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SAN ANTONIO -- After nearly three centuries, even the walls of history can use an occasional power wash.
That's among the many treatments the Espada Aqueduct is getting in a monthslong restoration and drainage project overseen by the National Parks Service. It includes repairing severe cracks and holes in the aqueduct walls, plus rerouting water to reduce erosion.
But although the aqueduct is a National Historic Landmark, you might be asking yourself two questions:
San Antonio has an aqueduct?
What exactly is an aqueduct?
You're not alone in wondering.
"We can't tell what it is," conceded tourist Julius Volgyi of Richmond, Va., who stopped with his wife, Maureen, to check out the limestone structure one sunny afternoon recently while on a break from their tour of the San Antonio Missions National Historical Park.
Though it's about a quarter-mile from the closest mission, the aqueduct was a crucial part of the settlers' survival in the mid-1700s, said Al R. Remley, the park's chief of interpretation.
Then as now, it carried water across Piedras Creek via the Espada acequia, a drainage and irrigation system constructed by the Spanish.
The acequia is the oldest one of its kind in the United States that has been used continuously since it was built in the 1730s or '40s. The system runs about four miles, from the Espada Dam all the way past Mission Espada.
"The acequia systems were really the lifeblood of the missions," said David Vekasy, the park's service facility manager.
Its design would be considered ingenious in nearly any time period, National Parks experts agree. What's even more remarkable is that the Espada acequia and aqueduct still work, and landowners still use the system to irrigate their properties.
"It's perfect frontier technology," Remley said.
But even brilliantly designed structures need a tuneup, not to mention a face lift: In several spots, black graffiti swirls line the aqueduct's interior walls.
Although the parks service cleans the channel each year, it rarely gets the chance to do such a large-scale preservation project. The price tag will be about $230,000, paid for by National Parks Service repair and rehabilitation funds, Vekasy said.
In the project's first phase, which began this month, workers drained the aqueduct and cleaned out its channels using a power washer.
They also cut back overgrown vegetation to inspect erosion damage to the south wall, caused by water that flows out from a drainage spillway. And they rebuilt the spillway, then lined the ground around the wall with limestone cobble, which later will be covered with topsoil.
Workers now are removing damaged mortar that has developed cracks and holes in the aqueduct's interior walls and floor, a process called repointing.
"It's fascinating to me how long it's been here, and that they were smart enough to do it," said Larry "Dean" Ferguson, one of two masons at the missions.
From afar, one could mistake the aqueduct for a stone bridge hidden beneath a lush canopy of trees.
A giant tunnel cuts through it, allowing Piedras Creek to flow through to the San Antonio River. Above, the aqueduct's top is hollowed into a cement channel that carries acequia water downstream.
Inside this hollow is where Ferguson and two apprentice masons, part of the American Youthworks volunteer organization, were busy this week chipping around fissures.
Tiny bits of Portland lime cement flaked off the stone as they chiseled around the cracks. The workers will refill the space with new mortar, followed by one last, thin coat of water-resistant cement. That could be finished in the next couple of weeks.
Later, a contractor will repoint the aqueduct's exterior walls.
The project's third phase involves correcting several drainage problems along the aqueduct's route, caused by a change in the grade of the land. That effort probably won't begin until next year, Vekasy said.
The key is to address these problems now, before more leaks and erosion creep up on the structure. Water has been flowing through the aqueduct and the acequias system for more than 260 years; why let it stop now?
"History is still made on a daily basis," Remley said. "If the acequia dries up, the farming is going to stop."
