Agenda - Council - 05/13/2025 - Laserfiche WebLink

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This has resulted in premature eroding of the valve bolts, which in recent years have resulted in valves separating when exercised, requiring emergency repairs to replace the valves and repair the streets. The sanitary sewer and storm sewer were televised to determine the condition of the pipes and structures. The sanitary sewer was found to be in good condition. The storm sewer under the streets was also found to be in good condition. The storm sewer outlet pipe to the Mississippi River was found to have some minor damage, which is not proposed to be addressed with this street reconstruction project, but will be addressed under a separate project in the future. The CIP included costs for addressing stormwater runoff from 6140 Highway 10 (the Lano property) as part of this project. During the project design process, an analysis of stormwater runoff from 6140 Highway 10 was performed. It was determined that a connection to the existing city storm sewer system under Tungsten Street, as well as on -site stormwater detention improvements on the 6140 Highway 10 property, will be required to treat stormwater runoff from this property to today's stormwater management design standards. This project includes a new storm sewer manhole with an adequately sized storm sewer stub to allow for the future connection of private stormwater improvements constructed on the 6140 Highway 10 property. Pavement History The streets within Dickenson's Mississippi Estates were constructed in 1990. Crackseal/sealcoat treatments were received in 1996, 2003, and 2013. Ground Penetrating Radar (GPR) was performed on the streets in 2020. At the time, the streets averaged 2.7 to 3.4 inches of bituminous over 3.7 inches of aggregate base. Staff review of the geotechnical report found clean sands, ideal for pavement and utility support within the project area. Additionally, groundwater is not anticipated to be a concern for the street reconstruction. Proposed Improvements Due to the age and condition of the existing watermain, this project includes replacing the existing watermain and water service lines up to and including the curb stops and fire hydrants. During construction, temporary water will be looped through the project and connected to the houses. The original project anticipated only spot curb and gutter replacements. However, by replacing the watermain, the majority of the existing concrete curb and gutter is impacted so the project calls for replacing all curb and gutters. Also, valley gutters will be placed along Tungsten Street to separate Tungsten Street from the private parking lots / drives on both sides of Tungsten Street. Because Tungsten Street handles frequent commercial vehicle traffic, it will be built to a 10-ton design including 4-inches of bituminous over 6-inches aggregate base. Rivlyn Avenue will be built to a standard neighborhood section of 3.5-inches bituminous over 6-inches aggregate base. The cul-de-sac at the west end of Rivlyn Avenue is partially within City -owned right of way and a roadway easement. Due mainly to the location of the existing houses and driveways, it was not deemed feasible to expand the cul-de-sac, and it will be constructed back to its current dimensions. The storm sewer at the intersection of Rivlyn Avenue and Tungsten Street will be required to be replaced due to the watermain replacement. Additionally, a hydrodynamic separator structure is being placed in the storm sewer outfall line to the Mississippi River. This structure, which will be located in the boulevard south of Rivlyn Avenue, is a cost-effective storm water quality retrofit solution that will serve to remove pollutants from the stormwater runoff before it is discharged into the Mississippi river. Similar structures have been added to storm sewer outfall lines that discharge runoff directly to the Mississippi and Rum Rivers. City staff has discussed, and is continuing discussions with Lano, to address stormwater runoff concerns from their property at 6140 Highway 10. Bolton & Menk performed stormwater analysis of the site and determined a combination of on -site rate control and connection to the city storm sewer system is required to fully address the concerns. After discussions with Lano, they prefer an underground stormwater storage system versus an above ground pond, as vehicle storage space is already limited on their site. This project includes placing a storm sewer manhole in the Tungsten Street right of way and a 12-inch storm sewer pipe stubbed to the right-of-way for a