Project Designs and Solutions
Lake Taylor Site Visit 11/15/2019
On November 15th, our team traveled to Norfolk, VA to visit three potential areas we would like to implement stormwater BMPs. The three locations we considered include Princess Anne Park, public land surrounding Lake Taylor, and drainage easements within the Lake Taylor neighborhood. We got a chance to talk with members of the community, our partners, and our advisors about potential design solutions and the best locations for each. From this visit, out team decided that adding BMPs to Princess Anne Park will have the largest impact on flood mitigation as well as providing benefits to the community. Click the link below to see our notes taken during our visit.
Design Solutions
After visiting the three potential locations our final design could be implemented, we decided on three potential solutions; bioretention, rainwater harvesting, and ditch retrofits. Each of these solutions were evaluated based on the following design criteria: Aesthetics, cost, maintenance, runoff reduction, nutrient reduction, community benefit, and repeatability. Below you will find a brief description of each solution, the completed decision matrix, and the weighting of each criteria by importance.
This is the Decision Matrix created to determine which design option best meets the design criteria. Each criteria was weighted based on importance. After rating each design, it was determined the Bioretention was the best design option for what we want to accomplish
Bioretention
Rain Gardens
Our first design solution is a bioretention basin - a depressed basin filled with vegetation meant to treat and slow runoff, similar to a garden. The placement of this bioretention garden within the public area of the Princess Anne Park gives it the unique opportunity both to alleviate flooding/water quality issues and to be seen and interacted with by a large portion of the community. Overall, this design solution received a total score of 93 based on the decision matrix criteria determined by the team.
Rainwater Harvesting
Cisterns
Many houses in the Lake Taylor neighborhood were converted to city water after being built with septic systems. Several of these tanks are still in place, and they represent a possible solution for runoff volume reduction if used as a storage tank for an RWH system. The tank would remain underground, meaning there would be minimal visible infrastructure, including a manhole-type access point for maintenance (Virginia Department of Environmental Quality, 2013). This could be a positive, as the BMP is largely out of sight, but community members expressed interest in BMPs that add aesthetic value to the area. Overall, this design solution received a total score of 85 based on the decision matrix criteria determined by the team.
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Virginia Department of Environmental Quality. (2013b). Virginia DEQ Stormwater Design Specification No. 6 Rainwater Harvesting. Retrieved from https://www.swbmp.vwrrc.vt.edu/wp-content/uploads/BMP_Spec_No_6_RAINWATER_HARVESTING.pdf
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Ditch Retrofits
Check Dams
Our third design solution is implementing check dams to retrofit incised stormwater ditches that are located throughout the Lake Taylor Neighborhood. The stormwater conveyance ditches carry water from one location to another; in this case, the water is being channeled to Lake Taylor. The side slopes of the ditches are heavily eroded and the channel is approximately 2.5 to 3 feet deep. Over the years, poor maintenance techniques have also affected the grade of the overall drainage system. The change in grade has impeded runoff from properly flowing through the conveyance system, which in turn has also caused ponding in many backyards. Check dams are structures used to dissipate energy and reduce flow velocities of runoff traveling through stormwater ditches (Otak, 2012). Overall, this design solution received a total score of 81 based on the decision matrix criteria determined by the team.
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Otak. (2012). Roadside Ditch and Shoulder Water Quality Enhancement Plan. Kitsap County, Washington: Kitsap County. Retrieved from https://www.kitsapgov.com/pw/Documents/KC_Roadside_Ditch_Plan.p