Disposal & recovery code
D4Surface impoundment, e.g. placement of liquid or sludgy discards into pits, ponds or lagoons
D4 is one of the 15 disposal operations (D1–D15) DEFRA recognises: surface impoundment, e.g. placement of liquid or sludgy discards into pits, ponds or lagoons. It records what happened to the waste at its destination, and is required on every movement filed to the digital waste tracking service.
- Code
- D4
- Operation type
- Disposal (D code)
Sourced from DEFRA’s digital waste tracking reference data, last checked 25 July 2026.
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Other disposal & recovery codes
- D1Deposit into or onto land, e.g. landfill
- D2Land treatment, e.g. biodegradation of liquid or sludgy discards in soils
- D3Deep injection, e.g. injection of pumpable discards into wells, salt domes or naturally occurring repositories
- D5Specially engineered landfill, e.g. placement into lined discrete cells which are capped and isolated from one another and the environment
- D6Release into a water body, except seas/oceans
- D7Release into seas/oceans, including sea-bed insertion
- D8Biological treatment resulting in final compounds or mixtures which are discarded by any of the operations numbered D1 to D12
- D9Physico-chemical treatment resulting in final compounds or mixtures which are discarded by any of the operations numbered D1 to D12, e.g. evaporation, drying, calcination
- D10Incineration on land
- D11Incineration at sea
- D12Permanent storage, e.g. emplacement of containers in a mine
- D13Blending or mixing prior to submission to any of the operations numbered D1 to D12