Thermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 1



### Thermal Electric Po wer Plant Water Uses; Improvements Promote Sustainabi lity and Increase Profits By : Paul L. F r eed m a n, P.E ., BCEE John R. Wolf e, Ph.D., BCEE Lim noTech 501 Avis Dri v e Ann Arbor, MI 481 08



### Preface This paper includes research conducted by Lim n oTech sponsored by the Electric Power Research In stitu te. It r e p r esents inf o r m ation extr a c ted f r om a more com p rehensive rep o rt en titled “Program on Technology Innovation: An Energy/W a ter Sustainability Research Program for the Electric Power Industry” (EPRI 2007). Any citations or m o re in-depth inform ation is best directed to this docum ent. 

### Background The electric power industry requires reliable supplies of water fo r cooling, for flue gas treatm ent, and for ash handling. Po wer generators accoun t fo r about 40% of U.S. fr eshwater withdrawals (USGS, 2004). Even though this am ounts to only about 3% of freshwater consum ption, (because most of the water withd r awn is retu r n ed) th is st ill represents a significant water resource need. As population grows, so does the dem a nd for electri c power and related water. This dem a nd will

com p ete with dem a nds for water us e d for agricu lt ural, m unicipal, reside n t ial, comm ercial, and industrial uses. According to a 2003 GAO report, 46 states expect water shortages during the next 10 years under drought conditions (GAO 20 03) . As competing dem a nds for water increase, the electric power industry will n eed to develop technologies to im prove their water ef ficiencies, in order to have a sustainable water-energy m odel. Water use at individual plants can be significant. Many olde r plants still use once-through cooling, which heats large volum es of water and th en returns those waters with m i ni m a l loss to the environm ent. Table 1 shows typical water withdrawal and consum ption values for oncethrough cooling system s. For newer installations , im proved efficiencies have been gained by using cooling towers, recirculating cooling sy stem s, and other technology im prove m e nts.

Table 1 

### : Cooling Water Withdrawal and Consumpt ion (E vaporation to the Atmo sphere) Rates for P o w er Plants Using Fossil, Biomass, or Waste as Fuel
Cooling Sy st em Ty pe Wa ter Wi thd r a w a l (g al/MWh) Wa ter C ons um ption (g al/MWh)
Once Throug h Cooli ng 20,000 to 50, 000 ~30 0

Cooli ng To we rs 500 to 600 ~48 0
To the credit of the industry, a changing m i x of once- through and recirculati ng cooling system s, in addition to water-conserving im provem e nts, ha s enabled the electric power industry to reduce its water withdrawals per unit of power generated by a factor of three, f r om 63,000 gal/MW h in

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 2 1950 to 21,000 gal/MW h in 2000. Over the sam e peri od, the industry has incr eased its output of electric power by a factor of 15. Therefore, the net result was a 5-fo ld increase in water withdrawals by the electric power industry. However, all of the in creases occurred before 1980: water withdrawals by the industry have actually declin ed since 1980 . These trends are shown in Table 2 and Figure 1 below.

Table 2: Water Withdraw als, Pow er Generate d, and Improvement in Water Withdraw al Efficiency, 1950 – 2000

1 9 5 0 1 9 6 0 1 9 7 0 1 9 8 0 1 9 9 0 2 0 0 0

Wate r Withdrawals (Billion gallons) 1 4 , 5 0 0 3 6 , 5 0 0 6 2 , 1 0 0 7 7 , 0 0 0 7 1 , 0 0 0 7 1 , 0 0 0

Power Gene rated (Billion MWh) 0

. 2 3 0

. 6 1 1

. 2 8 2

. 0 0 2

. 6 8 3

. 4 5

Wate r Withdrawal

Effic i enc y (gal/M Wh) 6 3 , 0 0 0 6 0 , 0 0 0 4 9 , 0 0 0 3 9 , 0 0 0 2 7 , 0 0 0 2 1 , 0 0 0

