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In the early 1700s, Benito Fernández de Santa Ana was passionate about his duty to settle the local native population at San Antonio’s missions. The Franciscan friar not only played an important role in the early history of the Alamo, but had charge of Nuestra Señora de la Purísima Mission Concepción from 1733-49 when construction began – sometime before 1745, according to records.
Concepción, the only mission named for a woman, was dedicated Dec. 8, 1755. Could Fernández have envisioned the missions still standing more than 250 years later? His faith, by all accounts, was very strong. But faith alone sometimes can’t overcome gravity and other natural forces, and San Antonio’s missions – a UNESCO World Heritage site – have required considerable and ongoing conservation efforts. Concepción, considered the best preserved of the five missions, has gotten off relatively easily, requiring little work other than an interior renovation in 2009.
Lately, however, Concepción has required attention. Rotted wood in its bell tower has been replaced with a new steel A frame, and a shiny, refurbished bell will ring out after two years of silence. A new HVAC system – the old one was causing interior plaster to flake – is being implemented. And, perhaps most importantly, its dome is undergoing structural reinforcement.
Over the next few months, a steel tension band – 6 inches high and 2 inches thick – will be installed around the drum that supports the dome, after slight movement in the masonry was detected. Rather than using solid stone blocks to build the drum, the original builders mixed tufa – a variety of limestone quarried on site – with mortar, and that mortar has become unstable in places.
“It’s the oldest unrestored masonry dome in the United States, and it’s the first structural work that’s being done on it,” said Anna Nau, an architectural conservator with Ford, Powell & Carson, the local architectural firm that has been doing mission work since the 1960s. The band is commonly used by structural engineers for similar work, Nau said, and a system of “stitching ties” – stainless steel rods – will be inserted into the mortar of the dome itself.
“Because tufa is a lighter material, similar to travertine, it allowed them to build higher,” she said. “The mission is not in imminent danger, but it’s something that needed to be addressed, so it will stand another 300 years.”
The dome stabilization project required intensive study, said Rebecca Simmons, executive director of Las Misiones, a missions support group, and the actual work will cost in excess of $1 million dollars. “Just the construction part that will be done with the band and securing the dome is estimated to be over $880,000,” she said. “We pray that it is finished by Easter, but recognize the project may take longer.”
The HVAC system has been another ongoing worry. According to Nau, the existing main HVAC system in the church is just over 30 years old and in need of replacement. Before the church could replace it with a new system, the Texas Historical Commission, which permits all preservation and repair work on the mission churches, requested a specialized study be undertaken of the effects of the air conditioning on the building.
The University of Texas at San Antonio School of Architecture carried out a 12-month study, which confirmed that the exterior condensing units caused deterioration of the interior plaster walls at the southwest corner of the church, including St. Michael’s Chapel, said Nau. “We are currently finalizing plans for the new system, which will include moving the new condensing units further away from the church walls, and new lower-profile – and much quieter – ductwork in the choir loft.”
Mission Concepción, still an active church, will be closed while the work is completed. Replacing the rotted wood in the north bell tower with the new support beam and refurbishing the bell has run $90,000. “We even redid the clapper,” Nau said. “It’s not the original bell, but was probably installed in the 19th century. It’s going to sound good for decades.”