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Maine’s Surface Water Ambient Toxics (SWAT) monitoring program was established in 1993 (38 MRSA §420-B) and is administered by the Department of Environmental Protection to determine the nature, scope and severity of toxic contamination in the surface waters and fisheries of the State. The authorizing statute states that the program must be designed to comprehensively monitor the lakes, rivers and streams, and marine and estuarine waters of the State on an ongoing basis. The program must incorporate testing for suspected toxic contamination in biological tissue and sediment; may include testing of the water column; and must include biomonitoring and the monitoring of the health of individual organisms that may serve as indicators of toxic contamination. The program must collect data sufficient to support assessment of the risks to human and ecological health posed by the direct and indirect discharge of toxic contaminants. The Commissioner of the Department of Environmental Protection (DEP) must prepare a five-year conceptual work plan in addition to annual work plans which are each reviewed by a Technical Advisory Group (TAG). The TAG is composed of 12 individuals, including two representatives with scientific backgrounds representing each of five various interests (business, municipal, conservation, public health and academic), and two legislators.

The SWAT program is divided into four modules: 1) Marine and Estuarine, 2) Lakes, 3) Rivers and Streams, and 4) Special Studies. This annual report follows the goals of the 2014 five-year conceptual plan, which are generally to continue to monitor previously identified and new toxic issues in the marine environment, lakes and ponds, and rivers and streams, including but not limited to providing baseline data for use by the Department of Marine Resources (DMR) in evaluating and assessing shellfish harvesting areas; providing fish and shellfish contaminants data to the Maine Center for Disease Control and Prevention (MCDC) for use in revising Maine’s fish consumption advisories; and continuing biological assessment of rivers’ and streams’ attainment of Maine’s Water Quality Standards.

This report more specifically presents the findings of the 2017 and 2018 annual work plans recommended by the SWAT TAG in meetings July 12, 2017 and June 4, 2018. The 2017 and 2018 work plans focused on monitoring of PCBs, dioxins and furans in lobsters, heavy metals, PCBs, PAHs, and perfluorinated compounds (PFCs) in marine shellfish in known or suspected contaminated marine areas, cyanotoxins in Harmful Algal Blooms, mercury in black crappie (a favorite panfish with anglers), PFCs in rivers below sewage treatment plants as requested by MCDC, contaminants in two urban streams, biomonitoring of aquatic life in waters in southern Maine, Penobscot Riverwatershed, and Downeast areas that need to be monitored for evaluation of discharge permits, and a study of mercury resistance in fish from the Penobscot River. Following is a summary of key findings from the 2017 and 2018 SWAT programs for each of the modules.


This 2017/2018 Surface Water Ambient Toxic (SWAT) monitoring program final report is organized into an Executive Summary, Introduction and 4 modules:

  1. Marine and Estuarine
  2. Lakes
  3. Rivers and Streams
  4. Special Studies

The full report is available on the DEP website at

Questions may be directed to authors of each study or to Don Witherill, Director, Division of Environmental Assessment, Bureau of Water Quality, DEP, SHS 17, Augusta, Maine 04333, tel: 207-215-9751; email:


Brunswick, Casco Bay, Casco Bay watershed, Falmouth, Maine, Portland



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