Dam Removal
David Rosenberg
Learning Objectives
• Describe current trends in removing dams
• Summarize physical, economic, social, legal, and political
conditions that prevent dam removals
• Outline a method to assess whether to remove a dam
• Summarize the economic impacts of removing the
Edwards Dam on the Kennebec River, ME
• Compare regional water scarcity, hydropower generation,
and water supply treatment costs with and without Hetch
Hetchy reservoir, CA
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Current status
(Graf, 2003)
• More than 467 dams removed in 20th century
– At least 30 in 2001
• Most common in the Northeast and West Coast
– In states with removal programs, leadership, and public support
• Increasing trend and interest in recent decades
David Rosenberg
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Current status
(Pohl, 2002)
• Different rationales to
remove
• Rationales vary by state
Total
Removed
Percent
Safety
52
34%
Failure
8
5%
Environment
60
39%
Economics
27
18%
Recreation
0
0%
Unauthorized
0
0%
Other
6
4%
Rationale
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Current status (cont.)
(Graf, 2003)
• Trend to remove bigger dams in recent decades
• But difficult to document and quantify
– No single responsible agency or organization
– Different definitions of “height”, “removal”, etc.
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Barriers to remove dams
• Each dam poses unique physical, ecological, economic,
social, regulatory, and legal constraints
• Difficult to quantify and assess full costs + benefits
– Particularly social, ecological, and historical values
• Inadequate inventories of existing and removed dams
• No clear guidance on rights and responsibilities of dam
operators, owners, and beneficiaries
• Limited money to involve all stakeholders
• Limited technical studies on dam removals
• Limited public understanding of dams and dam removal
(The Aspen Institute, 2002)
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Manage the sediment
• Potential impacts
–
–
–
–
–
Aggrade the downstream channel
Increase downstream turbidity
Release contaminants
Locate disposal sites
Continued erosion
• Management strategies
–
–
–
–
–
Do nothing (keep reservoir)
Natural river erosion
Remove mechanically (> $25/cubic yard)
Stabilize channel
Combinations
Lovett (2014)
Simple economic cvaluation
• Compare direct costs to remove or repair the dam
– Remove often 3 to 5 times cheaper!
– Even larger if count
• Avoided future liability, maintenance, dredging, etc.
• Increased river-based boating and fishing
• Economic development along riverfront
– Less if count costs to restore
•
•
•
•
Downstream channel
Vegetation
Land below reservoir
Manage silt/sediment
• Make sure to count all benefits, costs, jobs created, lost, etc.
• Difficult to include long-term effects
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Conflicting goals of science and
decision making (Graf, 2003)
Science
General principles
Decision Makers
Site-specific information
Deterministic
Slow science
Models
Probabilistic
Fast decision making
Data
Small dams
Small rivers
Humid area
Large dams
Large rivers
Arid areas
Private and public land ownership (along the shoreline)
Who benefits
Who pays
What science learns
What the publicDavid
believes
Rosenberg
9
Dam Removal Case Studies
Case 1. What sediment
management strategy was
used on the Conduit Dam,
White Salmon River, USA?
•
•
•
•
•
Built 1911
31 m3/s average flow
14.7 MW, 38 m height
~ $3 mill/year power benefits
https://vimeo.com/33584271
David Rosenberg
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Case 2: Maisons-Rouges Dam
Vienne River, France
Restore River Continuity for Large
Migratory Fish
12
1998-1999
Background
• Dam built in 1920s
– 3.8 m height, ~ 100 m width
– 198 m3/s mean flow
– Hydropower for paper mills
• Impound 15 km on Creuse & Vienne Rs.
• Ineffective fish passage structures
–
–
–
–
13
Atlantic salmon
Shad
Sea lamprey
Eels
Timeline
• 1920s - Dam built
• 1948 – EDF concession
• 1980 – Automation
• 1993 – EDF applied for renewal
license
• 1994 – Inter-ministry committee
long-term management plan
• 1994-1998 – Negotiations with
stakeholders
• 1998 – 1999 – Removal
• 1999 – 2005, 2009 - Monitoring
14
The Removal
• Install protective dikes and remove the dam
• Lower impoundment, remove
protective dikes on the right
bank
• Install protective dikes on
left bank; demolish buildings
• Lay concrete slab on the
channel bottom
Cost: 2.6 mill. Euro
15
9 years after removal
16
Outcomes
Component
Channel
structure
Sediment
volume (m3)
Flora
Shad (km)
Salmonidae
spawning (#)
Sea lamprey,
Mullet
17
Pre 1998
(with dam)
2000 – 2009
(after removal)
Sandy bottom
• Courser materials
• 10 riffles, gravel islands
900,000
400,000
0
Shrubs and trees on banks
35
0
57
Not present
Present
Conclusions
• Example of first major dam removal in France
• Expenditure to restore river connectivity
• Time to plan + get all stakeholders on board
• Monitoring key to demonstrate success
Onema (2010)
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Case 3:
Re-assembling Hetch Hetchy
Water Supply Implications of Removing
O’Shaughnessy Dam
Dr. Sarah Null
Dr. Jay Lund
19
Background
• Hetch Hetchy System provides water for San Francisco and
other Bay Area cities
– 2.4 million urban water users
– 11 reservoirs (O’Shaughnessy Dam is one in Yosemite Nat’ Park)
• 25% of the water
storage for Hetch
Hetchy System in
O’Shaughnessy Dam
• Talk to remove
O’Shaughnessy Dam
since the dam was
built
20
History of the
Hetch Hetchy System
• San Francisco earthquake (and
fires) catalyst for a stable
water supply.
