Kwasi Badu-Tweneboah, Ph.D., P.E. – Geosyntec Consultants Jacksonville, Florida, USA

Kenneth W. Cargill, P.E. – KW Cargill, P.A..Punta Gorda, Florida, USA

Challenges of Dredging and Material Disposal at a LNG

Facility in Savannah Harbor, Georgia, USA

Presentation Outline• Project Location and Background• The Business – LNG Operations• Contract and Permit Requirements• Dredging Challenges• Evaluation of Dredging Options• Disposal Challenges• Prediction of DMCA Life• Evaluation of Disposal Options• Summary

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Project Location and Background• Located 5 miles

East Northeast of Savannah

• Bounded by the Savannah River, South Channel, and Intracoastal waterways

• River Mile 7.5• Lower Savannah

Harbor• Most seaward

port facility 3

The Business – LNG Operations

• Storage capacity 11.5 Bcfe• Delivery rate capacity:

– Firm delivery rate 1,518 MMcf/d– Maximum delivery rate 1,755 MMcf/d

D-1D-4

D-5

D-6(future)

D-2D-3

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Relevant Infrastructure• Turning Basin – Approx. 33 acres conforming with U.S.

Coast Guard minimum (FERC Recommendation)

• Ship Slip – Approx. 44 acres, berths for 2 ships simultaneously

• DMCA 1 – Approx. 130 acres, dike last raised 2011, current dike elevation 50 ft MLW, being used for disposal

• DMCA 2 – Approx. 120 acres, dike last raised 2009, being intensively managed for drying and material harvesting, current dike elevation 44 ft MLW

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Dual Ship Off-loading

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2008 Elba IslandAerial Photograph

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Dredged Material Containment AreasDMCA 1~ 130

ac

DMCA 2~ 120 ac

Sedimentation Pond

Weir Outlet

Elba Island Aerial Photograph(August 2011)

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DMCA 1~ 130

ac

DMCA 2~ 120 acSedimentatio

n Pond

Elba Island Aerial Photograph(August 2011)

Contract and Permit Requirements

• Typical 1-month notification of LNG Tanker ship coming

• Huge Financial Penalty if ship cannot come or dock

• Maintain required dredge depths year round– Ship Slip: -42 ft MLW min. (-46 ft max.)– Turning Basin: -38 ft MLW min. (-42 ft max.)– Dredging ship slip every 2 to 3 months– Annual total volume ≈ 1 million cubic yards 9

Dredging Challenges• Rapid Sediment Accumulation

– Loading Conditions of Savannah River– Ship Slip and Turning Basin acting as Bath Tubs (Sinks)

• Permit Renewal Challenges– 20-month (in lieu of 5-yr) permit issued in July 2011– New renewal application tied with upper harbor users– Water quality and EFH conditions - NMFS, USFWS,

GAEPD, SCDHEC• Procurement and Mobilization of Dredging

Contractor– One hydraulic cutterhead dredger in Savannah River– Use by USACE and other harbor users– Scheduling of next dredging event

• Disposal Issues 10

Dredging Challenges

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Evaluation of Dredging Options• Long-term contract with hydraulic cutterhead dredging

contractor – Lump sum contract ($5/cy to $10/cy in lieu of typical $3/cy to

$4.50/cy) – Continual negotiations with USACE to release dredge

• Purchase and operate its own dredge • Contract dredging operations to a non-dredging contractor

• Pursue alternative dredging solutions

– Use of I-beam bed leveling – agitation dredging• Nationwide Permit (NW) 5 issued by USACE as research study • Four trial tests completed to date – results being analyzed

– Use of clamshell bucket dredging and ocean disposal• Permitting Challenges• Tier III testing and analyses 12

Disposal Challenges• Long-Term Dredged Material Management Plan

(DMMP)– Prediction of DMCAs Life using Corps’ PSDDF

software program• Impact of Increased Frequency of Dredging

– Rapid Filling of DMCAs– Less Time for consolidation and desiccation – Changes to Dike Raising schedules

• Dike Raising Constraints– Maximum dike height of 62 to 68 ft MLW– Stability Constraints– Availability of fill material 13

Prediction of DMCA LifeUsing Corps Model PSDDF

Cases CommentsDredging

Event

Thickness Deposited

(ft)

Estimated Life Expectancy

DMCA 1 DMCA 2

DMCA 1

DMCA 2

62 ft 68 ft 62 ft 68 ft

Case 1 

2 dredging events per year: SS and TB

1 April 3.94 4.22 Apr-25Apr-29

Oct-24

Oct-28

2 October 3.94 4.22        

Case 2 

3 dredging events per year: SS and TB

1 March 2.63 2.82 Jul-25Mar-29

Nov-24

Nov-28

2 July 2.63 2.82

3Novembe

r2.63 2.82        

Case 3 

3 dredging events per year: SS

1 March 1.07 1.15 Mar-49 - Jul-50 -

2 July 1.07 1.15

3Novembe

r1.07 1.15        

Case 4 

3 dredging events per year: SS

2 dredging events per year: TB

1 March 3.4 3.65 Mar-25Mar-29

Mar-27

Nov-28

2 July 3.4 3.65

3Novembe

r1.07 1.15        

Notes: SS = Ship Slip; TB = Turning Basin

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Evaluation of Disposal Options• Bed leveling in ship slip

o Nationwide Permit (NW) 5 issued – results of trial tests being analyzed

o Allow more drying time in DMCA by increasing time between dredging

• Intensive management of DMCA drainage and dredged material harvesting o Concepts developed during last DMCA 1 dike raisingo Concepts currently being implemented in DMCA 2o Final objective is system steady state where volume

capacity of DMCA is perpetually restored between dredging

• Negotiations with USACE – Use of SC DMCAs for dredged material disposal– Ship Slip and Turning Basin are for a single user

• Ocean Disposal

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Development of Interior Borrow Pits

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Concept of Intensive DMCA Management

• Rapid removal of decanted water immediately after end of dredging and constant removal of drainage

• Use of specialty equipment to create and enhance drainage pathways

• Early and continual removal of dredged material slurry at perimeter to promote interior desiccated crust

• Early and continual removal of desiccated crust on perimeter of DMCA

• Development of interior borrow pits for material mining as possible

• Removal of desiccated and consolidated material and hauling to stockpile areas 18

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Concept of Intensive DMCA Management

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Concept of Intensive DMCA Management

Concept of Intensive DMCA Management

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Concept of Intensive DMCA Management

Tracking Consolidationand Settlement

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On-going Settlement in DMCA 2

Preliminary Construction Costs

• 3-yr contract for $5.9 million signed in 8/2011• Average cost of $120,000 per month to date• 29% of contract expended thru 9/2012• $500,000 per ft of settlement gained thru 9/2012• Key equipment used to date:

– 1 Swamp buggy– 2 Long-reach excavators– 1 dozer– 1 harrow/tractor

Summary• Dredging Permits for Ship Slip and Turning

Basin– Dredge anytime of year– No DO Limit and no fish windows

• Ability to dredge when needed– Continual negotiations with USACE and dredge

contractor– Permit and implement bed leveling concept

• Have disposal capacity in DMCAs thru 2050– Intensive DMCA management– Ocean disposal

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Thank You

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