Williston, N.D. (AP) Thirty post offices in North Dakota's oil country that were scheduled to have their workdays reduced will maintain their hours of operation. The U.S. Postal Service this week formally agreed to not disrupt service at the 30 locations in the growing region. Officials in North Dakota have been pushing the postal service for months to improve service in the western part of the state, which is bustling with oil activity. U.S. Sen. Heidi Heitkamp has launched an initiative aimed at improving the state's postal woes. Heitkamp says she'll be closely monitoring that the postal service doesn't reverse its latest decision. U.S. Sen. John Hoeven earlier this year announced that the postal service will grant pay increases and bonuses to recruit and retain mail carriers in that region of the state.