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Supplemental Information PGA Summaries: South Dakota Navigator PGA Summaries: 2008 | 2007 | 2006 Purchased Gas Adjustments During 2006 (per therm) Northern Natural Gas Company Revision No. Effective Date Clause 1 Clause 3* Small, Medium & Large Volume Firm Small & Large Volume Interruptible 122nd Rev. Sh. No. 3   1/07/06 1.07153 1.04688 123rd Rev. Sh. No. 3   2/07/06 1.04803   .99662 124th Rev. Sh. No. 3   3/07/06  .88612   .00000 125th Rev. Sh. No. 3   4/07/06  .75008   .00000 126th Rev. Sh. No. 3   5/07/06  .65454   .00000 127th Rev. Sh. No. 3   6/07/06  .53915   .00000 128th Rev. Sh. No. 3   7/07/06  .54365   .00000 129th Rev. Sh. No. 3   8/07/06  .61507   .00000 130th Rev. Sh. No. 3   9/07/06  .68793   .00000 131st Rev. Sh. No. 3 10/07/06  .50160   .00000 132nd Rev. Sh. No. 3 11/07/06  .85000   .00000 133rd Rev. Sh. No. 3 12/07/06  .84281   .00000 * Effective March 1, 2006, Interruptible PGA Clause 3 has been replaced with daily market gas prices. The daily market gas price will be applied to customers’ daily consumption. Daily market prices for the previous month are posted on the Rates section on the Internet under Supplemental Information – Gas: Interruptible Commodity Prices. Navigator PGA Summaries: 2008 | 2007 | 2006 For Your Home | For Your Business | Safety | Rates | Energy Efficiency | Economic Development | Environmental Efforts About Us | Careers | News Room | Storm Center | Wind Energy | Contact | Streetlight Repair Request | System Outage Watch | Energy Choice | For Contractors | For Landlords | ©2008 MidAmerican Energy Holdings Company. All rights reserved.