Management System to Aid Water Quality …Sponsors: Lower Susquehanna Riverkeeper Design of a Dam...

Sponsors: Lower Susquehanna Riverkeeper

Design of a Dam Sediment Management System to Aid Water Quality Restoration of the Chesapeake Bay

Presented By: Sheri Gravette Kevin Cazenas Said Masoud Rayhan Ain

Faculty Advisor: George Donohue

Sediment Plume from Transient Scouring

West & Rhode Riverkeeper

Conowingo Dam

Agenda

• Context

• Stakeholders

• Problem/Need Statement

• Design Alternatives

• Analysis and Design of Simulation

• Design of Experiment

• Results, Analysis & Recommendations

2

Chesapeake Bay and The Susquehanna River

• Chesapeake Bay is the largest estuary in the United States

• 3 largest tributaries of the Bay are the Susquehanna, Potomac and James rivers – Provide more than 80% of the Bay’s freshwater

• Susquehanna River is the Bay’s largest tributary – Provides nearly 50% of freshwater to the Bay

– Flows from NY to PA to MD

3

Map of the Chesapeake Bay Watershed Source: The PA Dept. of Environmental Protection

Lower Susquehanna River and

Conowingo Dam

• Conowingo Dam (est. 1928) – southernmost Dam of the Lower Susquehanna

• Quality of water from the Lower Susquehanna is vital to the bay’s health

• Traps sediment and nutrients from reaching the Chesapeake Bay

– Water quality is closely related to sediment deposition

• The river provides power for turbines in hydroelectric plants and clean water to people

• Conowingo Hydroelectric Station

– Mainly provides power to Philadelphia, PA

– A black start power source

– Provides 1.6 billion kWh annually

4

Map of Conowingo Reservoir Source: US Army Corps of Engineers, (2013)

Lower Susquehanna River: Steady State vs. Transient State

Transient state: river flow rate higher than 300,000 cfs

– Major Scouring event: enhanced erosion of sediment due to:

– significantly increased flow rates

– constant interaction of water with the Dam

5 Chesapeake Bay: Before and After Tropical Storm Lee Source: MODIS Rapid Response Team at NASA GSFC

Current Steady State: river flow rate less than 30,000 cfs

– Sediment/nutrients enters Chesapeake Bay at low-moderate rate

– TMDL regulations are related to steady state

Flow and Sediment Build-up in Conowingo Reservoir

Rouse Number for Medium Silt Particle at 30,000 cfs Source: S. Scott (2012)

• Rouse number defines a concentration profile of sediment – Determines how sediment will be

transported in flowing water

• Rouse Number:

𝒁 =𝝎𝒔𝒖∗

𝝎𝒔=Sediment fall velocity 𝒖∗=shear velocity

• Significant amount of suspended sediment is located directly behind the dam (areas away from

turbines)

Holtwood Dam

Conowingo Dam

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Sediment Deposition at Conowingo Dam

• Deposition potential – expected sediment deposited over a given time

• At maximum capacity all Susquehanna River sediment flow s through to the Chesapeake Bay during normal, steady-state flow

Sediment Deposition in Conowingo Reservoir; Construction to 2008 with Gap Prediction Source of Data: Hirsch, R.M., (2012)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

50

100

150

200

1929 1936 1943 1950 1957 1964 1971 1978 1985 1992 1999 2006 2013 2020 2027

Percent Capacity

Sedim

ent Deposition (m

illion tons)

Year

Sediment Deposition

Expected

Threshold

Chesapeake Bay Total Maximum Daily Load (TMDL)

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• Established by US Environmental Protection Agency in conjunction with 1972 Clean Water Act

• Actively planned since 2000

• Covers 64,000 square miles in NY, PA, DE, MD, WV, VA, and DC

• Sets limits for farmers, plants, dams, and other organizations that dump sediment/nutrients into dam

• Designed to fully restore Bay by 2025 – 2017: 60% of sediment/nutrient reduction must be met

9

Lower Susquehanna Contribution to TMDL

Watershed limits to be attained by 2025 are as follows:

• 93,000 tons of nitrogen per year (46% of Chesapeake TMDL reduction)

• 1,900 tons of phosphorus per year (30% of Chesapeake TMDL reduction)

• 985,000 tons of sediment per year (30% of Chesapeake TMDL reduction)

Agenda

• Context

• Stakeholders






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Primary Stakeholders Objective(s) Issue(s)

