Canine Detection of Fecal Coliform Bacteria from Human Sources in the Pettaquamscutt Estuary, RI - Preliminary Results

Abstract

The Pettaquamscutt Estuary (Narrow River) in southern Rhode Island is typical of many east coast US estuaries in that it has seen a dramatic increase in watershed residential development since the 1960’s. This estuary has had some water quality measurements (nitrate plus nitrite and fecal coliform bacteria) taken at various sites since the early 1970’s. Since 1992, water quality data has been collected monthly from May through September from 10 stations in the estuary by the Narrow River Preservation Association (NRPA) in partnership with the University of Rhode Island Watershed Watch Program. Four stations (two streams, an outfall, and an estuary site) were added later in order to document sources. The nitrogen and bacteria concentrations found in a review of 25 years of sampling are high in the first half of that study but then decrease to near 1970’s levels. Several Best Management Practices (BMP) for stormwater have been built and appear to be reducing bacteria levels in the estuary itself. But highest bacteria levels were found in Mumford Brook, which flows through the adjacent Chafee National Wildlife Refuge (property of the US Fish and Wildlife, USFWS) and in Mettatuxet Brook, which flows through several large residential neighborhoods. Rhode Island Department of Environmental Management (RIDEM) also compiled two Total Maximum Daily Load (TMDL) Reports for this watershed in the early 2000s. The first TMDL report addressed bacteria impairments to the estuary itself and its tributary streams - Gilbert Stuart Stream, Mettatuxet Brook, and Mumford Brook. A second TMDL report addressed bacteria impairments to another tributary, Crooked Brook. Bacteria levels are of concern for human health. In 1979, sections of the Pettaquamscutt Estuary were closed to shellfishing and in 1994, the whole river was closed due to high fecal coliform levels. Most methods that measure levels of fecal coliform bacteria are not able to identify sources. There are methods that involve identifying DNA, but they are expensive and reference material needs to be established. But there is a relatively new method available now. A joint project between The Nature Conservancy, USFWS, NRPA and RIDEM, with cooperation from the towns of South Kingston and Narragansett, took place conducting human bacteria source tracking on critical areas within the Pettaquamscutt Estuary watershed. Bacteria source tracking is being conducted by Environmental Canine Service (ECS) of Otisfield, Maine using canines that are trained to immediately detect whether human contamination exists in water samples, stormwater systems, and/or surface water. Each canine is trained to give a different signal when human sources are detected. This method has been used nationally since 2009 in 14 different states with much success. Canine bacteria detection is being deployed in areas of the watershed that have shown persistent high bacteria concentrations, based on earlier sampling by NRPA or RIDEM. An advantage of this method over traditional methods is that human sources can be immediately identified while in the field and additional areas can be sampled. Also the canines can detect human sources in water with low levels of bacteria (less than 10cfm/100 ml), in old sewage (which may not have much bacteria), in sewage that has had ultraviolet (UV) treatment, and in dry areas that previously had sewage. The canine detection is being supported by laboratory analysis of water samples collected at key locations. With this project we were able to determine certain areas that were impacted by human sources of bacteria, and the sources were probably due to leaking pipes, faulty septic systems, or illicit connections. Such sources are probably repairable.