DWQ protects Great Salt Lake’s beneficial uses through the application of water-quality standards (i.e., narrative and numeric criteria), permit limits based on those criteria, and antidegradation reviews.
- Beneficial uses include drinking water, fish and aquatic life, wildlife, agricultural, industrial, and recreational uses. Once the beneficial uses are established, DWQ sets the narrative and numeric criteria.
- A numeric standard is the measurable level of a particular chemical or conditions allowable in a waterbody.
- A narrative standard establishes water-quality goals and prohibits activities that create significant negative impacts on water quality.
- Discharge permit limits are set to ensure that the standards in the receiving waters are not exceeded. Permit limits are typically developed by modeling the concentrations in the receiving waters after the mixing zone, the area where the initial dilution of a discharge occurs.
- Antidegradation Reviews ensure that waters that have better quality than required by the standards are not degraded unless the degradation is necessary for important social or economic reasons.
The unique nature of Great Salt Lake creates challenges for developing numeric criteria:
- Analytical methods for hypersaline waters are limited.
- A lack of baseline water-quality data makes it difficult to analyze conditions and trends.
- The presence of unique organisms with unknown toxicity responses complicates criteria development.
The numeric standard for selenium was the first water-quality standard established for the Great Salt Lake. The standard was incorporated into state rules in November 2008 and approved by the Environmental Protection Agency on December 12, 2011. The selenium standard of 12.5 milligrams per kilogram (mg/kg) is a tissue-based standard based on the complete egg/embryo of aquatic-dependent birds that use the waters of Gilbert Bay (Class 5A).
The process to develop a selenium standard took four years to complete. The Selenium Steering Committee, comprised of prominent stakeholders and advised by an international scientific panel of selenium experts, developed the standard through data-collection projects and conceptual models.
DWQ continues to protect the water quality of Great Salt Lake for selenium by:
- Monitoring egg tissue in aquatic birds
- Evaluating trigger selenium concentrations that initiate various monitoring, assessment, and management actions, and
- Identifying management actions to mitigate further increases in selenium concentrations if an upward trend is observed.
These results are reported in DWQ’s biennial Integrated Report.
Aquatic Life Use Standards Development
State rules specify the aquatic-life beneficial uses for waterfowl, shorebirds and other water-oriented wildlife, including their necessary food chain. Utah’s Narrative Standards and Antidegradation Policy apply to all Waters of the State including GSL. Additional numeric criteria to protect GSL’s aquatic life uses are currently under development to supplement the single available numeric criterion for selenium in Gilbert Bay. The process for developing these criteria is documented in DWQ’s GSL Water Quality Strategy Core Component 1.
Aquatic Life Use Species List
An initial step in the development of numeric criteria is to define the specific organisms or communities that comprise the beneficial use. In 2015, DWQ and EPA sponsored an Aquatic Life Use Workshop for GSL to identify and compile the available data for the aquatic species present in GSL and the specific bays where they were observed. The aquatic species identified include arthropods, rotifers, protozoans, bacteria, algae, fish, and fungi.
DWQ expects to continue modifying the resident taxa list as additional information becomes available.