Lower Susquehanna Riverkeeper and Stewards of the Lower Susquehanna, Inc. (SOLs)

- Find alternative uses for the sediment stored behind Conowingo Dam

- Highlight vulnerabilities in environmental law - Minimize effects of major scouring events to

the Chesapeake Bay

- Cost to remove sediment from Reservoir is high

- Providing pressure on FERC to require more strict relicensing requirements for Conowingo Dam Hydropower Plant

Chesapeake Waterkeepers- West & Rhode Riverkeeper

- Protect and improve the health of the Chesapeake Bay and waterways in the region


Maryland and Pennsylvania Residents (Lower Susquehanna Watershed)

- Maintain healthy waters for fishing and recreation

- Improve water quality of the watershed - Receive allocated power from Hydroelectric

Dam


- Value low cost for power production and better water quality

Exelon Generation – owner of Conowingo Dam

- Obtain relicensing of Conowingo Dam prior to its expiration in September 2014

- Maintain profit

- Sediment build up has no impact on energy production

Federal Energy Regulatory Commission (FERC)

- Aid consumers in obtaining reliable, efficient and sustainable energy services

- Define regulations for energy providers

- Pressure to update dam regulations

Agenda

• Context

• Stakeholders






12

Problem Statement

- Conowingo Reservoir has been retaining a majority of the sediment flowing down the Susquehanna River

- Major scouring events in the Lower Susquehanna River perpetuate significant ecological damage to the Chesapeake Bay

- This ecological damage is caused by increased deposition of sediment and nutrients in the Bay

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Need Statement

• Need to create a system to reduce the environmental impact of transient scouring events

• Need is met by reducing the sediment and nutrients currently trapped behind Conowingo Dam

– Reduce to 1,900 tons phosphorus per year

• Reduction is to be done while maintaining energy production and aiding TMDL regulations

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Mission Requirements

MR.1 The system shall remove sediment from the reservoir such that the total sediment deposition does not exceed 180 million tons.

MR.2 The system shall reduce sediment scouring potential.

MR.3 The system shall allow for 1.6 billion kWh power production annually at Conowingo Hydroelectric Station.

MR.4 The system shall facilitate Susquehanna watershed limits of 93,000 tons of nitrogen, 1,900 tons of phosphorus, and 985,000 tons of sediment per year by 2025.

MR.5 The system shall facilitate submerged aquatic vegetation (SAV) growth in the Chesapeake Bay.

Agenda

• Context

• Stakeholders






16

Sediment Mitigation Alternatives

1. No Mitigation Techniques (Baseline) – Sediment remains in reservoir

2. Hydraulic Dredging – Sediment removed from waters

– Product made from sediment

3. Dredging & Artificial Island – Initially: Sediment is dredged to make an artificial island

– Over time: Sediment is slowly forced through the dam into bay

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Conowingo Dam Source: D. DeKok (2008)

1. No Mitigation Techniques

2. Hydraulic Dredging

3. Dredging & Artificial Island

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WHAT

• Sediment will reach capacity by 2030

• Major scouring events will have the largest impact

HOW

• Normal Flow: < 30,000 cfs

• Major Scouring Event: > 300,000 cfs

Normal Flow at Conowingo Dam Source: E. Malumuth (2012)

WHAT

• Remove sediment mechanically

• Concentration on suspended sediment

• Product yield from sediment

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Hydraulic Dredging Process Source: C. Johnson

HOW

• Rotating cutter to agitate & stir up

• Pipeline pumps sediment to surface

• Collection for further treatment

WHAT

• Diamond-shaped structure to divert water is placed in front of the dam

• Larger sediment load through the dam (at steady-state); remaining amount is dredged

HOW

• Diverter made of dredged sediment product

• Diverts water left & right – increases flow velocity

• Decreases Rouse number near suspended sediment

• Sediment mixed into wash load

• Potentially decreases total dredging costs

Potential Artificial Island Location at Conowingo Reservoir Source: Original graphic by S. Scott (2012)

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Quarry

• Direct transportation from reservoir to quarry

• No opportunity to offset cost

• No one-time investment cost

21

Rock Quarry

Rotary Kiln Plasma Gas Arc Vitrification

Low Temperature Washing




Quarry

Primary Alternatives

Sub-Alternatives

22

Low-Temperature Sediment Washing

• Non-thermal Decontamination

• Potential use as manufactured topsoil

• One-time cost: Approx. $25 million (BioGenesis)

