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

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

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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

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SLIDE 1

Ocean Park Alternative Ocean Park Alternative Drainage Drainage Route Analysis Route Analysis

February, 2012 February, 2012

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SLIDE 2

Chesapeake Bay Bridge Tunnel NOAA Tide Gage

November 11 November 11 – – 14, 2009 14, 2009

Between 6 am to 4 pm the next day approximately 7.5 inches fell

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SLIDE 3

Hurricane Irene

Chesapeake Bay Bridge Tunnel NOAA Tide Gage

Between 5 pm and 7 am, 3 inches of rain fell

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SLIDE 4

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)

4.9’ 6.8’

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SLIDE 5

Focus: Ocean Park South of Shore Drive

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SLIDE 6

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

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SLIDE 7

Finished Floors in the Flood Prone Area

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SLIDE 8

2010 Flooding Evaluation Report

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SLIDE 9

Tidal Inflows

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SLIDE 10

Ocean Park South of Shore Drive Drainage Area Isolation Plan

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SLIDE 11

Ocean Park South of Shore Drive Drainage Area Isolation Plan

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SLIDE 12

PLUG AND REROUTE

Ocean Park South of Shore Drive Drainage Area Isolation Plan

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SLIDE 13

LIVE OAKS EVERYWHERE

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SLIDE 14

TIDE VAL VES AND GATES

TIDE VAL VE TIDE GATE

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SLIDE 15

TIDEFLEX CHECKM ATE VAL VE

  • Sand Accumulation
  • Maintenance Issues
  • Max Elevation 5.0 Feet (NAVD88)
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SLIDE 16

IM M INENT ACTION PLAN – IN PROGRESS

TEM PORARY PLUG AND REROUTE FLOWS RECONNECT EXISTING 15” PIPE WITH TEM PORARY WEIR

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SLIDE 17

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

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SLIDE 18

AL TERNATIVE CONSIDERATIONS

  • AL

TERNATE ROUTE ANAL YSIS

  • FEASIBILITY AND COS

T

  • IM PACT TO THE NEIGHBORHOOD
  • CONSIDERATION FOR TREES IN THE AREA
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SLIDE 19

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

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SLIDE 20

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

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

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SLIDE 22

Alternative A

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Alternative A

Pros Cons

  • M eets city standard for drainage in

this area

  • Only Dinwiddie Road south of East

Stratford is disturbed

  • Pruning of 5 Live Oaks and removal of

14 large pines.

  • Construction through the park

Duration: 8 months

  • $$$
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SLIDE 24

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

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SLIDE 25

Alternative B

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Alternative B

Pros Cons

  • Meets city standard for

drainage in this area

  • Removal of 1 Live Oak and 10 other trees (6”

diameter and up)

  • Construction along East Stratford Road (8 months)
  • $$$$
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SLIDE 27

AL TERNATIVE C AL TERNATIVE C

Reroute westward on Reroute westward on Dupont Dupont Circle with additional pipe Circle with additional pipe

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Alternative C

Pros Cons

  • Provides drainage relief for rainfall intensities up to 2” of

rain in 1 hour

  • No tree removals
  • Least Costly of 3 alternatives
  • Shorter construction duration (4 months)
  • Flooding will occur during

rainstorms with intensities more than 2 in/ hour regardless of tidal levels

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

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SLIDE 30

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

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SLIDE 31

SUM M ARY

IM M INENT ACTIONS

  • INST

ALL TEM PORARY PLUG AT INTERSECTION OF TAZEWELL AND EAS T STRATFORD ROAD

  • INSTALL TEM PORARY WEIR
  • RECONNECT ABANDONED

15” PIPE TO PUM P STATION AL TERNATIVES

  • A – INSTALL ADDITIONAL

PIPE THROUGH PARK

  • B – INSTALL ADDITIONAL

PIPE WESTWARD ON EAST S TRATFORD ROAD

  • C- INST

ALL ADDITIONAL 18” PIPE WESTWARD ON DUPONT CIRCLE

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Alternatives A-C Pros and Cons

Alternative Pros Cons

A

Reroute additional pipe along Dinwiddie Road and through the park

  • Provides drainage for large storms

with intensities 3 to 6 in/ hour

  • Only Dinwiddie Road south of East

Stratford is disturbed

  • Pruning of 5 Live Oaks and removal of 14 Pines
  • Construction in park and along Dinwiddie Road

(8 months)

  • $434,000

B

Reroute westward on East Stratford Road

  • Provides drainage for large storms

with intensities 3 to 6 in/ hour

  • Removal of 1 Live Oak and 10 other trees (6” diameter

and up)

  • Construction along East Stratford Road (8 months)
  • $454,000

C

Reroute additional 18” parallel pipe

  • Provides drainage for large storms

with intensities 1 to 2 in/ hour

  • Construction does not damage trees
  • Construction along Dupont Circle

(4 months)

  • Least Costly ($150,000)
  • M ay experience some flooding during very intense

rainstorms with intensities greater than 2 in/ hour.

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.)