Agenda Packets - 2021/07/06 - Laserfiche WebLink

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4.0 Recommendations and Conclusions 4.1 Future Evaluations To meet its MS4 requirements, the city must operate and maintain its stormwater management system in a manner so as to reduce the discharge of'pollutants to the maximum extent practicable, and must, at a minimum, inspect 20% of all outfalls, sediment basins, and ponds each year on a rotating basis. The work performed for this study can help the city to meet the 20% inspection requirement for 2012. Further, the assessment of Silver View Pond completed in 2012 will serve as a lielpfui tool as the city completes future phases of its pond inventory program. The Silver View Pond assessment was selected as a pilot project to assess the extent of sedimentation and guide the city in developing a future pond assessment maintenance program for managing all of its ponds and outfalls. Further, the information collected during this pond assessment has established a 'base] ine' condition that can serve as a foundation for future sedimentation surveys in Silver View Fond. It is recommended that the city continue to monitor the sedimentation in this pond in future years (perhaps every 5 years if sediment is not removed and every 10 years if major sediment removal has been performed). 4.2 Expansion and Maintenance Implementation Silver View Pond sediment removal recommendations were made based on the water quality treatment capacity found in the pond, its wetland characterization, the potential water quality benefits of increasing the permanent pool volume, the proximity and type of receiving waters, and the cost of pond improvements. It is recommended that before any dredging or expansion is completed, that the feasibility ofan extended detention structure is determined as this type of pond modification has the potential to provide significant water quality improvement at a comparatively low cost, and could enable the city to delay major fund expenditures and in turn plan for and save funds for expensive sediment removal to bring the pond back to its constructed configuration. This would require a hydraulic and hydrologic study of the pond's watershed to determine if there could be negative impacts to neighboring properties, homes, and businesses due to minor increased flooding inherent with the placement of an extended detention structure. It is also recommended that as part of any sediment removal project that the installation of a forebay downstream of each pond inlet be considered with that project. A forebay would likely make future sediment cleanout easier and more feasible. and would allow For large particle sediment removal in a localized area near each pond inlet. P. hlpls 21 MN 6_' ?36211182 Sll%VT VIC% Pond Acsessmcnl Wotki ile€ Rel,nn tiilver Vice Pond Amssmenl-1 omi.does 18