Archaeological Investigation of the Upper Labor Acequia, San Antonio, Bexar County, Texas

The Center for Archaeological Research (CAR) conducted an archaeological investigation of a section of the Upper Labor Acequia (ULA; 41BX2043) in Brackenridge Park, San Antonio, Texas. The work was in response to a request from the City of San Antonio (COSA) Public Works Department to provide information to the structural engineer for future remediation of the acequia. The project area is also within a previously designated site, 41BX1425 described as a large prehistoric campsite. The ULA is a contributing element to the Brackenridge Park National Register District and is also listed as a State Antiquities Landmark. The work described here was conducted under Texas Antiquities Permit (TAP) 31262, with Cynthia Munoz serving as the Principal Investigator.

The investigation, conducted in July 2023 and January 2024, included the excavation of three trenches to describe the exterior wall of the acequia and three test units to describe the interior wall of the acequia. In general, the acequia in the project area has been impacted, to varying degrees, as evidenced by highly fragmented wall sections, collapsing wall sections, missing stone, and/or wall sections with cracks. Trenching revealed that the exterior wall is comprised of stacked limestone rubble and larger stone that is not mortared. The interior of the wall consists of a mortared limestone facade. The foundation of the interior wall is limestone rubble resting on a clay matrix. No definitive acequia channel floor was found during the excavation. The test unit excavations within the acequia recovered modern debris, although a single flake was observed in the spoil pile of one of the test units.

All three external trenches contained prehistoric artifacts, including debitage and/or burned rock. The CAR documented an amorphous, ashy deposit in the floor of Trench 2 at approximately 80 cm below the top of the acequia wall. Designated Feature 1, it included burned earth, burned clay, ash, charcoal, and two burned rocks. The feature covers an area roughly 50 by 30 cm, with an unknown depth. A radiocarbon date on charcoal extracted from a sediment sample collected from the feature yielded a median date of 1306 cal BP with a two-sigma range of from 1345 to 1291 cal BP, documenting an occupation at the end of the Late Archaic Period. A burned rock cluster and a single flake was present in the western wall of the trench, roughly 30 cm above where the feature was defined. While the association of this material with Feature 1 is not clear, it is the case that an unknown portion of the feature was removed by the backhoe prior to the feature identification. Burned rock and debitage were also observed in Trench 1. Trench 3 contained these materials as well as faunal bone. Following the trench and test unit excavations the structural engineer, Shawn Franke, P.E., the City Archaeologist Matthew Elverson, and the THC’s Dr. Emily Dylla reviewed the exposed portion of the ULA.

Given the recovery during this investigation of cultural material and an archaeological feature with chronological information and integrity, CAR recommends that the deposits adjacent to the acequia on site 41BX1425 are eligible for listing on the National Register of Historic Places (NRHP) under criterion D, in that the deposits have yielded, and are likely to yield, information important to prehistory. In addition, the CAR recommends that this area of the site is eligible for designation as a State Antiquities Landmark (SAL) in that the site has the potential to contribute new and important information and thereby lead to a better understanding of Texas prehistory. Given that recommendation, and our current understanding of the proposed work, the CAR further recommends the development of a proactive testing program to mitigate impacts to this area of the site.

CAR will submit a site update (41BX1425) of this recent investigation to the Texas Archaeological Sites Atlas following comments by the COSA Office of Historic Preservation (OHP) and the Texas Historical Commission (THC), along with a GIS shapefile of the site and other information relevant to TAP No. 31262. Following completion of the fieldwork, all project-related materials, including the final report, were permanently stored at the CAR’s curation facility under accession number 2868.