Montana-Dakota is proposing a 6.6 percent overall rate increase, but residential customers face a 9.9 percent hike.

BISMARCK, N.D. (AP) — Senior citizens are intervening in the Montana-Dakota Utilities proposed rate increase.

The American Association of Retired Persons says of the 80,000 residential customers served by the utility company in North Dakota, 61 percent are seniors who rely on Social Security for half or more of their income. AARP says a third live only on Social Security.

The Williston Herald reports Montana-Dakota is proposing a 6.6 percent overall rate increase, but residential customers face a 9.9 percent hike. The proposal would raise fixed costs to nearly $20.

The AARP's filing to intervene gives it elevated status so members will be able to question the company directly during hearings and will receive filings along with Public Service Commission.