Agenda - Public Works Committee - 11/19/2024

Home

Alpine Drive west of Nowthen Boulevard. The ADT for this segment of Alpine Drive is 2,900. Review of the geotechnical report found clean soils under the pavement, however, groundwater was found within 3 feet of the pavement for an approximately 750-foot section of Alpine Drive which crosses wetland. Staff has observed pavement rutting in this area, likely caused by the high groundwater. The project is proposed to include raising a portion of this section of Alpine Drive, to give a minimum of 30-inches of separation between groundwater and the bottom of the pavement section. Staff is proposing to mill and overlay the 460 linear feet of Alpine Drive east of Sunfish Lake Boulevard. The 660 linear feet of Alpine Drive west of Nowthen Boulevard was found to be in good condition, and only refreshing the pavement markings is proposed in that section of Alpine Drive. Staff has noted several broken pieces of concrete curb and gutter, and is investigating if it would be more cost-effective to replace all curb in gutter in the reconstruction area between Sunfish Lake Boulevard and Nowthen Boulevard compared to spot repairs. Alpine Drive between Nowthen Boulevard and Saint Francis Boulevard (TH 47) is a combination of 44-foot- wide urban and rural section with an 8-foot bituminous trail on the south side of the street, and an 8-foot bituminous trail between Krypton Street and TH 47 on the north side of the street. The Anoka County signal upgrade at Nowthen Boulevard from 2024, including turn lanes for westbound Alpine Drive, reconstructed approximately 740 linear feet of Alpine Drive east of Nowthen Boulevard (generally to Krypton Street). This was found to generally be in good condition, with only refreshing of the pavement markings proposed in this section of Alpine Drive. The ADT for this segment of Alpine Drive is 2,500. Review of the geotechnical report found clean sands, ideal for both utility and pavement support. The total project length of Alpine Drive between Sunfish Lake Boulevard and TH 47 is approximately 1.02 miles. Alpine Drive is an MSA street and must meet MSA 10-ton pavement strength design requirements. To achieve this, staff is proposing to place 4.5-inches new bituminous over 5-inches aggregate base (9.5-inch total pavement section). The pavement cores produced as part of the geotechnical report found approximately 5- inches of bituminous over 4.5-inches aggregate base, which will allow the project to be built without additional subsoil excavation to achieve the proposed pavement section. The western 460 linear feet is proposed to only receive a 2-inch mill and overlay. Approximately 750 linear feet across the wetlands west of Nowthen Boulevard are proposed to be raised, which will require replacement of the concrete curb and gutter. Additionally, Staff will be reviewing the cost-effectiveness of replacing all concrete curb and gutter west of Nowthen Boulevard (in the areas proposed to be reconstructed). The section of Alpine Drive approximately 660 linear feet west and 460 linear feet east of Sunfish Lake Boulevard is not proposed to receive a bituminous treatment, only refreshing the existing pavement markings. The remaining pavement, generally between Krypton Street and TH 47 is proposed to be reconstructed using the FDR method with only spot curb and gutter repairs. Bituminous trail exists throughout the project area, including on both sides of Alpine Drive for approximately half the project. In general, the bituminous trail is functional, but has deteriorated to a point where improvements to the trail are recommended. Staff is proposing to include reconstruction of the bituminous trail and associated pedestrian ramps as an alternative bid. In total there is approximately 7,600 linear feet of 8-foot bituminous trail within the project area. Replacement of this trail is not included within the CIP. Staff believes the majority of the trail should qualify for MSA funding if desired, but will look further into potential funding sources as part of the project design process. Staff estimates construction costs for the trail replacement at $250,000. Staff has identified an unmarked crossing at Sodium Street, connecting the Alpine Acres subdivision with the Fox Knoll subdivision to the south. Alpine Drive is a 45 mph (high speed) road, staff does not support a crossing at this location and is proposing to remove the pedestrian ramp on the south side of Alpine Drive with this project. The bituminous trail continues west to Sunfish Lake Boulevard which provides safe crossings, including crossing westbound to Alpine Park; the most likely destination for local trail users in this region of the City. Additionally, a marked mid -block crossing exists between Nowthen Boulevard and Helium Street. There is only a footpath to the trail on the south side of Alpine Drive, and a marked crossing exists at Helium Street. Staff is proposing to eliminate the mid -block markings as part of this project.