Repair work on a deteriorating 87-year-old bridge along the only route around Oahu’s North Shore is slated to get underway on Monday.

Construction crews will close one lane to traffic, from 8 a.m. to 3 p.m. daily, at Paumalu Stream Bridge, situated between Paumalu Place and Ke Nui Road, near Sunset Beach on Kamehameha Highway. Lane closures will alternate between the inbound and outbound lane, depending on the construction schedule. The remaining lane will be contraflowed to maintain access over the bridge.

To expedite the repairs, DOT is also proposing work during nights and holidays. Lane closure hours may change depending on construction efforts.

In March, the state Department of Transportation began limiting travel across the bridge to vehicles weighing under 15 tons after discovering cracks in some of the bridge’s concrete support pillars.

The restriction was modified in early April then reset at the 15-ton limit in late April.

While overweight trucks and buses are being turned away, officials are permitting school and city buses as well as emergency vehicles responding to calls to cross the bridge.

“We are inspecting the bridge every day to monitor conditions to make sure deterioration doesn’t get worse, and to see what we can allow,” said DOT spokesman Tim Sakahara.

Even so, he said, “Everyone is safe.”

“The structure itself is safe. We just want to prevent additional damage.”

The DOT is “not putting new pillars on the ground at all,” Sakahara said. Instead, crews will construct concrete collars around some columns and install components around the current structure to support the existing bridge deck and columns, he said. Most of the repair work is expected to wrap up by late July.

Built in 1929, the bridge last had concrete supports reinforced in 2014.

Over the decades, stream flow — especially waters rocked by winter’s high surf — has contributed to the deterioration of the bridge’s pillars.

“I think the high surf might have accelerated the damage,” Sakahara said.

The Transportation Department plans to lift the weight restriction and restore the limit to its original 25 tons in the coming weeks.

The current restriction has affected residents, visitors and businesses.

For example, some tour bus companies are opting to use smaller buses, Sakahara said. Delivery trucks and various other commercial companies are making adjustments by not carrying full loads or by breaking up routes, he said.

In that case, “one driver will be on the Haleiwa side, and another driver will work the Kahuku side of the bridge,” he said.

Some North Shore sewage pumping companies have turned down jobs in certain areas and bumped up their rates to accommodate longer drive times.

“It’s a huge inconvenience,” said Rebecca Gonzales, co-owner of Gecko Enterprises, whose services include pumping septic tanks and cesspools. “It has more than doubled the time (to drive alternate routes), and it’s more expensive, fuel-wise.”

The Waialua-based company has suspended service to Kahuku, farther north and beyond the bridge.

“It’s unfortunate because it has to be done,” she said of the bridge repair. “We have to take care of our infrastructure.”

In early April the DOT attempted to “accommodate the community,” Sakahara said, by allowing vehicles weighing between 15 and 25 tons to traverse the bridge one at a time. Once fully off the bridge, another heavy vehicle was allowed to get on.

“It’s tough to say if we were getting full compliance,” he said, since monitoring at that time was less vigilant than it is now. Restrictions are now enforced from 6 a.m. to 6 p.m.