Source: USGS 2004; Energy Info rm ation Administration 2004

Figure 1: T rend in U.S. Thermoelectric Po w e r Water Withdraw al Efficiency, 1950-2000

0 10 , 0 0 0 20 , 0 0 0 30 , 0 0 0 40 , 0 0 0 50 , 0 0 0 60 , 0 0 0 70 , 0 0 0

19 50 19 60 19 70 19 80 19 90 20 00
Y

eargal/MWh

The issue of water availability and the choice of cooling technol ogies is generally a second-tier consideration in planning for new plants or pl ant expansions. New plan ts or expansions are prim arily dictated by electric power dem a nd forecasts and co nsideration of where fuel, transm ission capacity, and dem a nd are aligned. Hen ce, a location without su fficient water supply

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 3

m i ght require significant im prove m e nts in wate r use technology, different cooling technologies, or finding alternative water supp lies, such as waste water from m unicipal sources. Hence the issue of water use efficiency becomes m o re of a n econom ic issue of how to get a plant operating profitably, rather than an envir onm ental issue of where the m o st sustainable natura l water sour ce is ava ilab l e. The costs as sociated with water use are not trivia l and can represent a sig n if icant e c o n om ic prof it factor for a typical plant. For exam ple shown in Table 3 are the costs associated with acquiring, delivering, and treating/disposing of water used in power produc tion. For a typical plant of say, 350 MW these costs can be on the order of $6 m illion. To tals in Table 3 are not colum n sum s ; rather they represent approxim a te bounds or total costs com b inations enco untered at real plant sites. Table 3: Representativ e Costs of A c quiring, Transporting, and Treating/Disposing of Water ($/kgal)
Compon e n t L o w M e d i u m H i g h
Acqui re $ 0.50 $ 1.25 $ 3.00

Deliver $ 0.13 $ 0.57 $ 1.20

Treat/Di s p o se $ 0.22 $ 1.00 $ 4.28

Total $ 1.00 $ 2.82 $ 4.00

Hydroelectric power accounts for 5-10% of U.S. power generation, with the output depending on water flows generated by precipitation and resu lting runoff and snowm e lt. For exam ple the 2003 European heat wave demonstrated how susceptib le hydro power is to drought conditions, where hydropower generation capacity in France was re duced by about 20%. In com b ination with a loss of nuclear generation capacity due to heat di scharge restrictions, the shortfall in hydropower generation during a tim e of peak demand was challe nging. Although this is a significant issue, it is not addressed in this paper. This paper addresses the benefits of improving water efficiencies at thermal electric p o wer plants in the a r eas of water reu s e and re cov e ry; use of n ontrad ition a l water sour c e s; and use of advanced cooling technologies . This work was supported by the Electric P o wer Research Institute and is reported on in m o re detail a nd covering other related issues in a m o re lengthy report. (EPRI 2007) 

### Be nefits of Wat e r Re us e a n d R e c o v e r y Recirculating cooling system s require m u ch lowe r flows than once-through system s, but

consum e m o re water due to evaporation. In addition, water may be consum ed by flue gas scrubbing and lost due to cooling tower blowdown. Technology developm ent could reduce losses from each of these processes, as discus sed below related to evapo r ation, b l owdown and flue gas scrubbing.

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 4 Evaporation Evaporation represents the la rgest w a ter loss from recirculating towers, roughly 480 gal/MW h for a coal-fired power plant, and also th e greatest opportunity for savings (EPRI 2002). Evaporative losses can be reduced if water vapor can be condensed and returned to the cooling system . Sm a ll-scale tests of one technology, whic h uses cross-currents of am bient air for condensation, show potential to cap ture 12-30% of evaporative losse s when translated into full scale, reducing losses by about 60-140 gal/MW h, with the higher end of this loss range applying to hotter clim ates (Mortenson 2006.).
This reduction in water losses can be translated in to dollar savings at the plant level by assum i ng a cost of water and a plant capacity. Using th e representative m i drange value of $2.82/kgal, savings range from $0.17-0.39/MWh. For a typi cal 350 MW plant operating continuously throughout the year, the savings from re ducing evaporation range from $500,000 to $1,200,000, with a m i drange value of $870,000. Savings for la rger or sm aller plants would be roughly proportional to their capacities (EPRI 2004).

