For years, swimming has been prohibited in the Cockle Cove Creek that runs along the Cockle Cove Beach parking lot, where it bends east to merge with Buck's Creek and empty into Nantucket Sound. Consistently poor water quality readings resulted in essentially a permanent closure. A 2005 study failed to find conclusive evidence of a specific source of the contamination, ruling out effluent from the sewer plant, road runoff and septic systems. “It is believed,” the report concluded, “that the major causes of the bacteria levels are natural sources,” most likely from wildlife in the Cockle Cove marsh.
This summer, Chatham officials are faced with the mystery of what caused the half dozen instances of contamination at Pleasant Street Beach. The fact that the beach had only been closed because of water samples that failed to meet the state bacteria threshold for swimming seven times in the past 13 years indicates something unusual is going on. Yet there are no obvious indications of a source, and the recurrence of high counts would seem to rule out a one-time incident, such as a pooping seal or the dumping of a boat head offshore. Like the situation with Cockle Cove, it's possible the nearby Red River marsh is the source, given the summer's heat, and that tidal and other conditions just happen to be perfect to move the contamination east to Pleasant Street Beach at just the right time. That possibility is being investigated.
Since the problem has only occurred at one of the town's Nantucket Sound beaches, it is not likely a systemic issue. There could be a specific explanation, and officials could certainly use the eyes and noses of neighborhood residents to highlight anything unusual. Like the Cockle Cove Creek situation, however, there may never be a conclusive answer to the mystery of this summer's Pleasant Street Beach closures.