An Evaluation ofof Performance Measures for Prefabricated Submerged

Concrete Breakwaters: Section 227

Cape May Point, New Jersey

Demonstration Project

Donald K Stauble - Engineer Research & Development Center,Donald K Stauble - Engineer Research & Development Center, Coastal and Hydraulics LaboratoryCoastal and Hydraulics LaboratoryJ.B. Smith - Philadelphia DistrictJ.B. Smith - Philadelphia DistrictRandall A. Wise - Philadelphia DistrictRandall A. Wise - Philadelphia District

Beachsaver Reef

Double-T SillDouble-T Sill 2.5 Year Results2.5 Year Results

National Shoreline Erosion Control Development & Demonstration Program

Innovative Shoreline ProtectionUS Army Corpsof Engineers

DEMONSTRATION SITESDEMONSTRATION SITES

Cape May Point, NJCape May Point, NJ

National Shoreline Erosion Control Demonstration and Development Program

US Army Corpsof Engineers8

.… demonstrating innovative coastal shoreline protectionmethods with an emphasis on evaluation of nontraditionalapproaches to prevent coastal erosion and improve shorelinesediment retention.

OBJECTIVES OBJECTIVES

1)1) To evaluate the effectiveness of the two To evaluate the effectiveness of the two submerged structuressubmerged structures in retaining sand on the beach in retaining sand on the beach as compared with as compared with unprotectedunprotected groin compartments groin compartments

2)2) Compare the effectiveness of the more costly Compare the effectiveness of the more costly Beachsaver ReefBeachsaver Reef with the less costly with the less costly

Double-T SillDouble-T Sill in retaining sand in retaining sand in groin compartmentsin groin compartments

3)3) Evaluate ability of bothEvaluate ability of both structures to retainstructures to retain Beach Fill material Beach Fill material after placementafter placement

SITE LOCATIONSITE LOCATION

CAPECAPEMAYMAYPOINTPOINT CAPE MAYCAPE MAY

MEDOWSMEDOWSCAPECAPEMAYMAYCITYCITY

CAPE MAY POINTCAPE MAY POINT issouthern most beach in New Jersey atentrance to Delaware Bay

N

HISTORICAL SHORELINE CHANGEHISTORICAL SHORELINE CHANGE

Problem:Problem:Beach erosion Beach erosion due to wavesdue to wavesand tidal currentsand tidal currents

Atlantic Ocean

Del

awar

e B

ay

N

Tidal Currents

Tidal Currents

WavesWaves

18791899

1936

1943

19711977

1986

Photo 2003

BEACHSAVER REEFBEACHSAVER REEF

Interlocking line

Placed in ~ -9 ft NAVD of water ~ -2.7 m NAVDTop of reef just below water line at Low water

(1.5 ft)

(15.5 ft)(10 ft)

(6 ft)

Three reef units placed over each filter fabric scour prevention layer

Landward sideLandward side

Sand excavation Sand excavation Required under Required under some units, fill some units, fill under othersunder others

Filter Fabric Filter Fabric Layer PlacementLayer Placement

Beachsaver unitsBeachsaver units

PrefabricatedPrefabricatedConcreteConcreteBreakwaterBreakwater

waves

Landward sideLandward side

DOUBLE – T SILLDOUBLE – T SILL Units placed on sand (no filter cloth)At ~ -9 ft NAVD w/ crest at –6 ft at low waterAt ~ -2.7 m NAVD w/crest at –1.8 m at low water

30’–0” Long

9.14 m

3.66 m

3’-0” 6’-0”

12’-0”

4”

2’-10”

7 ¾”

length = 30’-0”

4 ¾” MARINE GRADE CONCRETE w/ REBAR

0.96 m

Alignment - PlanAlignment - Plan ViewView

Interlocking EndInterlocking End

Sill ConceptSill Concept

PrefabricatedPrefabricatedConcrete SillConcrete Sill

0.12 m

Cell 1Cell 1Rock Rock SeawallSeawall

Cell 2Cell 2

94 Beachsaver Reef

94 Beachsaver Reef

Cell 3Cell 3

94 Beachsaver Reef

94 Beachsaver Reef

01 Fill01 Fill

Cell 4Cell 4

Control w/Control w/

01, 04 Fills01, 04 Fills

Cell 5Cell 502 Beachsaver Reef02 Beachsaver Reef01 Rock & Gabion wall01 Rock & Gabion wall

