Agenda Packets - 2021/07/06 - Laserfiche WebLink

Home Browse Search

ponds and outfalls in accordance and compliance with its MS4 permit. It is also intended that the evaluation process established for this study and as refined for subsequent basins, be used when each pond is re-evaluated in future years. This would allow for a comparison of two or more surveys for each pond to help estimate continuing sedimentation and plan for the future maintenance work since the estimates for sedimentation could be used to develop a projected maintenance timeline for each stortnwater pond. In turn the city could use that information for developing its 5-year or 10-year capital improvement programs. 2.4 Stormwater Pond Historic Information Evaluation The city provided all available information on Silver View Pond. This information included the 1989 Silver View Pond Management Plan, the 1988 Edgewood District Drainage Plan, and nearby storm sewer information. Original construction contours for the pond were estimated based on depth readings and a normal water level reported in the 1989 pond management plan as well as the current side slopes of the pond. Since these measurements were not taken initially after the construction of the pond, these measurements likely represent a conservative estimate of the original design of the pond. These estimated contours were used to compare the original design pond volume with current conditions determined by performing the bathymetric survey for this study. 2.5 Stormwater Pond Survey and Visual Inspection A field survey of Silver View Pond was performed. The survey included performing a bathymetric survey of the pond. surveying the current water level, collecting data for each pond inlet and outlet photographing the inlet and outlet structures, and performing a visual inspection of pond's inlet and outlet structures and banks. A bathymetric survey is an elevation survey of the area below the pond's normal water elevation. Figure ? shows the results of the bathymetric survey. The bathymetric survey was performed by physically measuring the depth from the water surface to the pond bottom using a survey rod at various locations within the pond and recording the measurements using a Global Positioning System (GPS ) data logger that tracks latitude and longitude. Sonar/radar was not used to characterize the pond bottom because vegetation and floating organic material has been found to, at times, introduce significant error in these types of shallow water surveys using sonar/radar devices. At four locations in the pond.. an estimate of the soft sediments was also taken. This was measured by applying pressure to the GPS rod until the rod reached a more solid bottom. By comparing the "solid" bottom elevation to the elevation of the top of the sediment, an estimate of the depth of soft sediment was determined. i': A1pls 21 NIN 62 23t,=IOX2 Serer Vie% Pond Ati5,msntcnI Wor6I iles Report Soher Vie% I'Dad.Assessinem-rinal docx