THE ROMAN SEWAGE SYSTEM AT TRIMONTIUM BY WALTER ELLIOTIntroduction.
When a large number of people settle on one location, there are two problems which have to be dealt with. The first is the provision of bulk supply food and drink; the second is how to dispose of the residue after that has passed through the digestive systems of a large number of humans.
From the earliest days of urban occupation, this problem was solved by allowing the urine and excrement to flow/slide downhill through a pipe or drain, usually with some help from running water, until it reached a settlement tank. Here the denser excrement sinks to the bottom allowing the liquid to drain away through an overflow pipe. When the sediment rises to the height of the overflow, it is emptied and spread on the fields, for this is a valuable commodity.
This standard practice is still used in many modern countries.
Trimontium – The Curle Latrine.
The Curle excavations revealed a latrine immediately to the south of the baths but it had been badly damaged by draining operations in 1904. However enough remained for Curle to determine that it had two phases of construction. Both were supplied with water running through ‘a line of clay tiles (pipes) with neatly made faucet joints’ which ran from the neighbourhood of the west gate. It then ‘passed along an open channel cut into the flag stones and through the troughs, the water was discharged into the drain running south.’
This I found quite easily with divining rods. The main water pipe leading past the west gate of the fort to the Baths is tapped into at NT 56811 34433 with a pipe leading to the south-east corner of the latrine. Although Curle does not give a measurement for the size of the latrine floor, divining rods make it approximately 10m by 4.5m. No walls enclosing it (the latrine) could be made out except on the south side and ‘it is possible that the latrine may have been open to the sky’. As this was unlikely, I checked the outer edges of the floor, finding stone wall foundations on the east and south suggesting that one or more phases were stone-built structures. However rows of postholes enclosed the latrine area, inferring that one structure has been wooden.
(I had previously noted that the latrines of the fortlets and the latrines of the unexplained annexes of the marching camps along the length of Dere Street and the extended Devil’s Causeway through Berwickshire, were also of posthole construction.)
The Curle plan shows that the outlet drain from the south-west corner of the latrine joins with the main drain from the baths and leads off in a south-westerly direction. If the excavators had followed this further, they would gave found that it ran into a 3m square structure* at NT 56744 34396. An outlet drain comes from that structure and leads south. My reading is that this was the settling tank to separate the solid from the liquid.
*In the 1960s, lines of stones showed this square shape in the ploughed soil. This was due to deeper ploughing and heavier tractors. My stepped measurement of approximately 3m square shape, fits in with the much used Roman measure of a decempeda quadrata.
Going back to the latrine, I found another outlet drain leaving the north-west corner of the structure. This had a 12m run before joining another similarly sized decempeda quatrata at NT 56739 34409, before discharging in the direction of the river. This fits with the two constructions of the latrine although it is difficult to decide which came first.
It is worth noting that this line of drain goes through the site of the mansion. In the 1960, I was told that most of the intaglii from the Mason Collection came from this area but I don’t know the number or exact location of the finds.
Nota Bene. I have made no effort to fit these into the phases of the fort’s life as this part of the site has been reconstructed several times during the Roman occupation.
The Other Baths/Latrine Complex.
Curle’s Roman Frontier Post and its People is certainly the most quoted reference book of the British Roman world. It was far ahead of its time in site excavation and prompt publication and remains the standard of excellence to which all should aspire. Despite intensive excavation, there are large portions of the Trimontium site that remain untouched and await future exploration. In especial, the annexes have a lot of information to impart.
Curle wrote that the excavations had revealed ‘quite a small functional bathhouse’. Many archaeologists have commented that it would have been too small to provide services for the number of troops in the fort and that ‘a legionary bathhouse still remains to be discovered somewhere on the site’.
In Divining Archaeology p34, I give my reasons why I am convinced that a much larger bathhouse and an associated latrine can be found in the lower ground west of the south annexe. I stand by this deduction although this was made by divining rod deduction and has to be proved by excavation.
With this conviction, I took a more detailed look at the latrine on the north side of the proposed bathhouse. In size, this was much larger than the Curle latrine with a base 18m long by 4.5/5m wide. This is enclosed by four rows of postholes.
To supply water, a branch pipeline has been taken from the main supply pipe at NT 56836 34187 and enters the latrine on the north-east corner at NT56796 34251 then exits at the south-west corner. The outlet drain/pipe ran for about 20m before entering another 3m square shape (decempda quadrata) at NT 56770 34249. From there, an outlet pipe runs in a south-westerly direction.
26 April 2015. Walter Elliot.