1. Building a Combined 25F Nomogram Step 0: Define Terms Safe operating area: System remains within limits following the next worst contingency, regardless of PSA generation levels. Potentially safe operating area: Depending on PSA generation, the system may not remain within limits following the next worst contingency. Unsafe operating areas: System WILL NOT remain within limits following the next worst contingency, regardless of PSA generation levels. Danger area: blind spot: Depending on PSA generation levels, a specific contingency may cause a transmission element to exceed its limits. With current tools, the System Operators may not be aware of this risk.

2. Building a Combined 25F Nomogram Step 0: Define Terms Safe operating area: System remains within limits following the next worst contingency, regardless of PSA generation levels. Potentially safe operating area: Depending on PSA generation, the system may not remain within limits following the next worst contingency. Unsafe operating areas: System WILL NOT remain within limits following the next worst contingency, regardless of PSA generation levels. Danger area: blind spot: Depending on PSA generation levels, a specific contingency may cause a transmission element to exceed its limits. With current tools, the System Operators may not be aware of this risk.

3. Building a Combined 25F Nomogram Step 1: Import South-to-North Nomogram Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot

4. Building a Combined 25F Nomogram Step 2: Evaluate the S>N Operating Areas Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot

5. Building a Combined 25F Nomogram Step 3: Import & Invert North-to-South Nomogram Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot

6. Building a Combined 25F Nomogram Step 4: Evaluate the N>S Operating Areas Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot

7. Building a Combined 25F Nomogram Step 5: Combine & identify blind spots Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot N-2: Echo Lk-Maple VL/Rocky Rch-ML contingency will overload COVINGTN TO CRESTON CKT 1

8. Building a Combined 25F Nomogram Step 6: Combine all Operating Areas Tacoma-Covington #2 230kV line O/S Winter 2007 Heavy Loads Outage: 931 Temp: 25Fahrenheit Safe operating area Potentially safe operating area Unsafe operating areas Danger area: blind spot