DATA ANALYSIS AND SPATIAL MAPPING OF DISSOLVED OXYGEN IN THE ANDROSCOGGIN RIVER FROM 1930-2019

The Androscoggin River was one of the most polluted waterways in the United States in the 20th century and inspired Senator Edmund Muskie to write the Clean Water Act (CWA) of 1972. Untreated mill waste and raw sewage were regularly discharged into the river from the late 1800s to the 1970s, increasing biological oxygen demand and depleting dissolved oxygen (DO). Growing concern for the condition of the river led to increasing regulations, first on sulfite waste discharge and later on all point source pollutants. Executives from the paper companies were tasked with studying and remediating the river from the 1940s to 1970s, however financial interests superseded environmental concerns and progress was slow. The major accomplishment of this committee was replacing sulfite pulping mills with Kraft pulping mills, which produced less effluent, by 1965. Later, the CWA prompted the construction of wastewater treatment facilities along the river, further reducing organic waste. The environmental history of the river is well documented, however no study since 1978 has sought to quantify changes in DO beginning with the first water quality survey in 1930.

Average August DO data from 1930-2019 was considered spatially and temporally to evaluate remedial actions by the paper companies and government. August data were used in this study because it is the most consistently sampled month, and because DO concentrations and discharge are at their lowest. The shift from sulfite to Kraft pulping between 1959-1965 led to the first notable increase in DO since annual monitoring began in 1948. The CWA resulted in the most significant improvements in water quality, bringing the average DO above 5 ppm at almost every site following 1977 and making nearly every stretch of the river habitable by fish year-round for the first time in at least 35 years. Results also indicate reduced variation in average DO between June-September post-CWA, compared to pre-CWA data. Surveys focused on the Gulf Island Pond, a 14-mile-long impoundment north of Lewiston, document slight improvement in surface water DO levels after 1992. The reduction of organic-rich municipal and industrial waste discharges has greatly improved DO in the Androscoggin River, however it remains the dirtiest of Maine’s major rivers despite decades of remedial efforts.