Water Power and Dam Construction. Issue May 2010
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30 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
RCC
The capacity of spillway will be sufcient to convey the maximum
designed ood with retention in the reservoir storage available. The
designed ood would result in reservoir surcharge of 1.5m above
normal water level and maximum discharge over the spillway in this
case will reach 2380m
3
/sec for a PMF ood (ood peak 2870m
3
/sec).
Three radial gates with the clear gate opening of 11.5m are provided
at the three spillway bays. Gate height is 9.3m above the spillway
crest, while total gate height is approximately 10.2m. At the end of
the spillway a stilling basin, 74m long, is designed for dissipation of
the overow water energy.
Dam non-overow parts are located between the ll dam and the
dam spillway section, and on the other side, between the spillway and
the right river bank. They are composed of massive 15m wide blocks.
With the selected diversion scheme, a maximum discharge of
477m
3
/sec (in the case of 20-year return flood) will be diverted
through the diversion tunnel during the construction period.
The ll dam with central concrete diaphragm is designed on the left
bank. The dam crest, 9.2m wide, is at the elevation 719.5m (same as
the RCC dam) thus providing the free board of 3m above the maxi-
mum reservoir level during full discharge of the ood waters over the
spillway structure and free board of 1m in the emergency case when
one gate is not in operation. The upstream (1:1.7) and downstream
(1:1.7) outer dam slopes provide the usual safety margin against
sliding under critical loading conditions (full reservoir with steady
seepage for the downstream slope). The concrete diaphragm wall is
designed as an impervious barrier along the ll dam axis.
The water intake tower is a cylindrical concrete structure, 55m
high. It is located in the reservoir on the right river bank. The tower
is located on the route of the diversion tunnel (which will later be
adopted into water intake tunnel), which passes through the tower
bottom. The tower is connected with the right bank by a steel access
bridge (span of 25.8m).
Hydroelectricity will be generated as a by-product of the use of
water from the Tawooq Chai river at Bassara Dam. After construc-
tion of the dam, just 1m
3
/sec will be used from 8m
3
/sec (average
annual river runoff). For this purpose a hydro power plant was
designed with two 2.3MW turbines.
STABILITY ANALYSIS FOR THE RCC DAM
The General stability of the structures was checked for usual, unu-
sual and extreme load cases. For each of the load cases the necessary
load combination was applied on the structure and factors of safety
were calculated. General stability analyses were performed, in the
river ow direction, of the dam spillway and the non-overow part
(one critical block), showing that the structure will be stable for all
operational regimes.
According to the geological report for the foundation joint, the
applied value of the angle of friction is 47°. The cohesion contribu-
tion was not taken into account. The regional and local seismicity
studies determined peak accelerations for OBE 147.13cm/sec
2
and
for MDE 441.45cm/sec
2
. Strong motion record Manjil (June 20,
1990), as an oscillatory type, and Umbria (September 3, 1997), as an
induction type, were analyzed.
The rst part of the dynamic stability analysis of the concrete parts
of the dam structure was carried out in accordance with the Seismic
Coefcient Method (Pseudo dynamic method applying the equivalent
static load). For this method analysis values of peak ground accel-
eration for OBE and MDE are adopted for OBE (operating basis
earthquake) a = 0.12g and for MDE (maximal design earthquake)
a = 0.18 g.
Lateral interaction between the dam spillway and non-overow
part blocks has also been analyzed. Calculation is based on three-
dimensional stability of the blocks to determine the values of interac-
tion forces between the consecutive blocks. Based on calculations in
the lateral direction it can be concluded that each block is stable for
the usual load case. Lateral interaction forces occur for extreme load
case. Under assumption that all blocks will oscillate within the same
phase (which is almost impossible), maximal compression stress of
0.52 MPa will occur on the central block.
FEM ANALYSIS FOR THE RCC DAM
The nite element method (FEM) analysis of the RCC dam was
performed for the highest spillway section and related relevant
loadings. For the computational model of the dam-foundation
interaction, a plane 2D model was chosen. The spillway section
was approximated with 280 plane stress elements. Foundation was
approximated with 1800 plane strain elements. Contact between
concrete dam and foundation was simulated with nonlinear gap
elements. Upstream contact between conventionally placed mass
concrete (CMC) and roller compacted concrete (RCC) was simu-
lated with frame elements.
The main objective of the analysis of temperature effects on the
RCC dam structure was to determine the appropriate shape of the
dam body and zoning of the different types of RCC. Temperature
inuences were calculated as unusual load, and various constant
temperatures along sections were applied as input parameters
(temperature load). For practical calculation, change of the RCC
hydratation temperature was adopted as an exponential function,
while change of ambient temperature was assumed as a sinusoidal
function. Analysis of concrete placing for the warmest month and
stipulated placing temperature of 20˚C was performed.
For determination of the temperature differences, tempera-
ture of the mixture after 24h was selected as basic temperature.
Relation of the temperature change through sections was calcu-
lated through use of a numerical method of nite differences. This
approximate calculation provided satisfactory results for further
analysis of temperature effects on the dam structure.
Linear elastic FEM analysis (Static analysis) for the usual and
unusual loads (dead weight, hydrostatic inuences and tempera-
ture) was applied.
