Home Transit of Venus Sewer History in Leeds Sundials in Leeds William Gascoigne John Feild About

IX. THE BURDEN OF MAINTENANCE

By the late 1960's the sewerage system of Leeds comprised more than 1600 miles of sewers and 50 thousand manholes. These and various types of ancillary structures, such as two hundred storm sewage overflow chambers and several dozen pumping stations, demanded ever increasing resources for their maintenance.

There had to be constant vigilance to prevent the prolonged accumulation of silt, grit and organic material in the sewerage system. Virtually very ancillary structure demanded a regular visit from a maintenance gang. Each day of the week sewermen were at work beneath the city streets clearing blockages, de-silting or carrying out repair work. Although safety standards had improved markedly since the Nineteenth Century, the work was still hazardous by any standards. A horrifying reminder of this was given in 1965 when Thomas Griffin, a 53 year old sewerman employed by Leeds Corporation, was working down a sewer, trying to remove a blockage. He accidentally fell and in an instant was swept away by the force of the flow. Colleagues above ground frantically raced along the route of the sewer lifting manhole covers in desparate efforts to get ahead of Mr.Griffin. All to no avail: his body was later discovered on the screens at Knostrop Sewage Works - two miles away. A verdict of accidental drowning was delivered at the Coroner's inquest.

Exceptionally dry weather brings a different kind of hazard for sewer-workers: the sluggish nature of the flow in the sewers increases the rate of deposition of organic material. The decomposition of the deposited wastes gives rise to poisonous or explosive gases, such as methane or hydrogen sulphide. Every sewer gang would keep a lamp similar to the miner's Davy lamp to detect methane. Also, they carried a small cage containing a piece of paper soaked in lead acetate for the detection of hydrogen sulphide: in the presence of the gas the paper would turn from white to black. Hydrogen sulphide, which is frequently present in sewers, has the unmistakeable smell of bad eggs and it might be thought that unaided human nostrils would suffice for its detection. Unfortunately, after only a brief exposure to hydrogen sulphide, the sense of smell is numbed. Longer exposure causes loss of consciousness.

By the 1980's the sewer gangs in Leeds were equipped with modern electronic equipment for the detection of toxic and explosive gases or oxygen deficiency. They also now carry compressed air cylinders and breathing masks for use in emergencies. Nevertheless, the work still needs great care.

One further danger of sewer work should not go without mention. Rats! It is well known that the sewers harbour rats. It is not as well known that the principal danger from rats is not physical attack, but their urine. Leptospirosis, or Weil's Disease, can be contracted from contaminated rats' urine present in the sewage. If it is not identified quickly and treated accordingly, Weil's Disease can prove fatal. Sewer workers are especially at risk, and therefore strict rules of cleanliness are observed.

Whilst better hydraulic design of sewers in the 1950's and 1960's may have led to a decrease in the accumulation of toxic gases, another development was producing the opposite effect. The increasing number of automatic pumping stations being installed on the sewer network meant that sewage was travelling longer distances and staying in the sewers for longer periods. In the process of breaking down or putrefying the organic matter in the sewage, the bacteria involved used up much of the dissolved oxygen present in the waste water. When the sewage is then conveyed into an enclosed pumping main, without contact with the air, the bacteria which need oxygen gradually cease activity. A different type of process then comes into play - involving anaerobic bacteria, which can manage without oxygen. A by-product of their activity however is the deadly hydrogen sulphide. Sewage which has undergone this process is said to be septic and is commonly jet black in colour.

This septic sewage can cause obnoxious bad-egg smells to emerge from the manholes, as well as creating extra dangers below ground. A further product of septicity is sulphuric acid, which dissolves the cement in concrete sewer pipes or in the mortar of brick sewers. Corrosion of this nature usually occurs immediately downstream of septic pumping mains, before dilution with fresher sewage has been able to take place. Thus, it could be that wear and tear of some of the sewers in Leeds, as elsewhere, will have been brought about not by age but by 'progress' in the form of pumping stations.

It has been estimated that about one fifth of the sewer mileage in Yorkshire was constructed before 1914. Even after the sewer collapses in Leeds in the 1950's however, insufficient was done to monitor the condition of important old sewers in the city. Too few resources were available.

Not that monitoring and inspection would always be an easy task! Some of the larger trunk sewers in Leeds cannot be entered safely, even in dry weather, so high are the flows. Inspection is only possible, if at all, during the small hours of the morning. Sewer flows in dry weather do not remain constant throughout the day. Reflecting the fluctuation of water consumption at different times of the day, sewer flows usually reach a peak sometime around mid day and a further peak in the early evening. During the hours after midnight flows are generally very low and a significant portion of flow, especially in the older parts of the sewer system,is due to infiltration of ground water through joints or defects in the sewer structure.

10. The End of Municipal Ownership