Fort Purbrook 

 Tunnel No2

 Created 02-03-2003    Last update 17-01-2006

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Tunnel No2 - the final proof

As the research into this tunnel was developing I was contacted by Paul Wells who supplied several photos of a similar site in Dover. These suggested that the purpose of the Tunnel No2 was to carry sewage northwards away from the Fort.

Further research at the Public Records Office by Peter Cobb produced the original plans of the tunnel, and these are shown below.

It was indeed a service tunnel, built in 1898 - some 30 years after Fort Purbrook was built - and it housed a 6 inch cast iron sewer pipe. The Ventilation Tower was built because the pipework of this era leaked, and the tunnel had to be ventilated at high level to keep the smell clear of the Fort. A tunnel was used to carry the pipe, because in those days it was cheaper to tunnel than to 'cut and cover', especially at a depth of 20 feet. The tunnel did not enter the boundaries of the Fort, but stopped at the vent tower.

The cost of the project was 1815, and interestingly 500 of this was provided by the Portsmouth Water Company. The other Forts - e.g. Fort Widley - on Portsdown, discharged their sewage through pipes, SOUTHWARDS, to cesspits at the foot of the Hill. However to the south of Fort Purbrook are the Portsmouth Water Company Reservoirs, and the reason that so much trouble was taken to carry the sewage north, was to prevent the Fort's effluent from contaminating this water supply. 

 

plan of No2 tunnel  

The plan of Tunnel No2 to the east of Fort Purbrook.

Crown Copyright

Key

A Fort Purbrook
B The southeast ditch of the Fort
C Annotation showing the extent of the tunnel length
D The site of the 'ventilation tower' and the start of the tunnel
E The end of the tunnel. This corresponds exactly to the location of the 'manhole' described in the emails. From here the pipeline continues underground, and was laid using 'cut and cover'
F The old Crookhorn Lane
G An over explicitly named 'Straining Chamber' which separated the solids
H The 'Sewage Plot'. This was a field where the liquid sewage was discharged onto the surface.
 
 
 
 ventilation tower plan

The plan of the Ventilation Tower - A, the doorway into it - F, the arch at the base of the tower G, and the tunnel itself - H

Crown Copyright

Key

A Ventilation tower
B 6 inch cast iron stench pipe - with a wire guard on top
C Iron 'D' rungs set into the side of the shaft
D Annotation showing the end of the cutting
E 6 inch cast iron sewage pipe
F Shaft access door in the ventilation tower - in typical Victorian style
G The archway at the base of the tower leading to the tunnel
H The service tunnel showing the pipe laying on the floor
 
 

 

NEW 15-01-2006
Just when I thought things had settled down I received the following from David Moore and Geoff Salter of the Palmerston Forts Society . It was taken from the Gosport/Portsmouth Letter Books in the Royal Engineers' Museum archives at Chatham, dated 21 March 1862.
With reference to Fort Purbrook and outworks, I have to report that a 
shaft has been discovered in Crookhorn Wood at the position marked B in accompanying sketch, which is supposed to be part of a scheme which is said to have been contemplated for supply of Portsmouth with water from this point by means of a tunnel carried through Portsdown Hill. [This was part of the Farlington Aqueducts c. 1776]

I have caused this shaft to be explored to the depth of 79ft and the 
workmen were enabled from this depth to force a wooden rod 10ft further into the loose soil and bricks with which it had been filled. The strata is chalk of which the first 12ft is friable, the remainder portion being rock chalk. At this depth of 19ft 6in there are 2 headings driven one about north the other south. They each extend 18ft 6in from the shaft and are 4ft high and 3ft broad.

I would propose to clear this shaft to carry the whole of the sewage 
from Fort Purbrook Farlington and Crookhorn Redoubts into it as shown by the black lines on on accompanying sketch. The other proposal be entertained, the present contractors might be called on to cut the necessary tunnels from Fort Purbrook to Crookhorn Redoubt and also from Farlington Redoubt to the shaft.

 
This raises far more questions than it answers and will no doubt keep me busy for some time to come.
 
 

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