Friday, October 1, 2010

Daily Facts and Opinions, Wastewater Overflow

From Jacksonville (NC) Daily News, Friday evening.

City officials are continuing an investigation into why a system attached to a tank designed to help prevent overflows during severe rain events malfunctioned.
Using methodology provided by the State, the estimate is that between 150,000 and 250,000 gallons of untreated wastewater possibly flowed into Chaney Creek Friday morning, according to information from the City of Jacksonville.
The city is in the process of assembling a forensic engineering team to investigate how the system allowed an overflow to occur, according to Jacksonville officials. A preliminary review by the City Engineer indicates that a sensor that was to have stopped flow to the tank and alert City operators of a problem malfunctioned. A second backup sensor that would have done the same was also never tripped.
Tropical Storm Nicole was the first time that the Equalization Tank has been used during peak pumping times since its construction.
City crews visually inspected the tank at 4 a.m. Friday, according to the city. During another visual inspection at 6:30 a.m., it was discovered to be overflowing.
Crews immediately worked to stop the flow and succeeded about 7 a.m. Crews took steps to minimize damage from the overflow, notified state officials and took steps to manually control the overflow devices.
Water Quality crews from the city have been taking samples from the waterways surrounding the site, and will continue to monitor water quality over the next few days to determine if the water is a threat to health and safety.
The city installed the Equalization Tank to absorb high flows at the Main Pump Station during peak pumping conditions, according to city officials. A majority of the cCity’s wastewater flows to the city’s Main Pump Station. From there, the city has a fixed capacity within the lines and pumps that go to the city’s Wastewater Land Treatment Site and the tank is designed to receive the flow when that capacity is challenged, such as during excessive rain events.
The City has recorded nearly 20 inches of rain since Sunday evening including the Thursday evening passing of the remnants of the eye of Tropical Storm Nicole.
On Thursday, several City manholes experienced overflows as a result of the heavy rains. In some of the cases, the overflows resulted in unknown amounts of untreated wastewater being discharged into creeks and streams.
State officials have been notified about each individual overflow and about actions that were taken to minimize the damage from the overflows. The City also has notified several environmental groups who regularly monitor the New River.
Incorrect information from early reports on the scene indicated a fish kill, according to the city. However, that was wrong. Some fish were trapped in a scour that was created by the heavy flow, but were not killed.

Chaney Creek and Phillips Park,Thursday evening

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