Tristan da Cunha's Public Works: Tristan's Sewage System
Tristan's toilets drain into a large cess pit with excess outflow into the sea at Garden Gate Beach.

Tristan's Sewage System

Introduction and the old system
See below for Sewage System Improvements completed in 2015: Sewage System Upgrade and the sister page for Water Supply
Tristan da Cunha's Water Supply

Tristan da Cunha's Settlement site was ideal as a strong stream of pure fresh water known as the Big Watron (thought to be a corruption of 'Watering') rose from a spring at the base of the cliffs, flowed north down the slopes of the Settlement Plain and then cascaded down the low cliffs to the sea. The lack of a similar good water supply ruled out other settlement sites on Tristan and outlying islands - here was the only spot where a community could thrive. In early days the stream was diverted to provide rivulets to give houses easier access to fresh water.

Above: Photo taken by the Editor in 1983 looking down into the crater of the 1961 volcanic centre showing how the lava flow miraculously left the Big Watron (and the village but not the fishing factory) intact to continue to provide fresh water to the community. The spring and Big Watron can just be made out as it flows north between the lava flow and the village.

In the early 1950s a water supply and sewage system was installed. Water from the spring was siphoned into a large header tank and pipes provided the newly established Big Beach Fishing Factory and every house with fresh water. Wooden- framed outside toilets were constructed (usually at the front) by every house. A sewage system linked to a cess-pit with excess outflow into the sea at Garden Gate Beach.
The last remaining original wooden 'privies' outside one of the last thatched houses shown in this 1982 photograph.
 2014-2015 Sewage System Works
Report and Photos (unless stated) from Robin Repetto
View of the American Fence new sewage works on completion, with St Mary's School
(the field is the school playing field / cattle pasture / helipad).
Behind can just be seen a white construction that is part of the new water supply system at the spring
where the Big Watron emerges at the base of the cliffs.

Overview of the 2014-2015 Sewage Project from Robin Repetto

Due to the old septic tanks being structurally damaged, and not performing as they should, it was decided to build two new septic tanks. These would be built to a higher capacity to accommodate the change in the village growth since the installation of the previous septic tanks built pre 1961.

The sewage project started on the 9th October 2014 and Victor Cinamon MCIOB PrCM MIQ was contracted to visit Tristan and supervise the construction of the new sewage and septic tanks. These were designed with a single dividing wall and two containment areas. A soak away was constructed to maximise the coverage of drainage and to minimise the disruption to the grazing within the field.

Some pipe work was renewed within the village area, as these were made from old pitch fibre, but not all could be changed as the scope of work would be too large.

Flow meters were used to determine the amount of water consumed by the community to justify the size to build the tanks. The new sewer system would be gravity driven, with sewage being piped into the two new separate septic tanks. Built in the “American Fence” they are situated at the lower slopes of the settlement. These tanks require no pumps, settling ponds, drying sites and no mechanical dependence, nature doing all the work of breaking everything down. The new tanks were situated as close to the existing old tanks as possible so new piping could be transferred over quite easily, without any disruption.

A huge thanks to all who contributed in working on the water, sewage and also the electrical projects. Your participation was greatly appreciated.

Two views of the septic tank concrete base being laid
Concrete base nearing completion
Steel reinforcement being prepared
Wooden shuttering and steel reinforcements for septic tank walls being prepared
Septic tank wall shuttering almost ready to receive concrete
Concreting the septic tank walls

Pipe and manhole installation

Manhole construction almost complete

Further photos from Drew Campbell
Views of the new septic tank nearing completion - see top of this section for a more up-to date view of the construction.