Lake Oswego residents will see their water rates increase once again this summer so the city can pay to build a larger and upgraded water system.

The Lake Oswego City Council voted 6-1 on Tuesday to increase rates by nearly 13 percent, meaning the typical household will pay about $5.29 more for water each month come July.

As in years past, the increase helps cover the city's $118 million share of the new water system that will be shared by Lake Oswego and Tigard and is estimated to cost a total of $252 million. Construction for the project -- both cities largest and most expensive one yet -- is set to start this summer following five years of planning.

Both cities will have to make their biggest cash investments in the project next fiscal year. Lake Oswego will issue a $101 million bond that it will pay off over the next 25 years to cover its share.

To make the annual payments, city officials say a 12.5 percent increase in rates is needed for the next three years. It would increase by 5 percent and eventually 3 percent after that.

Councilor Karen Bowerman voted against the rate increase, saying she thought there had been too much fluctuation in project costs to accurately estimate how much rates should increase.

The council voted Tuesday to amend a contract with the company designing the upgraded water treatment in West Linn that's part of the project, since it owed it about $460,000 more than was originally expected after the design of the plant had to be revised in order to get the necessary permits from West Linn.

The city council also voted Tuesday to raise rates for waste water, storm water and street maintenance services by smaller margins than water rates. In total, the typical household will pay $8.02 more per month in utilities than it currently does with the four rate increases.

Since the city bills residents every two months for utilities, the average household’s bill will go from $242.44 to $258.48 starting July 1.

-- Victoria Edwards