As part of the Navajo-Gallup Water Supply Project, the Bureau of Reclamation was tasked with design and construction of infrastructure to treat and deliver potable water to the communities of Navajo Nation, parts of the Jicarilla Apache Nation, and City of Gallup. The Bureau of Reclamation has been evaluating the Public Service Company of New Mexico's (PNM) San Juan Generating Station (SJGS) reservoir as a possible water storage and sediment settling basin for the Navajo-Gallup Water Supply Project. The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation, was tasked with collecting reservoir sediment cores and pore water from SJGS reservoir. This data release contains reservoir sediment organic chemistry results.

The San Juan Generating Station in Waterflow, NM, owned by the Public Service Company of New Mexico (PNM) is a coal-fired power plant that operates on coal mined on the same property. This plant is scheduled to shut down in 2022. In light of this impending closure, the Bureau of Reclamation (Reclamation) is interested in purchasing the plant's raw-water reservoir for use in the Navajo-Gallup Water Supply Project (NGWSP). Concerns about contamination leaking from the reservoir or being mobilized by groundwater flow affected by the leaking reservoir have resulted in Reclamation eliciting a short study of the water and sediment chemistry surrounding the reservoir and the recovery system set up by PNM. The U.S. Geological Survey (USGS) New Mexico Water Science Center collected water and sediment samples in the area in January 2021. Water and sediment samples were sent the University of New Mexico to be analyzed in the Analytical Chemistry Laboratory (UNM-ACL) in the Earth and Planetary Sciences Department.

This study was done because elevated concentrations of metals including aluminum, arsenic, and lead were identified by Navajo Nation EPA staff in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah). An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology, and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. Water samples were collected in single-siphon samples and by grab sample at 59 ephemeral and perennial tributaries to the San Juan River in 2021 and 2022. Eighteen surface water sites along the San Juan River were sampled as grab samples in 2021 and 2022 and fifteen sites along the San Juan River were sampled by equal width increment and composited in a churn during a baseflow synoptic sampling campaign in February 2021. A total of 765 unfiltered and 282 filtered samples were analyzed for major and trace cations. All samples were analyzed through the USGS Analytical Chemistry Laboratory in Denver, Colorado (Taggart, 2022; USGS, 2023 Method 37).

This study was done because elevated concentrations of metals including aluminum, arsenic, and lead were identified by Navajo Nation EPA staff in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah). An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology, and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. Water samples were collected in single-siphon samples and by grab sample at 59 ephemeral and perennial tributaries to the San Juan River in 2021 and 2022. Eighteen surface water sites along the San Juan River were sampled as grab samples in 2021 and 2022 and fifteen sites along the San Juan River were sampled by equal width increment and composited in a churn during a baseflow synoptic sampling campaign in February 2021. A total of 765 unfiltered and 282 filtered samples were analyzed for major and trace cations. All samples were analyzed through the USGS Analytical Chemistry Laboratory in Denver, Colorado (Taggart, 2022; USGS, 2023 Method 37).

Elevated concentrations of metals including aluminum, arsenic, and lead were identified by Navajo Nation Environmental Protection Agency staff in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah). An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology, and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. Water samples that were filtered with 0.45 micron filters were collected in single-siphon samplers and by grab sample at 41 ephemeral and perennial tributaries to the San Juan River in 2021 and 2022. Eighteen surface water sites along the San Juan River were sampled as grab samples in 2021 and 2022. Samples were chosen randomly for filtration to compare to unfiltered sample results. The samples were analyzed for major and trace cations by inductively coupled plasma emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) at the US Geological Survey Analytical Chemistry Laboratory in Denver, Colorado. A sub-set of samples includes data for pH and alkalinity as calcium carbonate. A total of 282 filtered samples were collected.

Elevated concentrations of metals including aluminum, arsenic, and lead were identified by Navajo Nation Environmental Protection Agency staff in the San Juan River from below the Navajo Dam, through the Navajo Nation to Mexican Hat, Utah in the Four Corners Region of the United States (Colorado, Arizona, New Mexico, Utah). An interdisciplinary team applied approaches and principles of geology, geochemistry, geomorphology, hydrology, and statistics to gain a better understanding of the tributaries supplying the source(s) of metals to the San Juan River. Water samples that were filtered with 0.45 micron filters were collected in single-siphon samplers and by grab sample at 41 ephemeral and perennial tributaries to the San Juan River in 2021 and 2022. Eighteen surface water sites along the San Juan River were sampled as grab samples in 2021 and 2022. Samples were chosen randomly for filtration to compare to unfiltered sample results. The samples were analyzed for major and trace cations by inductively coupled plasma emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) at the US Geological Survey Analytical Chemistry Laboratory in Denver, Colorado. A sub-set of samples includes data for pH and alkalinity as calcium carbonate. A total of 282 filtered samples were collected.

