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Mercury — NDEP's Water Quality Monitoring Program

Background —The Nevada Division of Environmental Protection's (NDEP) Bureau of Water Quality Planning (BWQP) oversees the collection of environmental data that is used to characterize the physical, chemical and biological conditions of water bodies throughout Nevada.

Water Quality Monitoring Program — The water quality monitoring program includes routine sampling at more than 50 sites on the State's major river and stream systems.
Selected Water Monitoring Sites in Nevada Waters of Nevada
Additionally, in 2005, the NDEP began collecting samples at more than 50 stream sites in central and northwestern Nevada and the Snake River Basin that are targeted for the development of water quality standards. Water samples are usually collected two to four times per year.

A small subset of lakes and reservoirs are also monitored on a rotating biennial basis. Lakes and reservoirs targeted for the two-year period from July 2006 through June 2008 include: Rye Patch Reservoir, Chimney Reservoir, Southfork Reservoir, Wildhorse Reservoir, and Comins Lake. Water samples will be collected 4 times per year pending access and weather conditions.

Water quality samples are analyzed for standard chemical parameters and metals, including total recoverable and dissolved mercury. The river, stream and lake water quality data are available on this website ( BWQP - Monitoring Branch).

The specific mercury water quality data is available as follows:Data File (1 MB File)

Bioassessment Program — In 2006, the NDEP initiated a 2-year statewide probability based bioassessment monitoring program designed to assess the physical habitat, water/sediment chemistry and biological resources of 60 randomly selected and 20 reference site candidate "wadeable" streams. Water, aquatic sediment and a limited number of fish samples will be collected and analyzed for mercury. The data collected to date is currently being evaluated for quality control/quality assurance protocols.

Water Quality Standards — Water quality standards define the water quality goals of a water body by designating beneficial uses of the water and setting numeric or narrative criteria necessary to protect those uses. Beneficial uses established in the Nevada Administrative Code (NAC) 445A.122 include:

  • watering of livestock
  • irrigation
  • aquatic life
  • recreation involving contact with water
  • recreation not involving contact with water
  • municipal or domestic supply
  • industrial supply
  • propagation of wildlife
  • waters of extraordinary ecological or aesthetic value, and
  • enhancement of water quality

Water quality standards are adopted by the State Environmental Commission (SEC) and are approved by the U.S. Environmental Protection Agency (EPA). Water quality standards for metals (including mercury) and other toxic compounds are contained in the NAC 445A.144. The standards are based on concentrations found in the water column and do not include standards for fish tissue.

303(d) List of Impaired Waters — The Clean Water Act Section 303(d) and 40 CFR Part 130.7 require that states develop a list of waterbodies needing additional work beyond existing controls to achieve or maintain water quality standards. The 303(d) list is the basis for targeting water bodies for watershed-based solutions to address the water quality problems. The total Maximum Daily Load (TMDL) process provides an organized framework to develop these solutions.

    Criteria for including waterbodies on the 303(d) list include:
  1. Adequate documentation exists that beneficial uses are not supported and/or water quality beneficial use standards (BUSs) are not met. Waterbodies are listed when a BUS is exceeded more than 10 percent of the time. Usually at least 10 water quality sample analyses must be available for the listing period. Waterbodies may be listed when the sample set is less than 10 depending on the severity and frequency of exceedence.

  2. A fishing, drinking, or swimming advisory was in effect for the waterbody during the listing period.

  3. Waterbody was on a prior list and insufficient information exists to delist the waterbody.

Please note that waterbodies listed in the table above are based on exceedence of the mercury chronic 96-hour average water quality standard (0.012 ug/l) in effect at the time the 2004 303(d) list was developed. A review of the data used for the 2004 list and additional data collected through September 30, 2005 shows that, with the exception of Willow Creek, all waters meet the new mercury water quality standards adopted by the SEC on September 6, 2006.

Other Information — NDEP has compiled an informational database of projects and studies that investigate mercury in Nevada surface waters, sediment and biota. Related reports, website links, announcements and other information will be posted to this website as available.

Fish Consumption Advisories & More

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