Abstract

The City of Poughkeepsie, in southeast New York State, was founded in 1799 and, like many other older cities, it is largely served by a combined sewer system. The combined portion of the system serves a drainage area of approximately 788 acres (320 ha), with approximately 390,000 feet (118,900 m) of pipe, and it contains six combined sewer overflow structures (CSO’s). The City of Poughkeepsie is located directly on the Hudson River and the discharges from its overflow structures enter the river or its tributaries. Because the Hudson River is used for so many purposes (navigation, water supply, irrigation, recreation, and fishing), water quality is of major importance to the entire region. In addition, the Hudson River is a crucial element in the areas’ tourism industry and serves as a major international shipping lane.

During the 1970's and 1980's, the City of Poughkeepsie, prompted by new federal environmental regulations, completed several extensive studies on its combined sewer system. The studies were completed to determine the effect of the combined sewer discharges on the Hudson River. Once the impacts were quantified, options for mitigating the impacts were defined. The studies concluded that elimination of dry weather CSO discharges from the City of Poughkeepsie could achieve measurable benefits in the river. Implementation of the improvements recommended in these studies was successful in eliminating dry weather CSO discharges.

When the State Pollutant Discharge Elimination System (SPDES) permit for the City was renewed in 1993, it contained special conditions that required the City to develop a plan to continuously monitor and report overflows at the City's six CSOs. Faced with adverse environmental conditions in the overflow structures, difficult access issues, and new Federal requirements for confined space entry, the City decided that it would be too difficult and costly to install and maintain a conventional automated flow monitoring system. The City needed an innovative approach! In April 1993, the City retained Clough, Harbour & Associated (CHA) to develop a compliance program.

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