Italian to English Tech/Engineering Engineering: Industrial

Can anyone help with the translation of "colaggio in sorgente" in steel production as a method of filling the ingot moulds, as opposed to colaggio diretto and colata continua. The term occurs in passing in a description of steel production using the continuous casting method, so I have no other direct context. Wikipedia describes the process as "l'acciaio è scaricato in una colonna, essa è collegata a canali sotterranei che portano il metallo a sorgere nella lingottiera dal fondo", but I can't find anything equivalent in English. Thanks for any help.