Six more columns on the new Highway 520 floating bridge are defective, but contractors will replace them at no cost to taxpayers, a state manager said.

Julie Meredith, program director for the six-lane crossing now under construction, disclosed the findings Wednesday while briefing state legislators, in Seattle.

These columns are attached to the top of Pontoon W, the giant east end piece. One column was already broken and rebuilt in December after the concrete surrounding a steel reinforcing cage was found to be thinner than the required 1½ inches.

The state learned this spring that six more were deficient but didn’t say so publicly. Then on Friday, contractors from the Kiewit-General-Manson team said they would rebuild the columns rather than brace them, Meredith said. The piece is now moored in the Duwamish River. Column replacement will occur either there or on Lake Washington in the next four to six weeks, she said.

The other three of 10 columns were built correctly, she said.

Meanwhile, cracks in Pontoon W were sealed this summer, Meredith said. The state Department of Transportation is negotiating to reduce a potential $378 million cost that includes pontoon fixes and redesign, contract changes both on the water segment and on land for the Eastside segment of Highway 520 on land, and various delays within the $4.1 billion highway replacement. The floating bridge is now expected to open in April 2016, more than a year later than originally hoped.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com. On Twitter @mikelindblom