Ocean Park Alternative Ocean Park Alternative Drainage Drainage - PowerPoint PPT Presentation

Ocean Park Alternative Ocean Park Alternative Drainage Drainage Route Analysis Route Analysis February, 2012 February, 2012

November 11 November 11 – – 14, 2009 14, 2009 Between 6 am to 4 pm the next day approximately 7.5 inches fell Chesapeake Bay Bridge Tunnel NOAA Tide Gage

Hurricane Irene Between 5 pm and 7 am, 3 inches of rain fell Chesapeake Bay Bridge Tunnel NOAA Tide Gage

Tidal Flood Frequency Curve based on FEM A Tidal Flood Frequency Curve based on FEM A Flood Insurance Study City of Virginia Beach Flood Insurance Study City of Virginia Beach (Revised M ay 4, 2009) (Revised M ay 4, 2009) 6.8’ 4.9’

Focus: Ocean Park South of Shore Drive

Some ground elevations in Ocean Park are BELOW 4 FEET (NAVD 88)* – CANNOT PREVENT OVERLAND FLOW NAVD88 is a vertical control datum in the USA . All ground elevations are in NAVD88 unless otherwise stated

Finished Floors in the Flood Prone Area

2010 Flooding Evaluation Report

Tidal Inflows

Ocean Park South of Shore Drive Drainage Area Isolation Plan

Ocean Park South of Shore Drive Drainage Area Isolation Plan

Ocean Park South of Shore Drive Drainage Area Isolation Plan PLUG AND REROUTE

LIVE OAKS EVERYWHERE

TIDE VAL VES AND GATES TIDE VAL VE TIDE GATE

TIDEFLEX CHECKM ATE VAL VE • Sand Accumulation • Maintenance Issues • Max Elevation 5.0 Feet (NAVD88)

IM M INENT ACTION PLAN – IN PROGRESS TEM PORARY RECONNECT PLUG AND EXISTING REROUTE 15” PIPE FLOWS WITH TEM PORARY WEIR

IM M INENT ACTION PLAN (TEM PORARY) • PROVIDES RELIEF FROM TIDES UP TO APPROXIM ATEL Y 5 FEET (NAVD88) OR 5.9 FEET (M SL) • PROVIDES DRAINAGE FOR M OST STORM S • INTENSE PERIODS OF RAINFALL WILL RESUL T IN TEM PORARY FLOODING – APPROXIM ATEL Y 6-9 INCHES IN LOW L YING AREAS – DEPENDS ON INTENSITY AND LENGTH OF STORM

AL TERNATIVE CONSIDERATIONS • AL TERNATE ROUTE ANAL YSIS • FEASIBILITY AND COS T • IM PACT TO THE NEIGHBORHOOD • CONSIDERATION FOR TREES IN THE AREA

AL TERNATIVES • A – Reroute flows along Dinwiddie Road and through the park • B –Reroute along East Stratford Road • C – Install additional parallel 18” along Dupont Circle from Dinwiddie Road to intersection of Chesterfield and Dinwiddie Road

REGARDLESSOF THE ALTERNATIVE, TIDAL RELIEF IS ONL Y GOOD UP TO AN ELEVATION OF 5.0 FEET NAVD88 (OR 5.9 FEET M SL).

AL AL TERNATIVE A TERNATIVE A Reroute along Dinwiddie Road and through the park Reroute along Dinwiddie Road and through the park

Alternative A

Alternative A Pros Cons • Pruning of 5 Live Oaks and removal of • M eets city standard for drainage in 14 large pines. this area • Construction through the park • Only Dinwiddie Road south of East Duration: 8 months Stratford is disturbed • $$$

AL AL TERNATIVE B TERNATIVE B Reroute westward on East Stratford Road Reroute westward on East Stratford Road

Alternative B

Alternative B Pros Cons � Removal of 1 Live Oak and 10 other trees (6” • Meets city standard for diameter and up) � drainage in this area Construction along East Stratford Road (8 months) � $$$$

AL AL TERNATIVE C TERNATIVE C Reroute westward on Reroute westward on Dupont Dupont Circle with additional pipe Circle with additional pipe

Alternative C Pros Cons • Provides drainage relief for rainfall intensities up to 2” of rain in 1 hour � Flooding will occur during • rainstorms with intensities more No tree removals than 2 in/ hour regardless of tidal • Least Costly of 3 alternatives levels • Shorter construction duration (4 months)

APPROXIM ATE AREA OF FLOODING FOR AL TERNATIVE C LARGE STORM S WITH LARGE INTENSITIES 2-6 IN/ HOUR (FLOOD DEPTH 2-6 INCHES)

APPROXIM ATE AREA OF FLOODING FOR AL TERNATIVE C FOR HURRICANE IRENE: 2.5 INCHES DEPTH FOR 4 HOURS

SUM M ARY IM M INENT ACTIONS AL TERNATIVES • • INST ALL TEM PORARY PLUG A – INSTALL ADDITIONAL AT INTERSECTION OF PIPE THROUGH PARK TAZEWELL AND EAS T • B – INSTALL ADDITIONAL STRATFORD ROAD PIPE WESTWARD ON EAST • INSTALL TEM PORARY WEIR S TRATFORD ROAD • • RECONNECT ABANDONED C- INST ALL ADDITIONAL 18” 15” PIPE TO PUM P STATION PIPE WESTWARD ON DUPONT CIRCLE

Alternatives A-C Pros and Cons Alternative Pros Cons A • Pruning of 5 Live Oaks and removal of 14 Pines • Provides drainage for large storms • Construction in park and along Dinwiddie Road with intensities 3 to 6 in/ hour Reroute additional (8 months) • Only Dinwiddie Road south of East pipe along • $434,000 Stratford is disturbed Dinwiddie Road and through the park B • Removal of 1 Live Oak and 10 other trees (6” diameter • Provides drainage for large storms and up) Reroute • with intensities 3 to 6 in/ hour Construction along East Stratford Road (8 months) westward on East • $454,000 Stratford Road • Provides drainage for large storms C with intensities 1 to 2 in/ hour • M ay experience some flooding during very intense • Construction does not damage trees Reroute rainstorms with intensities greater than 2 in/ hour. • Construction along Dupont Circle additional 18” (4 months) parallel pipe • Least Costly ($150,000) NOTE: REGARDLESS OF THE ALTERNATIVE, TIDAL RELIEF IS ONLY GOOD FOR A TIDAL ELEVATION OF UP TO 5.0 FEET NAVD88 (5.9 FEET M.S.L.)