A six-month search that has so far uncovered 24 lead pipes in Medford's water system is almost complete and should be finished by the end of the year.

"We are nearing the end of this investigation," said Eric Johnson, interim manager of the Medford Water Commission.

Crews have looked at 4,770 meters in older east and west Medford neighborhoods and identified 305 suspect locations that predate 1946.

To date, 281 test holes have been dug near the suspect locations to determine whether there is a lead connector, known as a pigtail, that needs to be removed. So far, the test holes have revealed 24 lead pigtails, of which 22 have been replaced with copper connectors.

On Sunday, the two remaining pigtails, located on Central Avenue, will be removed.

Johnson said the objective is to finish the work by the end of the year, possibly by the second week in December.

The Water Commission has hired four temporary workers to speed up the lead pigtail search and removal.

Even with the effort so far, Johnson said, he couldn't say whether more lead pigtails might still be in the system that haven't been discovered through this investigation.

"Unfortunately we do not have Superman X-ray vision," he said. "There's no 100 percent assurance we got everything."

In the few cases where the Water Commission has tested water at houses with pigtails, it has found high lead levels. A house on Hillcrest Road tested at 2,890 parts per billion of lead Sept. 14, or 190 times higher than the federal action level of 15 parts per billion.

Water Commission crews offered to check all residences for lead where pigtails have been found, but they couldn't take reliable tests because many houses had numerous leaks. As part of the testing process, water must sit in the pipes for a minimum of six hours. Pipes located on the residence side of the meter are the homeowner's responsibility.

In other cases, customers have declined to have their water tested or didn't want follow-up tests to confirm lead levels had dropped below the federal threshold once the pigtail was removed.

The water system still has older pipes in the streets that were joined together with lead solder, though the solder is covered with oakum rope, a type of caulking that prevents it from coming in direct contact with water.

In the decades to come, Johnson said, the older lines with lead solder will be replaced as funding for large capital projects becomes available.

Johnson said the Medford Water Commission is about to undertake a corrosion study to determine whether the city's water sources leach out metals in pipelines. The Water Commission has two sources of water — Big Butte Springs and the Rogue River.

Johnson said the study, which will take a year to 18 months, will determine how the different types of water react with pipes and indicate the best way to chemically treat the water, if necessary, to reduce the leaching.

He said a pilot study will determine how the treatment affects pipes with water from the springs, from the river, as well as a mixture of both.

He said the treatment would benefit older homes that have lead fixtures that predate a 2014 federal law that requires all fixtures have very low levels of lead. With a corrosion inhibitor, less lead would leach out of older fixtures and lines.

"This will be more for the protection on the private side than the municipal side," Johnson said.

Leigh Johnson, Water Commission board chairman, said the commission has been working diligently toward the goal of identifying and removing lead pipes by the end of the year.

"They've been making such good headway, I haven't been bugging them about it recently," Johnson said.

— Reach reporter Damian Mann at 541-776-4476 or dmann@mailtribune.com. Follow him on www.twitter.com/reporterdm.