• Process includes: – Loose screening – Dewatering – Aeration – Sediment washing/remediation – Oxidation and cavitation

Low Temperature Washing Facility Manufactured Topsoil




Quarry Plasma Gas Arc Vitrification

Rotary Kiln Low Temperature

Washing


Sub-Alternatives

Rotary Kiln (Lightweight Aggregate)

• Thermal decontamination process

• Process includes: – debris removal

– Dewatering

– Pelletizing

– Extrusion of dredged material

• One-time investment cost: Approx. $180-510 million (HarborRock)

23

Rotary Kiln Operation




Quarry Plasma Gas Arc Vitrification

Low Temperature Washing

Rotary Kiln


Sub-Alternatives

• 99.99 % Decontamination and incineration of all organic compounds

• Intense thermal decontamination process

• Output: vitrified glassed compound “slag”

• One-time cost: Approx. $430 million (Westinghouse Plasma)

Plasma Gas Arc Vitrification (Glass Aggregate)

24 Glass Aggregate (Slag)




Quarry Low Temperature

Washing Rotary Kiln

Plasma Gas Arc Vitrification

Sub-Alternatives Primary Alternatives

Sub-Alternatives

Cost/Revenue ($ per cubic yard) Distribution (Triangular) Comparisons:

Quarry, Topsoil, and Lightweight Aggregate

Sources: LSRWA (Quarry); M. Lawler et al and D. Pettinelli (Topsoil); JCI/Upcycle Associates, LLC (LWA)

25




00.020.040.060.080.1

0.120.140.160.180.2

$0 $50 $100 $150 $200 $250 $300

Cost/Revenue PDF (Triangular)

Lightweight Aggregate

00.020.040.060.080.1

0.120.140.160.180.2

$0 $50 $100 $150 $200 $250 $300


Topsoil

Revenue

Cost

00.020.040.060.080.1

0.120.140.160.180.2

$0 $100 $200 $300

Cost PDF (Triangular)

Quarry


Washing Rotary Kiln



Sub-Alternatives

26 Source: Westinghouse




0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

$0 $50 $100 $150 $200 $250 $300


Low Grade Tile

Revenue

Cost

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

$0 $50 $100 $150 $200 $250 $300


High Grade Tile

Revenue

Cost

Cost/Revenue ($ per cubic yard) Distribution (Triangular) Comparisons:



Washing Rotary Kiln



Sub-Alternatives

Agenda

• Context

• Stakeholders






27

Project & Modeling Scope

Problem Overall:

Sediment build up at Conowingo Dam has been detrimental to the Chesapeake Bay’s ecosystem health following major storms (transient events)

Problem Addressed by Model:

1. Sediment removal

2. Associated cost of remediation due to deposition of sediment and nutrients to the Chesapeake Bay

3. Sediment processing , sediment product production

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Model Simulates Model Type

Sediment Removal Model

Sediment flow from upstream and sediment outflow at Conowingo Dam

- Microsoft Excel Spreadsheet

Ecological Impact Model

Cost of remediation and recovery based on phosphorus deposition to the Chesapeake Bay and hypothetical waste treatment upgrade costs

- Java - Microsoft Excel Spreadsheet

Reuse-Business Model

Sediment product production, cost and revenue generation

- Microsoft Excel Spreadsheet (Crystal Ball)

Sediment Management Model Decomposition

Stochastic Sediment Management Model

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31

Source: USGS

Stochastic Sediment Removal Model Input Flow Rate (1967 – 2013)

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DRY FUTURE - 400,000 cfs max: • Average Flow: 38,908 • Median Flow: 26,826 • Standard Deviation: 38,855 • Avg. days/yr. > 150kcfs: 7.4

SIMILAR FUTURE-700,000 cfs max: • Average Flow: 43,464 • Median Flow: 28,638 • Standard Deviation: 46,335 • Avg. days/yr. > 150kcfs: 13.3

WET FUTURE - 1,000,000 cfs max: • Average Flow: 43,975 • Median Flow: 30,685 • Standard Deviation: 46,570 • Avg. days/yr. > 150kcfs: 9.8

Historical Data: • Average Flow: 41,271 • Median Flow: 28,100 • Standard Deviation:

47,095 • Avg. days/yr. >

150kcfs: 12

Sediment Removal Model Three Different Future Worlds

33

Conowingo Dam

Velocity Profile at 700,000 cfs. Source: U.S. Army Corps. Of Engineers

Reservoir Bathymetry Source: USGS

Scaled x10 Vertically

𝑊

𝐿

𝐷

𝑳 = Length 𝑾 = Width 𝑫 = Depth 𝑾 ∗ 𝑳 = Surface Area (SA) 𝑾 ∗ 𝑫 = Cross-Sectional Area (A) 𝑾 ∗ 𝑳 ∗ 𝑫 = Volume (V)

Actual Proportions

Sediment Removal Model Bathymetry and Gridding

1 mi.

