Extensive drainage improvements are planned for the area surrounding eastern Shore Drive, from First Landing Park on the east to Lynnhaven Inlet on the west. The ultimate drainage service area extends to the north and south of Shore Drive to serve surrounding neighborhoods. As background, this area was originally developed without a comprehensive stormwater management system (pipes, outfalls, etc.), and as a result, has been impacted by repetitive street flooding during rainfall events over the years. Infill development has increased the basin’s imperviousness, and has worsened the situation. In addition, a large portion of the developed drainage basin is relatively low in elevation and is subjected to tidal inundation during storm events with higher tides. The inadequate stormwater system and the impacts of direct tidal inundation combine to increase the cost and complexity of improvements for the drainage basin. It is anticipated that the improvements will include upgraded systems of pipes and inlets to collect stormwater runoff, deepening and widening of the Cape Henry Canal, stormwater pump stations, automated tide gates and elevated roadways.
Phase I, Section I consists of seven sub-sections with three pump stations and automated tide gate protection. A Tidal and Rainfall Flooding Evaluation was completed on September 7, 2010 followed by a Feasibility Analysis for Near Term Backflow Prevention that was completed on June 18, 2013. The project then entered detailed design with an alternatives evaluation phase that was completed in Summer 2018. Final design is currently underway for Section 1B and Sections 1C and 1D. Design for the first construction project (Interim Section 1C.1) has been completed. This initial project was advertised for bids on April, 28 2019 and bid opening occurred on July 23, 2019. The project will include improvements to the Cape Henry Canal, storm drain improvements along several side streets south of Shore Drive and associated utility adjustments. These improvements are part of Section 1C and are necessary to accommodate drainage from the future Shore Drive Corridor Improvements – Phase III project. The total low bid amount was $4.6 million submitted by Tidewater Utility Construction. Project was Awarded with Notice to Proceed November 4th, 2019.
During the September 2019 Hurricane Dorian, the automated tide gates installed in June 2017 protected Cape Henry Drive and Cape Story by the Sea residents from an additional 1-foot of flooding which would have caused structural damage as depicted by the following photographs.
Minor Ponding with Tide Gate Protection Structural Flooding before Tide Gate Protection
For the Phase I, Section II Poinciana Pump Station project in the Cape Story by the Sea area, Whitman, Requardt and Associates, LLP was retained to develop a comprehensive drainage analysis and identify improvements to address flooding issues. Findings were documented in a Preliminary Engineering Report dated October 2018.
PAST DRAINAGE IMPROVEMENT PROJECTS
Lynnhaven Colony Tide Valve Installation, CIP 7-409: A study was conducted in June 2013 to determine if check valves or tide gates could be installed at critical locations as an interim measure to protect areas in Lynnhaven Colony. Five check valves were installed in early 2014.
Cape Henry Ditch Sluice Gates, CIP 7-151: This project included the construction of three automated sluice gates along the Cape Henry Ditch. It was completed in June 2017. While these sluice gates offer a significant level of tidal flood protection, there are limitations. There may come a time when overland tidal or rainfall flooding will occur and the low-lying areas cannot be protected without the use of stormwater pump stations. The automated sluice gates protected residents from structural flooding damage from Hurricane Dorian in August 2019.
CURRENT DRAINAGE IMPROVEMENT PROJECTS
Section 1C – Cape Henry Canal Phase II, CIP 7-065: This project includes deepening and widening of the Cape Henry Canal and upgraded pipe crossings from Starfish Road to Beech Street. Sections of the multi-use path along Cape Henry Drive will be relocated to allow space for the canal to be widened. Portions of Section 1C will be constructed early to accommodate drainage from the future Shore Drive Corridor Improvements – Phase III project.
Section 1D – Lynnhaven Drive Pump Station, CIP 7-069: This project includes a pump station and automated tide gate near the intersection of Lynnhaven Drive and West Great Neck Road. The pump station will be interconnected with the Lynnhaven Colony Park Pump Station via the Cape Henry Canal and will provide automated pre-storm drawdown to achieve a 10-year level of protection. The water surface elevation drawdown of the canal will closely match the normal rise and fall of the tides. Tidal inundation protection will be provided to elevation = +7.0 at the pump station. Other overflow areas in the watershed will need to be elevated to achieve that level of protection to the upstream watershed.
Section 1B – Lynnhaven Colony Park Pump Station, CIP 7-068: This project includes a pump station on the south side of Lynnhaven Colony Park and upgraded pipes along the Cape Henry Canal west of Starfish Road. The pump station outfall will be located at the Lynnhaven Municipal Marina and will be a shared outfall with the Vista Circle Pump Station. The outfall chamber will have structural provisions to control discharge velocity and sediment collection. Lynnhaven Colony Park Pump Station and Lynnhaven Drive Pump Station will be interconnected via the Cape Henry Canal and will provide automated pre-storm drawdown to achieve a 10-year level of protection. The water surface elevation drawdown of the canal will closely match the normal rise and fall of the tides.
Section 1A – Vista Circle Pump Station, CIP 7-070: This project includes a pump station at the intersection of Shore Drive and Page Avenue at the parcel planned for a temporary stormwater basin for the Shore Drive Corridor Improvements – Phase III project. The pump station outfall will be located at the Lynnhaven Municipal Marina and will be a shared outfall with the Lynnhaven Colony Park Pump Station. The outfall chamber will have structural provisions to control discharge velocity and sediment collection. The design for the opening year pump station construction will accommodate the potential future expansion of the wet well and pumps to accommodate an extended connection along Page Avenue for the ultimate drainage area.
Section 1E – Elevate Lynnhaven Drive, CIP 7-066: This project includes elevating portions of West Great Neck Road, Lynnhaven Drive and Ebb Tide Road to create a berm with barrier elevation = +7.0. The current overflow elevation is approximately = +5.0. This will protect 120 acres in the 100-year floodplain in conjunction with the Lynnhaven Drive Pump Station tide gate.
UNFUNDED DRAINAGE IMPROVEMENT PROJECTS
Section 1F – Neighborhood Storm Drain Improvements North of Shore Drive
Section 1G – Neighborhood Storm Drain Improvements South of Cape Henry Drive
Phase I, Section II Poinciana Pump Station and Outfall (Cape Story By The Sea): This project includes replacing the existing pump station on Sandalwood Road. Collection system improvements will be constructed along Sandalwood Road, Bayberry Street and Poinciana Drive. The current proposed outfall force main alignment is down the center of Maple Street.