WASHINGTON — William Koch says he sent flowers to his wife’s grave at Arlington National Cemetery for several years before learning she was not there — buried instead at the site next to it.

“Over almost five years, I sent flowers… I sent wreaths at Christmas,” he said. “I even took her mother up there so she could see her daughter’s grave site, and all she saw was a headstone and an empty grave.”

The retired Air Force colonel, who lives in Raleigh, N.C., spoke Thursday at a Capitol Hill hearing on the progress being made since an investigation revealed a mix-up of graves at the nation’s premier military resting ground.

Arlington officials said they’ve added staff and equipment, set new burial rules and tightened operations in the months since the investigators revealed the mix-ups. One lawmaker said that that’s not enough progress. A family advocacy group warned about the emotional toll taken by the most “invasive measures” the cemetery has used so far to correct the problems, such as digging up remains and DNA testing.

An Army Inspector General report in June found there were at least 211 discrepancies between burial maps and grave sites — that is, the location of some people’s remains were recorded incorrectly on some maps. Officials found cemetery operations were poorly managed, understaffed and antiquated. Employees still rely on paper records to keep track of more than two dozen interments a day and to maintain existing sites where some 300,000 troops, spouses and U.S. dignitaries have been laid to rest since 1864.