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Water Quality Community Summary Report

By Anna Lee Vargas

For a copy of the community Report, you can go to: 

In 2022/2023, the SLV Ecosystem Council (Conejos and Saguache), Shirley Romero Otero (Costilla County), and Augusto Basterrechea (Center & Rio Grande), under the direction of Dr. Kathy James and Nick Stoll MPH (valley-at-large), together coordinated efforts throughout the SLV to encourage over 725 families with household wells, to participate in a free water quality testing project. 

This effort was sponsored by the Colorado School of Public Health whose purpose was to test for 17 different heavy metals that may be present in household drinking water. This project has contributed critical baseline to our understanding of what is happening in the aquifer and how climate change (and receiving less recharge due to drought conditions) may impact the quality of drinking water. 

In the first phase of this multi-year project, the objectives were to engage with the community and facilitate a regional sampling of private wells. Overwhelming support was received from the community and the School of Public Health was thrilled to provide “results reports” to each participant. This information will be used to create geospatial models to identify trends related to regional drought and predict future levels of metals in groundwater. Eventually, the aim is to use these models to further investigate health effects associated with exposure to heavy metals.

The San Luis Valley is a region rich in history and nature. Its characteristics as a high intermountain valley are due to the formation of the San Juan and Sangre de Cristo Mountains. During the uplift and volcanic activity that formed these ranges, many elements were raised to the surface level of the earth's crust. Some elements are commonly found in water (e.g. iron, zinc, calcium) and pose little risk to health, whereas others, like heavy metals (e.g. arsenic, lead, uranium) are known to have adverse health effects. 

Over time, these metals naturally accumulate into the present layers of clay and alluvial soil beneath the valley floor. The ecology of the SLV has led to the development of longstanding communities, agriculture practices, and tourism that is unique to its characteristics - all of which has been supported by the balanced use of water resources. 

Historic drought conditions have been present in the SLV for the past two decades. Decreased precipitation, increased groundwater usage, earlier snowmelt, and other factors have caused a disturbance to the balance. With naturally occurring aquifer recharge no longer counteracting the demand on the Rio Grande Aquifer system, the region risks subsidence. This occurs when the water deprived subsurface layers of earth compacts, preventing water from re-entering the once porous sub-terrain. 

As water scarcity becomes an increasing concern, multiple factors are compounding the severity of the issues at hand. The team assembled by the CO School of Public Health consists of scientists across multiple institutions who are investigating the impacts of climate, drought, and water quality on human health. While it’s know from past research that metals can have a negative impact on health, there is still much that isn’t known. Additionally, recent research from the San Joaquin Valley, California has found that subsidence may cause an increase in the amount of heavy metals in groundwater. 

From June of 2022 to September of 2023, 736 private well owners signed up to get their well tested. Sample numbers were submitted by the following counties: 150 from Alamosa, 86 from Costilla, 184 from Rio Grande, 119 from Conejos, 8 from Mineral, and 158 from Saguache. The metals that were tested for include: Antimony, Arsenic, Barium, Cadmium, Chromium, Copper, Lead, Thallium, and Uranium. 

Major heavy metals with known health effects


  • 60 wells have levels above the EPA maximum contaminant level of 10 ug/L

  • And additional 51 have levels above 5 ug/L – this level has been associated with adverse health outcomes with chronic exposure

  • Arsenic is a systemic toxicant meaning it affects every system in the body

  • Health effects that have been identified in the SLV and globally

  • Cardiovascular outcomes (heart attack, hypertension, peripheral arterial disease)

  • Diabetes and elevated glucose

  • Reproductive outcomes (low birth weight, preterm deliverer, spontaneous abortion)

  • Health effects that have been identified globally however have not been investigated in the SLV

  • Cancer—bladder, skin, renal, and lung cancer

  • Asthma

  • Skin conditions


  • 14 wells have levels above the EPA MCL of 30 ug/L

  • 28 have levels above 10ug/L which has been shown to impact health

  • Health effects

  • Uranium is currently being explored in the SLV for health impacts (diabetes)

  • Health effects globally

  • Cancer (multiple systems)

  • Cardiovascular outcomes

  • Diabetes (glucose and metabolism)



  • <10 wells are elevated above the 50ug/L EPA MCL


  • <10 wells are elevated above the 1000ug/L EPA MCL

  • 15 have levels above 300ug/L where some symptoms can occur

  • Health effects are mostly cardiovascular



  • <10 wells elevated above 4ug/L EPA MCL

  • Similar health outcomes as arsenic



  • 65 wells elevated – in the SLV has been associated with kidney injury and disease



  • < 10 wells elevated with similar outcomes as uranium


  • 10 wells elevated at the action level for EPA (10 ug/L)


  • 80 wells elevated above the EPA MCL of 50

  • Health effects are neurocognitive, similar to lead, can be associated with dementia and declined IQ


75% of wells are considered Hard to Extremely hard

While this project focuses on heavy metals, there are many other health hazards that can be associated with drinking water. It is important to do your own research to identify a solution that best addresses the needs of your household water. The Center for Disease Control & Prevention (CDC) 

and EPA to provide additional information on identifying other health hazards, and appropriate water filters and treatment options.      

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