OF-24-13 Baseline Radiological Study Year 3: San Luis Valley

The Colorado Geological Survey (CGS), a department of the Colorado School of Mines, has been funded through a grant from the Colorado Department of Public Health & Environment (CDPHE) to conduct a 5‐year study of baseline naturally occurring radionuclides and metals in groundwater obtained from privately owned residential water wells throughout Colorado. This report presents the methodology and results of Year 3 conducted in 2024 in the central portion of the San Luis Valley (SLV) located in south‐central Colorado. The study area included parts of Alamosa, Conejos, Costilla, Rio Grande, and Saguache counties (Figure 1). Principal towns within the study area from north to south include Moffat, Center, Hooper, Alamosa, Blanca, Fort Garland, A Jara, and Sanford. Digital PDF download. OF-24-13D

For additional information, please see OF-24-08, a similar study conducted in the Uravan Belt in western Colorado.

From the report:

The SLV is greater than 100 miles long and 65 miles wide, extending from the Colorado Continental Divide on the northwest rim into New Mexico. Within Colorado, the valley is bordered by the Sangre de Cristo Mountain Range on both the southeast and east sides and to the north, west, and southwest by the San Juan Mountain Range. Streams carrying sediment shed from the surrounding mountains form alluvial fans around much of the valley floor, the most extensive being the Rio Grande fan. Additionally, wind deposited (eolian) silt and sands migrate across the basin from the west to east. Although outside the study area, the eastern edge of the SLV contains the Great Sand Dunes National Park and Preserve, an important tourist destination.

The San Luis basin consists of a northern and southern basin divided at the structural and physiographic high terrain of the San Luis Hills, close to the Colorado‐New Mexico state line. The San Luis Hills consist of a series of upthrown geologic blocks arranged northeasterly across the central part of the basin. Thus, our study area is contained within the northern basin, known as the Alamosa Basin.