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River Pollution Case Study

Summary Report on pollution of the Tolka River near Clonee, Co. Dublin
Date of Offence: July, 2005

Members of local angling groups reported a poor quality discharge of effluent (and an associated fish kill) on the Tolka River to the ERFB in mid July 2005. On arrival at the reported discharge location and on visual inspection in the vicinity of the implicated surface water discharge point, it was noted that there was no discharge coming from the pipe. However significant ‘chemical burning’ of bank-side vegetation around the discharge pipe, a discolouration of the river bed and a general absence of in-stream aquatic flora and fauna downstream of the discharge point were noted. Live fish (juvenile stickleback) and invertebrates were observed approximately 5 metres upstream of the discharge point but were absent downstream of this location. An ammonia-like odour was
present in this area. There was no other apparent discharge above or below this point in this area.

Tolka pollution incident 2005

A series of samples were collected at the site. During collection of water samples, the investigating Fishery Environmental Officer (FEO) experienced the sudden effect of a noxious (ammonia-like smell) gas which manifested itself in shortness of breath, and skin / eye irritation. Approximately 10 seconds after initial effects of the gaseous plume were felt, the surface water pipe discharged a voluminous effluent which was initially propelled a distance of approximately 5 metres directly into the river channel. This discharge continued for 5 minutes. Sample were collected of the effluent from the pipe and from the river channel downstream.

ERFB FEO’s visited the plant from which the pipe was discharging immediately and explained the urgent situation to senior staff. FEO’s insisted that a guarantee be given that no further effluent would enter the channel from the plant. Senior staff gave this guarantee. Subsequent inspection of the Tolka River downstream of the surface water discharge pipe revealed a massive fish kill (1000’s of dead fish) in addition to an apparent wipe out of most macroinvertebrate life from the discharge point downstream for a substantial distance. A subsequent electrofishing survey carried out by ERFB staff revealed 100% mortality of all salmonid fish species for a distance of approximately 7km downstream of the discharge point.

Download the report [.pdf, 360 KB]:

Summary Report on pollution of the Tolka River near Clonee, Co. Dublin


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