Publication Detail

Analysis of Boston Inner Harbor Dye Study

Eric Adams, Drew L. McGillivary, Seung-Won Suh
50 pp.
MITSG 94-08

During July 1992 a fluorescent dye study was conducted in Boston's Inner Harbor in support of MWRA's System Master Planning Combined Sewer Overflow (CSO) program. Approximately 500 pounds of 20% Rhodamine Wt dye were released over a period of 5 1/2 hours into the Charles River just upstream of its entrance to the Inner Harbor at the Charles River Dam. Dye concentrations were recorded throughout the Inner Harbor over the following six days. After the first day, dye was reasonably well mixed laterally, but showed decreasing concentration with depth and distance toward the mouth. The mean residence time of Charles River water in the Inner Harbor, computed from the time variation of total dye recovery, was in the range of 3.5 to 4 days, suggesting that about half of the freshwater leaving the Inner Harbor during ebb tide returns during flood tide. Fecal coliform are often used as indicators of sewage pollution. Reported half lives of fecal coliform, determined by calibrating models to field measurements in Boston harbor, fall in the range of 0.2 to 0.7 days-- significantly shorter than the mean residence time. This suggests that most bacteria entering the Inner Harbor with the Charles River inflow, or from nearby CSOs, die by the time they reach the Outer Harbor.

type: Technical reports

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