Water Power and Dam Construction

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SMALL HYDRO

energy supply contract (RES contract) on 24 November 2004.

This RES contract will contribute to the government of Ontario’s

goal of producing 2700MW of new renewable electricity. With an aver-

age production of approximately 109,102MWh, the Umbata Falls pro-

ject will avoid the release of more than 90,000 tons of CO

annually

(based on electricity generated from coal). Certified by the EcoLogo

Program, Umbata Falls benefits from the ecoENERGY Initiative of the

Canadian federal government to support renewable energy produc-

tion in the country. The programme provides a C$10 (US$8) per MWh

incentive payment for the first ten years of operation.

CONOMIC BENEFITS

The RES contract provides for a firm price for the energy produced

at the Umbata Falls facility, with a specified inflation escalator over

a period of 20 years. This agreement offers long-term income sta-

bility during a long portion of the debt repayment period, reducing

the financial risk or uncertainty for both partners and bringing sta-

bility to the expected returns.

Michel Letellier, president and chief executive officer of Innergex,

explains: ‘Innergex understands the importance of working in har-

mony with its surroundings. As such, the Innergex management

team analyses closely how to minimise the environmental impact of

its projects and listens to the hopes and expectations of the sur-

rounding communities, from the planning stage to completion.’

Indeed, the Umbata Falls hydroelectric projec t not only helps

Ontario in reducing its CO

emissions, but also provides long-term

economic growth opportunities for the Ojibways of the Pic River

First Nation, with significant positive impacts on the community in

the short and long term. Twenty per cent of the jobs during con-

struction were allocated to the co mmu n ity, while two permanent

operators have been employed there since the plant entered opera-

tion. Also, income from the project will provide funding to imple-

ment long-term programs developed by the First Nation community,

including housing improvements, community infrastructure invest-

ments (ie, roads, water, sewer, fire a n d emergency services, recre-

ational facilities), educational programming, health and social

services and further economic development.

ESIGNED TO RESPECT

The site of Umbata Falls offered a natural gross head exceeding 30m,

including a fall of 27m and rapids flowing through a narrow canyon.

With a drainage area of 5267km

, the average flow of the river at

Umbata Falls is about 64m

/sec. The highe s t flows occur in May

and June in association with snowmelt and spring rains, while lowest

flows occur in February and March.

WWW.WATERPOWERMAGAZINE.COM MARCH 2009 31

Powerhouse equipment

Turbine type: Kaplan

Number of units: 2

Rated capacity: 11.8MW each unit

Maximum capacity: 12.5MW each unit

Rated flow: 37.5m

/sec by unit

Maximum flow: 42.5 m

/sec by unit

Rated net head: 34.5m

Nominal speed rotation: 360rpm

Power of generator: 13,665kVA each generator

Voltage of generator: 6000V

Top, left: General layout of the scheme

Above, top: Upstream works

Middle: Dam and spillway, looking downstream in October 2008

Bottom: The intake under construction, June 2007

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WWW.WATERPOWERMAGAZINE.COM MARCH 2009 33

SMALL HYDRO

Acres International from Niagara Falls was involved in prelimi-

nary design studies as well as the complete environmental assessment

of the project. Design engineering during construction was assumed

by BPR Groupe Conseil from Quebec working for the general con-

tractor. After analyzing several options with different layouts and

capacities, as well as considering environmental and visual impacts,

the project was developed with the following key components:

• A concrete ov erflow crest wei r located approximately 180m

upstream of the crest of Umbata Falls within the main river chan-

nel. This structure has been located far enough from the Umbata

falls to preserve their natural aspect.

• A head pond creat ed by weir and sluice st ructures, exten ding

approximatel y 850 m upstream and inun dating an additional

3.2ha of land.

• An intake/diversion channel approximately 210m in length, 6-8m

in depth and 18m in width. The channel, excavated to the favour

of an existing depression, conveys the water to the tunnel intake

and diverted the river flow during the construction of the main weir.

• A three bay spillway structure lo cated approximately 150m

upstream of the crest of Umbata Falls within the intake/diversion

channel on the northwest side of the White river. The spillway

includes two bays equipped with sluice gates and a third bay

equipped with two sectional gates. The maximum discharge capac-

ity of the spillway is 610 m

/sec. With the additional discharge

capacity of the overflow crest weir of 160m

/sec, the total maxi-

mal capacity of the upstream structures is 770m

/sec, exceeding

the 720m

/sec required for a flood of occurrence 1:1000 years.