Water flow

34

𝑍 =𝑤𝑠

κ ∗110 (𝑣𝑖)

𝑄 =222196.84

𝑍

𝑆𝑆 = 0.000012(𝑄)1.88623

𝑆𝑆𝑖 = 1.2 × 10−5222196.84

𝑍𝑖

1.88623𝑆𝐴𝑖 𝑆𝐴𝑖

𝑖 = 1, . . , 400

𝐴𝑛+1,𝑖 = 𝐴𝑛,𝑖 −

4×106∗32.67

365

𝑉𝑖 𝑉𝑖400𝑖=1

𝐿𝑖+𝑆𝑆𝑖∗32.67

𝐿𝑖+

𝐷𝑆∗108

365

𝑆𝐴𝑖 𝑆𝐴𝑖200𝑖=1

𝐿𝑖

𝑖 = 1, . . , 400; 𝑛 = 1, . . , 7305

Initial Cross-Sectional Area

Area Decrease: Redeposition

Area Increase: Scoured Sediment

Daily Cross-Sectional Area

Daily Scoured Sediment

Rouse Number

Source: U.S. Corps. of Engineering

Variable Description

L Reservoir Length

W Reservoir Width

D Reservoir Depth

A Cross-Sectional Area

SA Surface Area

V Volume

Q Flow Rate

v Flow Rate Adjusted Velocity

SS Scoured Sediment

DS Dredged Sediment

Z Rouse Number

ws Particle Fall Velocity

k Von Kármán Constant

Sediment Removal Model Continuity & Shear Est. Equations

Area Increase: Dredged Sediment

Correlations: Flow, Rouse, Scoured Sediment

Sediment Removal Model Assumptions

• Flow rates follow same trend from past 46 years

• Seeded correlation distributions are lognormal

• Redeposition is a fixed rate (4,000,000 tons/yr.)

• Particle fall velocity is fixed throughout reservoir

35

Average Daily Sediment Scoured (≤ 6,800 tons/day)

• Pdaily = Pavg(SS)

• 0.001320 ≤ Pavg ≤ 0.002933

Above Average Daily Sediment Scoured ( > 6,800 tons/day)

• Pdaily = Pmajor (SS)

• Pmajor = 0.0005578

SurrogateRemediation Expense (Waste Treatment Plant Renovations)

• 𝑹 = 𝑳𝑺𝑹𝑷𝑻𝑴𝑫𝑳 − 𝑷 𝑾𝒄𝒐𝒔𝒕

36

Ecological Impact Model Equations

Pdaily – daily phosphorus in tons

SS– daily sediment scoured in tons

Pavg– random number that denotes average percent of phosphorus per ton of sediment

Pmajor– denotes percent of phosphorus per ton of sediment during major scouring

LSRPTMDL – Lower Susquehanna TMDL limit for phosphorus (1895 tons)

Wcost– average expense of phosphorus waste treatment renovations per TMDL limits

Ecological Impact Model Assumptions

• Linear correlation between sediment scoured and phosphorus scoured

• Linear correlation between hypothetical waste treatment upgrade costs and phosphorus scoured

• Nitrogen scoured is negligible with relation to waste treatment plant upgrade costs

37

38

Average ANNUAL Pollution Loads

(tons)

Tropical Storm-Lee Related Pollution Loads (tons)

Phosphorus (Ps) 2,600-3,300 10,600

Sediment (Ss) 890,000-2,500,000 19,000,000

Ratio (Ps/Ss) 0.00132-0.0029 0.000558

Ecological Impact Model Surrogate Data

Based on surrogate data on Chesapeake Bay watershed wastewater treatment plant upgrades: Average expense of waste treatment renovations based on P TMDL :

