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Animas River Updates from Fort Lewis College
with Ray Kenny, professor of Geosciences
To help people understand the complex issues surrounding the Animas River mine waste spill, we're offering insights from Fort Lewis College faculty on questions people in the community are asking.
Responses from: Professor of Geosciences Ray Kenny. Dr. Kenny specializes in environmental geology and geomorphology.
The EPA has released more data, but interpretation of these data remains a point of confusion for the many. Concerned citizens have told me they appreciate the Animas River Updates. Many, though, still have unanswered questions and have contacted me requesting more information. This update is provided to address some of those lingering questions.
What types of contaminants are in the water?
- Suspended solids: These are materials such as silt, plant matter, and waste products carried in the river that can be trapped on a filter. Clarity of water is reduced by these, which can impact temperature (particles can absorb and/or reflect sunlight), fish (particles can clog fish gills), etc. Neither the EPA or the State of Colorado provide a standard for total suspended solids (TSS) in drinking water.
- Dissolved solids: This is the material in water not captured on a filter, such as calcium ions. You may have noticed a white deposit on your faucets at home, this is calcium that was in solution that combined with other ions to form a deposit. Usually measured as total dissolved solids (TDS), the EPA recommended standard is 500mg/l for TDS in drinking water (TDS is considered a “secondary” standard; levels are not enforceable).
- Primary Drinking water standards: These cover many organic and inorganic substances, including: Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), Mercury (Hg), Selenium (Se), and Silver (Ag), to name a few (a full list and levels is available at: http://water.epa.gov/drink/contaminants/index.cfm). Units are usually listed as milligrams per liter (mg/l), which is equivalent to parts per million (ppm), and micrograms per liter (µg/l), which is equivalent to parts per billion (ppb).
How is the safety of drinking water measured and monitored?
Drinking water standards are set by the EPA according to health criteria, and are listed as maximum contaminant levels (MCL), usually in units of mg/l or µm/l. All public water systems must conform to these standards by conducting regular water analyses. You likely have seen some of these test results before because the City of Durango periodically includes them with your water bill.
Why did it take so long for the EPA to reopen the river?
EPA lists river water data and compares it to drinking water standards (MCL) and recommended levels. These data provide a momentary or instantaneous “snapshot” of river water quality at several sample location sites along the river. Concentrations can vary and a lot of data is needed to confirm that contaminant levels have stabilized.
Here’s a recent example of data from the Animas River-Rotary Park area collected on 8/8/15 @ 1:50 p.m.:
- Zinc (Zn) river values: 3770 ppb (3.77 ppm)
- Recommended standards (Zn is a secondary water standard): 10 ppb
Same site, same time, but at 11:10 a.m.:
- Zn river values: 66 ppb
- Recommended standard: 10 ppb
This illustrates the need for continued water monitoring and sampling, and explains why it took so long to reopen the river.
A lot more data is available on the EPA webpage. The information provided herein should help you read, interpret, and better understand these data.
What is the orange “sediment” or sludge on the river bottom?
This material is neither dissolved nor suspended in the river, but occurs as a gelatinous deposit (which can be remobilized during storm events, etc.). The units are in milligrams per kilogram (mg/kg) which is equivalent to ppm. These units are used because the sediment (or “sludge”) is a solid, and we are measuring the weight of the solids. EPA has now released some analyses of the “sludge.”
Here are some examples of the data collected on 08/11/15 @ 9:20 a.m.:
- Zn Sediment value: 540 ppm (Recommended standard: 1.8 ppm)
- Manganese (Mn) sediment value: 960 ppm (Recommended standard: 0.21 ppm)
- Copper (Cu) value: 87 ppm (Recommended standard: 0.23)
These data clearly show that some contaminants in the sludge are elevated. EPA recommends washing with soap and water if you come in contact with the sludge.
Some open questions related to the remaining sludge, include:
- How mobile are the contaminants?
- What volume of sludge is actually present in the river?
- Will the contaminants be released and move into the groundwater?
- Will the contaminant levels decrease during infiltration into the subsurface and thereby not have a significant impact on water supplies?
- During flood events, will the sludge pose any health concerns?
- Can these contaminants be reintroduced into the river and will the quality of the river water temporarily decrease again?
These are all valid questions and concerns. However, we don’t have enough information yet to answer these questions. More data is needed to determine the long-term impacts. Additional updates will be provided when more information becomes available.
Additional resources