Blowdown As cooling water evaporates from a cooling tower, the concentrations of dissolved and suspended solids increase. To m i ni mize scaling, f ouling, and corrosion of the cooling system
, these concentrations are reduced by blowdown. Bl owdown is the discharge of water from the cooling sys t em , with rep l acem ent by fresh intak e water. Figure 2 shows th e relation s hip between water losses due to blow down and cycles of conc entration (assum ing the t ypical evapo r ation rate of 480 gal/M W h cited above). Cycles of con centration describe the proportion by which evaporation increases co nstitu ent co ncentration s

. For exam ple, at two cycles of concentration, evaporation doubles con s titu ent con c entra tions, relative to intake water. Research to develop cooling syst em m a terials that are resistant to scaling, corrosion, and fouling

can m a ke it possible to operate at higher soli ds concentrations, produc ing significant reductions in blowdown losses. Do ubling cycles of concen tration from 4 to 8, which exceeds th e usual allowable range, could reduce blowd o wn by about 100 gal/MW h (DeFillippo 2003 ). As was done for reductions in evaporative losses, th is reduction in water lo sses can be translated into dollar savings at the plant level by assum i ng a cost of water and a plant capacity. Using a range of $1-4/kgal, savings range from $0.10-0.40/MW h. For a 350 MW plant operating continuously throughout the year, the poten tial savings range from about $300,000 to $1,200,000, with a m i drange value of $860,000.
Flue Gas Scrubbing Flue gas desulfurization, or sc rubbing, can be accom p lished with either dry or wet system s. Plants are likely to increase scrubb in g capacity in com i ng decades to m eet tightening air

em issions requirem e nts, causing water use for this purpose to increase unless there are conservation m easures adopted. W e t scrubbers entr ain flue gas in water spray, capturing sulfur dioxide and other pollutants, which are then rem o ved by creating an alkaline slurry. Dry scrubbing injects the alkaline partic les directly into the flue ga s stream , obviating the need for water, but th e m o re lim ited contac t b e tween re act ants in the a b sence of water resu lts in lower pollutant removal efficiencies.

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 5

Research to reduce o r recover evapo r ative los s es from flue gas, or to increase the rem oval efficiency of dry scrubbing, could reduce water us e and associated costs. Water requirem ents for wet scrubbers are about 25 gal/MW h, so this is the am ount of water that w ould be saved at a plant by shifting from wet to dry scrubbing or by capturing all of the evaporation that results from wet scrubbing (National Energy Tec hnology Laboratory, 2006). Us ing a range of $1- 4/kgal, savings range from $0.025-0.10/MW h. Fo r a 350 MW plant operating continuously throughout the year, the potential savings range from shifting from wet to dry scrubbing range from about $75,000 to $300,000, with a m i drange value of $220,000. Figure 2: T y pical Water Losses from Cooling To w ers, at Varying Cycles of Concentration

Combined Savings If all three loss processe s could be reduced as described abov e for an existing 350 MW coal-fired plant, total annual cost savings would ra nge from $ 875,000 to $2,700,000, depending on clim ate and the cost of water, with a m i drange to tal of $1,950,000. Figure 3 show s a potential savings,

assum i ng an interm ediate cost of $2.82/kgal for wate r use. Most of the poten tial savings are from reductions in blowdown and evaporative losse s, with the elim ination of wet scrubbing contributing a sm aller share of savings.

