A road outside the main entrance of the hospital reception where a sinkhole opened up, is due to remain closed until the spring.
West Herts Hospital NHD Trust said the leak had been fixed, but “significant underground damage” needed repair.
In a statement, the trust said the hole had been backfilled and there was no sign of further subsidence. However, it said it would be a “long and painstaking process to restore the road”, as investigations were needed to prevent further damage.
Diversions remain in place, and patients and visitors can continue to access the hospital via Thomas Sawyer Way.