Cell 6Cell 602 Double-T Sill02 Double-T Sill

Cell 7Cell 7ControlControl

Cell 8Cell 8ControlControl

CAPE MAY POINT SITE LAYOUTCAPE MAY POINT SITE LAYOUT

Recent Shore Protection History:Recent Shore Protection History:1950’s 9 Groins constructed1950’s 9 Groins constructed6/94 Cell 2,3 - 6/94 Cell 2,3 - Beachsaver ReefBeachsaver Reef 1/01 Cell 3,4 - 1/01 Cell 3,4 - Beach fillBeach fill2001 Cell 5 - 2001 Cell 5 - Rock & Gabion wallRock & Gabion wall9/029/02 Cell 5 Cell 5 - - Beachsaver Reef Beachsaver Reef

w/ filterw/ filter 10/0210/02 Cell 6Cell 6 - - Double-T SillDouble-T Sill3/043/04 Cell 4Cell 4 -- Beach FillBeach Fill12/04 Cell 1-6 - 12/04 Cell 1-6 - Eco Sys ResEco Sys Res Bch FillBch Fill

SECTION 227 PROJECTSECTION 227 PROJECTCell 5Cell 5 – Beachsaver Reef– Beachsaver ReefCell 6 – Double-T SillCell 6 – Double-T Sill

Cape MayCape May LighthouseLighthouse

#

#

#

#

#

#

#

#

##

#

##

#

#

$T

$T

$T

$T

$T

$T$T

$T

$T

SITE BATHYMETRYSITE BATHYMETRYElevation Range (ft)

-60 - -55

-55 - -50

-50 - -45

-45 - -40

-40 - -35

-35 - -30

-30 - -25

-25 - -20

-20 - -15

-15 - -10

-10 - -5

-5 - 0

0 - 5

5 - 10

10 - 15

15 – 20

25 - 30

10/28/03

Marginal Flood

Channel

She

lf29 Profile Lines

ScourHole

Cel

l 1 -

Co

ntr

ol

Cel

l 2 –

94

Bea

chsa

ver

Shoal

Cel

l 3 –

94

Bea

chsa

ver

Cel

l4 –

Con

trol

/Fill

Cell 5

– B

each

save

r Ree

f

Cell 6 – D

ouble-T

Cell 7 - Control

Cell 8 - Control

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP45 200007 CMP45 200101 CMP45 200203 CMP45 200304CMP45 200307 CMP45 200310 merged CMP45 200402 CMP45 200404CMP45 200407 CMP45 200410 CMP45 200501 CMP45 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP41 200007 CMP41 200101 CMP41 200203 CMP41 200304CMP41 200307 fix CMP41 200310 merged CMP41 200402 CMP41 200404CMP41 200407 CMP41 200410 CMP41 200501 CMP41 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP37 200007 CMP37 200101 CMP37 200203 CMP37 200304CMP37 200307fixsmo CMP37 200310 merged CMP37 200402 CMP37 200404CMP37 200407 CMP37 200410 CMP37 200501 CMP37 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP29 200007 CMP29 200101 CMP29 200203 CMP29 200304CMP29 200307 CMP29 200310 merged CMP29 200402 CMP29 200404CMP29 200407 CMP29 200410 CMP29 200501 CMP29 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP26 200007 CMP26 200101 CMP26 200203 CMP26 200304CMP26 200307 fix CMP26 200310 merged CMP26 200402fix CMP26 200404fixCMP26 200407 CMP26 200410 CMP26 200501 CMP26 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP23 200007 CMP23 200101 CMP23 200203 CMP23 200304CMP23 200307 CMP23 200310 merged CMP23 200402 CMP23 200404fixCMP23 200407 CMP23 200410 CMP23 200501 CMP23 200504

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP20 200007 CMP20 200101 CMP20 200203 CMP20 200304CMP20 200307 CMP20 200310 merged CMP20 200402fix CMP20 200404CMP20 200407 CMP20 200410 CMP20 200501 CMP20 200504

Cell 1Cell 1ControlControl

Cell 2Cell 219941994BeachsaverBeachsaver

Cell 3Cell 319941994BeachsaverBeachsaver

Cell 4Cell 4ControlControl

-60

-50

-40

-30

-20

-10

0

10

20

30

0 1000 2000 3000 4000 5000 6000 7000

Ele

vatio

n (

ft)

Distance Offshore (ft)

