HYDROGEOLOGIC ASSESSMENT OF THE EUTROPHICATION OF THE SIEUR DE MONTS SPRING, ACADIA NATIONAL PARK

The Sieur de Monts spring is a historically significant place in Acadia National Park, providing fresh water for early residents and visitors on Mount Desert Island. The water quality of this spring has deteriorated as severe algal blooms now occur that compromise the ecological integrity and reduce the aesthetic quality of this popular attraction. Several sources for nutrients responsible for the algal blooms have been suggested including on-site wastewater treatment systems and nitrogen-fixing blue green algae. To assess the impact of these sources the following activities were undertaken: near-surface geophysical surveys, interpretation of hydraulic-head data, ground-water sampling for parameters including nutrients and pharmaceuticals, and collection of algal biomass water samples for nitrogen isotope analysis. Geophysical and drilling data indicate that the area is underlain by silty clay inter-bedded with thin sand layers in two basins overlaying medium-grained sand. Hydraulic head data indicate that ground-water flow is generally to the north and west, and is depressed near the Sieur de Monts spring in both the silty clay and deeper sand layer. Downward hydraulic gradients occur in the southern portion of the site, whereas upward hydraulic gradients occur near the spring and northern potion of the study area. Maximum total nitrogen and reactive phosphorous concentrations are 1.1 mg/l and 454 ug/l, respectively, and trace amounts of 4-nonylphenol, caffeine, and N,N diethyltoluamide are present in several ground-water wells and a spring pool. The presence of these constituents indicating that the silty clay layer is either discontinuous (supported by geophysical measurements) or has been breached, allowing wastewater-tainted ground water to migrate into the deep sand layer.