Selenium and Nitrogen Background
Selenium is a naturally occurring element necessary for life at low levels, but it becomes toxic at slightly higher levels. Selenium is also bioaccumulative, meaning that it accumulates in the food chain and can cause adverse effects on species at higher trophic levels, such as fish and birds. Addressing bioaccumulative pollutants is complex, because the pollutant levels in water or soil do not necessarily reflect what is happening in the ecosystem. Selenium occurs in many forms in the environment, and can convert between different forms, each with different toxicity characteristics, depending on various biogeochemical conditions.
Nitrogen is an essential nutrient for plants, but it can cause harmful algal blooms when nitrogen levels are excessive. Excessive algal blooms (referred to as eutrophication) decrease dissolved oxygen in surface waters and can result in fish kills and other adverse effects to the aquatic environment.
The Problem with Selenium and Nitrogen
in the Newport Bay watershed
In the Newport Bay Watershed (Watershed), selenium derived from ancient marine sediments in local foothills accumulated over thousands of years in an area known as “La Cienega de las Ranas”, or the Swamp of the Frogs. This ancient swamp, though now drained, has become an almost limitless source of selenium through passive and diffuse sources such as weepholes, cracks, and seeps, and to a much less extent through active dewatering discharges into surface waters. Selenium levels in the watershed widely exceed the California Toxics Rule (CTR) criterion, but the actual impacts to fish and birds in the watershed, and the Newport Bay (Bay) ecosystem in general, are uncertain at this time despite elevated levels found in tissue samples.
During the 1980's and 1990's, large mats of algae were common in the Bay and were attributed to excess nitrogen. These extensive mats threatened beneficial uses by lowering dissolved oxygen levels and impeding recreational boating. The peak bloom of 1985-1986 resulted in a fish kill in the Bay. Historically the major source of nitrogen in the Watershed was runoff from commercial nurseries and other agricultural activities. Improvements in nursery operations and reduction of agricultural practices have reduced nitrogen runoff, but currently one of the major sources of nitrogen is shallow groundwater, which has high nitrogen levels from historical agricultural land uses.
There currently are no feasible and economically practical treatment technologies to remove selenium and nitrogen from groundwater-related discharges in an urbanized watershed, such as the Newport Bay Watershed. This then presents the challenge of how to deal with elevated levels of selenium and nitrogen from diffuse groundwater sources and meet regulatory requirements (discussed below) when no feasible treatment options exist.
To address nutrient issues in the watershed, the Santa Ana Regional Water Quality Control Board (Regional Board) adopted an amendment to the Basin Plan in 1998 to establish a Total Maximum Daily Load (TMDL) for nutrients. A TMDL is a regulatory process that sets an allowable limit for a particular pollutant in a waterbody at a level, or load, from all sources such that the beneficial uses of the waterbody are protected. In 2002, the United States Environmental Protection Agency (USEPA) issued a Toxics TMDL for the watershed, which is now being broken down into 5 separate TMDLs by the Regional Board (including a TMDL for selenium).
In 1998, the Regional Board adopted a general National Pollutant Discharge Elimination System (NPDES) permit (Order No. 98-67) prescribing general waste discharge requirements for short-term (i.e. one year or less) discharges to surface waters that pose an insignificant (de minimus) threat to water quality within the Santa Ana Region. This permit was issued prior to the adoption and promulgation of the Nutrient and Toxics TMDLs, therefore groundwater-related discharges were still considered an insignificant threat to water quality in the Watershed at that time.
However, when this permit was renewed in 2003 by Order No. R8-2003-0061, the Newport Bay Watershed was specifically excluded from its terms and conditions due to concerns that elevated levels of selenium and nitrogen in short-term groundwater-related discharges had the potential to adversely affect surface waters and would not comply with the existing TMDLs in the Watershed. The Regional Board subsequently developed and issued a separate general NPDES permit specific to the Newport Bay Watershed - Order No. R8-2004-0021, which was amended by R8-2007-0041 and R8-2009-0045 (collectively Order). The Order acknowledged that while current groundwater levels exceeded the CTR limit of 5 ug/L selenium, a feasible treatment technology did not exist to lower the levels in the discharges to the CTR standard. Therefore, the Order incorporated an alternative compliance approach by authorizing the formation of a Nitrogen and Selenium Management Program (NSMP) Working Group and the implementation of a Work Plan to develop a comprehensive understanding of and management plan for groundwater-related selenium and nitrogen discharges in the Watershed. The NSMP Work Plan tasks included monitoring, testing and evaluation of best management practices (BMP), and development of a BMP Strategic Plan, an offset and trading program, total maximum daily loads (TMDLs) and site-specific water quality objectives (SSOs), among others.
Since 2005, the NSMP Working Group has made significant progress and completed essentially all Work Plan tasks. The Order was subsequently extended by Time Schedule Order (TSO) No. R8-2009-0069 on December 10, 2009. Currently, watershed stakeholders are implementing the tasks outlined in the TSO, including receiving approval of the BMP Strategic Plan for the Santa Ana-Delhi and San Diego Creek Sub-Watersheds and the Selenium Regional Monitoring Plan for the Watershed from the Regional Board on December 5, 2013. The current focus is on developing the TMDLs and SSOs. Please visit Newport Bay Selenium TMDL webpage on the Regional Board website for more information.