Engineers will be literally hanging around the Gateway Arch this week examining stains on the monument’s stainless steel exterior surface.
The engineers plan to descend from the hatch at the top of the 630-foot-tall Arch and use a rope system to descend down the north leg to an area about 425 feet above the ground where they will collect samples that could help determine the best way to clean the monument.
Weather permitting, the engineers hope to begin their work Tuesday, said Steve Kelley of Wiss Janney Elstner Associates, a Chicago firm that specializes in providing exterior assessments for monuments.
He noted that the Arch job is particularly dangerous, even for his crew that is experienced in such work.
“Everybody is trained to do this type of work. We’ve done it on other monuments like the Washington Monument. We did the Oklahoma state capitol two weeks ago,’’ Kelley said. “But this is a unique monument because of its profile and shape. There’s nothing straight up or down about it, and so we’re going to have to be very careful.’’
The engineers will use suction cups to hold themselves in place while they do their work. Spotters on the ground will direct them, using walkie-talkies.
Weather will be a major factor, Kelley said.
“We’re worried about rain, lightning and wind. We actually have a command center set up on site, and we have a weather station where we’re watching all those parameters very closely,’’ he said.
The Arch will remain open during the project, though there will be some restricted areas on the observation deck and on the park grounds, according to Ann Honious, public information officer for the Jefferson National Expansion Memorial. Visitors will use the entrance to the south leg. The park service will have an information table and provide binoculars so visitors can watch the engineers at work.
This is the third phase of a condition assessment of the Arch that began in 2005, Honious said.
“Through the previous phases we have documented that the Arch is structurally sound,’’ she noted.
The previous studies have indicated that some of the stains were probably the result of the building process and industrial pollution, while those at ground level were caused by the use of de-icing salts -- and visitors who scratched the stainless steel surface.
Kelley said that even though the structure of the Arch is sound, this study isn’t about “cosmetic” concerns.
“I don’t like to use the term ‘just cosmetic’ because we’re really concerned about the durability of the monument, and we haven’t been able to see all of the stains,’’ he said.
The stain samples will be studied to determine the best way to remove them; those findings will not be completed this week.
Estimates for this phase is estimated at about $340,000. The funds are coming from the Bi-State Development Agency, World Monuments Fund and the Kemper Fund for Missouri and Kansas of the National Trust For Historic Preservation.
