storm sewer pipe in Orono Parkway. The City's Comprehensive Storm Drainage Plan has always showed a small portion of property north of County Road 30 being directed southerly through this trunk line to the Mississippi River. In fact, when this trunk line was put in, the cost of it was prorated against Mississippi Oaks, Heritage Landing, and the area north of County Road 30. The distribution was 29% to Mississippi Oaks, 49% to Heritage Landing, and 22 % for the area north of County Road 30. 4. The flow from north of County Road 30 is a 24-inch pipe outletting into a 24- inch pipe in Mississippi Oaks. The question which arises is whether there is adequate capacity for all this flow. There is, in fact, a 24-inch pipe being connected from Country Crossings First Addition. However, the pipe south of County Road 30 is 27 inches in diameter. The flow in a pipe is dependent not only on its size, but on the slope of the pipe. The 24- inch pipe exiting Country Crossings is relatively flat. The 27-inch pipe in Mississippi Oaks has approximately 2% times as much slope as the pipe from the north. There is adequate capacity in this pipe system to handle the flow from north of County Road 30. . 2301223.1905.sep