Many drainage systems in the Neponset watershed outfall to the wetland that surround streams, rivers, ponds, and lakes. Using the MassDEP wetlands dataset, we assigned AU IDs to outfalls based on which impaired waters were associated with those outfalls. Figure 5. Using the MassDEP wetlands dataset to assign more outfalls to AU IDs. In some cases, an outfall may be situated on a rivulet that is too small to be depicted in any of the three hydrological datasets described above. In those cases, the topographic contours can help assign these outfalls AU IDs (Figure 6). The contours show areas where higher hills and ridges separate riverbeds into distinct basins. Finally, the last few ambiguous outfalls can be assigned the MassGIS drainage sub-basins layer. Figure 6. Using topographic contours to associate outfalls with Impaired Waters Figure 7. Topographic Contours in Sharon. Figure 8. Drainage Sub-basins. Ranking Catchments Once we delineated outfall catchments for Milton and linked outfalls with Impaired Waters in Milton and all Neponset Watershed Municipalities, we ranked Milton’s outfall catchments according to how likely they were to contribute illicit discharges to the receiving waters. We used CommunityViz, a GIS-based assessment tool for planning, to prioritize outfalls and catchments using the program’s suitability wizard. This suitability analysis evaluates sites based on a set of specified quantitative criteria. In this case, the presence of older homes, industrial uses, septic systems, and other physical features were summarized into a composite score from 0 to 100. Catchments with a median score or below were considered low priority, catchments within the third quartile were considered medium, and those within the top quartile were considered high priority, or most likely to contribute illicit discharges to impaired waters. Land use were designated as medium or high potential for illicit discharges using information found in the 2004 manual from Center for Watershed Protection, titled Discharge Detection “Illicit and Elimination: a guidance manual for program development and technical assessments”. The guidance manual provided illicit discharge pollution potential for a variety of land uses and included their SIC codes in Attachment A, which were compared to and converted to NAICS codes during this process. We used the following criteria for the analysis:
Many drainage systems in the Neponset watershed outfall to the wetland that surround streams, rivers, ponds, and lakes. Using the MassDEP wetlands dataset, we assigned AU IDs to outfalls based on which impaired waters were associated with those outfalls. Figure 5. Using the MassDEP wetlands dataset to assign more outfalls to AU IDs. In some cases, an outfall may be situated on a rivulet that is too small to be depicted in any of the three hydrological datasets described above. In those cases, the topographic contours can help assign these outfalls AU IDs (Figure 6). The contours show areas where higher hills and ridges separate riverbeds into distinct basins. Finally, the last few ambiguous outfalls can be assigned the MassGIS drainage sub-basins layer. Figure 6. Using topographic contours to associate outfalls with Impaired Waters Figure 7. Topographic Contours in Sharon. Figure 8. Drainage Sub-basins. Ranking Catchments Once we delineated outfall catchments for Milton and linked outfalls with Impaired Waters in Milton and all Neponset Watershed Municipalities, we ranked Milton’s outfall catchments according to how likely they were to contribute illicit discharges to the receiving waters. We used CommunityViz, a GIS-based assessment tool for planning, to prioritize outfalls and catchments using the program’s suitability wizard. This suitability analysis evaluates sites based on a set of specified quantitative criteria. In this case, the presence of older homes, industrial uses, septic systems, and other physical features were summarized into a composite score from 0 to 100. Catchments with a median score or below were considered low priority, catchments within the third quartile were considered medium, and those within the top quartile were considered high priority, or most likely to contribute illicit discharges to impaired waters. Land use were designated as medium or high potential for illicit discharges using information found in the 2004 manual from Center for Watershed Protection, titled “Illicit Discharge Detection and Elimination: a guidance manual for program development and technical assessments”. The guidance manual provided illicit discharge pollution potential for a variety of land uses and included their SIC codes in Attachment A, which were compared to and converted to NAICS codes during this process. We used the following criteria for the analysis:
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