The dynamical analyses were carried out in accordance with
the time history method. The time history earthquake response
analysis is based on linear-elastic analysis for all characteristics
and elements except for contact between concrete and foundation
where non-linear analysis was applied. It means that linear time
history analysis with material nonlinearity in the gap elements was
performed. Interaction between the dam and impounded water
was determined using generated Westergard formulation with
added masses attached to the dam.
Seismic input data in the analyses were represented by the scaled
series of acceleration time histories of the recorded earthquake
strong ground motion, considered as appropriate for this site.
The calculation of structure was performed by step by step
method, with the adopted damping of 5-8% which corresponds
to the prevailing conditions. For the numerical integration a step
DT = 0.005 sec was adopted.
Maximal compression stresses appeared at foundation contact
level on upstream and downstream edge and its values did not
exceed 4.0 MPa. In all other zones of the structure compression
stresses were less than 1.5 MPa. Maximal tension stresses for tem-
perature decrease load case and usual load case amounted to 2.25
MPa and they occurred approximately in the middle of the foun-
dation contact level. In the upper zones of the upstream dam face
tension stresses were up to 1.0 MPa for the main part of the dam
structure and up to 2.5 MPa in dividing walls. Comparing with
stresses for usual load case, there was no signicant increase of
stresses for the case of temperature rise. At CMC and RCC contact
level, tension stresses did not occur even for seismic load cases.
CONCLUSIONS
Taking previous analyses into consideration, one layer of CMC, 2m
thick, was designed on the foundation contact level. Reinforcement
within that layer will be sufcient for acceptance of supercial tension
stresses and bending moments on downstream - toe part. CMC will
be used for all superstructures on spillway part, for dividing walls and
radial gate support, as well as for protection layer 1.5 m thick along
spillway surface. First horizontal RCC layer, 3m thick, with better
characteristics, was designed right above the CMC layer. Beside lon-
gitudinal forces, the rst horizontal RCC layer of the highest blocks,
WWW.WATERPOWERMAGAZINE.COM MAY 2010 31
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0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
0.20
-0.25
Acceleration (g)
01020304050
Time (sec)
Acceleration time history
1.65
6.80
295
2.82
6.67
1
2.83
6.70
21
Displacements (cm)
Above, top: Figure 2 – Dam cross section – overflow part – concrete zoning;
Above, bottom: Figure 3 – Modified time history for OBE, Manjil earthquake,
second horizontal component; Right: Figure 4 – Deformation shape for dead
weight and hydrostatic pressure
32 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
RCC
3m thick, shall accept lateral forces as well. Thus, this layer shall be
composed of RCC Type 3, with better characteristics and compres-
sive strength of 16 MPa. On the upstream dam face one zone of
RCC Type 2, with better characteristics and compressive strength
of 14 MPa, shall be placed. It is located between the CMC zone and
the upstream face of the drainage galleries. All other concrete zones,
except spillway superstructures, will be of primal RCC Type 1 with
compressive strength of 10 MPa.
The upstream dam face will be covered with precast elements
0.12m thick and 1.5m high, which will be protected from water leak-
ing and used as a formwork during RCC placing. Expansion joints
will be provided with two waterstop layers. Between these layers, ver-
tical drainage pipes will be placed. Drainage pipes will collect even-
tual leakage water and drain it through the drainage galleries to the
stilling basin. This 1m wide zone, in which waterstops and drainage
pipe will be placed, shall be made of CMC.
Contact between CMC and RCC layers in spillway surface
zones shall be provided with anchors 25mm dia. Anchors shall
be placed in hardened RCC, in drilled holes of 72mm dia, on
distances of 1m and 0.5m on upstream face. The same anchors
shall be provided for connection between CMC and RCC on the
downstream spillway surface.
The authors are: Vicko Letica, Deputy Director for
Civil Structures Engineering; Vladislav Skoko, Head
of Structural Department, Chief Structural Engineer,
Project Manager; and Ivana Grubljesic, Senior Structural
Engineer, IK Consulting Engineers
www.ikconseng.co.rs
IWP& DC
Anchor ø22, L=1.00m’
Anchor ø22,
L=1.00m’
Anchor ø22,
L=1.00m’
Anchor ø22, L=1.00m’
Construction (expansion) joint
Fill
Joint
Rubber plug
Waterstop M35
Precast element
concrete class
CMC 40
Precast element
concrete class
CMC 40
.49 .49.02
Drainage ø150
.38.75
1.50
.37
A A
.12 .40 .10.25 .25
1.00
ø1.50
.03
.30.30.30
1.50
.30.30
.03.03.03 .27.27.27.27
.27
.27
Section A-A
-10.00
-12.50
-15.00
-17.50
-20.00
Stress (dNa/cm2)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4.00
3.00
2.00
1.00
0.00
-1.00
-2.00
Displacement (cm)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Vertical stress at Joint 1Horizontal displacement at the Joint 10
0.00
-2.50
-5.00
-7.50
-10.00
0.00
-2.00
-4.00
-7.60
-8.00
Stress (dNa/cm2)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Displacement (cm)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Vertical stress at Joint 10 Horizontal displacement at the Joint 295
-5.00
-7.50
-10.00
-12.50
-15.00
-4.00
-6.00
-8.00
-10.00
Stress (dNa/cm2)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Displacement (cm)
0.000
1.000
2.000
3.000
4.000
5.000
6.000
7.000
8.000
9.000
10.000
11.000
12.000
13.000
14.000
15.000
16.000
17.000
18.000
19.000
Time (sec)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Vertical stress at Joint 21 Vertical displacement at the Joint 295
Max/min -6.470 -16.87 Max/min 2.303 -0.207
Max/min -1.987 -5.05 Max/min -0.621 -7.510
Max/min -4.949 -13.387 Max/min -5.979 -9.824
Above, top: Figure 5 – Vertical stress at foundation contact and displace-
ments at the characteristic joints; Above: Figure 6 – Detail of the upstream
dam face
34 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
RCC
L
OCATED near Lakeside, an incorporated community of
San Diego County, San Vicente Dam was built in 1943.