• An intake located adjacent to the sluice structure.

• An unlined power t unnel going do wn wi th a slope of 8.13%,

D-shaped, ap proximately 6m wi dth by 6.1m high and 460m

in lengt h.

• A steel penstock, 4.6m diameter and 41m long, including 35m of

tunnel concrete embedded steel lining and 6m outside of the tunnel

and consisting of a bifurcation.

• A powerhouse, 22m wide by 37.5m long, situated approximately

375m downstream of Umbata Falls on the northwest side of the

White River. The powerhouse houses two Kaplan turbines supplied

by VA Tech Hydro Canada (now Andritz Hydro) and two synchro-

nous generators supplied by Indar from Spain. The powerhouse

includes additional equipment including static exciters, hydraulic pres-

sure units, DC battery system, protections, station service transformer,

sump pumps, overhead crane and a SCADA system.

• A tailrace channel approximately 22m width and 25m length.

• A switchyard located adjacent to the powerhouse including step-

up transformer (generator voltage to 115kV) and line protection.

• A 23km long 115kV transmission line, interconnecting the pro-

ject to Hydro One’s existing 115kV M2W line.

• Appr oximately 6km of new access roads and 23km of existing

access road upgrades.

• The two units were commissioned during the fall of 2008 and the

Commercial Operation Date (CO D) has been fixed to 12

November 2008 according to the requirements of the Ontar io

Power Authority. Turbines and generators have been successfully

submitted to performance index tests and the annual expected pro-

duction of the plant is approximately 109,102MWh.

Design and construction of the project components have a perfor-

mance expectati on of 40 years, according to industry recognized

standards (Good Utility Practice).

CLEAN BALANCE SHEET

The Umbata Falls pro ject was completed within a few months

beyond its expected five-year development life with a budget right

on target . The estimated capital costs of C$60.4M (US$48.6M),

including C $43.5M (US$35M) direct costs and C$16.9M

(US$13.6M) indirect costs, were strictly adhered to. The budgeted

amount of C$3M (US$2.4M) for contingencies covered additional

delays and design changes. Financing of the capital costs was 85%

through non-rec ourse project financing cove red by the Bank of

Montreal with the remaining 15% of equity provided by UFLP.

The RES contract was signed with construction to start in 2005

and commercial operation to begin by 1 March 2007. Meanwhile,

Above, top left: Tunnel jumbo machine in operation in October 2006; Top, right: Construction of the powerhouse in March 2007; Bottom, Left: The spillway and

inake in June 2008; Bottom, right: The powerhouse in July 2007

34 MARCH 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

SMALL HYDRO

environmental regulations changed in Ontario, requiring permit and

planning changes that impacted the timeline. Thus, with the agree-

ment of the Ontario Power Authority the expected commercial oper-

ation date was moved to July 2008.

However, with construction and development of hydroelectric

projects at peak, suppliers of components were in high demand to

satisfy orders from around the world. With delays incurred in the

manufacturing of some electromechanical components, the expect-

ed commercial operation date was postponed to November 2008.

Construction of the project, despite the fact that the site was iso-

lated and far away from all suppliers, was successfully conducted.

The general contractor, CRT Construction from Quebec (QC) was

responsible for site and scheduling management. In addition to the

civil contract awarded to CRT Construction, five other contracts

were signed:

• VA Tech Hydro Canada (now Andritz Hydro) for supply and

installation of electromechanical components.

• Hydro ECI from Granby QC for supply and installation of elec-

trical and automation components.

• MGB from St-Pie QC for supply and installation of the switchyard

components.

• Powertel from Whitefish, Ontario (ON) for the construction of

the transmission line.

• Pic River Development Corporation from Pic River, ON for all the

clearing works.

Rehabilitati on of an existi ng 20 km long road started during the

winter 2005/2006 and the 4km of new access road was completed

during spring 2006. The road construction works were often inter-

rupted because of the nature of the substrate, a thin silty sand easily

eroded during freshet and rain events. This required re-design of the

erosion protection to prevent creek contamination an d landslide

along the open cuts.