Cape May Point

CMP33 200007 CMP33 200101 CMP33 200203 CMP33 200304CMP33 200307 all CMP33 200310 merged CMP33 200402fix CMP33 200404fixCMP33 200407 CMP33 200410 CMP33 200501 CMP33 200504

Cell 5Cell 5227 227 BeachsaverBeachsaver

Cell 6Cell 6227 227 Double-TDouble-T

Cell 8Cell 8ControlControl

Cell 7Cell 7ControlControl

Scour Hole/Flood Channel

FloodChannel

FloodChannel

FloodChannel

Shoal

Shoal

Shoal

Shoal

Shoal

Shoal

Shelf

Shelf Shelf

Shelf

Shelf

Shelf

Shoal

Shoal

• Functional PerformanceFunctional Performance

SandSand Retention -Retention - Volume ChangeVolume ChangeChange in MHW Shoreline PositionChange in MHW Shoreline Position

• Economic PerformanceEconomic PerformanceReduction in Renourishment Quantities -Reduction in Renourishment Quantities -& Lengthening Fill Cycle & Lengthening Fill Cycle

• Structural PerformanceStructural PerformanceStructural Stability -Structural Stability - Change in Structure Crest ElevationChange in Structure Crest Elevation

Alongshore IntegrityAlongshore IntegrityDepth of ScourDepth of Scour

MONITORING PROJECT PERFORMANCEMONITORING PROJECT PERFORMANCE

Improve ProtectionImprove ProtectionReduce UncertaintyReduce UncertaintyReduce CostsReduce Costs

FUNCTIONAL PERFORMANCEFUNCTIONAL PERFORMANCE

Cell 4 Control

Cell 5 Beachsaver Reef

Pre -Fill

Post -Fill

4 Months

Volume Change

%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U

%U%U%U%U%U%U%U%U%U%U%U%U%U%U%U

##########################################################################

Pre fill - October 2004 Post-Fill – Jan/Feb 2005 4 Months – April 2005(Photo October 2003)

FUNCTIONAL PERFORMANCEFUNCTIONAL PERFORMANCEMHW Shoreline ChangeMHW Shoreline Change

Cell 4 - Control

Cell 5 - Beachsaver

Cell 6 - Double-T

Cell 3 - 94 Beachsaver

Cell 2 - 94 Beachsaver Cell 1 - Control

ECONOMIC PERFORMANCEECONOMIC PERFORMANCE – Construction CostsConstruction Costs

5 weeks @cost of $1,440/lf5 weeks @cost of $1,440/lf

72 10-ft-long units covering 720 ft72 10-ft-long units covering 720 ft• Filter cloth installationFilter cloth installation• Excavation and fill requiredExcavation and fill required• Placement of units w/ diverPlacement of units w/ diver

Beachsaver ReefBeachsaver Reef – – 16 Aug to 25 Sep 0216 Aug to 25 Sep 02

4 days @ cost of $345/lf4 days @ cost of $345/lf

22 30-ft-long units covering 660 ft22 30-ft-long units covering 660 ft• NO Filter cloth installationNO Filter cloth installation• Excavation and fill NOT required Excavation and fill NOT required • Placement of units w/ diverPlacement of units w/ diver

(Cost of rock used in both cells to tie into groin tips not included in linear foot cost)

Double-T SillDouble-T Sill – 26 Sep to 2 Oct 02 – 26 Sep to 2 Oct 02

ECONOMIC PERFORMANCE -ECONOMIC PERFORMANCE -

Reduction in Renourishment Quantities & Lengthening Fill Cycle Reduction in Renourishment Quantities & Lengthening Fill Cycle (Economic Performance/Life Cycle Cost Analysis)(Economic Performance/Life Cycle Cost Analysis)

Structures designed to act as a sill to retain sand within the groin compartmentStructures designed to act as a sill to retain sand within the groin compartment

Lower Cape May Meadows/Cape May Point Eco System Restoration ProjectLower Cape May Meadows/Cape May Point Eco System Restoration Projectconstructed December 2004 will document fill retention and extension ofconstructed December 2004 will document fill retention and extension ofrenourishment cycle time in cells with and without structuresrenourishment cycle time in cells with and without structures

Based on present monitoring Based on present monitoring Anticipated savings in:Anticipated savings in:• Initial fill retentionInitial fill retention• Longer renourishment intervalsLonger renourishment intervals in cells with Beachsaver Reefsin cells with Beachsaver Reefs

Purpose:Purpose: Relate engineering Relate engineering performance to economic costsperformance to economic costsGoal:Goal: Evaluate improved Evaluate improved performance (benefits) performance (benefits) in relation to investment (costs)in relation to investment (costs)

