RAF Davidstow Moor had two sewage plants. One was at Trewassa to the north east and one at Hendrawalls to the south.
The site at Trewassa had:
Tool House - [Drawing no: 7493/40] (Map ref: 622)
Destructor House - (Map ref: 623)
Humus Tanks  - [Drawing no: 1927/42] (Map ref: 624)
Percolating Filter Beds  Rotary - [Drawing no: 1927/42] (Map ref: 625)
Sedimentation Tanks  - [Drawing no: 1927/42] (Map ref: 626)
Sludge Drying Beds  - [Drawing no: 1927/42] (Map ref: 627)
These were all of temporary brick. The site took all the sewage from the communal sites, the hospital and the technical site.
The tool shed contained items such as spades and rakes for removing sludge and the general cleaning of humus, septic and percolating tanks.
The septic and percolating tanks were two circular brick lined tanks. The septic tank dealt with the solid organic matter which was partly digested and liquefied. It then passed to the percolating tank where further bacterial purification took place. A very even distribution was required and so rotary sprayers were used.
The destructor house was a small building which housed the refuse bins, coal store and an incinerator to burn the combustible waste.
The site has been redeveloped in recent years to meet the requirements of Dairycrest and the village of Davidstow.