The excavation of the tunnel was conducted conventionally with

a drill and blast method using t wo Jumbo ma chines and scoop

trams. Beginning in August 2006, the 460m long tunnel excavation

was completed in under three and half months including the intake

excavation, consolidation and final cleaning. The installation of the

steel liner and the penstock bifurcation w as completed in two

months, including the concrete embedment.

The diver sion channel excavation began in July 2006 and was

completed in two months excluding the rock plugs maintained until

November 2007. The civil part of the intake and spillway were com-

pleted and the gates installed during the summer 2007. Due to the

exceptional flows occurring during spring and summer 2008, the

construction of the gravity overflow crest dam had been delayed and

its construction was finally completed in fall 2008.

The powerhouse construction really began in April 2007. Most

parts of the building, including concrete phase 1, superstructure and

overhead crane, were completed early in 2008. The deliv ery of

electromechanical equipment started in November 2007 with the

draft tube liners, the turbines in April 2008, the generators in June

2008 and finally the Butterfly inlet valves in August 2008. The ini-

tial synchronization occurred on 4 November followed by the com-

mercial operation date fixed to 12 November 2008.

The project proved to be a win-win situation for al l partners

involved, during its construction, and into the future.

Renaud de Batz, Vice President Eastern Region –

Hydroelectric Energy, Innergex Renewable Energy and

Project Manager for Umbata Falls.

For more information on this project and other renewable

energy schemes, please visit www.innergex.com.

IWP& DC

Partners in Umbata Falls

Projects partners

The Ojibways of the Pic River First Nation: Byron Leclair, Director of

business development

Innergex Renewable Energy Inc: Michel Letellier, President and CEO and

Renaud De Batz, Vice President Eastern Region – Hydroelectric Energy

Preliminary design: Acres International

Construction design: Groupe BPR

Civil contractor: CRT Construction Inc.

lectromechanical supplier: VA Tech Hydro Canada Inc. (Now Andritz Hydro)

Electric and automation supplier: Hydr o ECI Inc.

Switchyard components supplier: Gestion MGB Inc.

Transmission line construction: Powertel Inc.

Project timelines

Partnership between the Ojibways of

Pic River and Innergex: September 2002

Start of environmental assessment: June 2003

otice of commencement: August 2003

nvironmental scr eening report issue: December 2004

Notice of completion: January 2005

Environmental assessment approval: November 2005

Start of construction of road and access: November 2005

Start of facility construction: July 2006

Interconnection to the grid: August 2008

Commercial operation date: 12 November 2008

Above: Installing the turbines in the powerhouse; Bottom, left: Powerhouse

turbines and draft tubes before concreting in May 2008

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36 MARCH 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

SMALL HYDRO

called the Goring Gap. On average, more than five million tonnes

of water flows through the Goring Gap every 24 hours, repre-

senting a significant amount of energy. In the past, scores of m ills

along th e Thames exploited this ene rgy, but with the introduc-

ion of the national electricity grid after 1945, virtually all mil ls

have been dismantled. One that still survives is at Cleeve, just

1km north of Go ring.

ORING AND

TREATLEY HYDRO SCHEME

The idea of generating hydroelectricity from the river was pre-

sented to Goring Parish Co uncil (GPC) in October 200 5 by Dave

Holt. It m et with unanimous support, so three hydro c onsul-

tancie s were approached to undertake a feasibili ty study. At the

same time the desi re to gener ate hydroelectricit y was added to

the first Goring-on-Thames village plan. During this time Holt

broac hed the idea with Rob Alexander of the Environment

Agenc y (EA), Ian Bacon (now freelance) of Thames Valley

Energy (TVE) and Heathe r Saunders, responsible for environ-

mental project s with Sout h Oxford District Council (SODC). All

were ver y supportive.

The feasibility study – part funded by GPC and SODC – was deliv-

ered in June 2006 indicating that it was a financially and environ-

mentally sound project capable of generating 170kW of electricity

from three ka plan turbines and 12 polymer turbines saving 300

tonnes of CO

emissions per annum. The total cost of the scheme

was estimated at £1.5M (US$2.3M).