Sixty-six years later, in July 2009, construction began to
raise the existing 220ft-high concrete gravity dam by 117ft
and add 152,000 acre-feet of water storage.
The project is the largest component of the fourth and nal phase
of the San Diego County Water Authority’s (SDCWA) $827M
Emergency Storage Project (ESP). The ESP, which has been under
development for more than a decade, is a system of reservoirs, pipe-
lines, and other facilities that work together to store and move water
around the county in the aftermath of a disaster, such as an earth-
quake. When complete, the entire ESP system will provide more than
90,000 acre-feet of water stored locally for emergency use, enough to
supply the region for up to six months.
This new water storage will serve two purposes. About two-thirds
of the additional storage will capture surplus water during wet sea-
sons for use in subsequent dry years. The other third of the new reser-
voir capacity will store water for use in an emergency if the San Diego
region’s imported water supply is cut off.
San Diego currently imports about 90% of its drinkable water
supply from more than 400 miles away, making this a critical project.
“The San Vicente Dam Raise project is a critical part of the Water
Authority’s $1.5 billion plan to ensure that our region can call upon
locally stored water reserves during emergencies or other periods of
limited imported supplies,” said Maureen Stapleton, Water Authority
General Manager. “In addition to its importance to regional water
supply reliability, this project also brings major economic benets,
creating 5,500 job-years of employment to the San Diego region.”
CONSTRUCTION WORK
The San Vicente Dam Raise construction is scheduled to run from
2009 to 2012 and is split into several distinct construction phases.
The rst construction phase, foundation excavation, will not affect
the integrity of the existing dam, and has been closely monitored
throughout construction. This phase includes all the preparation
work before concrete can be applied to raise the dam. The contrac-
tor, Barnard Construction Company, Inc, will excavate down to the
existing dam’s foundation and will pour concrete in any crevices.
The contractor will also remove about two to three inches of the
On the up – the San
Vicente Dam raise project
The contractor is excavating a new
foundation, and preparing the dam
surface so that the new concrete
that will raise the dam can establish
a firm bond to the existing concrete.
Photograph courtesy of the
San Diego County Water Authority
Construction Schedule
Construction of the San Vicente Dam Raise project began in June 2009 and
will take about four years. Construction will take place in multiple phases, as
follows:
Foundation preparatory work: summer 2009 – summer 2010
Dam raise: spring 2010 – early 2013
Replacement pipeline: summer 2012 – summer 2013
New marina construction: summer 2013 – summer 2014
Site restoration: summer 2013 – summer 2014
Reservoir open to recreation: between late 2014 and late 2017
Construction is underway at the US’ tallest dam raise which will help drought-stricken San
Diego County respond to emergency water needs once complete
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36 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
RCC
dry side of the dam to create a good bonding surface for the new con-
crete. Other work in the rst phase includes installing new pipelines
and other components near and inside the existing dam.
The next phase of construction will raise the dam with roller com-
pacted concrete (RCC) and is anticipated to begin in the next few
months. The downstream side of the existing dam will be completely
covered by RCC and will have a new, stair-stepped appearance.
The SDCWA Board of Directors on April 22 approved the award
of a $140.2M contract for the application of the RCC to a joint ven-
ture partnership of Shimmick Construction Company Inc. /Obayashi
Corporation. The JV was selected after a competitive bidding process
that drew interest from companies around the globe.
In addition to raising the dam, the construction phase covered by
the new contract will include construction of a new saddle dam, a
new outlet tower, a new pipeline and control facility and new access
roads. Construction is expected to be complete by early 2013.
Later phases of the project will more than double the size of the
existing marina facility at the San Vicente Dam, a popular destination
for local water sports enthusiasts. A six-lane boat ramp, new docks,
additional parking, new service buildings, picnic tables and shade struc-
tures will be added. The project is expected to be complete in 2012.
CURRENT SITUATION
Currently, the foundation preparation is more than halfway com-
plete. Barnard Construction has built a small, semicircular steel cof-
ferdam on the upstream (wet) side of the dam. This allows workers
to install a new water outlet pipe through the dam. All of this work
is being monitored by the State Division of Safety of Dams and will
not affect the integrity of the existing dam.