• Huge controversy when Hetch
Hetchy Reservoir proposed
(John Muir vs. San Francisco).
• Raker Act passed in 1913 by
Wilson (allowed a dam to be
built in a National Park).
• O’Shaughnessy Dam completed
in 1923.
Michael O’Shaughnessy’s plans for San Francisco’s
water system
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Hetch Hetchy Valley
Circa 1900
Today
22
O’Shaughnessy Dam
• A Hetch Hetchy System component.
• Operated by SFPUC
– ~25% of storage in the Hetch
Hetchy System, 14% of storage on
Tuolumne River.
• Operated for water supply and
hydropower production.
• Removal could open Hetch Hetchy
for restoration and recreation.
– Water is scarce
– Yosemite Valleys are scarce
23
Tuolumne River, 1908
Hetch Hetchy Valley, 1908
Network Flow Optimization
(CALVIN)
Minimize:
(1) Z =  cij Xij
(Minimize costs)
Subject to:
(2)  Xji =  aij Xij + bj (Continuity)
(3) Xij  uij
(Upper bounds)
(4) Xij  lij
(Lower bounds)
Cherry Creek
Tuolumne
River
Eleanor Creek
Cherry Power
Tunnel
Lower Cherry
Aqueduct
Holm
Powerhouse
O'SHAUGHNESSY
DAM
ELEANOR DAM
CHERRY DAM
Kirkwood
Powerhouse
Mountain Tunnel
Tuolumne
River
Lower Cherry
Diversion Dam
Early Intake
Cherry Creek
Tuolumne
River
Mountain Tunnel
Priest Reservoir
NEW DON PEDRO
RESERVOIR &
POWERHOUSE
Foothill Tunnel
Moccasin
Reservoir &
Powerhouse
La Grange Dam
Modesto
Canal
San Joaquin
Pipelines 1,2,3
Ag. & Urban
Demand
Turlock
Canal
Ag. & Urban
Demand
San Joaquin River
Crystal Springs
Bypass Tunnel
cij = economic costs (ag. or urban)
Xij = flow from node i to node j
bj = external inflows to node j
aij = gains/losses on flows in arc
uij = upper bound on arc
lij = lower bound on arc
Canyon Tunnel
LEGEND
Other Bay
Area Cities
LOCAL
SAN FRANCISCO
RESERVOIRS
Reservoir
Powerhouse
River
Pipeline
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Non-storage
Reservoir
SFPUC
Demand Regions
Treatment Plant
Model Limitations
• Ignores political and institutional constraints
• No flood control or recreational benefits
– current flood storage rules are respected
• Simplified costs, water quality, hydrology
• Operates reservoirs with perfect foresight
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Model runs
• Existing Conditions
• Remove O’Shaughnessy Dam
– Add inter-tie to connect Hetch Hetchy Aqueduct & New Don
Pedro Res.
26
Hetch Hetchy System Water Storage
with and without O’Shaughnessy Dam
3000
With O'Shaughnessy
Dam
Maximum Storage
2000
Minimum Storage
1500
Mean Storage
1000
Without
O'Shaughnessy Dam
500
0
Month
Au
g
n
Ju
Ap
r
Fe
b
ec
Maximum Storage
D
O
ct
TAF/month
2500
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Minimum Storage
Mean Storage
Flow through the Hetch Hetchy
Aqueduct
Diversion (TAF)
30
25
20
15
10
5
0
Oct
Nov
Dec
Jan
Feb
Mar
Wettest
Apr
May
Mean
Jun
Jul
Aug
Sep
Seasonal Flow in
Hetch Hetchy
Aqueduct upstream
of New Don Pedro
Driest
Diversion (TAF)
30
25
20
15
Flow through New
Don Pedro Inter-tie
10
5
0
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
28
Driest
Mean
Wettest
Aug
Sep
Water Scarcity
Annual Average Agricultural Scarcity
80
Scarcity (taf)
• No scarcity to urban
areas.
• No scarcity to
environmental
demands.
• Small increase in
scarcity to TID and
MID without
O’Shaughnessy Dam.
• No scarcity to other
agricultural
demands.
