HT-2023-000321 - [2025] EWHC 1764 (TCC)

Mr Moore’s assessment of downtime in respect of what he calls unfavourable seabed conditions amounted to 194 hours 31 minutes. Mr Scott did not separately calculate any period of time which might be associated with seabed conditions, but these periods were included within his general ‘Tool Downtime’ category. The contents of Mr Moore’s report in this respect were not materially challenged, no doubt because KML rely upon its contractual/risk allocation arguments. The following summary of the 5 longest seabed condition related events (accounting for over 177 of the lost hours) in the following paragraphs is drawn largely from his report.

Event 4 - 09:12 on 29/06/2022 to 18:45 on 04/07/2022 (129 hours, 33 minutes) The UTV-670 became trapped on a high incline of 29° during jetting and burial works at around KP 0.154. from 09:12 on 29/06/2022 and remained so until around 23:05 on 30/06/2022. As a result of worsening weather conditions the UTV-670 could not be driven back to the Susanne-A and had to be parked on the beach while the vessel returned to port. The UTV-670 was then transported back to the port by road arriving at 09:00 on 04/07/2022. The UTV-670 was brought back into operational status at around 18:45 on the same day. The root cause of the downtime including the waiting time at the beach, road transport to port and remediation was recorded by Mr Moore as downtime due to seabed conditions.

KP 0.154 is within the very nearshore area of the trenching route. This lies in an area of the cable route between KP 0.14 and KP 0.27 which underwent an MBES survey prior to trenching works starting in the nearshore area. It was KML (or its other sub-contractors) carrying out the MBES survey along the full cable route between KP 0.14 and KP 2.48. There is no dispute that, in fact, as noted in the MBES survey itself the final part of the MBES survey performed on 23 June 2022 was only between KP 0.196 – KP 2.5. The survey boat was not able to survey KP 0.14 – KP 0.195 due to weather restrictions.

Event 13 - 14:08 to 20:05 on 10/08/2022 (5 hours, 57 minutes) At the start of this event the relevant DPR indicated that trenching work had ceased at KP 0.694, the UTV-670 had been repositioned and was undertaking survey work at KP 0.396 when it became submerged in fluidised soils.

According to the DPR records, cable trenching had taken place across KP 0.396 during dive 19 and dive 20, 11 days earlier on 30/07/2022. KP 0.396 lies on the edge of a slope at a seabed depression which falls from 4.7m to 6.0m. Whilst no report of high inclinations was noted in the POG DPR, this seabed feature may have contributed to the TROV becoming stuck.

Event 14 – 11:25-18:52 on 11/08/2022 (7 hours, 27 minutes) The DPR for 11/08/2022 at 11:29 reports that the UTV-670 was caught in a sink hole at KP 0.309. Because of tidal limitations and the fact that the Susanne-A had insufficient time to transit over the offshore sandbank, the UTV-670 was recovered back to deck. The area adjacent to KP 0.309 on the August 2022 MBES survey results shows evidence of localised depressions, some of which are just outside of the 2m depth offset lines, depicted in dark blue, to the north and the south of the cable route. Mr Moore considered that the depressions may have been the reported sink hole.

Event 19 – 20:16 on 12/08/2022 to 06:20 on 13/08/2022 (10 hours 4 minutes)From KP 0.261 at 19:54 the UTV-670 started to move along the cable line increasing water pressure on the pumps. At 20:02 (KP 0.277) it is reported that the UTV-670 is trenching steadily at 2.2m depth. Following on from this report around 20:14 (KP 0.296), the DPR indicates that the TROV is out of the ditch and is trenching. The DPR does not report what this ditch was or its severity.

At 20:16 (KP 0.296) the UTV-670 is reported as being stuck and an all stop command was issued. The UTV-670 remained stuck until grading in operations were started at 06:20 the following day. This event is close to the KP 0.309 position of Event 4 and therefore this event may have been caused by the same reasons as Event 4. Some 12 minutes after this event the aft of the TROV sank in collapsed soils at KP 0.148 where the vehicle is reported to have experienced roll inclination angles of 22.8° to 24.3°. This second incident (Event 20) incurred further downtime of 1 hour 23 minutes.

Event 21 -14:46 on 13/08/2022 to 14:16 on 14/08/2022 (23 hours 30 minutes)Shortly after Event 19, the TROV became trapped again at KP 0.182. This was resolved at 15:59 but the vehicle became trapped again in what the POG DPR refers to as ‘the same trench’ and remained so until 14:16 the following day. The KP 0.182 location is shortly after the position where Event 4 took place to the west. It can be seen from the location of Event 21 the contour lines are close together and change direction significantly, indicating the presence of localised seafloor trenches or depressions. The DPR also reports at 15:42 and 19:25 that (static) roll measurements showed angles of 17.2° on each occasion. This is a further indication of the high seabed slope at this location.

I consider in more detail below the question of liability for time spent dealing with unfavourable seabed conditions.