DESIGN, ENGINEERING AND MANAGEMENT
The nal design and engineering services for construction of the
San Vicente Dam Raise Project was performed by MWH through
a $20.4M contract from SDCWA. MWH engineers developed the
RCC design, making the San Vicente Dam raise project the tallest of
its kind in the world using this method of building concrete dams.
During the three-year construction phase, MWH will provide engi-
neering services, including resident design engineering staff to validate
that site features are constructed consistent with design intent and
assumptions. MWH engineers will review key submittals for con-
sistency with design requirements and address design-related ques-
tions and unexpected issues that may arise during construction. A
critical aspect of this review will be the performance of the on-site
quarry that will be used for RCC aggregates, which has won awards
from American Water Works Association (AWWA) and American
Society of Civil Engineers (ASCE) for its environmental stewardship,
eliminating thousands of truck deliveries for concrete aggregates from
off-site sources.
MWH also engineered SDCWA’s nearby Olivenhain Dam and
Reservoir project with the RCC design – which uses no-slump con-
crete and soil placing techniques to provide an efcient, economical
and resilient product. The Olivenhain project, which was completed
in January 2005, is a 318ft high dam that added 24,000 acre-feet of
reservoir storage as the rst phase of the ESP.
The MWH dam design and engineering work for the San Vicente
Dam raise project, which was part of the contract awarded in 2006,
also included project management, outlet works design, quarry
design, value engineering and cost estimating. In addition, MWH
scheduled and coordinated quality assurance/quality control reviews
with the internal design team technical review committee and owner’s
board of senior consultants, as well as coordination and permitting
with the State of California Division of Safety of Dams.
A joint venture of consultants Parsons and Black & Veatch (B&V)
will manage the raise project. In an agreement with SDCWA, the
JV was contracted to provide pre-construction services through con-
structability reviews, independent construction management sched-
ules and cost estimates, and contractor pre-qualication. During
construction, the construction management staff, working with the
Water Authority, are providing construction administration, inspec-
tion, change management, schedule monitoring and quality control
services for the project, including startup support.
The Parsons/Black & Veatch also has extensive experience with
other aspects of the Emergency Storage Project, including work on
the state-of-the-art pump station, which will help move water from
the San Vicente Reservoir to one of SDCWA’s aqueducts.
FUNDING
Water Authority construction projects such as the San Vicente Dam
Raise are funded through bond sale proceeds. In January 2010, the
Water Authority successfully completed a $627M bond sale to pro-
vide funds for capital improvement projects for scal years 2011 and
2012. Because the bid awarded for this portion of the dam raise con-
struction was signicantly below Water Authority estimates, savings
derived from the lower bid will allow the funds from the bond sale
to be used over a longer period of time.
For further information on the San Vicente Dam Raise
Project, please visit: http://www.sdcwa.org/infra/esp-
sanvicentedamraise.phtml
Extremely high pressure water jets on
vertical rails blasted away an outer layer
of concrete on the dam in preparation for
the new concrete that will raise the dam.
Photograph courtesy of the San Diego
County Water Authority
IWP& DC
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26 MARCH2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
SMALL HYDRO
firstBC companies to introduce the concept of clustering projects
to share the substantial cost of longer transmission lines. For
instance, at Plutonic Power’s East Toba and Montrose project, the
two run-of-river developments will share a single 150km long,
230kV transmission line. Without this sharing arrangement, nei-
ther development would be financially viable. The environment
also benefits from this arrangement, as line sharing reduces the
potential development footprint. Furthermore, the lines are routed
as much as possible along existing logging roads, resulting in less
clearing for transmission line corridors. This environmental advan-
tage is in turn important for First Nations partners, as transmis-
sionlines often cross their territory.
Asimilar sharing of transmission lines is occurring in Cloudworks
Energy’s Kwalsa Development site, 90km northeast of Vancouver.
I
NBritish Columbia (BC), Canada, Knight Piésold has worked
closely with several private and institutional developers on pro-
ject development, applying many new and innovative techniques
in all aspects of designing hydro schemes. These include project
identification, stream gauging and hydrological assessment, engi-
neering design, project optimization, environmental assessment, per-
mitting and licensing, and First Nations involvement.
P
ROJECT IDENTIFICATION
In the early 1990’s, Knight Piésold worked with developers on
identifyingand optimizing run-of-river projects that wereclose to
existing transmission lines. But in the last few years, as prime sites
have been identified in more remote areas, it became one of the
Since engineering its first hydroelectric scheme in 1926, Knight Piésold has gained
considerable experience in the design of power generation facilities. In the 21st century,
the company is working with its partners to create a legacy of clean, renewable energy
through run-of-river hydro projects
Technical and design innovations
in run-of-river projects
Assessinghydro power development in Gargoyle
Creek Valley –- Plutonic Power’s Bute Inlet Project
MARCH 2009
Serving the hydro industry for 60 years: 1949-2009
Examining excavation work
Focus on small hydro
Data collection
Innovations in run-of-river hydro schemes
28 MARCH2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
This method has also improved the company’s ability to predict
flows at one site on the basis of flows at another site, even if the
relative timing of flows at both sites do not exactly coincide. The
flow prediction methodology has proven to be acceptable for bank-
able feasibility studies, enabling clients to secure project financing,
saysthe company.