The Goring and Streatley Sustainability Group (GSSG) was found-

ed by Kay and Martin Baker of Streatley in 2006 and is made up of

local people concerned about the environment, living sustainably

and reducing CO

emissions. It has around 80 members, a

Constitution and bank accounts. Holt joined this group as hydro

project leader with Chairman Nikki Swan, Secretary Trevor Coombs

and Treasurer Jonny Riggall.

Encouraged by the findings of the feasibility study, stakeholders

were brought together in March 2007 incl uding the EA, S ODC,

Ch ilterns Ar ea of Outst anding Natur al Beauty ( AONB), North

Wessex Downs AONB, St reatley Parish Council, Goring Parish

Council, GSSG and relevant land owners. It was agreed that funds

should be raised to produce an outline design study that would

provide more detailed information as indicated below.

PROFIT COMMUNITY PROJECT

The hydro s cheme is a large, non-profit community proj ect that

intends to plough the income from the sal e of hydroelectricity

into other local sustainable projects and is therefore striving to

obta in a significant proportion of the fund ing through UK and

EU grants.

At a subsequent meeti ng with the EA it reco mmended that the

group consider utilising (reverse) Archimedes Spirals as they are fish

and eel friendly. Extensive tests under controlled conditions and 24hr

video surveillance on the newly commissioned 55kW Archimedes

Spiral a t the Dart Co untry Park in Devon showed no damage to

hundreds of fish passed through the Spiral. Other advantages of this

technology include:

• Simple to construct with low CO

emissions during manufacture.

• No need for a fine mesh to deter fish, thereby enhancing efficiency.

• Easy maintenance, as both bearings are above the normal level of

the river.

HE non-tidal river Th ames fall s 110m from its naviga-

ble source at Lechlade in the county of Gloucestershire

to Teddington lock in London. Within that 256km the

river p asses throug h many famous Englis h cities and

towns such as Oxford, Henley and Windsor. Goring an d

Streatley, two villages straddling the ri ver, are located exactly at

the mid-point of the no n-tidal Thames at a po int historically

An innovative community-led hydro

project is being undertaken on the

River Thames in the UK

Power to the people

The Archimedes Spiral installation

on the River Dart in Devon is a

good example of the technology

munity projects in the future. Thirteen other communiti e s on the

Thames have now approached GSSG to learn from the group’s expe-

rience and seek advice.

GSSG will ensure that the scheme will educate the general public

and children on sustainable, zero carbon, zero pollution energy pro-

duction. Remote displays indicating how much power is being pro-

duced and a schematic of the project and its benefits for all to read

will be located near the lock and road bridge. It is forecast that school

parties will travel to the site to learn from the project.

Likewise this project will provide a huge tourism magnet which

will be beneficial to the local economy and local businesses. All spon-

sors and financial contributors to the project through all the phases

will be given prominence on the displays.

The Swan Hotel at Streatley and the owners, Nike Group, will be

able to advertise that they obtain the majori ty of their electr icity

from clean, sustainable sources for at least three generations.

Not least the parishes of Goring and Streatley will be trailblazers

as this will be the first such installation visible to the public and river

users on the Thames. Incidentally, Goring Mill was the first on the

Thames to produce electricity from the river – in 1895 – and this

project will be a perfect ‘closing of the circle’.

Dave Holt, Hydro Project Leader, Goring & Streatley

Sustainability Group, UK. Email: Info@gssg.org.uk or

visit www.gssg.org.uk for more details

• Low installation costs as there is no need to dig down into the river

bed as for vertically mounted turbines.

• Performance is maintained over a wide range of flows.

• Visually entrancing and audibly relaxing.

The outline design study funded by SODC, Chilterns Sustainable

Development Fund (SDF), North Wessex Downs SDF and Streatley

Parish Council was completed in March 2008 by Dav e Mann of

Mannpower Consulting and Chris Elliot of WRE Consulting, and

confirms the viability of the scheme. The recommended location and

technology consumes the maximum amount of water (21m

/sec)

allowed by the EA to maintain flows over the rest of the weirs. With

three 3.5m diameter Archimedes Spirals located next to the lock-

eeper’s house, the peak output is estimated at 246kW (equivalent

to the average daily consumption of 250 homes), saving over 500

tonnes of CO

each year if conventional electricity losses in trans-

mission cables are taken into account. Total cost of the scheme is

estimated at £1.1M (US$1.6M).

