A group of about 30 civilians traveled through the large metal gates barricading TVA's Raccoon Mountain Pumped-Storage Facility. White passenger vans descended a short, man-made tunnel into the mouth of the mountain as anxious families looked onward toward the plant that supplies power to more than a million homes.
Most were happy to be out of the day's rain, but workers in the hyrdoelectric plant had a different perspective.
"We like rain in the hydro business," joked plant manager Thomas Gamble. "It's a refueling time for us."
The gates closed slowly behind, and with that, the group was beginning its tour. It was one of the first since the utility company closed all its dams and facilities to the public shortly after 9/11 due to safety concerns.
"It's just a phenomenal facility," Knoxville resident Robert Cole said. "With it being closed up, this was a very rare opportunity."
Cole was a TVA employee at the Watts Bar Nuclear Plant until 2013. He jumped on the opportunity when the company announced it was opening for a trial run of public tours. He loaded a van full of family members - three of whom are civil engineers - and traveled to the facility to give them a behind-the-scenes look at how power is produced in the Tennessee Valley.
Inside, the mountain opened to unveil much of the operation. Under the lake atop the mountain, inside its rock walls, a room longer than a football field and more than 100 feet high housed purple, green and red machines, reminding visitors of a not-so-long-ago era when bright colors dominated interior design. The color scheme may have other purposes, though, Gamble said. He's heard several theories. The bright colors help with depth-perception from the overlook, providing engineers a better look at where exactly problems may be occurring. They also may just help enhance the mood, standing out in a sea of shades of grey.
"Choose whichever theory you'd like," he said.
In the middle of the room, the heart of the operation churns. Four green generators revolve, producing 410 megawatts each.
After the dams were built in the 1970s, thousands of visitors toured TVA facilities annually. At Raccoon Mountain, guests would start atop the mountain at the visitor's center and descend more than 30 stories to overlook the operation. It was something that continued until 9/11, TVA historian Pat Ezzell said.
However, after the terrorist attacks, power and water facilities across the U.S. were closed to the public and underwent extra security measures. TVA personnel wanted to reintroduce the tours, but it would take time and approval. In 2016, the TVA dams were added to the National Register of Historic Places ahead of the 85th anniversary of the TVA act, and a plan to reintroduce the tours was implemented. The team comprised a more secure way to open the facility and announced a pilot program in May.
The program opened several TVA dams - Chickamauga, Wilson, Norris, Kentucky and Guntersville - along with the Raccoon Mountain hydro facility to four tours each. Within a week, the tours were booked and hundreds remained on waiting lists.
"This year, it's been great," Ezzell said. "[The tour] is very similar to what they would have gotten if they visited before."
The major difference is heightened security. Guests are no longer allowed to hop on an elevator and walk right out to the generators. They are approved weeks and months in advance. Tour spots are limited, and each guest undergoes a background check and search upon arrival. A quick briefing starts the tour at the bottom of the mountain, where guests are then given safety equipment and shuttled through the gate at the bottom of the facility.
TVA personnel plan to meet before the end of the year to decide if they will fully reintroduce the tours. Guests were asked to give feedback and took exit surveys.
"We'll all get together and debrief and make a decision," Ezzell said. "And hopefully, well, we'll have to see."
Contact staff writer Mark Pace at mpace@timesfreepress.com or 423-757-6659. Follow him on Twitter @themarkpace and on Facebook at ChattanoogaOutdoorsTFP.