I
NTAKEDESIGN
Aprimary goal of a run-of-river intake design is to extract water
from a river while excluding sediment and debris, which can cause
impact damage and excessive wear to the conveyance system and
turbines. Sediment exclusion has traditionally been achieved through
the use of expensive and often extensive desanding facilities. Knight
Piésold has refined the design of two types of intakes that incorpo-
rate efficient sediment exclusion systems, which have proven very
effective in high energy, glaciated river systems: Coanda Screen and
Rubber Weir Type Intakes.
Coanda Screen Intake
The Coanda screen intake relies on the Coanda effect of flowing
water to stay attached to an adjacent curved surface to direct water
through a fine meshed screen. It was used for the first time on a
Canadian run-of-river project in 2004. Over the past five years, the
company has worked closely with the manufacturer, Norris Screens
and Manufacturing, and contractor partner, Peter Kiewit Sons, to
optimize the screens’ design. The screens’ water diversion capacity
has been designed to make it more “fish friendly”, while its ability
to exclude sediment has been maximized and maintenance needs
have been decreased. The new stainless steel screens are self-clean-
ing and eliminate particles of less than 2mm in diameter. They are
substantially more robust than the first-generation type and better
able to withstand the high flood levels and heavy debris loads of
streams in BC’s coastal mountains. In 2005, the design for the
McNair Creek Green Power project, which included a Coanda
Intake, received an Award of Excellence from the Consulting
Engineers of British Columbia (CEBC).
Rubber weir intake
The rubber weir intake incorporates a large diameter, cylindrical
rubber weir that automatically inflates and deflates in response to
sensorsmeasuring water levels in the headpond. Under very high
flows, the weir deflates completely, providing passage for flood
waters and debris.
SMALL HYDRO
Above:Coanda screen intake – Renewable Power’s McNair Creek project
Right:Weholite pipe low pressure conduit – Rutherford Creek Power/
Innergex’s Rutherford Creek
ciency of stage discharge data collection.
The operation of so many gauging stations and the huge amounts
of data they generate has necessitated the development of a special-
ized hydrology module for Knight Piésold’s centralized, web-based
Fulcrum environmental data management system. This module was
created specifically for the storage, management and processing of
stream gauging data. It allows field staff to upload, view, and process
all information from remote locations, and any changes to the data-
base can be viewed in real time by staff and clients.
To as si st w it h ra ti n g cu rv e de ve lo pm en t, a nd p ar ti cu la rl y th e
extrapolation of a curve beyond the range of measured stage-dis-
charge values, a ranked regression modeling approach has been
developed. When combined with an understanding of the physical
processes dictating hydrologic response in compared watersheds,
this approach provides guidance for the delineation of a curve.
The company is currently constructing four of eight planned run-of-
r
iver projects. This group of facilities is sharing the significant trans-
mission and interconnection costs to tie into BCTC’s 360kV
transmission system.
S
TREAM GAUGING AND HYDROLOGICAL
ASSESSMENT
Knight Piésold has developed considerable expertise for the collec-
tion and analysis of hydrological data in isolated, challenging envi-
ronments, including watersheds in coastal mountainous BC, Arctic
permafrost terrain on Baffin Island, and dense, tropical jungles in
Africa. It currently operates over 150 stream gauging stations around
the world. Most of these are in high velocity, glacier-fed streams in
BC’s Coastal Mountain range. The quality and value of the data
depend on several factors including gauging site selection, flow mea-
surement technique, data quality assurance and control, rating curve
development, and data analysis.
Proper gauging site selection is critical for ensuring a definable
and consistent relationship between water stage and discharge.
Considerable skill is also required to identify, assess and establish a
proper gauging site. Accurate flow measurement is also of para-
mount importance, and for this the company uses several flow mea-
surement instruments and techniques including a traditional velocity
meter, an acoustic Doppler current profiler, and salt and rhodamine
dye dilution. The method of choice depends greatly on channel char-
acteristics and flow conditions: the salt and rhodamine dye tech-
niques are generally preferred for the turbulent, fast flowing
conditions that developers often face. These methods present chal-
lenges, however, as they involve expensive equipment that requires
calibration and is sensitive to changing conditions. A high level of
skill is also needed to select an appropriate site to ensure complete
mixing of the tracer compound.
However, with constantly evolving knowledge of technological
constraints in difficult field conditions, the quality of site data con-
tinues to improve. Knight Piesold is now developing an automated,
multi-discharge rhodamine dye type measurement device that will
remotely record a series of flow values at predetermined water levels.
This will allow several stage-discharge points to be obtained during
asingle large flow event, thereby dramatically increasing the effi-
WWW.WATERPOWERMAGAZINE.COM MARCH2009 27
SMALL HYDRO
Right:Helicopter access to a remote site in the East Toba River Valley –
PlutonicPower’s East Toba and Montrose project
Below: Stream gauging on Raleigh Creek –Plutonic Power’s Bute Inlet project
The latest issue of
Dam Engineering
is on its way to subscribers.
This issue contains the following papers:
•
Design procedure for a spiral casing for hydraulic turbines with a numerical flow study by Ahmed
Alnaga & Jean-Louis Kueny.
