Revealing The
Swansea Main Drainage Scheme 1931-6

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The Main Trunk Sewer:

Swansea's original sewers were laid down in the 1850s and 60s with additional work carried out in 1895. The system, which discharged directly into the River Tawe and Swansea Bay, was inadequate for the 20th century. With the extension of Swansea's borough boundaries in 1918 to include Oystermouth, Brynau, Cockett, Llansamlet and parts of Penderry and Clase (many parts of which were unsewered) a drainage scheme for the whole, enlarged Borough was essential. Plans were drawn up for a huge project, to be known as the Main Drainage Scheme.

WORK ON THE GREAT SEWER

A Comprehensive Programme of Works:

The solution to the sewerage and drainage problems of the enlarged Borough was to construct some 40 miles of district (subsidiary) sewers which would then drain into a new Main Trunk (Intercepting) Sewer running over 11 miles from Clydach down to Mumbles Head. Here the sewage would be stored in four huge tanks inside Mumbles Hill before being discharged via an outfall into the current of the Bristol Channel 220 yards east of Mumbles Lighthouse. (OHA Archive 'Down The Drain' ).  

The End of Pollution:

At the official opening Alderman Harris declared that although "it had cost a huge sum" the scheme had not only relieved unemployment but also the pollution of the River Tawe and Swansea Bay which had existed for over 100 years would cease." The Evening Post was rather cynical: "The employment has disappeared, the wages spent, but the debt remains and the unemployed. Moreover, the latter were never at best more than a fraction of the army available. As a consolation we have the sanitation of Swansea secured for all time."

However, nothing could alter the fact that the scheme was an amazing feat of engineering and tribute should be paid to those who designed and worked (in often unenviable conditions) upon the construction of the Swansea Main Drainage Scheme in the 1930s. (OHA Archive 'Down The Drain' ). 

The Attendant's House

Over the week following the opening of the scheme, the general public and schoolchildren were allowed to walk through the tunnels.
W.G. Archives, holds a film which records that on teh day of the opening ceromony, The Mayor of Swansea and his entorage, entered the scheme via the Bungalow, built above the Screening Room and from there they were able to walk down into one of four Storage Tunnels (see later photo) each nearly 2,000 feet long, to the Penstock Chamber. The party then climbed a temporary staircase into the Control Chamber (photo) and were then able to exit along the access tunnel, to the Bracelet Bay entrance, near 'The Big Apple.' where refreshments were served.  

Unemployment Grant from the Government: 

Because of high unemployment in the late 1920s the Government were the 19zys offering grants to local authorities for public utility schemes which would provide employment. Therefore, in 1931, Swansea's Main Drainage Scheme was approved for a Government grant of 63%. Over 1000 men were employed on the main sewer construction, nearly all of them local. But in 1932, 15 miners from Cumberland were recruited (with their specific skills) to construct the tunnels in Mumbles Hill and there were many complaints reported in the local press about labour being imported from outside the area.  (OHA Archive 'Down The Drain' ).  

"It was very clean inside!"

After the official opening and before sewage use began the works were open to the general public for one week. Visitors to the 4 storage tanks inside Mumbles Hill walked into the tanks and saw some of the 10 million bricks used in the sewer construction. "I think the bricks were white and it was very clean," recalls one Mumbles resident from her visit as a child. The Evening Post described the tanks (each 1995 feet long, 16 feet wide and over 10 feet high and lined with bricks) as "stretching into infinity ... electric lights twinkling smaller and smaller into the distance ..."    (OHA Archive 'Down The Drain' ).  

By 1936, large quantities of stone had been mined to creat the various tunnels for the scheme. Most was used to create the popular Bracelet Bay car park (seen below) and  some stone infilled the old Iron Mine cutting  on the Hill, from above Knab Rock.

Disruption at Bracelet Bay and Mumbles Head:

A series of photographs taken in 1935 by M.A. Clare illustrate just how Bracelet Bay had become unrecognisable. The Evening Post described it as "one huge silver grey spoil bank of excavated limestone, down which shutes run and over which electric lights glitter. ... It is possible to see 50 yards or so down one of the tunnels, and, when it is aglow with electric lamps, it is [like] Aladdin's Cave, from whose inky depths comes the pulsating of a hidden engine."