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 6

Figure 3: Annual Cost of Water C oo ling, 350 MW Coal Burning Plant, Typical and After Potential Reductions

0 1 2 3 4 5 6 7

T y p i c a l A fte r P o te n t i a l R e duc t i o n s$Millions/year B l ow dow n

E v a por a t i v e

S c r ubbi n g



### Be nefits of N on- Traditional Water S o urce s Where clean water is unavailable at a reasona ble cost, lower-quality non-traditional water supplies m a y be good substitu tes, as long as depr eciation of cooling sys t em s can be minim i zed by lim ited pretreatm e nt of intake waters. Pote ntial sources of non-trad itional water include treated urban wastewater, storm w ater, m i ne dr ainage, quarry dewatering, and produced waters from oil and gas operations.

Wastewaters from public treatm ent works can be a very low-cost water source, at the low end of treatm ent/disposal costs shown in Table 3, taking advantage o f treatm e nt already received. This water source will also in creas e, because gr owing populations requiring electric power also generate growing wastewater flows in the sam e locations. New sewage flows can be expected at a rate exceeding 40 gallons per day per capita, including dom e stic water use alone, whereas about 16 gallons per day per capita are sufficien t for new power generation, assum i ng current average rates of 33 kW h per day electricity de m a nd per capita and a cons um ptive use rate f o r power generation of 480 gal/MW h (Metcalf & Eddy, Inc 1991, California Energy Commission 2003).

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 7 In locations where population growth does not pr ovide sufficient new wastewater flows for new power plants, advances in technol ogies allowing use of degraded waters m a y also present great opportunities for cost savings. As Figure 4 shows, the cost of treatm ent required to safely use produced waters can ex ceed $4/kgal for produced wate rs and agricu ltu ral return waters, in which case it is the largest com ponent of the cost of wa ter. At such a high cost, use of these degraded waters is not often com p etitive. However, advances in the ability to use degraded waters without extens ive pretreatm e nt, such as Spray

- Enhanced Dry Cooling could reduce the overall cost of cooling water, m a king produced water com p etiti ve with m o re trad itional groundwater and surface water source s (McGowin 2006). To roughly estim ate the potential saving from advances in use of degraded waters, we can

assum e a reasonable decrease in the cost of pret reatm e nt, based on the range of current costs. Produced waters from oil and gas exploration and agricu ltu ra l re turn wate rs have trea tm ent costs of $4/kgal o r m o re, according to estim ates of DeFilippo, cited by EP RI (EPRI 2004, DeFillippo 2003). The sam e sources estim ate treatm ent costs fo r fresh water supplies of about $1/kgal. It is unlike l y tha t resea r ch in to trea tm ent and/or co m p atible m a terials for degraded waters could reduce costs to that level. It is possible, however , that the difference in treatm ent costs could be significantly reduced, by $0.25-0.75/kgal. For a 350 M W plant operating continuously throughout the year, requiring 480 g/MW h, the savi ngs from reducing costs associated with degraded water sources by $0.25-$0.75/kgal would range from $370,000 to $1,100,000, with a

m i drange value of $740,000. Figure 4: E xample Wa ter Treatment Costs p er 1,000 Ga llons for So urce Cases [7]

$0

. 0 0 $0

. 5 0 $1

. 0 0 $1

. 5 0 $2

. 0 0 $2

. 5 0 $3

. 0 0 $3

. 5 0 $4

. 0 0 $4

. 5 0

R e cy cl e d WW T P Wa t e r Fr e s h Wa t e r P r od uc ed Wa t e r Ag r i c u l t u r a l Re t u r n Wa t e r$/kgal

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 8


### Be nefits of A d v a nce d C ooli ng Te chnologie s Where water supplies are very lim ited, cooling w ith air or a com b inati on of air and water can

m a ke it possible to site n e w facilities. Air- a nd hy brid coo ling technolog ies exist and are in lim ited use, but have cost and efficiency disadva ntages. There is strong interest in the industry for research to develop improved advanced cooling technologies, and overcom e these disadvantages, especially in the southwest. Full scale air cooling sys t em s are in place and op erating in so m e locations , but they su ffer from a “hot weather penalty” of reduced cooling effici en cy. Especially in hotter clim ates, the warm er
am bient air that is present during periods of p eak air cond ition i ng loads is less ef f