A smart design procedure for a spiral casing for hydraulic
turbines has been developed and described.
•
Dynamic analysis of anchored concrete linings of plunge pools loaded by high velocity jet
i
mpacts issuing from dam spillways by Maziar Mahzari & Anton J Schleiss.
A
theoretical stochastic
approach for the structural analysis of plunge pool liners dynamically loaded by the impact of free-falling jets.
•
Investigation of compaction methods of embankment cores in high rainfall regions by J Jalili & M Jahanandish.
In this paper a
literature review of trends applied in the construction of embankment dam cores in wet regions is presented, followed by an
experimental procedure, as a rule for choosing the best compaction method for such soils.
•
Performance evaluation of a vortex-type sediment extractor with diaphragm by Nayan Sharma, D Das & Gopal Das Singhal.
The
study reported in this paper investigates the effect of the variation of key components of a vortex extractor.
•
Shape optimisation of the new section in raising existing concrete gravity dams using genetic algorithm by Mahmoud R Maheri & M
Ranjbarzadeh.
A simple genetic algorithm (GA) is adopted to optimise the shape of the new section in a raised gravity dam.
Dam Engineering is an academic journal, published quarterly. It contains refereed papers on subjects related to all areas of
dams and hydro power. At present there is no restriction on the length of submitted papers.
For information on submitting papers, or for more details about subscribing to
Dam Engineering
, contact: Tracey Honney,
Dam Engineering, Progressive House, 2 Maidstone Road, Foots Cray, Sidcup, Kent DA14 5HZ
tel: +44 20 8269 7767 , fax: +44 208 269 7804, email: thonney@progressivemediagroup.com
New Issue of
Dam Engineering
38 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
WAVE AND TIDAL POWER
T
HE Mersey estuary has one of the largest tidal ranges in the
UK and is a prime location for a tidal power scheme. It has
a catchment area of over 4600km and includes the major
cities of Liverpool and Manchester. Indeed, it has previ-
ously been shown that a substantial scheme in the estuary could sat-
isfy the electricity needs of a large part of the Liverpool City region.
A noteworthy feature of the Mersey estuary, which makes it an
attractive option for a tidal power project, is its narrow mouth. It
is unlike most other estuaries which tend to become progressively
wider towards the sea. Here, the narrow area extends from the estu-
ary mouth to an area upstream of the Tranmere oil terminal, and its
width varies between 1-2km. Furthermore, the deepest sections of the
estuary are located in this area and the current velocities are great-
est. There is very little mudat exposure at the lowest astronomical
tide. Upstream of the narrow area the width of the estuary increases
signicantly and the depth reduces. Extensive areas of mudat are
exposed at the lowest astronomical tide.
The basic geography of the estuary is important in the context of
tidal power development. In other UK estuaries such as the Severn
and the Solway Firth, the width of the estuary progressively increases
towards the sea. The provision of a barrage or tidal fence in such
estuaries is therefore associated with an increasing length of structure
as the alignment is moved seaward. This increase in length is associ-
ated with an increased volume of water commanded and an increased
quantity of energy captured. Movement of alignment in a seaward
direction therefore increases both investment cost and energy yield,
and a balance must be found between these two variables.
In the Mersey estuary the reverse applies. The movement of an
alignment in a seaward direction increases energy capture and reduc-
es the length of the structure required. Both these trends encourage
consideration of alignments towards the downstream, narrow section
of the estuary. A similar trend applies when tidal stream velocities are
considered. In estuaries that widen in a seaward direction, the average
stream velocities will reduce as you move downstream. In the Mersey
the highest stream ow velocities are in the downstream, narrow sec-
tion of the estuary.
FEASIBLE TECHNOLOGY
For several years Peel Energy, in partnership with the Northwest
Regional Development Agency (NWDA) and with the backing of the
Mersey Basin Campaign, has been examining the development of a
power scheme in the estuary. In 2006 stage 1 of the project got under-
way with a pre-feasibility report, which was completed in October
2007. This rst stage was completed in January 2010 with the produc-
tion of a long list of technologies to be evaluated in more detail.
Stage 2 of the scheme, the full feasibility study, began in September
2009 and is expected to be nished in January 2011. A feasibility
report will be published in March 2011. The feasibility study is being
led jointly by a consulting team comprising Scott Wilson, Drivers
Jonas and EDF, on behalf of Peel Energy and NWDA. They are sup-
ported by a group of advisors including APEM, HR Wallingford,
Regeneris Consulting, RSK, Turner and Townsend, the University of
Liverpool and the Proudman Oceanographic Laboratory.
The study team has strived to include as many relevant technologies
as possible in the assessment. Existing and emerging technologies for
use in a range of water depths were examined, and consideration was
given to work on tidal power generation from the Mersey stretching
back nearly 30 years – schemes have emerged in the past for gener-
ating up to 700MW of electricity from the estuary. The study also
took account of similar work being done to assess the possibility of
generating power from the tides within the Severn estuary and of a
related government-backed programme to promote new tidal power
technologies, the Severn Embryonic Technologies Scheme (SETS).
