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A World of Solutions

Lessons Learned from a Rocky Situation: The Story of the

North Topsail Beach Phase 5 Project

Ken Willson

NCBIWA Fall Conference 2015


1

• Geologic Setting

• Marine Sand Search / Characterization of the Beach

• Additional Context

• Construction Sequence

• Lessons Learned

Presentation Outline

2 A World of Solutions

Geologic Setting

Town of North Topsail Beach, Onslow County, North Carolina

Project Area

High

Low


Geologic Setting

Project Area

High

Low

Coastal Change Along the Shore of Northeastern South Carolina:

The South Carolina Coastal Erosion Study

W. A. Barnhardt (Editor)


Geologic Setting

Rock

Outcrops

Thin Veneer

of Sand Over

Rock

Town of North Topsail Beach, Onslow County, North Carolina

Thin Veneer

of Sand Over

Rock


2005 and 2006 Offshore Sand Search

– Geophysical Surveys

– Vibracore Surveys

– Cultural Resource Surveys

Sand Search Investigation

Fathometer Magnetometer CHIRP

Seismic Fish

Survey Vessel

Sidescan Sonar Fish


Final Borrow Area Design




Vibracore Investigations

Rock Rock


Characterization of the Beach

Native Beach: 3,421 Clasts > 3 inches in Diameter in 50,000 ft2 area


Project 100% LOCALLY FUNDED (No Federal, State, or County* Funds)

USDA Rural Development Loan

Local Government Commission (LGC) approval required

Bidding – Who’s responsible for “unsuitable material”

Permits only allow dredging up to April 30 (Environmental Windows)

Negotiations with low bidder / Decreased mob/demob cost contingent on Town agreeing not to require return the following dredge season (no guaranteed minimum volume)

Additional Context

* County ended up contributing funds after the construction


Project Overview

Contingency Portion

Of Project

Project Start:

December 18, 2014

No Dredge

Area

Pipeline


12

December 18, 2014 at 7:00 P.M. pumping begins.

Construction


13

Construction

Early AM December 19, 2014 rocks are first observed in the fill.

Contractor adjusts cutterhead elevation and is able to avoid rock.

Dredging continued with minimal rock until 6:00 AM December 23, 2014 (Christmas Break)


During Break: Review of vibracore data, geophysical data, extensive coordination with contractor, identify suggested dredge areas, begin discussions regarding methods to handle rock

December 28 – 29, 2014: Dredging resumes, dredge moved to a different location, material has much less rock in it

December 30 – 31, 2014: State and CPE-NC discuss rock concentrations on beach. Conduct an official rock survey

Construction


Construction

View Looking North At Sta. 750+00

View Looking South At Sta. 748+50


Construction Continued from Dec. 28th – Jan. 16th with minimal rock contained in the fill.

– Multiple Site Visits by DCM and USACE Representatives

– Coordination regarding rock removal (Town, Engineer, Contractor, NC DCM, and USACE)

January 15, 2015: Town executed a change order with contractor to remove rock (Rock Picker).

January 16, 2015: Higher concentration of rock observed at the discharge.

January 16 – February 6, 2015: Intermittent periods of higher rock discharged. Coordination with DCM and USACE.

February 6, 2015 - Execution of Change Order to Install Rock Boxes.

Construction


Construction

Rock Picker


Rock Boxes: Installed

February 12, 2015

Construction


Mid-February: Rock Picker working, Rock Boxes Installed

Mid-February – Mid-March: Continued monitoring of the beach fill shows intermittent areas with higher concentrations of rock.

March 17, 2015: Multi-Agency Site Visit Conducted to evaluate rock situation

Construction


Following March 17, 2015 Inter-Agency Site Visit:

Implement Post Hole Digger Monitoring.

Implement Bulk Gravel Analysis.

Hire 3rd Party Contractor (Tigerhole Landscaping) to remediate upper 36 inches of fill

Reduce mesh size of Rock Boxes to 1.5 inches.

Modify Rock Box opperations (No Overflow / Stockpile Proximity).

Officially requested to maintain Rock Box log.

Construction


Construction

Post Hole Digger – Rock Analysis


Construction

Bulk Gravel Analysis


Construction

Remediation of Upper 36” of berm


Construction

Reduced Mesh Size on Rock Boxes


April 2, 2015 – USACE orders project to shut down unless a cutterhead screen is installed (USFWS recommendation)

– USFWS agrees to allow work to continue for the evening and then shut down for weather

April 3 – 4, 2015: Contractor Installs cutterhead screen

April 5, 2015: Dredging Resumes w/ Cutterhead screen

Construction


April 7, 2015 Inter-Agency Site Visit:

Inspect Rock Box Mesh

Inspect Bulk Gravel Analysis.

Inspect 3rd Party Contractor (Tigerhole Landscaping) remediation of upper 36 inches of fill

Inspect Rock Box Emptying /Disposal Operations .

Results of Inter-Agency Site Visit:

Methods being used are resulting in an acceptable beach

Cutterhead Screen can be removed

Continue monitoring

Construction


27

Construction

April 7, 2015

USACE Permit Modification

USFWS Formal Consultation

NMFS Informal Consultation

NC DCM Permit Modification


AGENCIES ARE NOT YOUR ENEMIES!!

Use best available science

Sediment Criteria may require modifications:

– 3 inch clast threshold

– Threshold for Rock in the Borrow Area – Screens

Have contingency plans in place a head of time

Methodology for successfully screening rock

Methodology for monitoring bulk gravel / buried rock

Lessons Learned


Offshore borrow areas with rock can be used if necessary

Lessons Learned


Lessons Learned



32

Jan. 1 – March 31

April 1 – June 20

Lessons Learned

Dredge Window Expansion (With Conservation Measures)


33

Turtle Monitoring

Benthic Monitoring

Bird Monitoring

Light Survey

2 Nests: Project during construction

2 Nests: Along pipeline during construction

3 Nests: Project after construction (1 Green)

Lessons Learned

Dredge Window Expansion (With Conservation Measures)


Project Completion

Cooperative Approach to Resolution of Issues (Town, Contractor, Agencies)

Completed Project Within Budget

Constructed a Successful Project (Provide Storm Damage Reduction to homes and infrastructure and a beach environment conducive to natural ecology)


35

Comparison of Pre- and Post-Construction Conditions

Project Completion


36

Thank You

lessons learned from a rocky situation: the story of the north … › files › willson_rocky...

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