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Supplemental Information PGA Summaries: South Dakota Navigator PGA Summaries: 2008 | 2007 | 2006 Purchased Gas Adjustments During 2008 (per therm) Northern Natural Gas Company Revision No. Effective Date Clause 1 Clause 3* Small, Medium & Large Volume Firm Small & Large Volume Interruptible 146th Rev. Sh. No. 3   1/07/08   .84177 .00000 147th Rev. Sh. No. 3   2/07/08   .93887 .00000 148th Rev. Sh. No. 3   3/07/08 1.07785 .00000 149th Rev. Sh. No. 3   4/07/08 1.09061 .00000 150th Rev. Sh. No. 3   5/07/08 1.18897 .00000 151st Rev. Sh. No. 3   6/07/08 1.21069 .00000 152nd Rev. Sh. No. 3   7/07/08 1.23847 .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.