Liverpool Training Walls (Revetment)

By 1907, the usability of the main shipping channel into Liverpool was becoming a problem, with ever-larger liners unable to navigate through at low tide. A commission of experts recommended a solution to the Mersey Docks and Harbour Board, which solved the problem. The position and depth of the Crosby Channel are now maintained by underwater 'training walls' - banks of tipped limestone.

The first of the training banks, or underwater walls, was Taylor's Revetment, which runs along Taylor's Bank, around the outer edge of the channel. It was begun at the east end in April 1909 and completed in November 1910, two and a half miles to the west. The sandbank is faced with piles of limestone dumped from vessels on the surface. Many more training bank works were to follow. The upper part of the estuary almost dries out at low water and fills with the incoming tide to become a gigantic reservoir, some 78 sq km in surface area. This is combined with a high tidal range of over 10m. The movement of water is enormous and the system of training banks stabilise and deepen the Port of Liverpool's 19 km of sea approaches. The alignment of the banks is critical. Hydraulic modelling was undertaken in 1930 to determine the way forward. Most of the banks are limestone from North Wales, dumped by a fleet of hopper vessels able to carry 660 tonnes each. In the deepest water, the banks have base widths of about 60m and are 7.5m to 9m wide at the tops. In shallower water, the crest widths are reduced to 4.5m and the banks have nominal side slopes of 2:1.
  See here for my survey of the wall width near buoy Alpha.

Modern charts show these training walls - with gaps for access to the Rock Channel, and to the (no longer viable) Formby channel. What they do not show is the height of the walls. At the time they were installed, the target heights were 10ft (3m) above CD everywhere except the section on the foreshore off Crosby (called Crosby East) which was planned to be 6-7ft (2m) above CD. These heights are stated in the 1948 and 1960 Admiralty Sailing Directions (West Coast Pilot).

Current Hydrographic Office (HO) charts show more detail of the small section of the training wall near Murphy's Gut (on chart 3490) with the wall marked as two lines. Elsewhere chart 1951 just shows a single dotted line. The charts quote survey dates of 2000-5 near the banks of the main channel with the channel itself surveyed 2009-17. Areas such as Murphy's Gut were surveyed 1988-98 and Taylor's Bank in 1970-81.

Advice from Liverpool Port Authority is that smaller vessels should always remain within the buoyed channel due to the proximity of the Training Walls and Revetments, however, if they should for any reason navigate outside the buoy line, they should ensure that other traffic and Mersey VTS are informed.

I have navigated in and out of Liverpool for over 30 years and I had never seen these training walls until 2019. This is, of course, mainly because I rarely pass them at LW, and then not at springs. What is of concern, however, is that the training walls can have wreckage sticking out above them. The bend near Taylor's Bank (known as Taylors Revetment) was a magnet for wrecks: several large vessels were stranded and broken up: Ulstermore(1913); HMS Cochrane(1918); Armagh(1923); Lochmonar(1927); and, the best known example, PEGU(1939) which is charted as drying 5.9m and is just visible at half tide [north of C6 buoy]. However, I have crossed the training walls successfully in certain areas (near Murphy's Gut; near Alpha buoy; entering Alt) and have surveyed them from my boat. I have actually tied alongside the wreck of the PEGU over neap LW - without seeing the training walls. In these surveys, I have not found any areas more than 2.5 m above CD, but a more comprehensive survey would be to inspect the walls at tidal height 2.5m above CD to check nothing shows above water. The sailors who use the Alt recommend that it is feasible to cross the East Training Wall in a yacht within 2 hours of HW.

Here I present my survey results: depths in metres are reduced to CD using tidegauge results for Liverpool Gladstone Dock. The actual tidal range in the outer Mersey estuary is somewhat less than at Gladstone and HW is somewhat earlier. I have not corrected for those small changes. Distances are in metres.

Taylor's Bank Training Wall (on North side of Queen's Channel close to Alpha buoy which is central to the plot):

Here the wall appears to be less than 2m above CD - for more discussion see Going North.

Near Murphy's Gut (this is the western training wall just north of the Rock Channel opening). The black crosses and line represent the HO chart position of the eastern edge of the training wall [Also 3D image of part of same data]:

This shows that the wall mostly does not dry more than 2m and, moreover, that its location is further east than on the HO chart. For more discussion see Rock Channel. Note that the Navionics chart of this area shows a further magenta line west of the two lines that appear on the HO chart - and this magenta line does not appear to be close to the wall either.

I have recently [2019] visited this area at LW and taken some images of the Training Wall [near Murphys Gut - southern end of west training wall].
At LW [0.6m above CD; buoy is C23]:

From these observations near LW, I could see that the training wall in this area is covered at a time when the tidal height was 2.2m above CD from the tidal gauge data from Gladstone Dock for that time; although the training wall a bit further north seems to be slightly higher.

I have found some nice images of the training banks (at a low water corresponding to 1.0m at Gladstone) from a microlight flight over the wreck of the PEGU.
An image of the PEGU wreck on the Taylors bank training wall (NE corner of channel) and, looking towards Liverpool in the distance, at left the Crosby East Wall and at right the wall on the other (west) side of the channel:

In summary: the training walls (also known as training banks and as revetments) are solid obstacles either side of the main shipping channel. The buoys are located so as to avoid them. For a vessel drawing 2m or less, it is feasible, with sufficient tidal height at that time, to cross the training walls with local knowledge: namely after ensuring that they do not protrude by more than 2.5m above CD in the region to be crossed.

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