ective in condensing steam . This reduces pow er output per unit of fuel and, for base load facilities, requires cos t ly purchas es of i m ported power to replace lost ou tput. It is only in the m o st adverse c lim ates, subject to the highest cost s of water, that air cooling is cost-com petitiv e with w a ter cooling. This is i llu s t ra ted by Fig u re 5, which shows the r e lationship between total annualized cooli ng costs using wet vs. dry coo ling for a hypothetical 350 M W coal-burning plant in El Paso, Te xas. Cost estim ates in clude b o th capital and O&M costs, and a r e based on cooling system designs optim ized for this location (EPRI 2004). The figure shows that dry cooling is cost-com petitive only for a cost of water exceeding about $3/kgal. Beyond that cost level, d r y cooling costs are low e r becau se they are affected very little by the cos t of water. If the hot weather penalty could be reduced through im proved design, such as advanced hybrid cooling system s, this would pr ovide substantial savings. Comput ational fluid dynam i cs research can assist in this goal by im pr oving understanding of air flow and heat transfer across fin surfaces, un der a range of tem p erature and wi nd conditions, supporting m o re efficient designs. The m a gnitude of potential savings for generato rs in warm er clim ates approaches 20% of cooling costs, and can be envisioned by com p aring cost schedules for El Paso, a relatively hot location, with Portland, Oregon, which has m u ch le ss extrem e hot weather. Figure 6 shows this difference, which is due entirely to El Paso’s hot w eather penalty, re lative to Portland. Figure 6 shows that there is a hot weather pen a lty on the o r der of $1.5 m illion/year in cooling costs in the

warm er southwestern clim ates, for a 350 M W coal -burning facility. The goa l of research into im proved air-cooled and/or hybrid technologies w ould be to reduce costs for a plant of this capacity by a significant fraction of $1.5 m illion / y ear. Reductions of 33-6 6 % in th e ho t weather penalty would result in savings of $500,000 - $1,000,000/year.

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 9

Figure 5: Costs of Wet vs. Dr y Cooling, Hypothetical 350 MW Coal-Burning Plant, El Paso, Texas

1 3 2 4 Cost of Wa t e r ($ / k g a l ) C ool in g Co st ($ M / y r )
8 Dr y ( E l P aso) We t

Figure 6: Costs of Wet vs. Dr y Cooling, Hypothetical 350 MW Coal-Burning Plant, El Paso, Texas

1 3 2 4 Co st of Wat e r ($ / kgal ) Co ol ing C o s t ($ M / y r )
8

6. 5 Dr y (E l P a s o )

Dr y (Por tl an d, OR) We t

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 10 

### Summary of Estimated Benefits Potential cost savings have been estim a ted above for a se ries of innovative and em erging technologies. To provide a consistent point of reference, cost savi ngs have been roughly estim ated for a 350 MW plant. Table 4 presents the full set of estim ates for the 350 MW plant and shows that in each case, the po tential savi ng s for a facility of this size for each technology are on th e order of hundreds of thousands to m illions of dollars per year. E s tim ated potential annual savings from capture of evaporation, re ductions in blowdown, use of degraded waters, and air cooling technologies are all of about th e sam e m a gnit ude, given the approxim a te nature of the estim ates. Potential econom ic benefits fr om elim inating water losses from scrubbing are

sm aller, due to the sm aller volum e of water lost to scrubbing. Table 4: Ranges of Potential Savings in Water Costs for 350 MW Power Plant

Res earc h Ar ea Lo w Mid High
Captu r e Evap oration $500,0 00 $870,0 00 $1,200,0 00

Red u ce Blow Down $300,0 00 $860,0 00 $1,200,0 00 Dry Scrubbi n g $75,00 0 $220,0 00 $300,0 00
Use of Deg r a ded Waters $370,0 00 $740,0 00 $1,100,0 00

