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Plum IslandShoreline Protection & Management

A Review of Current Design & Construction InitiativesBy David Vine, Vine Associates, Newburyport, MA

David Lager, NETCO, Lexington, MA

PRESENTATION TOPICS• Introduction• Coastal Conditions• Shoreline Changes• Community Response• Design Issues• Construction Progress• Plum Island Coir Envelopes, Anchors

• Other Recent CoirApplications

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INTRODUCTIONCase Study• Short Term Dune

Stabilization• Community Alliance to Deal

With Beach Management• Still Going On

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COASTAL GEOLOGICAL FACTORS

• Jetty Construction

• Active Ebb Tidal Delta (Sandbar)

• “Reversal”Northern Littoral Drift

• Stone Groin Impact

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COASTAL PROCESSES

• Groin Limiting Northern Sand Flow

• Degraded Jetty• Refraction• Funneling into Area

Causing “Hot Spots” per Particular Storm

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COASTAL PROCESSES

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SHORELINE CHANGES• Long-Term Shoreline

Changes Since 1928• About 3 – 4 feet per

Year 1928-1994

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SHORELINE CHANGES• Shorter Term 2000-2007• 13.3 Feet per Year• Most Significant at Town Center • Circa 1995• Order of 100 Foot Shoreline

Erosion• Groin Fully Covered

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FORMATON OF MERRIMACK RIVER BEACH ALLIANCE

• Newbury• Newburyport• Salisbury• State Senators/Representatives• Seaport Bond Council• Department of Conservation &

Recreation• State Regulatory Agencies

DEPCZM

• Federal Regulatory Agencies• Local Citizens Groups• Newspapers• Local Residents• Privately Retained Lobbyist• Monthly Meetings – Totally Open Process

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DESIGN CONSIDERATIONS• Protect Public

Infrastructure• Sand Nourishment• Less than 3 Ton Sand

Bags• Geotube (High Strength

Plastics)• Bio-Degradable Fabrics• Stone/Timber/Steel• Plantings (Limited)REGULATORY REQUIREMENTS• Off Site Sand Source• Must be Bio-Degradable

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LIMITED SOLUTIONS/FUNDS• Design had to be of large Bio-Degradable Sand Bags or

Envelopes• Considered Placement of Fabric Covered in Sand and

Covering it with Fabric• Considered Pre-Fabricated Coir Forms Placing sand and

then stitching together (Netco Product)

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PLUM ISLAND DESIGN• Investigating Past Coir Projects

How Past Designs Evolved• Consider more like Design of

Revetment• 5 Terrace System• Buried First Terrace 4’ Below Grade• Second Terrace 6’ Wide Section 90°

to Dune• Upper 3 Terraces Paralleled to Dune• Helical Anchors• To be Covered with Sand and

Planted

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OCTOBER/NOVEMBER 2008• Design Set• Permit Approvals Received• Bid Project• Award/Fund Project• Start Construction• November 26, 2008 Storm

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NOVEMBER 28 THRU END OF DECEMBER

• Construction Continues (Accelerated)

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CONSTRUCTION COMPLETED• Mid January Construction Completed

(Though tested along the way)

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MARCH/APRIL 2009SAND NOURISHMENT

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DIFFICULT SPRING/SUMMER• Wave Activity• Several Eastern

Storms• Some Damage

Encountered

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THE PRESENT• Presently USACE Sand Nourishment

to start January 2010• Modest Repairs Scheduled for 6’ Bags• Hope for Mild Fall/Winter Awaiting

Nourishment

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LIMITED REPAIR TO APPROXIMATELY TEN SIX FOOT BAGS

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Coir “Soft Technology”

• Biodegradable Material

• Renewable Resource• Relatively High

Tensile Strength• Imported From Far

East• Custom Fabricated

For Each Project In Massachusetts

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Building Block – Matsof Different Weights, Dimensions

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Mats Fabricated In MA Into Different Sizes, Shapes

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Plum Island Application

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Key – Bottom “Foundation”Terrace

• Bottom Terrace Below Beach Face, Avoid Wave, Surf Undercutting

• 4’ Wide Terrace – Add. Mass, Weight

• 2 x Layers Coir Mat, 1 x Layer Jute Liner

• Helical Tie Down Anchors• Continuous Sand Filled

Envelope 500 Feet Long

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Bottom Foundation Terrace

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Plum Island Application – 2nd

Terrace

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2nd Terrace Level

• 3’ x 3’ x 6’ Envelopes• Attached to Bottom

Terrace and to Adjacent Envelopes

• Imported Sand• Slowest Part of the

Project• 2 x Layers Coir Mat,

1 x Layer Jute Liner

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3rd, 4th, 5th Terraces

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3rd, 4th, 5th Terrace Levels• Coir Envelope Tubes• 3’ x 3’ x 500’• Imported Sand• Attached on All Sides

to Form Continuous Envelope

• Minimize Possible Beach Debris

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Upper Level Terraces In Progress

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Completed Project – January, 2009

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Conclusions• Permit Allowed Excavation Below Beach Face

– Minimized Potential for Undercutting By Waves/Surf• Second Terrace Level Used 6’ Envelopes –

Robust/Durable Design, Repairs Easier• Terraced Stepped Back 3 Feet, Natural Slope

Face Maintained, Increase Stability • Helical Tie Down Anchors Installed @ 50’

Spacing, Decrease to 25’ Spacings• No Recent TV News Coverage of Plum Island

Homes Taken By Ocean• Allowed Time To Develop Longer Term Beach

Nourishment Program With U.S.A.C.E. and Local Communities

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Eastham Toe Protection Design(Engineering/Permitting – LEC Environmental)

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Eastham – Existing Conditions –December, 2006

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Coir Envelope Construction

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Coir Envelope Solution - 2006

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Completed Toe Protection –Ready for Vegetation

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Vegetated Bank – Sep., 2009