BEACH FILL Performance –BEACH FILL Performance –

Placed Cell 1-6 - December 2004To Protect Coastal Wetland

4 months later4 months later

Post-fill: +7 ft to –42 ft shoreline gain/retreat 100% to 79% volume remaining

Cell 4Cell 4 Cell 5Cell 5

1 Source:• Nearshore

Placed 326,917 cu yd

Cape May Point toCape May MeadowsEco-System RestorationProject

Cape May Point 227 Beachsaver Reef

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

050100150200250300350400450500550600650700750

Distance NW from Groin 5 (ft)

Ele

va

tio

n b

elo

w N

AV

D8

8 (

ft)

Construction 8/16-9/25/02 As-built 10/07/02 4/14/2003 7/11/2003

10/24/2003 02/20/2004 5/5/2004 7/19/04

10/11/04 2/7/2005 4/21/2005

off line

CMP 34 CMP 33 CMP 32CMP 35

BEACHSAVER REEF - SETTLEMENTBEACHSAVER REEF - SETTLEMENT

A’

A

A’ A

CELL 5

Cell 5-Beachsaver

Area of most SettlementArea of most Settlementup to 4 ft (1.2 m) within 6 monthsup to 4 ft (1.2 m) within 6 months

10/2002 to 4/2005

SeawardBeach

Area of cutArea of fill

-3 ft

-9 ft

Design Depth

CPM33

CPM34

CMP33CMP34

STRUCTURAL PERFORMANCESTRUCTURAL PERFORMANCE – – Structural StabilityStructural Stability

Cape May Point 227 Double-T

-12

-11

-10

-9

-8

-7

-6

-5

-4

-3

-2

-1

0

050100150200250300350400450500550600650700

Distance NW from Groin 6 (ft)

Ele

va

tio

n b

elo

w N

AV

D8

8 (

ft)

as-built 10/07/02 4/14/2003 7/25/2003 11/04/2003 02/20/2004

05/05/2004 07/19/2004 11/08/2004 02/07/2005 4/21/2005

sand covered between arrows

since 7/25/03

onlyexposedDouble-T's

onlyexposedDouble-T's

Post-Fill

CMP36CMP37CMP38CMP39

DOUBLE T SILL - SETTLEMENTDOUBLE T SILL - SETTLEMENT

B’

B’

B

B

Cell 6-Double-T

CELL 6

2 to 3 ft (0.5 to 1 m) Settlement & 2 to 3 ft (0.5 to 1 m) Settlement & Complete Burial under 1 to 2 ft (0.3 to 0.6 m)Complete Burial under 1 to 2 ft (0.3 to 0.6 m)

of sand within 6 monthsof sand within 6 months

10/2002 to 4/2005

-6 ft

Design Depth

-9 ft

CPM37

CMP37

STRUCTURAL PERFORMANCE -STRUCTURAL PERFORMANCE -

-14

-13

-12

-11

-10

-9

-8

-7

-6

-5

-4

-3

400 500 600 700 800

Ele

vatio

n, ft

(N

AV

D)

Distance from Baseline, ft

Cape May Point

CMP37 200203 CMP37 200304 CMP37 200307fixsmo

Pre-installation

6-month post

9-month post Double-T Sill Location

Installation Depth

Approximate Settlement

Line CMP33 6-month postLine CMP33 9-month post

Beachsaver Reef

Line CMP34 9-month postLine CMP34 6-month post

Beachsaver ReefBeachsaver Reef

Double-T SillDouble-T Sill

CHANGE IN STRUCTURECHANGE IN STRUCTURECrest Elevation,Crest Elevation,Alongshore Integrity Alongshore Integrity &&Depth of ScourDepth of Scour

ScourTrough

SUMMARYSUMMARY

227227 Project constructed August - October 2002Project constructed August - October 20022.5 Year Quarterly Monitoring Results Reported Here 2.5 Year Quarterly Monitoring Results Reported Here Eco System Restoration Project const. - December 2004Eco System Restoration Project const. - December 2004

Preliminary Findings:Preliminary Findings:

• Retention of sand greatest in groin compartments w/ Beachsaver Reefs even w/ settlement

• Double-T Sill vs. Beachsaver Reef could not be evaluated due to settlement of Double-T Sill

• Anticipated savings in retention of beach fill w/ Beachsaver Reefs

Cape May Point, NJ Demonstration Site