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Supplemental Information PGA Summaries: South Dakota Navigator PGA Summaries: 2008 | 2007 | 2006 Purchased Gas Adjustments During 2007 (per therm) Northern Natural Gas Company Revision No. Effective Date Clause 1 Clause 3* Small, Medium & Large Volume Firm Small & Large Volume Interruptible 134th Rev. Sh. No. 3   1/07/07 .82066 .00000 135th Rev. Sh. No. 3   2/07/07 .89644 .00000 136th Rev. Sh. No. 3   3/07/07 .92448 .00000 137th Rev. Sh. No. 3   4/07/07 .76718 .00000 138th Rev. Sh. No. 3   5/07/07 .73808 .00000 139th Rev. Sh. No. 3   6/07/07 .72622 .00000 140th Rev. Sh. No. 3   7/07/07 .62159 .00000 141st Rev. Sh. No. 3   8/07/07 .49926 .00000 142nd Rev. Sh. No. 3   9/07/07 .56988 .00000 143rd Rev. Sh. No. 3 10/07/07 .65500 .00000 144th Rev. Sh. No. 3 11/07/07 .77260 .00000 145th Rev. Sh. No. 3 12/07/07 .81802 .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.