20230830 Environmental Board Packet Combined

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Amelia Ditch Study August 10, 2023 Page 8 Figure 3: OP Results Results show Lake Amelia having steady water quality throughout the 2022 season. Total phosphorus levels within the lake were below the state standards for shallow lakes. During sampling events it was noted that the lake was visually clear to the bottom and is heavily vegetated. Overall, the TSS, TP, and OP concentrations are much lower in the lake compared to the ditch. The drought conditions in 2022 provided very low to no flow within the ditch. No visible flow was observed while sampling. Sampling at times of flow would provide better understanding on sediment and nutrient transport into the lake. Increased pollutant loading in the ditch could contribute to an increase of pollutants entering Lake Amelia during large rain events. Dredging existing sediment deltas and stabilizing erosion within the ditch would limit the amount of TP and TSS that would be able to reach the lake. PERMITTING As this work takes place in a ditch draining wetlands to a public water, local, state, and federal permitting will be needed. VLAWMO is the LGU for the Wetland Conservation Act (WCA) and the City of Lino Lakes regulates stormwater management. As this project has been undertaken collaboratively with VLAWMO, communication will continue regarding the required regulations that must be followed for any proposed work. WCA compliance must be demonstrated for work on drainage systems such as this ditch. Short- term work will consist of maintenance of the ditch to its original capacity based on historical aerials and field visits. There are numerous wetlands around the ditch, however they have not been delineated as part of this phase. These wetlands have current or recent cropping history based on aerial imagery and field visits. Filling or excavation of wetlands not proposed as short- term work will be limited almost entirely to the ditch channel. The full maintenance history of the system is not known as it has been under private ownership; a full cleanout of the ditch has not been performed. Recent maintenance history includes culvert replacement at Culverts D and E by the City, plus evidence of past maintenance of Culvert F based on observations during a field visit. As the proposed long-term improvements will change the drainage system beyond its historical constructed conditions, more involved permitting will be required and factored into final design. Compliance will need to be demonstrated around ditch capacity expansion and