Wcost = $ 6,300 /ton of phosphorus

% range of average ton of phosphorus per ton sediment

% of ton of phosphorus per ton sediment during major scouring

Waste Treatment

Plant Plant Name or Areas Served

Upgrade Costs

(millions)

Plant 1 Lexington and

Rockbridge County(VA) 15.2

Plant 2 Hopewell (VA) - 1997 50

Plant 3 Hopewell (VA) - Current 62

Plant 4 Buena Vista (VA) 30

Business Reuse Model Equations

Production Equation: 𝑹𝒊 ∗ 𝒂𝒊 = 𝒑𝒊

Net Cost Equation: 𝑻𝒊 = 𝒄𝒊 +𝑴𝒙 − 𝒓𝒆𝒗𝒊 ∗ 𝑹𝒊

39

𝒂𝒊 = amount of sediment needed to make one unit of product i

Ri = amount of sediment removed and used for product i

p𝒊 = units of product i produced

rev𝒊 = revenue per cubic yard of product i

c𝒊 =cost to produce product I per cubic yard of sediment processed

Ti = total cost

Mx = mitigation cost for one cubic yard of sediment

Business Reuse Model Assumptions (20 year NPV)

• Sediment can be processed on time

• Cost/revenue distributions are the same for all amounts of sediment input

• Cost/revenue values all follow a triangular distribution across all alternatives

• Market values will stay the same (no inflation for cost and revenue)

• Time horizon (20 years) is not a variable

• Discount rate=5%

• One-time set up cost excluded (included in utility analysis)

40

Agenda

• Context

• Stakeholders






41

42

Inputs Outputs

Flow Rate

(per day)

Reservoir Bathymetry (per day)

Reservoir Velocity Profile

(per day)

Sediment Scoured (per day)

Sediment Redeposited (per year)

source: U.S. Corps. of Engineering

Sediment Dredged (per year)

(note: dredging evenly 5 miles upstream daily)

Reservoir Bathymetry (per day)

Scoured Sediment (per day)

No Mitigation

𝑸 𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝒗𝒊 𝑺𝑺𝒊 4,000,000 tons 0 cy. 𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝑺𝑺𝒊

Dredging 𝑸

𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝒗𝒊 𝑺𝑺𝒊

4,000,000 tons

1,000,000 cy. 𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝑺𝑺𝒊

𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝒗𝒊 𝑺𝑺𝒊 3,000,000 cy. 𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝑺𝑺𝒊


Dredging & Island

(note: 2 years @ 5 million

cy./yr. dredged before

simulation start)

𝑸

𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝒗𝒊 𝑺𝑺𝒊

4,000,000 tons

0 cy. 𝑳𝒊,𝑾𝒊, 𝑫𝒊 𝑺𝑺𝒊




Inputs to Feedback

Sediment Removal Model – Design of Experiment For three future worlds (x3)

Ecological Impact Model - Design of Experiment

43

Input Outputs

Scoured Sediment (per day)

Estimated Remediation Expense Scoured Phosphorus

(per year)

No Mitigation 𝑺𝑺 𝑹 𝑷

Dredging

𝑺𝑺 𝑹 𝑷

𝑺𝑺 𝑹 𝑷

𝑺𝑺 𝑹 𝑷

Dredging & Island

(note: 2 years @ 5 million cy./yr. dredged before simulation start)

𝑺𝑺 𝑹 𝑷

𝑺𝑺 𝑹 𝑷

𝑺𝑺 𝑹 𝑷

𝑺𝑺 𝑹 𝑷

For current world view (700,000 cfs max)

Business Reuse Model - Design of Experiment

44

Product Alternative

Inputs Outputs

Sediment Dredged (per year)

(note: dredging evenly 5 miles upstream daily)

Dredging and Transportation Costs

Cost to produce product

Revenue Generated from product

Net cost to produce product

Amount of product produced


1,000,000 cy.

𝑴𝒙 𝒄𝒊 𝒓𝒆𝒗𝒊

𝑻𝒊 𝒑𝒊

3,000,000 cy. 𝑻𝒊 𝒑𝒊

5,000,000 cy. 𝑻𝒊 𝒑𝒊

…

1,000,000 cy.


𝑻𝒊 𝒑𝒊

3,000,000 cy. 𝑻𝒊 𝒑𝒊

5,000,000 cy. 𝑻𝒊 𝒑𝒊

Plasma (high-grade)

1,000,000 cy.