 (OHA Archive 'Down The Drain' ) 

Additional research by Jack Hartley

The visitors were taken on a conducted tour of the workings. 

The report in the South Wales Evening Post was vivid:

"The visitors were conducted behind the bungalow. There, under the wire screen which catches debris which escapes occasionally down the steep cutting into the tall hill, they had their first glimpse of the immense proportions of the work. From there until they emerged upward into daylight through the access tunnel into the Bracelet cliff, and on to promenade roadways created by the use of debris from the excavations in the hill, they were surrounded by brickwork or concrete.

Everything was cleaned for the occasion, and stewards, police, stairways and barricades prevented any deviation from the route chosen. Lights will remain, till the time comes for the scheme to operate, along the roofs of the storage tanks, and in the case of the one traversed precautions were taken against the remote possibility of a failure in lighting. First the visitors passed down steps to the screen house, rounded its machinery, and then walked along the large access tunnel running into the hill. A stairs took them into the storage tanks. They arrived in No.3 of the four. A floodlight placed here showed only a little distance along this immense tunnel of brickwork, its lines of specially hard bricks beautifully finished. Then they crossed into No. 2 - there are 20 feet of solid material between each - and passed along its whole length of almost 2,000 feet. To say that each tank has a capacity of nearly two million gallons does not convey much to the average person, but the length is hinted at when it is stated that apparently the eye sees the overhead lights to only about half the length, that is where the access from the Cutting road reaches the tanks. And the tanks are so wide that on each side of the deeper central channel four people walk abreast easily. Here and there along the side were noticed the controlled escapes for the many pockets of water, characteristic of limestone, met with in the hill. These escapes close as the tanks begin to fill.

At the end of the tank the guests lowered their heads to pass underneath a steel penstock through which the tank is to be emptied, across a tunnel and up stairs to the control room of the penstock chamber, where Alderman Edward Harris operated one of the main penstocks to open tanks to the sea. Guests then proceeded to the Pier where tea was served."

In the same edition a long article by Mr. J. R. Heath described the early attempts at drainage, the pre-1918 expansions and planning, the sewering of the town and the construction of the Main Trunk Sewer. He paid tribute to his predecessor, Mr. H. H. Wyrill, to Alderman Edward Harris, vice chairman Alderman Daniel Evans, and the Committee members, to the contractors, and to the Ministry of Health's chief engineer and his staff for their help and advice. Finally, "and by no means least", to the unemployed men who performed the manual work, many of them adapting themselves to arduous, difficult and unaccustomed work. "The results speak volumes for their tenacity, especially as many of them began with the great handicap of having been without work for long periods. After only brief training they adjusted themselves to what was often specialist work and have done work, the quality of which could not be excelled in this country."

The public were invited to inspect the work during the following week. Then subsidiary sewers were connected to the Main Trunk Sewer in stages beginning at Southend and ending at Clydach, gradually bringing the system into operation.

Early Plans of the Scheme

When the idea of an outfall at Mumbles Head was considered in 1911 it was necessary to prove that currents and tides would take the effluent away from land out into the open sea. This was done by series of float trials. A floating object was placed in the water at the proposed site of the outfall, followed in a sea-going motor boat with a crew of two, and a surveyor or pilot plotting the course by sextant readings of prominent buildings or features on the shore. This procedure was repeated at each hour of a daily tide cycle and on several days so that every stage of the monthly tide cycle had been tested. 

The results were plotted on 12 large scale charts. Such tests at Swansea Pier in 1894, 1896 and 1911 showed it an -unsuitable outlet. 101 tests from a point just east of Mumbles Lighthouse from 26 August to 8 October, 1911 showed that effluent discharged from 3 hours before to 5 hours after High Water would be carried down channel and away from the land.

The outlet would have to be closed for four hours of each tide during which sewage would continue to flow and would need to be stored. Only by creating space within Mumbles Hill could this be done.

The Sewage Pumping Station at Knab Rock 

More: The Opening  of Swansea Main Drainage Scheme >
Includes full details of the scheme up until the opening, including  Contracts and Contractors. 

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