The San Juan Estuary, located in northern Puerto Rico, comprises lagoons, channels, streams, and rivers. In the early 1930s, industrialization and hurricanes led to an influx of residents settling along the Martín Peña Channel. Years of unregulated construction and the absence of a sewer system gradually reduced the channel’s width from over 100 feet to as narrow as 10 feet in some areas. High fecal coliform levels have rendered the water unsafe for swimming or recreation.
Following a community petition, a three-phase dredging project was funded, consisting of (1) vegetation removal, (2) bridge reinforcement, and (3) channel dredging. This study aims to assess the impact of the first dredging phase on microbiological contaminants, as well as physical and chemical water parameters.
Water samples were collected monthly before, during, and after the first phase at five stations, including sites both inside and outside the channel. Physical and chemical parameters were measured using a YSI instrument, while fecal coliforms, enterococci, and Escherichia coli were enumerated using Enterolert and Colilert assays. Results showed that temperature and pH remained stable across the sampling period, but oxygen levels fluctuated, indicating high levels of biological activity. As expected, salinity and conductivity increased near the sea. However, fecal coliform, E. coli, and enterococci levels did not decrease and frequently exceeded water quality criteria limits. This research will continue throughout all three dredging phases. Results will be shared with community leaders, PR Department of Natural and Environmental Resources, the US EPA, and the U.S. Army Corps of Engineers to support the development of more effective coastal watershed plans.