Sediment traps were deployed in thirty-three ephemeral and perennial tributaries to the San Juan River during 2021 and 2022. This dataset includes the chemical concentrations of the sediment samples collected in sediment traps during storm events. These traps collected sediment during storm events that typically occur as monsoonal convective storms from June to September. Because of the rural nature of the watershed, sediment traps were collected every 3 weeks so the sediment collected is a composite of that time period. The date listed is the date the trap was collected. Major ions are reported in weight percentage, while all other elements are reported in parts per million. Each sample was split and analyzed following two different methods of sample preparation. In one method, the sample is decomposed using a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids at low temperature. In the second method, samples are fused at 750°C with sodium peroxide and the fusion cake dissolved in a dilute nitric acid. The resulting solution for both methods is analyzed by ICP-OES and ICP-MS.

Sediment traps were deployed in thirty-three ephemeral and perennial tributaries to the San Juan River during 2021 and 2022. This dataset includes the chemical concentrations of the sediment samples collected in sediment traps during storm events. These traps collected sediment during storm events that typically occur as monsoonal convective storms from June to September. Because of the rural nature of the watershed, sediment traps were collected every 3 weeks so the sediment collected is a composite of that time period. The date listed is the date the trap was collected. Major ions are reported in weight percentage, while all other elements are reported in parts per million. Each sample was split and analyzed following two different methods of sample preparation. In one method, the sample is decomposed using a mixture of hydrochloric, nitric, perchloric, and hydrofluoric acids at low temperature. In the second method, samples are fused at 750°C with sodium peroxide and the fusion cake dissolved in a dilute nitric acid. The resulting solution for both methods is analyzed by ICP-OES and ICP-MS.

Sediment traps were deployed in tributaries to the San Juan River during 2021 and 2022. These traps collected sediment during storm events that typically occur as monsoonal convective storms from June to September. Because of the rural nature of the watershed, sediment traps were collected every 3 weeks so the sediment collected is a composite of that time period. The date listed is the date the trap was collected. This dataset includes the chemical concentrations of the sediment samples. Major ions are reported in weight percentage, while all other elements are reported in parts per million. Samples were fused at 750°C with sodium peroxide and the fusion cake dissolved in a dilute nitric acid. The resulting solution was analyzed by ICP-OES and ICP-MS. This method was done to include all of the rare earth elements. Results from this method may differ slightly from the results in the 49-element analysis because of the differences in digestion procedure. The 60 element dataset includes aluminum, calcium, iron, potassium, magnesium, phosphorous, sulfur, silicon, titanium, silver, arsenic, boron, barium, beryllium, bismuth, cadmium, cerium, cobalt, chromium, cesium, copper, dysprosium, erbium, europium, gallium, gadolinium, germanium, hafnium, holmium, indium, lanthanum, lithium, lutetium, manganese, molybdenum, niobium, neodymium, nickel, lead, praseodymium, rubidium, antimony, scandium, selenium, samarium, tin, strontium, tantalum, terbium, tellurium, thorium, thallium, thulium, uranium, vanadium, tungsten, yttrium, ytterbium, zinc, and zircon.

Sediment traps were deployed in tributaries to the San Juan River during 2021 and 2022. These traps collected sediment during storm events that typically occur as monsoonal convective storms from June to September. Because of the rural nature of the watershed, sediment traps were collected every 3 weeks so the sediment collected is a composite of that time period. The date listed is the date the trap was collected. This dataset includes the chemical concentrations of the sediment samples. Major ions are reported in weight percentage, while all other elements are reported in parts per million. Samples were fused at 750°C with sodium peroxide and the fusion cake dissolved in a dilute nitric acid. The resulting solution was analyzed by ICP-OES and ICP-MS. This method was done to include all of the rare earth elements. Results from this method may differ slightly from the results in the 49-element analysis because of the differences in digestion procedure. The 60 element dataset includes aluminum, calcium, iron, potassium, magnesium, phosphorous, sulfur, silicon, titanium, silver, arsenic, boron, barium, beryllium, bismuth, cadmium, cerium, cobalt, chromium, cesium, copper, dysprosium, erbium, europium, gallium, gadolinium, germanium, hafnium, holmium, indium, lanthanum, lithium, lutetium, manganese, molybdenum, niobium, neodymium, nickel, lead, praseodymium, rubidium, antimony, scandium, selenium, samarium, tin, strontium, tantalum, terbium, tellurium, thorium, thallium, thulium, uranium, vanadium, tungsten, yttrium, ytterbium, zinc, and zircon.