The environment survey to examine the ecology of the river

and to identify any exotic species that could be compromised by

the sche me was be gu n in June 2008 funded by Streatley Parish

Counci l, GSS G (fro m voluntary fund raising activ ities) and

Goring Amenity As sociat ion. In parallel, gr ant appli cations were

made to Chilterns SDF, N orth Wessex Downs S DF and SODC to

complete the survey in summer 2009 and they have all once again

contribut ed to the scheme.

The flood risk anal ysis (FRA) is required as the spirals consti-

tute an o bstruction on the existing overfall weirs. Rob Alexander

of the EA kindly offered the resources of the EA for the initial FRA

computer modelling, complete d in the summer of 2008. This has

indicated a very slight increase in upstream and downstream river

levels when the river is in f ull spate. Further modelling is required

to u nderstand how this increase could be ab sorbed by bett er util-

isatio n of the ex isting Streatley s ide sluice gates, an additional

sluice gate and by the existing meadows and flood plains. Funding

sources are now bei ng researched and it is hope d that the com-

puter modelling can be completed to the satisfaction of t he EA by

end of 2009.

Planning applications will require fairly detailed drawings to be

submitted to both the EA and SODC. SODC planning was informed

of the scheme from the beginning, have received the outline design

study and have made no objections to the project on any grounds.

A land drainage consent licence and impoundment licence must be

obtained from the EA.

ROJECT FUNDING

At the moment, several sources of funding are being evaluated for

the project itself. These include EU grants for which the group has

enlisted the services of James Elles, the European MP for the South

East of England, who visited the site in October 2008. GSSG is also

seeking philanthropic contributions from local wealthy individuals

and is considering a local share issue, such that all residents of both

communities may participate in the project. A noti fication of the

possibility of a share issue was publicised in the Goring Gap News

in November 2008, resulting in dozens of individuals accessing the

web site www.gssg.org.uk indicating how much they would be pre-

pared to invest.

Major fund raising is expected to take all of 2009 and the best

part of 2010. It is hoped to be able to order the Archimedes Spirals

in autumn 2010 – as there is a six-month lead time – for installation

in the summer of 2011 when river flows ought to be low.

ENEFITS

Although the amount of electricity produced does not sound signif-

icant, the financial return of around £120,000 (US$179,000) per

annum will be sizeable and will grow in line with energy price infla-

tion (>12% per annum this century). This will be returned to the

communities of Goring and Streatley to fund other sustainable com-

WWW.WATERPOWERMAGAZINE.COM MARCH 2009 37

SMALL HYDRO

Computer generated schematics of the three 3.5m Archimedes Spirals

IWP& DC

Acknowledgements

GSSG would like to thank the following organisations for their generous

support of this community project:

SODC, Chilterns and North Wessex Downs Sustainable Development Funds

(part of the AONBs), the Environment Agency, Goring and Streatley Parish

Councils, Goring Amenity Association, Mann Power Ltd and WRE Ltd.

38 MARCH 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

demonstration projects undertaken as part of the NSF grant was to

inject DO into the North Fork River which is formed by the release

of water from Norfork Dam in Baxter County, Arkansas (Figure 2).

Norfork Dam, operated by the US Army Corps of Engineers

(USACE), is a multi-purpose project for control of floods and gen-

eration of hydroelectric power – the project has a rated capacity of

80.5MW, generated by two 40.25MW turbines.

Several different flow rates of water through the dam can occur

ranging from low flow conditions of around 75ft

/sec (2m

/sec) to

a maximum generation flow rate of 7000ft

/sec (1981m

/sec).

The North Fork River is 303(d) listed by the Arkansas

Department of Environmental Quality (ADEQ) for having low DO

(below 6 mg/L). Releasing water from the anoxic hypolimnion of

Lake Norfork causes the low DO in the river. This problem typically

occurs seasonally in August through November as warm water from

summer heating settles on top of the lake and blocks cold bottom

HE patented and patents pending Supersaturated Dissolved

Oxygen (SDOX) delivery technology from Arkansas, US-

based BlueInGreen is a different approach to adding dis-

solved oxygen (DO) to water (Fig ure 1). The system –

based on technology originally developed at the University of

Arkansas – removes a side-stream of water from the river and passes

it through a saturation vessel where oxygen gas and water are mixed

under ideal conditions such that oxygen is immediately dissolved in

the water stream at a concentration of around 350 mg/L or more.

