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January 26,2024 Don Peterson Page 14 of 21 Reference: Water Quality Assessment of Silver View Pond,Mounds View,MN additional benefits in addition to the spring application. If the application strategy is deemed successful, annual or semi-annual applications may be needed until nutrient loading has been significantly reduced from the watershed. Based on the sediment phosphorus chemistry data, we have calculated an alum dose that is appropriate for a water column stripping dose in Silver View Pond, along with estimated material cost per application. Note that these unit prices do not include contractor mobilization and demobilization. Additionally, alum unit prices are subject to market fluctuations, so$3.25/gallon of alum is based on our experience with alum treatment projects of small and large scales in Minnesota. Stantec can support the City with development of technical specifications and bid documents, and contractor selection when ready to move forward with the pilot application. Table 7. Alum Dose and Cost Estimates Areal Application otal volume ! Assumed Unit Estimated Aluminum k Area Dose of Alum Cost of Alum* aterial Cost 11 acres 22 g AI/m2 4,370 gallons $3.25/gallon $14,200 * Subject to market fluctuations External load reduction P8 modeling was used to estimate TP loading to Silver View Pond. Based on modeling results, BMPs were then designed to treat runoff from the subwatersheds with the highest loading rates. The modeling results and BMP design are presented below. Subwatershed Modeling Figure 6 shows the subwatersheds defined along with the estimated annual TP loadings, based on P8 modeling. As indicated on Figure 6, primary TP loadings to Silver View Pond are occurring at: • The forebay on the western edge • From Lake Court Drive along the north side of the pond • From the H2 Flats apartments on the southeast side of the pond • From County Road H2 on the southwest edge of the pond Design with community in mind