𝑻𝒊 𝒑𝒊

3,000,000 cy. 𝑻𝒊 𝒑𝒊

5,000,000 cy. 𝑻𝒊 𝒑𝒊

Sediment Management System Value Hierarchy

45

• 𝑼𝒊=Utility of dredging alternative i

• 𝑺𝒊=scour potential decrease percentage of dredging alternative i

• 𝑺𝟓=scour potential decrease percentage of dredging 5 million cy per year (the best option)

• 𝑬𝟎=normalized cost of remediation of no mitigation after a scouring event

• 𝑬𝒊=normalized cost of remediation of dredging alternative i after a scouring event

• 𝑬𝟓=normalized cost of remediation of dredging 5 million cy per year with artificial island(the best option)

Minimize Susquehanna

Sediment Impact to Chesapeake Bay

Sediment Scour Potential (0.5)

Ecological Impact (0.5)

𝑼𝒊 = 𝟎. 𝟓𝑺𝒊𝑺𝒎𝒂𝒙

+ 𝟎. 𝟓𝑬𝒎𝒊𝒏 − 𝑬𝒊𝑬𝒎𝒊𝒏 − 𝑬𝒎𝒂𝒙

,

𝒊 = 𝟏,…𝟖

Agenda

• Context

• Stakeholders





• Results , Analysis & Recommendations

46

47

Sediment Removal Model Results Future Looks Like Past - 700,000 cfs

48

For every 1 million cy dredged: • 2% drop in scour (initial) • 0.41% decrease in scour (final with maximum dredging)

Sediment Removal Model Results Future Looks Like Past - 700,000 cfs

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

no mitigation Island 1-million Island,1-million 3-million Island,3-million Island,5-million 5-million

Total Percent Decrease in Scour

Percent Decrease in Scour After 20 years (700,000 cfs. max)

49

$(4,000,000,000.00)

$(3,500,000,000.00)

$(3,000,000,000.00)

$(2,500,000,000.00)

$(2,000,000,000.00)

$(1,500,000,000.00)

$(1,000,000,000.00)

$(500,000,000.00)

$-

$500,000,000.00

$1,000,000,000.00

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ne

t P

rese

nt

Val

ue

Year

Plasma high-grade

$(4,000,000,000.00)

$(3,500,000,000.00)

$(3,000,000,000.00)

$(2,500,000,000.00)

$(2,000,000,000.00)

$(1,500,000,000.00)

$(1,000,000,000.00)

$(500,000,000.00)

$-

$500,000,000.00

$1,000,000,000.00

1 2 3 4 5 6 7 8 9 1011121314151617181920

Ne

t P

rese

nt

Val

ue

Year


1 million cy/year

3 million cy/year

5 million cy/year

Business Reuse Model Results Marginal Cost Time Flow Comparison :Two Sub-Alternatives

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-$1 $0 $1 $2 $3 $4

Uti

lity

Cost (Billions, Net Present Value, discount factor=5%)

Island, 5 million 5 million

Island, 3 million

3 million

Island, 1 million

1 million

Island

No mitigation

Plasma High-Grade Lightweight Aggregate Quarry

Utility vs. Cost

50

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-$1 $0 $1 $2 $3 $4

Uti

lity



Island, 3 million

3 million

Island, 1 million

1 million

Island

No mitigation


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-$1 $0 $1 $2 $3 $4

Uti

lity



Island, 3 million

3 million

Island, 1 million

1 million

Island

No mitigation


Utility vs. Cost

51

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-$1 $0 $1 $2 $3 $4

Uti

lity




Island, 3 million

3 million

Island, 1 million

Recommendations

52

• Best Alternative: Dredge 5 million cy/year and process into high-grade arc. tile via plasma gas arc vitrification

• Contact specializing company to perform further analysis for Conowingo Reservoir

• Next Best Alternative after Plasma: Dredge 1 million cy/year and process into lightweight aggregate with construction of artificial island

Future Work

• Conduct additional cost benefit analysis with any additional cost data attained for ecosystem impact

• Look into dredging dams/reservoirs further North on the Susquehanna River

– Dispersion of cost

– Sediment reduction prior to entrance into Conowingo Reservoir

Rank Alternative

1 Plasma, 5 million

2 Plasma, 5 million with Island

3 Plasma, 3 million with Island

4 Plasma, 3 million

5 Lightweight Aggregate, 1 million with Island

Questions?

53

Management System to Aid Water Quality …Sponsors: Lower Susquehanna Riverkeeper Design of a Dam...

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