This supersaturated side stream of water is continuously added back

into the river and is broadly mixed to provide any target DO con-

centration that is desired (up to saturation).

BlueInGreen was awarded a Small Business Innovation Research

(SBIR) grant from the National Science Foundation (NSF) back in

the Spring of 2008 to demonstrate the SDOX oxygen injection

system for improving environmental water quali ty. One of the

Injecting dissolved

oxygen at Norfork Dam

A dissolved oxygen injection system developed to aid aquatic ecosystem restoration has

been tested at Norfork dam in Baxter County, Arkansas, US. Scott Osborn, Anna McCain

and Grace Richardson provide details on the initial test results

Trout fishermen downstream

of SDOX during operation

costs of $0.10/kW-hr for electricity and $0.08/lb for oxygen, the oper-

ational costs of the SDOX would be $0.23 per lb DO delivered.

• The untreated sec tion of the North Fo rk River belo w Dry Run

Creek exceeded a DO of 6 mg/L 33% of the non-pulsing opera-

tion time (Figure 4 top).

• The SDOX treated section exceeded 6 mg/L 83% of the time for

non-pulsing operation (Figure 4 bottom).

• An SDOX unit 65% larger in capacity than the unit used during

the test would have maintained a DO in the river (at low flow)

exceeding 6 mg/L for the entire testing period.

• Base d on the design parameters obtained through these tes ts,

SDOX units were sized for varying flow rate scenarios.

• Anecdotal evidence supports improved trout fishing conditions

during operation of the SDOX (see main picture).

Conclusions of the study are that injection of DO on river side of

dam was successfully conducted for the study period of one-week.

The SDOX was able to add DO to the river with the same high

oxygen utilization efficiency (95%) as measured with smaller units

waters from circulating to the surface, thereby cutting off the source

of oxygen. Since the bottom waters have no access to oxygen, the

DO that is consumed by living matter in the water and sediment is

not replaced which results in anoxic conditions. The water intake

for the dam is located in this anoxic region, so the river formed by

the water exiting the dam is low in DO from late summer through

ovember. A lack of DO in water adversely affects fish health and

can cause fish kills in the trout population in the river. The North

Fork River is a popular location for fishing, and the tourism dollars

associated with fishing have a very large impact on the local econo-

my. Not only are the trout in the river threatened during seasonal

periods of low DO, but also additional trout cannot be stocked. The

low DO problem surrounding Norfork Dam has been studied and

iscussed for more than 20 years, and several small-scale solutions

have been explored, but the fundamental problem of low DO in the

river remains. Several groups that have a strong interest in solving

this problem include USACE, Southwestern Power Administration

(SWPA), Arkansas Game and Fish Commission (AGFC), Norfork

National Fish Hatchery (NNFH), ADEQ, local chambers of com-

merce, recreational fishing organizations, as well as state and fed-

eral political leaders.

EST INJECTION

BlueInGreen built the largest SDOX that could be afforded through

the grant funds awarded. The goal of this test injection was to deter-

mine the parameters required to design an SDOX system for treat-

ing generation flows released from the dam. For th e te sts,

non-generation flows through the dam of 75ft

/sec (2m

/sec) were

provided by USACE th roughout the nine day study period in

November 2008. Pulsing flow averaging 960ft

/sec (27.2m

/sec) was

conducted twice daily for a period of one hour per pulse. DO injec-

tion was conducted on the river side of the dam (Figure 3) because

of several ecological and economic advantages over DO injection

into the lake.

Since the SDOX technology adds DO as a pre-dissolved stream

of water with no gas bubbles or off-gassing, there is no minimum

requirement for water depth to attain high oxygen utilization effi-

ciency. The absence of off-gassing makes treatment of the relatively

shallow river water economically feasible. Treatment of the river

saves operating costs as only the water being released through the

dam is treated and DO addition matches flow rate. The rate of DO

addition is metered in real-time based on input from a downstream

DO sensor and assures that the minimum DO requirements of the

tailrace are continuously met under all operating conditions. Under

this scenario, operation of the dam is freed from tailrace DO con-

straints and is based solely on efficiency of power generation and

flood control.

