Big Lake Water Quality Monitoring, 2009

Nonpoint Source Water Pollution Control
Waters in the Spotlight

State of Alaska > DEC > Division of Water > Non-Point Source Water Pollution Control

Big Lake Water Quality

The public comment period has now closed for the Big Lake Total Maximum Daily Load (TMDL) draft document. DEC will be finalizing the TMDL and submitting to the Environmental Protection Agency (EPA) for review and approval. The TMDL is part of the recovery plan to address the water quality impairment by petroleum hydrocarbons (gasoline). General information on TMDLs may be found here: General information on TMDLs.

Introduction
Big Lake is an important recreational resource for the residents of south-central Alaska, providing opportunities for year-round fishing, boating and swimming in the summer and snowmachine usage in the winter. Lake usage greatly increases on weekends in the summer as residents of nearby communities utilize their personal properties, the three private marinas, the two state recreation sites located at Big Lake or the Borough's public boat launch in the west basin.

Water Quality Summary
DEC performed water quality monitoring in Big Lake in 2004 and 2005, and the data showed that the shallow waters (less than 15 feet) of Big Lake had elevated levels of petroleum hydrocarbons. Specifically, total aromatic hydrocarbons (TAH) exceeded the water quality criterion of 10 µg/L (micrograms per liter) during the summer months. Based on these data, DEC added Big Lake to the Section 303(d) list of impaired waters in 2006. The 303(d) list represents those waters in the state that do not meet applicable water quality standards. Additional water quality monitoring in 2009 verified the 303(d) listing and the elevated TAH concentrations.

Compounds in petroleum hydrocarbons are highly toxic and tend to accumulate in the fats and oils of organisms. This can impact or kill aquatic organisms such as insects that serve as a food source for fish and wildlife. The negative effects of petroleum can move up the food chain from the aquatic insects to fish to wildlife and potentially to humans. Impaired water can also affect fish and wildlife through direct contact and consumption. Because petroleum hydrocarbons contain known cancer causing compounds (carcinogens) such as Benzene and Benzo(a)pyrene, controlling their concentration in Big Lake is important not only to protecting the environment but ultimately human health. All of the water quality data reports are available on the right side of this page.

What is the source of the petroleum?
The primary source of petroleum hydrocarbons to Big Lake is motorized watercraft. Results from monitoring conducted in 2004, 2005 and 2009 show that elevated concentrations of petroleum hydrocarbons occurred at times and locations of increased motorized watercraft usage on Big Lake, including on high use weekends and near marinas, boat launches and other high traffic areas in the east basin. The hydrocarbons can come from gasoline leaks and spills but most of it likely results from the combustion process of gasoline motors, which are designed to directly release unburned fuel out of the exhaust into the water during combustion. This is especially the case with 2-cycle motors. More gasoline motors on the lake at any given time increases the amount of gasoline being released.

What is being done to fix the petroleum pollution?
Efforts to address the petroleum-related impairment in Big Lake are already underway. There is currently a coordinated effort with the Big Lake community and other local, regional and federal stakeholders to develop an action plan to improve Big Lake water quality. The stakeholder-led process is focused on identifying community supported and implemented actions that address the most critical issues and areas and that also contribute to the long-term health of the lake. To date, key actions include the development of an education campaign that describes and encourages clean boating and fueling practices. In addition, local marinas are encouraged to participate in the Clean Harbors statewide certification program, with one marina already working towards their certification. The Action Plan and workshop notes are on the right of this screen.

For more information please contact:
Laura Eldred
1700 E Bogard Rd, Bldg B, Ste 103
Wasilla, AK 99654
Phone: (907) 376-1855
Fax: (907) 376-2382
Email: laura.eldred@alaska.gov