Though Congress has paid out about $13 million in settlements over the past 13 years, a large chunk has gone to Architect of the Capitol employees — and not to House or Senate staffers.

From 1997 to 2007, the AOC paid about $6.1 million in settlements to its employees, according to budget documents. That’s about 80 percent of the settlement total for the entire legislative branch during the same period, which was about $7.5 million. The Capitol Police comes in as a distant second, paying almost $880,000 in settlements to its employees.

In comparison, House and Senate employees netted about $328,000, or a little more than 4 percent. That includes not only staffers but also employees for offices such as the Chief Administrative Officer. The Office of Compliance — which handles the settlements and only has about 20 employees — paid out about $174,000.

Details on the payouts are slim, since both parties often sign confidentiality agreements. But a significant portion of the AOC settlement total went to a case involving tunnel workers in 2007, according to several sources.

AOC spokeswoman Eva Malecki declined to comment on the AOC’s high settlement payout, citing confidentiality agreements with “all parties involved.” But the tunnel workers’ case helps shed some light on the issues that can lead to such settlements.

In 2007, 10 “tunnel rats” publicized their concerns with the Capitol’s asbestos-filled utility tunnels. Nine had discovered scarring on their lungs, and several had worked for Congress for years.

Their comments fueled months of hearings and outrage on the Hill, resulting in the AOC signing an agreement that they would rid the tunnels of asbestos by 2012. But the tunnel workers were also somewhat out of luck: Federal law prohibits employees from suing the government for injuries or illness. Instead, they had to sue for retaliation under whistle-blower laws.

The AOC paid an unknown settlement in 2007, and at least eight of the 10 employees no longer work for the AOC. But settlements for retaliation and discrimination are usually far lower than those for injuries, and the workers now worry about how they will pay for a lifetime of medical bills.

Meanwhile, the AOC still grapples with 6,300 safety hazards, 25 percent of which are rated as “high risk” to employees and visitors, according to the OOC’s recent annual report. On Wednesday, Speaker Nancy Pelosi (D-Calif.) asked the AOC to submit a report on the steps taken to abate the hazards, expressing concern “that any that are determined to be serious safety risks be addressed without delay.”

But House and Senate appropriators have kept a close watch on the hazards — and the money appropriated to them — for the past several years. Each year, Architect Stephen Ayers presents Members with a list prioritizing every abatement, in an effort to get a larger budget from an appropriations bill notorious for being short on funds.

Rep. Debbie Wasserman Schultz (D-Fla.) — who chairs the House Appropriations Subcommittee on the Legislative Branch ­— has “prioritized the health and safety of legislative branch employees, so that they won’t need to go to court to have a safe workplace environment,” spokesman Jonathan Beeton said.

“Employers need to take responsibility for the health and safety of their employees,” he said, “and legislative branch agencies are no exception.”