At 8 a.m. Tuesday, four engineers are scheduled to begin rappelling down the Washington Monument.

They will begin an exterior survey of the damage done to the monument by a magnitude-5.8 earthquake on Aug. 23. The monument has been closed to the public since the earthquake, which cracked the structure both inside and outside, according to Bob Vogel, superintendent of the National Mall and Memorial Parks, who spoke Monday at a news conference about the monument’s condition.

Videos from security cameras within the monument were posted Monday on the National Park Service’s website.

So far there is no timeline for reopening the monument to visitors. Vogel expects that the review of this week’s exterior survey will be completed by mid-October, giving officials a better idea of when the monument can be reopened.

“We want to be as careful as we can and make sure the monument is safe before we open it to the public. And we want to get this right,” he said.

The engineering firm Wiss, Janney, Elstner Associates Inc. will conduct the survey, which is expected to take five days. Engineers will examine the exterior for damage and remove loose material, including dislodged pieces of stone and mortar.

The Northbrook, Ill.,-based firm has already conducted an initial interior survey.

“Although they found no evidence that it has been structurally compromised, they did find a number of things that will require further review and stabilization,” Vogel said.

The National Park Service calculates the total cost to date, including this week’s exterior survey, at $207,000, and it will be able to estimate the repair costs after the exterior assessment is completed, Vogel said.

After the exterior survey, the National Park Service will begin to weatherize the open joints and cracks. The majority of the large cracks, which are about 1.25 inches wide, are located at the top of the monument. According to Vogel, daylight can be seen through the vertical joints that lost mortar during the earthquake. Water is also getting in through these and other gaps, which has led to further damage.

National Park Service officials stressed that no visitors were hurt during the earthquake. Those who were on the observation deck walked down the stairs to evacuate, according to Jennifer Talken-Spaulding, acting chief of resource management for the National Mall and Memorial Parks. The building’s elevator was damaged, but it was on the ground floor at the time of the quake. Initial repairs were made to bring it back into service, but it is running at a slower speed.

Park officials are optimistic about the assessment. “The monument is structurally sound and is not going anywhere,” Vogel said. Its builders “obviously knew what they were doing.”