Competing DO delivery technologies based on bubble aeration

require significant water depth in order to dissolve bubbles before

they rise through the water column and exit the anoxic hypolimnion.

This makes bubble aeration economically feasible only on the lake

side of the dam and results in the formation of a plume of DO in the

forebay. Operation of the dam under this scenario must consider the

size of the DO plume when releasing water for flood control and

power generation. Furthermore, the attraction of fish (such as striped

bass) to the DO plume has resulted in fishing restrictions in some

lakes using bubble aeration to remediate low DO.

A summary of findings from the tests of SDOX treatment of the

North Fork River is provided below:

• The average DO rise produced throughout the experiment was

1.15mg/L once natural stream reaeration was removed.

• The DO delivery rate measured in the river was calculated to be

1152lb/day with a corresponding oxygen use rate of 1209lb/day

resulting in an oxygen delivery efficiency of 95% (oxygen con-

sumed that was delivered as DO).

• A total of 3.32 tons (81,000ft

) of dissolved oxygen was added to

the North Fork River through the testing period.

• Power efficiency was measured to be 1.94 lb DO added/hp-hr. Using

WWW.WATERPOWERMAGAZINE.COM MARCH 2009 39

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Pressure

regulator

Oxygen

source

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Oxy

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Level

control

Level

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Head

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Pressure

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Water level

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liquid-liquid mixing

no gas phase O

saturated water side-stream

njected back into river through

calibrated oriface tube

SDOX

System

Figure 1: Schematic of the SDOX

Figure 2: Norfork dam in Baxter County, Arkansas

40 MARCH 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

in wastewater treatment plants. The SDOX unit used for this study

was undersized for maintaining a DO of 6 mg/L continually at low

flow in the North Fork River, but was able to increase the time the

river e xceeded DO requirements from 33% to 83% . SDOX DO

injection is a feasible solution to the chronic low DO problem in the

North Fork River.

BlueInGreen is currently seeking opportunities to install a full scale

unit in the North Fork Riv er. Once the full-scale unit is installed

parameters such as yearly average operating costs and increases in

power generation and flood control efficiency will be measured and

compared to published data regarding fine bubble diffusion systems.

The full-scale unit will allow for maximum efficiency in power gen-

eration and flood control while maintaining state mandated water

quality requirements at a wide range of flow rates.

For further information please visit www.blueingreen.biz

or contact Scott Osborn, President, scott.osborn@

blueingreen.biz, Anna McCain, Technical Liaison,

anna.mccain@blueingreen.biz or Grace Richardson,

Applications Engineer, grace.richardson@blueingreen.biz

NEW TECHNOLOGY

IWP& DC

8.5

7.5

6.5

5.5

4.5

3.5

DO above 6 mg/L (mg/L)

No SDOX treatment

8.5

7.5

6.5

5.5

4.5

3.5

DO above 6 mg/L (mg/L)

SDOX treated

Day of injection

Norfork Dam - Key facts

• The dam is located on the North Fork River, 4 miles NE of Norfork,

Arkansas, in the White River Basin. The lake and dam are in Baxter County.

• Dam construction began in October 1940 and was completed in June

1944. The powerhouse and switchyard were completed in October 1949,

with the first unit entering commercial operation in June 1944 followed by

second unit in February 1950.

• Norfork Dam was the third hydro power project to be completed by the US

Army Corps of Engineers in the US.

• The project features two Francis turbines, each with nameplate capacity

40.25MW (total plant 80.5MW nameplate capacity) and overload capacity

46.3MW (total plant 92.6MW overload capacity); flow rates are 3100 cfs

(87.7m

/sec) each unit at nameplate and 3600 cfs (101.9m

/sec) each

unit at overload. Downstream channel capacity is 10,000 cfs (283m

/sec).

• Dam type is concrete gravity with 1 .5M cubic yards (1.15Mm

) of

concrete in the dam; Length 2624 fe et (800m); Height 21 6 feet (65.8m)

above the st reambed.

Figure 4: Percent of time when 6mg/L DO requirements were met when not

treated with SDOX (top) and when treated with SDOX (bottom)

Figure 3: Set up of the liquid oxygen tanks, evaporator and trailer

mounted SDOX in the North Fork River just downstream from the dam

Water Power and Dam Construction - Issue March 2009

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