Agenda - Council - 01/26/2016 - Laserfiche WebLink

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based on field observations is a valid assumption. NTI recommends a pavement design of 8" aggregate base, 21/2" bituminous base course, and 2" bituminous wear course, which assumes less than 300 heavy commercial vehicles will travel on these streets daily. Since this development is built out, Staff firmly believes that less than 150 heavy commercial vehicles will use these streets on a given day and recommends proceeding with the City staff proposed design. Staff will work with NTI and State Aid during final design to ensure the proposed pavement design meets State Aid 9 -ton design standards. As noted earlier, NTI recommends completing a 12" minimum subgrade correction by scarifying and compacting existing subgrade soils, then test rolling the corrected soils after and checking for poor or unsuitable areas and making spot corrections as needed. NTI recommends also adding sub -drain pipe along the outside bottom edges of subgrade on all streets and draining the pipe into catch basins or daylighting the pipe. The proposed pavement design should result in a pavement life of at least 60 years, assuming that proactive, regular pavement maintenance treatments are performed during the life of the pavement. Stormwater Improvements: The existing drainage and storm sewer system will be improved by adding concrete curb and gutter and providing additional catch basins along curb lines to reduce the width of stormwater encroachment onto the pavement surface during rainfall and snowmelt events. Sub -drain pipe will also be added along the outside edges of subgrade correction at low points to ensure adequate subgrade drainage. Deficient and undersized storm sewer pipes will also be replaced. Existing storm sewer pipe will be inspected and televised as needed to evaluate the condition of the pipe sewer. Stormwater modeling will be completed to determine if any existing pipes are undersized. Stormwater quality treatment improvements may also be required for this project since the street is proposed to be widened up to 8 feet over approximately 35% of the project corridor. Staff will evaluate the need for additional stormwater treatment improvements using stormwater modeling. If needed, structural pollution control devices and/or surface treatment improvements such as infiltration basins or trenches will be constructed. The engineer for the Lower Rum River Watershed Management Organization will be consulted to determine whether infiltration practices will be required with this project. 4.1.3 Geotechnical Considerations This project involves reconstructing two bituminous streets that have been in service for over 30 years. NTI completed a Geotechnical Evaluation Report, which is included in Appendix D. 4.1.4 Other Considerations Driveways: Feasibility Report Andrie Street and 164th Lane Reconstruction City of Ramsey Project No. 16-00 Division C Page 10