The following email was received from Deputy City Manager Dave Hansen in respone to requests that immediate stormwater solutions similar to the one used in Ocean Park be installed in flood prone areas east of the Lesner Bridge in Cape Story, Lynnhaven Colony and Cape Henry neighborhoods.
Eastern Shore Drive Leaders,
Let me begin by attesting the Eastern Shore Drive Storm Water Drainage Area Improvement Initiative is one of our top focus areas as we roll into the new year. The staff and City leadership are very sensitive to the hardships created when we have intense and long-lasting weather events such as Sandy, Irene, and the Nor’easter of Nov 09. Following Public Works attendance and briefing last Saturday with the Lynnhaven Colony Civic League and concerns we have received from Cape Henry Shores, Cape Story By the Sea and other concerned citizens in the eastern Shore Drive drainage area, our engineering and operations staff will be undertaking an accelerated analysis of several interim solutions which have been suggested and on the face seem to have merit in providing various degrees of protection from tidal inundation. Below is a summary of the two phases I have asked our engineering staff to pursue. Phase I is a data map with summary descriptions so we identify all infrastructure, elevations and drainage areas east of the Lesner. Completing this on 7 Dec allows us to define the study aspects of Phase II. I have asked Public Works to complete their assessments and recommendations by the first week in April and to publish a written report NLT 12 April. Intent will be to post this report on-line for the civic leagues and citizens to review. Here are summaries of the first two phases:
1. Using City topographic mapping as the base, delineate the drainage sub basins, the drainage systems (open and closed), and the outfalls for the Lynnhaven Colony/Cape Henry/Cape Story by the Sea areas. This will provide a clear graphic that depicts the ground elevations, drainage areas, and drainage system elements – including outfalls. This will be used as a tool for the additional analyses identified in Phase 2 and will be suitable for discussions with the BAC and civic leagues when describing how the systems function and why engineering analyses are necessary to support any proposed interim measures such as backflow preventers. I.e., it’s not as simple as just keeping the tide out, the rainfall runoff has to be able to either be safely stored within the particular drainage area or be able to be discharged with the backflow preventers in place (or a combination thereof). These products will be ready by December 7.
2. Each sub basin will have an analysis done to determine the suitability of backflow preventers on the outfall for the particular subbasin; if a backflow preventer is suitable, the type of backflow preventer; the amount of rainfall runoff the subbasin can handle without structural flooding; the stand-by pumping requirements (if any); and the probable costs. While simply jumping to a “solution” as has been suggested by some, it is absolutely necessary that the City allow the responsible level of engineering to be done to assure that we do not inadvertently worsen the drainage situation for any particular subbasin. We are estimating four months for this effort. Expect to deliver a written analysis with recommendations and preliminary costs and timeline by mid-April.
Phase III will be the review and approval process leading to design and construction. Once we firm up the costs and the competitive process we’ll use to get the work done we can provide a reasonable timeline. I wish to close this email by ensuring our citizens fully understand these interim solutions as with the permanent solutions have definitive limitations. At some level of tidal surge and some accumulation and intensity of precipitation all infrastructure improvements will be overcome and mother nature will prevail. Hopefully implementing interim measures will reduce the risk of moderate storm damage and buy the time for us to consider even grander infrastructure solutions to tackle the bigger more threatening hurricanes and nor’easters we seem to be weathering of late. Happy Thanksgiving and fingers crossed for a quiet winter storm season. Regards, Dave
Deputy City Manager
City of Virginia Beach