In January this year an archaeological investigation was carried out on the Leasowes Lane Dam. We wanted to find out what existed below the modern tarmac surface, and to see whether we could find any part of Shenstone's original 18th century dam.
Back in April 2001 a narrow trench was dug across the road which exposed part of a cobbled surface, it was hoped that the archaeological investigations would tell us if these cobbles were the surface of the dam in William Shenstone's time. We also wanted to know how far the cobbles extended, and whether there was any further evidence of the original walls of the dam.
The investigations proved to be hugely informative revealing sufficient information to enable us to piece together the history of the Leasowes Lane dam and to establish how its structure has changed over time.
In simple terms the dam's history can be divided into 4 clear phases.
The tarmac was cleaned off the dam and was dug down to a depth of about 450mm, removing soil containing fragments of brick, clinker and small pieces of industrial slag. Below this material was the cobbled surface. This was found to cover most of the dam below the area of the tarmac road. The cobbles were a dark grey-green Rowley Rag, which is a local basalt. The size of the cobbled stones varied quite considerably from large flat slabs 150mm square, and upward, to thinner rectangular pieces only 50-70mm across. The cobbles had been set into yellow-brown clay to form a fairly level surface across the dam. The basalt from which the cobbles are made seems to have been chosen for its hardwearing properties. The stones do not therefore show many signs of wear and tear such as scratches on the surfaces if they had it would have suggested that vehicles once travelled over the dam.
Deep bore holes were also drilled into the core of the dam; these did not reveal any other road surfacing below the cobbles, which would suggest that the cobbles are indeed the original surface of the dam. Whilst we have no evidence that the cobbles were laid
by Shenstone himself, the nature of the rock material used is consistent with his era; and we are therefore confident that this cobbled surface is of William Shenstone's time.
There was also some evidence of the base of the original wall of the dam, on the lower side. This wall has lost most of its upper courses making it impossible to determine its original height. Was it of a height that visitors to the park could lean on it to admire the view down the valley? Or was it actually little higher than the surface of the cobbled road? It is hoped that the excavations required to rebuild the dam will reveal more about this wall, providing further information about its structure and appearance. However, it is possible to say that this wall was constructed from sandstone/gritstone rubble sourced locally. This was faced with a local 'Espley' Rock. In later years this wall was used as the foundation for newer walls which were built off the top of it.
From the location of this wall we are able to say that Shenstone's dam was about 6m wide.
The remains of a simple land-drain was unearthed it was formed from upturned tiles laid into a shallow trench. As the cobbles have been cut through to lay the drain it is clear that this is a later addition to the dams construction.
Sections of brick wall from various eras were found along the lower side of the dam. The heights of these walls correspond to the level of the road surface which was gradually raised over time. It appears that the dam has also suffered from partial collapse on the downside; this has been dealt with by the part reconstruction of the walls in an attempt to hold the dam up.
However, it seems that these measures proved to be insufficient and that eventually it was considered necessary to completely remodel the dam to make it stable. The rebuilding of the dam was probably carried out in the 1930's, after the local authority had taken ownership of the Leasowes.
Interestingly, this historic photograph shows the dam with a tall brick wall with regular spaced piers on both sides. The style of the ladies dress would suggest that the picture was taken around the end of the 19th century, or perhaps early into the 20th century. Close inspection of the photograph reveals that the lower wall is already beginning to tilt indicating some movement in the structure of the dam.
The tarmaced roadway is the result of the remodelling of the dam in the 1950's. The work was quite extensive, and included the widening of the dam to its present width, and the creation of a new lower face to the dam with an outflow for water from the pool behind. The area behind the new wall was back filled with a mixture of ash and clinker. The present low walls on each side of the dam have been made from reused paving slabs and date back to the same period.
When the archaeological investigations had been completed a protective layer was placed over the cobbles, using a geotextile membrane. The dam was then temporarily back filled with the loose material which had been dug out at the start of the excavations.
The design for the reconstruction of Leasowes Lane dam is now almost complete. This artists impression shows how it will look once rebuilt. The drawing also shows that the cascade on the lower side of the dam will take on a strikingly different appearance with stone being imported and placed by crane to form the appearance of stone strata over which the water will flow (from a stone arch in the dam) to create a cataract effect.