MYRTLE CREEK — Residents will begin paying higher water rates next month to help pay for a new $7.2 million water treatment plant and an upgraded river intake port. Water rates will go up $5 a month, the first of four annual increases that after four years will add $20 to the $32 monthly fee residents now pay. The City Council approved the increase Tuesday, at the same time it awarded the construction contract for the new plant to R&G Excavating of Scio. Construction is expected to take 15 months. “An analysis showed our water rates were too low to …