This report presents the results of monitoring measurements of waterborne noise taken at Town Quay, Southampton, during piling operations at Red Funnel's Southampton Terminal in September 2003. Simultaneously, observations were made of caged brown trout (Salmo trutta) to determine whether there was any observable effect of the piling on their behavior.
The piling was required as part of a construction project for Red Funnel, installing improved loading facilities at their Southampton Terminal, illustrated in Fig. 1. The project was required to provide infrastructure for improved ferry services, and in particular to allow twin-deck access to ferries. As part of the project piling in the water adjacent to the dock wall was required to provide foundations for the new structure. Existing ferries were also modified during the period of construction to allow twin deck access; during this period a temporary ferry was provided.
Driving of piles in water have been recorded as generating high levels of underwater noise (Abbott & Bing-Sawyer (2002)), and there was consequently concern by the Environment Agency (EA) and English Nature (EN) who have remits to control construction projects so as to mitigate adverse impacts on fish stocks. Their concern related to the possible effects construction noise might have on local fish populations, and in particular on migration of salmon.
A consent had previously been given by the Environmental Agency for Red Funnel's contractors to undertake the piling between the 1st December 2003 and the 31st March 2004, during which period no significant impediment to the migration of salmon through the area and into the Test was expected. However, due to significant economic and commercial factors connected with the required timescales for withdrawing the ferries from service, and the need to accomplish the engineering work outside peak travel periods for passengers, a consent was sought from EA and EN to bring forward the piling project to commence on the 1st September.
Permission was subsequently given for the piling to be brought forward to September 2003, subject to two requirements, namely:
- the mitigation of impact piling noise by use of bubble curtains as required, and
- the work being monitored by means of measurements of underwater noise.
In addition, Red Funnel provided some funds for direct visual observation of a tethered cage of fish in order to make direct visual observations of any effect. Owing to the problems of obtaining salmon for testing, farmed brown trout (Salmo Trutta) were used in the tests, being the most closely related species with a similar hearing ability.
These measures were deemed sufficient to ensure there was no increased likelihood of salmon in Southampton Water and the River Test being affected by the piling.