1. Wyoming Pipeline Authority October 2008 Sunstone Pipeline LLC

2. Agenda 1.Sunstone Pipeline Project 2.Route Details 3.Capital Costs 4.Transportation Rates 5.Value To Shippers 6.Project Progress 7.Project Schedule 2

3. 1. Sunstone Pipeline JV partnership among Williams Gas Pipeline Company, TransCanada Pipeline and Sempra Pipelines & Storage Corp. Provides the lowest cost transportation service to the broadest market –Pacific Northwest –California –Northern Nevada Lower risk than greenfield construction –Existing corridors, existing infrastructure, existing operators –Lower miles –Reasonable, scrubbed cost estimate Majority of the capacity subscribed 3

4. 2. Sunstone Route 4 OPAL CHEYENNE MEEKER Denver MALIN Powder River Powder River Big Horn Big Horn Wind River Wind River Greater Green River Greater Green River Uinta Piceance Paradox Sand Wash Sand Wash Denver/ Julesberg Denver/ Julesberg WCSB Williston Anadarko NIT Northern Border Foothills (Sask.) NGTL GTN Foothills (B.C.) Northwest Pipeline TC Mainline WAMSUTTER STANFIELD Sunstone RUBY PG&E RENO Paiute ELY Tuscarora 1.2 Bcf/d of capacity 598 miles, 42” 57,300 HP, 1440 MAOP 0.83% fuel (@ 90% LF) Largely parallels existing NWP and utility corridors Mist Jackson Prairie

5. 3. Estimate Reflects Current Cost Trends Cost estimates in 2011 “as spent dollars” –Escalating steel prices and contractor costs factored into the estimate Validation of costs & route –Williams recent and extensive experience in the Rockies (i.e. Kern River Expansion) –TransCanada engineers independently validated the Sunstone estimate –Third party review Based on November 2011 start date Engineering, Design & Project Management 15 Line Pipe746 Other Materials 68 Pipeline Construction981 Other Construction73 Land49 Environmental29 Line Pack and Commissioning30 Compression201 Total Direct Costs2,192 AFUDC and A&G152 Total Project Costs ($millions) 2,344 5

6. 4. Proposed Rates 6 $0.80 $0.85 Equal to or greater than 10 years but less than 15 years Fixed Rate Option 10 Year Negotiated Rate $0.75Equal to or greater than 15 years but less than 20 years $0.72Equal to or greater than 20 years but less than 25 years $0.69Equal to or greater than 25 years but less than 30 years $0.6830 years or greater Estimated Levelized Recourse Rates ($/Dth/d)

7. 5. Competitive Option For PNW, Northern California and Northern Nevada Consumers Diversification: Replace high dependence on Canadian imports with access to Rockies production Reliability: As Canadian Supply declines, supply into western markets becomes the marginal market for Canadian producers Transport capacity to the PNW from Rockies currently at maximum utilization High efficiency transportation reduces fuel costs Access to storage at Jackson Prairie (22 Bcf capacity) and Mist (14 Bcf capacity) 7

8. 5. Sunstone Offers Rockies Producers Valuable Market Access 8

9. 5. Valuable Access For Rockies Producers Sunstone features: Highest netback out of the Rockies –Lower cost to access Malin Of the two-thirds capacity already committed, 376 MMcfd represents long-term subscription from end- users, reducing producer commitment to launch project Lowest reservation charge, minimizes risk and financial commitment Term differentiated rate options without huge disparity among shippers maintains competitiveness for ALL shippers 9

10. 5. Valuable Access For Rockies Producers (continued) Sunstone provides access to multiple markets and end-use meters: From Stanfield through interconnects with Northwest Pipeline and GTN Increase in electric generation loads fueling market growth –Electric generation loads counter-seasonal to California generation loads Downstream expansions proposed to serve PNW market growth No expansion required on GTN to serve Northern California and Northern Nevada –Currently 329 MDth/d available –GTN motivated to retain and expand customer base 10

11. Sunstone Provides Access To Target Markets Sunstone provides access to the broadest market –3.3 Bcfd currently flows into PNW area from the Rockies and Canada –Of which, 1.4 Bcfd flows into Northern CA and Northern NV via Malin 0.8 Bcfd expected growth in PNW and CA for 2008-2018 (Wood Mackenzie) 11 Source: Lippman Consulting, average deliveries, January, 2007 – May, 2008

12. Existing & Proposed PNW Gas-Fired Generation 12 3.5 Gw of existing facilities served by NW Pipeline 2.9 Gw of existing facilities directly connected to GTN 3.2 Gw of new gas generation proposed

13. Major End-Use Markets Served by Northwest Pipeline & GTN Northwest Pipeline Washington Puget Sound Energy Cascade Natural Gas Avista Corp PacificCorp (Chehalis Power) Oregon Northwest Natural Portland General Electric Avista Corp Cascade Natural Gas Idaho Intermountain Gas Idaho Power Nevada Southwest Gas Sierra Pacific GTN Washington Avista Corp Cascade Natural Gas Oregon Avista Corp PPM (Klamath Falls) Cascade Natural Gas Hermiston Power Portland General Electric Nevada Sierra Pacific California PG&E Sacramento Municipal Utility District Southern California Gas/SDG&E Conoco Phillips 13

14. 5. NW Region – Key to a Viable Project 14

15. 6. Project Progress On Track Route is essentially fixed, with formal approval process for small reroutes Survey progress: –Wetland surveys complete by year end –Cultural surveys complete by year end –Paleontology surveys complete by year end –Survey permission received from 82% of landowners Meetings with regulatory agencies continue to go well –Successful FERC pre-filing meeting on October 7 –Formal request for pre-filing scheduled for October 21 Seven open houses scheduled for mid-November 15

16. 7. Schedule Conducted Open Season: March 17 – May 30, 2008 Perform Biological and Cultural Surveys: Summer/Fall 2008 NEPA Pre-Filing Request with FERC: October 2008 Place Pipe and Materials Order: No later than May 2009 FERC filing: Q2 2009 FERC Certificate: Q2 2010 Construction Start: Summer 2010 In-Service Date: November 1, 2011 16

17. These Economic Times… Three financially sound partners able to execute on construction of a large pipeline project The silver lining: –Economic slowdown means pipe and construction costs may drop before partners need to commit to these costs –For every drop of $100 per ton of steel, project saves $40 million

18. Sunstone Mantras Existing corridor Fewer miles Realistic cost Market diversity and size Lowest cost transportation 18