French to English Tech/Engineering Engineering (general) waste treatments

See the second bullet point down

Trois documents sont joints:
- la note de synthese;
- le logiciel de dimensionnement des brins sub-horizontaux de recirculation de lixiviats
- la notice d'utilisation du logiciel de dimensionnement

I am unsure of the meaning of 'brins' here - obviously part of the structure used for recirculating the leachates. I have looked at 'brin' in the glossaries, but it is one of those words that can have many different meanings depending on the context. Can anyone help? Thanks in advance.