Air Cooli ng $500,0 00 $750,0 00 $1,000,0 00

The estim ated savings shown in Table 4 would significantly increase pr ofitability for power generators. Power generation costs f o r a 350 MW baseload coal-burning facility are about $100- 125 m illion annually, b a sed on a ran g e of leve lized cost of $33-41/MW h (Yahoo Finance 2006, Tolley and Jones 2004). W ith the exception of dry scrubbing, each techno logy listed in Table 4-1 has the potential to reduce annua l production costs by about 1%, in creasing the rate of profit by the sam e percentage. P r ofit rates for power generato rs currently average about 7-8% of costs, so the im plem e n tation of these technologies, singly or in com b ination, has the potential to raise profit rates by roughly 1-3 percenta ge points, increasing profit rate s from about 7-8% to about 8- 11%, a substantial increase.



### Summar y a nd Conclusions

W ith population and en ergy dem a nds increasing ther e is goin g to be a co mpelling need for the electric power industry to be m o re water efficient. As with m a ny business, the environm ental aspects of operations and development are not usually a prim ary consideration. This paper has shown that improved water efficiencies thr ough reuse and recovery, use of non-traditional waters, and improved cooling effici encies can be effective strategies for the industry to not only conserve increasing l y scarce water b u t also im pr ove the econ o m i c line fo r plant profitability. By considering econom ics and well as the environm en t, we have a better chance of achieving a sustainable f u ture for water use in the power industry.

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DCThermal Electric Power Plant Water Uses: Improvements Promote Sustainability & Incr ease Profits Freedman & Wo lfe
Page 11 

### REFERENCES

California E n ergy Comm ission. 2003. U.S. Pe r Capita Energy Use by State in 2003. http://www.energy.ca.gov/electricity /us_percapita_electricity_2003.htm l
DeFillippo, M. 2003. Use of Degraded W a ter So urces as Coo ling W a ter in Power Plants. Palo Alto, CA and Sacram ento, CA: EPRI a nd California Energy Co mm ission. October. 1005359.
EPRI, 2007 Program on Technology Innovation: An Energy/Water Sustainability Res earch Program for the Electric Power I ndustry. EPRI, Palo Alto, C A : 2007. 1015371.

EPRI. 2002. W a ter and Sustainability (Volum e 1): Research Plan. 1006784. Palo Alto, CA.

EPRI. 2004. Com p arison of Alternate Cooling T ec hnologies for US Power Plants. Palo Alto, CA.

Governm e nt Accounting Office. 2003. Freshwat er Supply, State' s Views of How Federal Agencies Could Help Them Meet the Challe nges of Expected Shortages. GAO-03-514; July 2003.
McGowin, Chuck. 2006. Im proving Water Use Effici ency in Western-Fueled Power Plants. Sym posium on W e stern Fuels. Denver, CO.
Metcalf & Eddy, Inc. 1991. W a stewater Engine ering, Disposal and The Use, 3rd Edition. McGraw-Hill, New York, NY.

Mortenson, Ken. 2006. Use of Air2Air to Recover Fr esh Water in Evaporat ive Cooling at CoalBased Thermoelectric P o wer Plants. Sym posium on W e stern Fuels, Denver, CO.
National Energy Technology Laboratory. 2006. Estim a ting Freshwater Needs to Meet Future Therm o electric Generation Requirem e nts. DOE/NETL – 2006/1235.
Tolley, George S. and Donald W

. Jones. 2004. The Econom i c Future of Nuclear Power. University of Chicago. August.

USGS. 2004. Estim ated Use of W a ter in the Unit ed States in 2000. USGS Circular 1268; March 2004. http://pubs.usgs.gov/circ/2004 /circ1268/pdf/circular 1268.pdf
Yahoo Finance. 2006. Industry Browser-Utili ties-Electric Utili ties-Com p any List. http://biz.yahoo.com /p/911qpm d.ht ml

Prepared for : Canadian-US October 2, 2007 Water Policy Wo rkshop Washington, DC