Selenium, a metal ore that is found natural in our earth’s surface is essential for all life in small amounts. However, if excessive quantities are consumed it can be toxic and can cause reduced reproductive performance and blind staggers in  animals. In humans consuming excessive quantities of Selenium for over a long period of time could lead to hair or fingernail loss, numbness in fingers and toes, or problems with circulation.

 Selenium Concentrations by Stream for the sampling period of January 2010 to October 2011:

The sampling site on the South Fork of Powder River saw selenium concentrations ranging from below the detection limit of 5 µg/L to 37µg/L. The highest total selenium concentration was measured in May 2011. There are two sampling sites on Murphy Creek. The first site is located near the Murphy Creek Bridge on the TTT Rd. This site saw concentrations varying from below the detection limit to 20 µg/L. The other site located near the Murphy Creek Bridge on Old US Highway 87 had concentrations that were below the detection limit in approximately 23 % of the samples collected. A maximum total selenium concentration of 23 µg/L was measure in September of 2010. The Willow Creek site measured below the total selenium detection limit in approximately half of the 22 samples collected. The highest concentration of 10 µg/L was measure in May of 2010. Overall, selenium concentrations continue to frequently exceed the Wyoming Department of Environmental Quality (WDEQ) water quality standard of 5 µg/L. Similar to previous results, there are no apparent correlations between selenium and field parameters and additional water quality constituents.

 Murphy Creek Use Attainability Analysis (UAA) Update

The PRCD completed an assessment of the Murphy Creek watershed in 2009 and found that the selenium in this watershed is naturally occurring and not attributable to human activities. Following this assessment the District submitted a UAA Petition to the WDEQ requesting site specific selenium criteria on Murphy Creek in June of 2010.The WDEQ reviewed the petition and requested additional information on the bentonite mines and oil wells in the watershed, livestock grazing impacts, and additional water quality analysis. In addition, the WDEQ toured the watershed in June 2011 and concurred with the preliminary findings. The most recent conversation with the WDEQ (January 2012) indicated that the EPA is in the process of reviewing the petition and developing site specific selenium criteria for Murphy Creek.

 Arsenic in the Powder River Watershed

In January 2012, the WDEQ published the Draft 2012 Integrated 305(b) and 303(d) Report. The report indicated that arsenic concentrations in the Powder River exceeded the total arsenic criterion protection of drinking water use between the USGS sampling site near Sussex downstream to the Arvada USGS gauging station. Based on these results the Powder River from the confluence with Salt Creek downstream to the confluence with Soldier Creek was added to the 303(d) list of impairments.

The WDEQ surface water quality drinking standard for arsenic in water sources with a drinking water use is 10 µg/L. In 2009 the USGS gauging station at Sussex measure an arsenic concentration of 270 µg/L. Although the source of the arsenic is unknown, the WDEQ indicated that Salt Creek is a big contributor.

Arsenic is a naturally occurring trace element found in the Earth’s crust and can be released into the environment through natural or human activities. Arsenic is a health concern because it can cause thickening and discoloration of the skin, stomach pain, nausea, vomiting, diarrhea; numbness in  hands and feet; partial paralysis; and blindness. Arsenic has also been linked to several types of cancer including bladder, lung, skin, kidney, liver, and prostate.