60
40
20
0
1921
1931
1941
1951
Without O'Shaughnessy
Average annual scarcity (taf)
Max annual scarcity (taf)
% years with scarcity
Average annual demand (taf)
Average annual delivery (taf)
1961
1971
1981
1991
With O'Shaughnessy
With O'Shaughnessy Without
Dam
O'Shaughnessy Dam
0.85
1.42
29.3
72.5
0.04
0.03
5259
5259
5258
5257
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Hetch Hetchy System
Hydropower Generation
Average Annual Hydropower Generation
3000
2000
1000
Oct 1921 - Oct 1993
With O'Shaughnessy Dam
Without O'Shaughnessy Dam
Average annual difference
30= 457 GWhr/yr
Average annual cost difference = $11,107,050
1993
1989
1985
1981
1977
1973
1969
1965
1961
1957
1953
1949
1945
1941
1937
1933
1929
1925
0
1921
GWhr / year
4000
Water Treatment Changes
 Without O’Shaughnessy Dam and filtration
avoidance, SFPUC will need to treat water
 Significantly raises treatment costs
 Construction costs, about $1-2 billion ($50-100 million/year)
 O&M costs, about $6 million/year
 Filtration avoidance makes O’Shaughnessy
very valuable.
 Water quality would remain high.
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Potential Restoration
Hetch Hetchy Restored – Brooks Anderson
• Dam Removal
– Remove portion of dam
above ground
– Leave dam with hole in it
• Vegetation
– Grasses return in 1-2 years
– 5 years for shrubs to return
– 20+ years for trees
• Bathtub ring
– 100+ years for lichen to
grow back on cliff walls
– Rock stains over geologic
time
• Sedimentation
– Not a problem
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Additional considerations
• MID, TID, and SFPUC must reach new political and
legal agreements
• Harder to replace hydropower than water storage
– But there are alternatives (Environmental Defense)
• Fill additional information gaps
– Economic benefits to restore valley
• Political support
– Gov. Schwarzenegger said restoration may be in public interest
(Nov. 2004)
– 2005 Pulitzer Prize to Tom Philp for “Hetch Hetchy Reclaimed”
in The Sacramento Bee
– CDWR releases “Study of Studies” (2006)
• Existing Hetch Hetchy results not flawed
• Restoration expensive (estimated $3-10 billion)
• Controversy remains
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Case Study Conclusions
1)

Removing O’Shaughnessy Dam need not substantially
increase water scarcity.
if New Don Pedro Reservoir is connected directly with the
Hetch Hetchy Aqueduct.
2)
Conveyance can sometimes substitute for water
storage.
3)
Loss of filtration avoidance would be very costly.
4)
Removing O’Shaughnessy Dam reduces hydropower
generation and revenues.
5)
Politics and legal arrangements may be more limiting
to the Hetch Hetchy System than physical
constraints.
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Overall Conclusions
•
•
•
•
•
•
•
•
Increasing number of dam removals in recent decades
Can generate substantial economic benefits
Loss of water storage need not harm users
Further needs to monitor and evaluate all effects
Difficult to include nonuse benefits in analysis
Also benefits at points long in the future
New emerging science
Many more dam removals scheduled or under
consideration
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References and Further Reading
• American Rivers, www.amrivers.org
• (2002). "Dam Removal and River Restoration." Bioscience, 52(8),
http://www.jstor.org/stable/i256265.
• Bohlen, C., and Lewis, L. Y. (2009). "Examining the economic impacts of
hydropower dams on property values using GIS." Journal of
Environmental Management, 90(Supplement 3), S258-S269,
http://www.sciencedirect.com/science/article/B6WJ7-4TYPJH02/2/055bac52e56445d5fa5debbd7da02e52.
• The Heinz Center (2002). "Dam Removal: Science and Decision Making."
The H. John Heinz III Center for Science, Economics and the Environment,
Washington, D.C.
• Graf, W. L. (2003). "Dam removal research: status and prospects." THE H.
JOHN HEINZ III CENTER FOR SCIENCE, ECONOMICS AND THE
ENVIRONMENT,
http://www.heinzctr.org/publications/PDF/Dam_Research_Full_Report.pdf
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References and Further Reading
(cont.)
• Institute, T. A. (2002). "Dam Removal –A New Option for a New
Century." The Aspen Institute, Queenstown, MD.
• Null, S. E., and Lund, J. R. (2006). "Reassembling Hetch Hetchy: water
supply without O'Shaughnessy dam." Journal of the American Water
Resources Association, 42(2), 395-408, http://dx.doi.org/10.1111/j.17521688.2006.tb03846.x.
• ONEMA (2010). “Removal of the Maisons-Rouges dam over the River
Vienne”.
http://www.onema.fr/IMG/EV/publication/rex_r1_vienne_vbatGB.pdf.
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References and Further Reading
(cont.)
• Pohl, M. M. (2002). "Bringing Down Our Dams: Trends in American dam
removal rationales." Journal of the American Water Resources Association,
38(6), 1511-1519, http://dx.doi.org/10.1111/j.1752-1688.2002.tb04361.x
• Robbins, J. L., and Lewis, L. Y. (2008). "Demolish it and They Will Come:
Estimating the Economic Impacts of Restoring a Recreational Fishery.“
Journal of the American Water Resources Association, 44(6), 1488-1499,
http://dx.doi.org/10.1111/j.1752-1688.2008.00253.x.
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