Climate Change and Seattle City Light Operations Wing Cheng and Ron Tressler Seattle City Light September 16, 2009

Presentation Outline Background on Seattle City Light Climatic Effects on Hydrology and Operations Potential Impacts –Power Generation –Power Delivery –Power Management –Asset Management Moving Forward

Seattle City Light Facts Municipal Electric Utility 376,000 customers About 90% hydro Skagit River – 711 MW capacity Boundary (Pend Oreille River) – 1,047 MW capacity Carbon Neutral for last 5 years Skagit is certified Low Impact Hydro

Power Resources SourceAverage Megawatts (2007) 5 SCL-owned Hydroelectric Projects Skagit, Boundary, Newhalem, Cedar Falls, Tolt 745 Power Purchase Contracts with Federal Bonneville Power Administration (BPA) 682 Contract with BC Hydro (Canadian) - International Treaty 38 Contracts with other Utilities in Washington, California and Idaho 34 Wind and Small Biomass Plant Contracts 44 TOTAL1,543

Canada United States Ross Dam

Climate Change in the PNW Temperatures: 1.5°F  (1920 and 2003) Precipitation: 14%  ( ) April 1 SWE: 25%  in Washington Cascades Runoff Timing: Shifted 0-20 Days Earlier Following Charts Shows Climate Change in the Skagit Watershed as observed by SCL Source: CIG website

Note: More than 1 Deg. F increase in January, February and July

Note: An annual decrease of about 1/3 inch

Climate Change Impacts Detected Reduced spring-summer inflow PDO Positive PDO Negative No official PDO Classification

An 14.5% annual reduction and an 18.2% May-July reduction.

Note: Trends of runoffs shifting to earlier starts and ends

Power Generation Skagit Project Managed for “Fish First” –All Pacific salmonid species –Listed Chinook salmon, steelhead, and bull trout Intricate annual flow management planning with monthly updates –Protect salmonids during spawning and fry development –Meet Corps flood control mandates and recreation pool elevations in Ross Lake

Power Generation Model Skagit Hydrology based on the following: –3Tier’s DHVSM Water Years –Temperature +2.7 o F by 2020 and +4.1 o F by 2040 over –Precipitation Unchanged Output is Reservoir Inflow Optimize Ross Reservoir Outflow based on Inflow Data

More power will be generated during winter and less during spring and summer

Skagit River Fisheries High-flow events scouring redds and rearing habitat Thermal barriers during low flows Increased frequency of extreme events

SCL Owned Generation Only – BPA and Other Power Contracts not Included, e.g. in 2007, SCL Generated 48.3% and Purchased 42.3% from BPA Power Management Power Exchange with California Peak Load in winter (California Summer) Surplus Power in Summer (California Winter)

Power Management….. continued California Load-Resource Change Currently Lacking for Understanding SCL Load-Resource Change Slight Load Decrease in Winter and Increase in Summer SCL Adaptation Strategies Explore Exchange with Other Regions Expand Sales and Purchases in Spot Market Develop Prudent Hedging Strategies Improve System Load Forecast

Cooling Load on 07/29/09 Heat Wave

2020 Hourly Peak Load = MW Hours Peak Load = 2175 MW Uncertainty in System Load Modeling

Power Delivery Transmission/Distribution Line Rating + 5 o F on 1000’ span = 2’’ more Sag Not Significant Now; but Could be at + 10 o F Transformer Thermal Rating Aging Acceleration Factor = 1 with Hottest Spot at 110 o F Insulation Deterioration Rate Doubles every 7 o F Increase Water Spray Now Required During Very Hot Days De-rate or Replace with Increasing Hot Days?

Healey Fire Protection – Outdoor Transformer Protection with Water Spray System

Slide 13 Heavy Glacial Runoff Downstream Asset Management Normal Period for Plant Maintenance Possible Loss of a Month

Asset Management …..continued Decision on Capital Investments Example of Gorge Second Tunnel Three 30-MW Units Completed in 1929 A 4 th 67-MW Unit Added in 1951 One 20.5’ Diameter, Feet Long Tunnel Tunnel Loss at Full Capacity about 60 Feet or 34 MW

New 18 Feet Diameter Tunnel to Supply Water to the Large Unit Only Recover Slightly More Than Half of Tunnel Loss at Full Capacity Annual Reduction in Tunnel Loss Enough to Power over 7000 Households

Climate Change May Favor this Project but What About Others?

Moving Forward Expand Conservation Program (12 aMW in 2009) Purchase power to meet I- 937 renewable energy portfolio requirement Adapt hydroelectric project operations to changing conditions (cannot solely use historical data)

Research and Next Steps Improve River Flow Forecasting Track Frequency and Timing of Floods Need Improved Downscaling of Global Climate Models – Dynamic and Statistical Methods Gain Additional Understanding of Glacier Melting Patterns Continue to Monitor Impacts on Fisheries