Assessing influence from wastewater treatment facilities on Glorieta Creek and the Pecos River within Pecos National Historical Park, New Mexico, February–October 2022

The Pecos National Historical Park protects 2.9 miles of the Pecos River and part of Glorieta Creek within the park boundaries. Updated water-quality data can assist resource managers in determining if effluent from two nearby wastewater treatment plants (WWTPs) is affecting the quality of the water in the Pecos River and Glorieta Creek within the park. Water samples were collected four times in 2022 at two WWTP outfalls, two locations on Glorieta Creek, and two locations on the Pecos River. Water quality parameters (dissolved oxygen, water temperature, pH, turbidity, specific conductance) were measured in the field, and samples were collected and analyzed for major ions, trace elements, rare earth elements, nutrients, bacteria, and per- and polyfluoroalkyl substances (PFAS).

Specific conductance values in all samples collected from Glorieta Creek exceeded the New Mexico Surface Water Quality Standard (NMWQS) of 300 microsiemens per centimeter at 25 degrees Celsius. Concentrations of dissolved oxygen in three samples collected from Glorieta Creek and one sample for the Pecos WWTP did not meet the standard for high-quality cold-water use. Concentrations of Escherichia coli in samples from the Pecos WWTP exceeded the NMWQS of 235 colony-forming units per 100 milliliters during every sampling event. Concentrations of E. coli in samples collected from two sites on Glorieta Creek in August exceeded the NMWQS.

The chemical signature of water from Glorieta Creek indicated groundwater and (or) septic system contributions. Water samples collected from the Pecos River all had similar chemical signatures of calcium-bicarbonate type. Although concentrations of several trace elements were higher in samples from Glorieta Creek than in samples from the Pecos River, no concentrations exceeded the drinking-water standards. No concentrations exceeded aquatic life standards except for copper concentrations in two samples from the downstream location on Glorieta Creek. The trace element signature and the gadolinium anomalies in the WWTP samples indicate anthropogenic contributions.

Eleven of the 28 PFAS compounds analyzed were detected in samples during this study, with the treated wastewater effluent samples having the highest total PFAS concentrations. The total PFAS concentrations in samples from Glorieta Creek decreased by an order of magnitude as the creek flowed downstream. At the downstream site on the Pecos River, there was only one sample that had a detection of PFAS.