Fourteen options for the Mersey were assessed and evaluated
against a set of ve criteria:
Power across the Mersey
The Mersey tidal power project has passed a notable milestone with completion of the
rst stage of a major feasibility study. Further research is now underway to select the best
scheme to start generating power across the Mersey estuary in 2020
Study phase
Anticipated timeline
Activities Pre-feasibility
Preliminary
options
Preferred
options
Planning
consent
Project
commissioned
FeasibilityConsenting procurement Construction
Output
Phase 1
2006 2007 2009 2011 2015 2020
Phase 2
Mersey – points for consideration
When selecting a preferred choice for tidal power generation across the
Mersey, consideration has to be given to the following factors:
Water quality – This has been a signicant issue for the Mersey estuary for
some time. The Water Framework Directive has classied the area as a heavily
modied waterbody with unsatisfactory quality. Improvements have been made
over recent years and a river basin management plan is underway, which
predicts that some water bodies within the Mersey catchment will achieve good
ecological status before 2015. The Mersey tidal power project has to ensure
that these plans are not compromised by the chosen power scheme.
Natural environment – Large parts of the estuary and Liverpool Bay are
European Community designated protected areas for conservation. The area is
also rich in wildlife, particularly birds. Any tidal power scheme here is likely to
have some effect on water levels and will alter habitats. This will be a key issue
for the siting, design and operation of the chosen scheme.
Shipping – The Mersey estuary has nine shipping destinations and is the third
busiest estuary in the UK. Site selection must also take into account tankers
using the Tranmere oil terminal which need to turn in the river.
Geology - A deep and variable bedrock prole has been identied as a signicant
geotechnical constraint in the Mersey estuary. A feature of the area is the
presence of deep valleys called Tunnel Valleys formed by subglacial or englacial
meltwater owing under great hydrostatic pressure beneath ice sheets.
Much of the Mersey estuary is located above one of these Tunnel Valleys. The
valleys contain isolated, over-deepened depressions where bedrock levels
can reach depths of 70-80m below ground level. However, extensive ground
investigation information is not available and whilst the presence of a Tunnel
Valley is generally accepted, the exact bedrock depths and the variation in
those depths are less well established.
Any tidal power scheme comprising a structure across the estuary upstream
of Birkenhead will traverse a Tunnel Valley and appropriate foundation
solutions will be required.
WWW.WATERPOWERMAGAZINE.COM MAY 2010 39
WAVE AND TIDAL POWER
r1: Estuary width and water depth$BOUIFUFDIOPMPHZCFJNQMF-
NFOUFEJOUIF.FSTFZFTUVBSZHJWFOJUTXJEUIBOEXBUFSEFQUI
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NBUJPOJTBWBJMBCMF5IFGPVSUFDIOPMPHJFTTFMFDUFEBUUIJTTUBHFBSF
rHorizontal axis turbines in an impounding barrage5IJTJTBDPO-
WFOUJPOBMCBSSBHFJNQPVOEJOHUIFUJEBMSBOHFPGUIF.FSTFZUP
PCUBJONBYJNVNFOFSHZZJFMEPGGFSJOHUIFNPTUFDPOPNJDTPMVUJPO
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rA tidal gate comprising Hydromatrix turbines and creating a very
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CFMPXUIFPQFSBUJOHSBOHFPGDPOWFOUJPOBMIPSJ[POUBMBYJTQMBOU
5IFUJEBMHBUFTPMVUJPOFNQMPZTTNBMMEJBNFUFSVOJUTBOEXJMMUIFSF-
GPSFCFTVJUBCMFGPSBTIBMMPXXBUFSBQQMJDBUJPO
rVertical axis, cross-ow or horizontal axis, ducted stream ow
machines in a tidal fence:"QBSUJBMPSDPOUJOVPVTCBSSJFSBDSPTTUIF
FTUVBSZXJMMDPOTUSBJOUIFUJEBMáPXBOEJODSFBTFUIFWFMPDJUZMPDBMMZ
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Peel Energy has a generating portfolio of more than 3GW
comprising tidal power, wind, biomass and multi-fuel
plants. www.peelenergy.co.uk
The NWDA works to deliver economic success in this
region of England. It is working towards a low carbon
economy by ensuring the region reduces its environmental
impact, adapts to climate change and capitalises on key
business opportunities. www.nwda.co.uk
For more information see www.merseytidalpower.co.uk
Severn Embryonic Technology
Scheme (SETS)
The rst River Severn tidal power consultation was launched in the UK in
January 2009. A £500,000 government fund was established for developing
schemes incorporating embryonic technologies which may offer less
environmental impact than those shortlisted for the Severn estuary.
The fund is managed by the Department of Energy & Climate Change; the
Department for the Environment, Food & Rural Affairs; the Welsh Assembly
Government and the South West Regional Development Agency. The basis for the
programme was that the technologies selected should be deployed commercially
at the scheme within 10-15 years. The scheme was open to proposals already
submitted to, but not shortlisted for, the Severn tidal power feasibility study. New
proposals which met the scheme criteria were also welcomed.
Seventeen proposals for SETS funding were received and six proposals
(including new technologies, tidal fences and tidal reefs), were put through to
the next stage. Applicants were informed of the results of this initial stage in
May 2009 and successful applicants then worked up their bids with engineering
and environmental consultancy advice funded through the scheme.
