Summary of BMT SeaTech Ltd Presentation

Posted on 23 Apr 2008

It is proposed to introduce new ferries on the Lymington/Yarmouth route. As part of this process it is important that any change in the marine risk on the route is as low as reasonably practicable. This consideration is especially important in the Lymington River as it is a waterway with a large number of leisure users, especially at the height of the sailing season. With this in mind, BMT SeaTech Ltd (BMT) was commissioned by the Lymington Harbour Commissioners (LHC) to carry out a risk assessment for the introduction of the new ferries.

The study falls naturally into two parts:

  • Phase 1: An assessment of the present situation with informed predictions of the situation with the new ferries.
  • Phase 2: A re-assessment of the situation after initial trials with the new ferries.

This report deals with Phase 1 of the overall study. It discusses the present situation on the river and lists the concerns of local users regarding the introduction of the new ferries. With these in mind, the design of the new ferries is then discussed in some detail and their possible impact on operations is predicted. The effect of the present international intact and damaged stability requirements as a primary driver in the design of the new ferries is discussed, and the way that this has led to the hulls of the new vessels being the size and shape they are is described.

The present level of marine risk on the river then assessed and, in terms of the incidents per vessel movement, the historical value is found to be very low, implying that the present safety levels are high. A Risk Register is proposed which combines risks and their magnitudes with suitable control measures. Arising from this, it is concluded that, at times when the river is congested with leisure and other craft, an increased presence of LHC patrols in the lower reaches would be beneficial to all concerned.

In order to provide a further basis for comparison in Phase 2, measurements of water disturbance caused by the ferries and other craft were made at two locations on the river – one in the vicinity of the passing place in Short Reach and one in Horn Reach. The ferries and a self-propelled dredge barge created their own characteristic disturbance patterns, as did smaller vessels such as work boats, fishing vessels and RIBs. Natural waves were also measured during a period of reasonably high winds from a direction somewhat to the north of that which prevails in the area, resulting in some shelter from the wind and a reduced fetch. Nevertheless such waves were in general higher than those produced by the ferries and other boats, although one fishing vessel produced large free waves.

Although it is made clear that the final assessment of the actual impact of the new vessels must await the completion of the trials in Phase 2, an attempt is made to predict the orders of magnitude of some of the effects the new ships could have on leisure users. From this, and with the information presently to hand, we are of the opinion, at this stage, that there is no need for leisure craft risk control measures which are any more demanding than those presently in place. This is especially so in Horn Reach where most of the Junior Sailing takes place; indeed we see no need for the new ferries to reduce their speed from the advisory 4 knots in this part of the river, thereby causing no additional disruption to Junior Sailing activities there. However, some aspects of operation and behaviour with the new ferries have been identified as requiring special attention in the Phase 2 trials.

It is, however, concluded that the present practice of ferries waiting in the river should be abandoned where practicable, with the norm being unhindered passing.

In conclusion, therefore, the following recommendations are made:

  • Make ferry waiting in the river the exception and unhindered passing the rule
  • In peak season, increase the Harbour Master’s patrols in Short Reach, especially near the passing place
  • Ensure that ferries continue to make sound signals on leaving the terminal when junior sailing is in progress, and make it common practice to give similar signals when inbound at the Cocked Hat navigation post.
  • Ensure that the navigation posts in the river mark the limits of the navigable channel and provide a visual indication of the channel in all conditions, including fog.
  • Install visual tide boards on navigation posts.
  • Ensure that a structured programme of trials is undertaken with the new ferries. (A preliminary template for such trials is suggested in the report)