The final price tag for renovations at the Cannon House Office Building, already potentially more than $100 million over budget, remains unknown as the project attempts to meet its scheduled 2024 completion date, the acting Architect of the Capitol told the House Administration Committee on Tuesday.

New mitigation efforts after hazardous materials were found in the building would require more money from Congress, and the project may need to combine phases, push deadlines and move additional offices out of the building for a longer period of time, acting Architect of the Capitol Thomas Carroll III said.

Phase 1, which was expected to be completed in November 2018, still has outstanding items on a “punch list” that need to be addressed.

“We are down to approximately 200 items with under 10 of those ‘punch list’ items being associated with member offices,” said Carroll, adding that most of those will be completed by the end of this month.

Despite the hurdles, Laura Condeluci, a spokesperson for Architect of the Capitol, said in an emailed statement that the project is on track to be delivered on time. “Based on what we currently know, the project continues to be on schedule,” she wrote.

The Architect of the Capitol reported in June that it expected the project’s cost to increase by 10 percent to 15 percent to about $828 million to $866 million, compared with its initial estimate of $753 million, Terrell Dorn, managing director for infrastructure operations at the Government Accountability Office, noted in his written testimony.

But two new reports are forthcoming on the expected cost, and Carroll didn’t say whether those could exceed the June figures. “Until the risk analysis is complete and the final report is issued, we must refrain from making cost assumptions on future funding needs,” he said.

A number of modifications, about 54 percent of which were requested by the Architect of the Capitol, in Phase 0 and Phase 1 drove the cost of the project up, said Christopher Failla, the Architect’s inspector general.

Written testimony from Brian Abt, who oversees the Cannon Renewal Project for Clark Construction Group, also indicated that requests from the Architect of the Capitol to alter original design plans delayed the project.

One example, Abt wrote, happened when the Architect of the Capitol decided to implement a hot-food service vendor instead of the original plan to accommodate limited service and prepackaged foods, which required the abatement of hazardous materials and the installation of additional food service equipment. Abt also pointed to an instance in which the Architect of the Capitol requested changes for the Budget Committee and Homeland Security Committee rooms, which required new infrastructure and work around hazardous material in plaster walls.

Rep. Barry Loudermilk, R-Ga., who said he grew up in a construction family, described change orders as a “way of life” in any construction project, adding that he was “sympathetic” to them.

Chairperson Zoe Lofgren of California asked Carroll about whether the unforeseen conditions, such as the presence of polychlorinated biphenyls (PCBs), are built into the plan going forward to avoid more change orders.

Carroll said Phase 1 provided them with the ability to better understand where these contaminants are and in what amount.

“We can reasonably infer that some of those patterns will replicate in the future phases,” Carroll said.

Marcel Goldstein, a spokesperson for Clark Construction Group, said once work began, PCBs were discovered in the caulk of the exterior masonry of Cannon.

“We understood that, in working on a 110-year-old building, we might encounter hazardous materials; however, the scope and type could only be known upon beginning work on the building,” he wrote.

The Environmental Protection Agency’s peer-reviewed cancer reassessment concluded PCBs are probable human carcinogens, according to the agency’s website.

PCBs are not the only dangerous materials discovered during the renovation.

A Government Accountability Office report released Tuesday notes that the Architect of the Capitol found “unforeseen conditions that led to more extensive exterior stone restoration than anticipated and the unplanned mitigation of asbestos in roof materials.”

Asbestos exposure is associated with adverse health effects, including lung cancer, according to the EPA’s website.

The Architect of the Capitol did not respond to emailed questions about the hazardous materials.