The nal selected SETS were: Tidal fence concept proposed by the Severn
Tidal Fence Consortium (Severn Tidal Fence Group led by IT Power and
CleanTechCom); Low head barrage concept proposed by Atkins and Rolls
Royce; Spectral Marine Energy Converter proposed by VerdErg.
The selected developers are due to report in mid 2010.
IWP& DC
40 MAY 2010 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
UNDERWATER INSPECTION
A
IRSUB is a research project funded by the Spanish
Ministry of Science and Technology with the aim of
exploring the use of advanced underwater robotics tech-
nology for the visual inspection of hydroelectric dams.
Two particular application scenarios have been studied: the bottom
oor inspection for habitat mapping purposes of the zebra mussel;
and the visual inspection of the concrete of the dam wall.
In both cases the same technology is used. An ultra short base line
(USBL) system connected with a differential global positioning system
(DGPS) and a motion reference unit (MRU), mounted on a moored
buoy (or alternatively on a support boat), are used for tracking and geo-
referencing the robot position. The vehicle is equipped with a doppler
velocity log (DVL) sensor and a MRU used for onboard navigation.
Two video cameras (one looking forward and one looking down-
ward) are used for visual inspection and mechanical scanning imaging
sonar is used for helping the pilot when the robot is operated manu-
ally. The entire data gathered onboard, as well as the data gathered
on the buoy, is time-synchronised. At the end of the mission both the
navigation data and the images are post-processed to build a geo-
referenced photo-mosaic. Navigation data is exploited to provide a
consistent, globally-aligned optical map, reducing the inherent drift
as much as possible if only optimal imagery were used.
The results in two different scenarios are illustrated in this paper. In
the rst case, the robot was tele-operated while in the second it was
operating autonomously: A geo-referenced bottom mosaic gathered
in Mequinenza dam on the Ebro river in Spain was used for habitat
mapping of the zebra mussel; and a geo-referenced photo-mosaic of
the wall of the Pasteral dam in Girona (on the Ter river in Spain).
UNDERWATER ROBOTICS
The AIRSUB research project was devoted to the research and devel-
opment of advanced underwater robotics and image processing
techniques with applications to dam inspection. During the project,
the research team met with the civil engineers of a Spanish power
generation company, as well as with biologists of an environmental
monitoring company. The aim was to dene potential application
scenarios of both industrial and environmental monitoring interests.
The following cases were considered:
r Visual survey of the dam wall to assess the state of the concrete.
r Visual survey of the protecting fence of the water inlet to the pen-
stock gallery to assess the quantity of vegetal residuals obstructing
the water ow.
r Visual survey of the bottom for habitat mapping of the Zebra mussel.
Currently, these inspections are commonly performed through a careful
visualisation of a video recorded by a professional diver, often without
any localisation information. Sometimes a GPS reading gathered at the
surface is overlaid on the image introducing an approximate location of
the underwater camera. A diver tracking system may also be used, but
even in this case the system does not have enough accuracy to stitch all
the images together to obtain a global map of the surveyed area.
Over the past years, several companies have offered underwater
robots for dam inspection. Normally they propose the use of small
class remotely operated vehicles (ROV), working as tele-operated
cameras for video recording, to replace the professional diver who
traditionally carried out this task. There exist few research precedents
providing an added value solution.
One of the most relevant works is the ROV3 system developed by the
researchers of the Institut de Recherche Hydro Québec in Canada [1].
This is a small ROV, localised through a long base line (LBL) system,
which makes use of multi-beam sonar for collision avoidance. The
system is able to control the distance to the wall and includes several
video cameras as well as a laser system for 2D and 3D measurements.
COMEX and Electricité De France developed a similar project [2].
In this case, an ROV manufactured by COMEX was localised using
ve LBL transponders. Again, several video cameras together with a
2D (double spot) laser system was used to take measurements.
During 2002, in collaboration with the Research Development and
Technological Transfer Centre (CIFATT) IPA-Cluj, the research team
used the URIS robot working as an ROV to build an image mosaic
of a small area of the wall of the Tartina dam in Romania [3]. This
A new project has been researching the use
of advanced underwater robotics technology
for dam inspections. Members of the
research team from the University of Girona
Spain give more details
Table 1: Ictineu AUV sensor suite
Sensor Model Characteristics
Mechanically
Scanned
Imaging Sonar
Tritech Miniking Maximum range: 100m
Horizontal beamwidth: 3º
Scan rate: 5-20 sec./360º
sect. Frequency 675kHz
DVL Sontek Argonaut Accuracy: 0.2 % of measured
vel. Frequency: 1500kHz
MRU+FOG Tritech iGC/iFG Accuracy: better than 1º
Vision system B&W Camera
Halogen lights
1/3” CCD 0.01 Lux 50Hz
625 lines
Echo sounder Airmar Smart Sensor Frequency: 235 kHz
USBL Linkquest Tracklink
1500 HA
Angular acc.: 0.25º . Range
acc.: 0.5% slant range.
Frequency: 31 to 43.2 kHz
Figure 1: The Ictineu vehicle during a mission
Advancing
underwater
robotics