BOISE, Idaho (AP) — Low natural gas prices brought on by a glut in the resource are prompting Intermountain Gas Co. to propose a total 7.1 percent rate reduction for customers in Idaho.  The Idaho Public Utilities Commission says it will take public comment on the proposal through Sept. 20. A production boom has created a surplus of natural gas, driving down prices. Customers all over the U.S. are benefiting with reduced heating bills Intermountain proposes to reduce the rates of residential customers who use natural gas for both water and space heating by 3.1 percent, or about $1.51 per month, effective Oct. 1. In addition, Intermountain proposes to grant a one-time credit of $3.7 million to customers in December as a result of credits that accrued before a previous price adjustment in February.