Methods

First, a number of storm water control and green infrastructure technologies were researched. These technologies included downspout disconnection, green roofs, rain gardens, rainwater harvesting, green streets, vegetated filter strips, dry swales, and permeable pavement. These technologies are discussed further in the Technology Review, found under the "Resources" tab.

A site visit was conducted and the vast majority of these technologies were found to be unimplementable due to the flat topography and high water table within the region as well as the limited space available for BMP implementation. Of the potential storm water control and green infrastructure technologies, only a bioretention, dry swale, infiltration trench, weir, and floating wetlands were found to be feasible for implementation. The analysis of these technologies are discussed further in the Analysis of Potential Solutions report, found under the "Resources" tab.

Although the implementation of a dry swale and infiltration trench was found to be the best solution to the design problem, further analysis found this solution to be infeasible. As shown in the following image, the vast majority of the Poplar Hall neighborhood had a depth to water table of only 1.5 to 2 feet (orange areas represent a depth to water table of 1.5 feet while yellow areas represent a depth to water table of 2 feet).

After the dry swale with infiltration trench solution was eliminated, the second place solution of weirs in conjunction with floating wetlands was considered. GIS analysis found the area of Duck Pond Drive between Duck Pond and Silver Lake to be of particular flooding concern. This area is shown by the dark blue topographic lines near the top center of the following image, separating the two ponds.

Pictures were taken of this area. The leftmost of the following images shows the existing inlet into Silver Lake from Duck Pond, which is an oddly tilted pipe. The rightmost of the following images shows the area of Duck Pond right next to Duck Pond Dr., and shows that it is nearly flooding the road even when storm conditions are not present.

Installing a weir in Duck Pond to maintain a more reasonable water level, and modifying Silver Lake's existing outlet weir to allow more water to outlet into the Elizabeth River was found to be an ideal solution to mitigate Poplar Hall's flooding problem. Installing a few floating wetlands in Silver Lake was found to be an ideal method to provide water quality benefits to the water being outletted from Silver Lake into the Elizabeth River by decreasing nutrient loadings. For more precise hydrologic analysis of the area, a SWMM model was needed. The SWMM model has been developed by the team and provided a more precise evaluation of the specifications of weirs and wetlands needed for installation -- the model suggested that the weir installation would have negligible effect on water quality but will prevent flooding during a 5-year storm. Further options for water quality remediation were then researched and sized, including floating wetlands, vegetated buffer strips, and single-home bioretention cells linked to rain barrels collecting water from house roofs.