PRELIMINARY GEOLOGICAL INVESTIGATION OF MISSION NUESTRA SEÑORA DE LA PURÍSIMA CONCEPCIÓN DE ACUÑA FOR SAN ANTONIO MISSIONS NATIONAL HISTORICAL PARK & WORLD HERITAGE SITE

Mission Nuestra Señora de la Purísima Concepción de Acuña (Mission Concepción) is one of four missions that make up San Antonio Missions National Historical Park and World Heritage Site. Subsidence of the church's limestone foundation is an ongoing issue for the National Park Service, and its impacts on the integrity of the building include cracking of the Southwest corner of the church’s walls, dissolution of the limestone wall’s lower exterior, and past appearance of a sinkhole beside the foundation. Preliminary data was gathered over the span of a month to assess the current state of the compound’s historical structures and examine potential causes of damage to the foundation. The preliminary geological assessments presented include a subsurface survey to detect changes in the bedrock under the compound utilizing ground penetrating radar and a compilation of high-resolution coordinate and elevation data to monitor future changes in subsidence. In addition, chemical analysis testing was conducted on rainwater runoff from the church’s roof to better understand the role of precipitation in the dissolution of the Mission Concepción foundation. Furthermore, comparisons between topographic profiles rendered through GIS using county-wide lidar elevation datasets and independently gathered elevation data will be used to evaluate areas that may warrant future concern and maintenance.