The drive to East Oahu is the pits.

Or, rather, a massive pit — singular — continues to snarl the eastbound afternoon commute. And will do so for days.

A water main break on Kalanianaole Highway on Saturday is proving be a particularly pesky project.

Board of Water Supply crews typically use backhoes to reach broken water mains. But this one required workers to bring in excavators to dig deep enough to reach the ruptured transmission line, resulting in a massive hole in one of Oahu’s most heavily used routes.

The Honolulu Board of Water Supply said it hopes to have repairs completed by Thursday on the 24-inch line between Kilauea Avenue and Waikui Street.

“But we’re working very hard to try to accomplish that even earlier,” said Ernest Lau, manager and chief engineer at the Board of Water Supply, at an early morning news conference at the site. “Unfortunately, (the transmission line) broke probably over the worst place it could break.”

By Monday morning crews had excavated a gaping trench about 40 feet long and 15 feet wide.

The city initiated a traffic mitigation plan for the estimated 11,700 vehicles that travel through the area at the peak of weekday afternoon traffic, according to the state Department of Transportation.

After the rupture early Saturday, all eastbound lanes were closed, causing major gridlock. At about 11 p.m. Saturday, one eastbound lane was opened.

By Monday afternoon two coned, narrow eastbound lanes were open to motorists to help relieve congestion.

To maximize traffic flow, the city said, motorists will not be allowed to make a left turn onto Ainakoa Avenue from the eastbound lanes of the highway, and no right turns onto Waikui Street are allowed. Motorists can make a right turn on Waieli Street to access Waikui Street.

The Department of Transportation Services will also manage traffic lights and make necessary adjustments.

“These things happen,” Lau said. “Pipes do break. We’d like them not to break, but they’re sometimes not very cooperative. And things like corrosion, settlement, corrosive soils can cause pipe breaks. It’s really hard to predict, but we’re doing the best we can to get this repair done quickly.”

He added, “This water main break is a difficult one to repair.”

Not only is the pipe 20 feet down, but also there is an abandoned line “almost directly on top of the line that was leaking,” Lau said. “We had to dig even deeper to get to it.”

The cast-iron pipe was installed in 1969. The broken section, 20 feet long, will be replaced with ductile iron pipe, which is as strong as cast iron but lighter.

“When we start doing the work, we’ll see if we have to go and replace more,” he said.

Contractors lowered shoring equipment inside the excavation site to allow crews to clear the dirt around the broken main. Once the broken section is removed, Lau said they will inspect it to determine the cause of the rupture.

“Sometimes we find corrosion causes a smaller leak that over time can grow, and once it gets big enough, it may cause a pipe to fail and blow out,” he said.

The transmission line, encircled in a “concrete jacket,” runs underneath the stream near the highway.

The Board of Water Supply provided a water wagon to 11 customers who were directly affected by the broken line. Lau said other customers in East Honolulu were unaffected by the broken main because another water main, which runs from Diamond Head, provides water to the community.

One of the water sources that runs through the broken transmission line comes from the Keanu Street line booster in Palolo.

The state, meanwhile, temporarily suspended road projects on Kalanianaole Highway in Waimanalo until repairs are completed, allowing for a smoother alternate route to East Honolulu.