Cornwall Fire and Rescue Service has requested a second pump from the National Coordination Centre in London to help with the operation to relieve flooding in the decommissioned Wheal Jane tin mine near Truro.
The Centre has also been asked to send a high volume pump advisor to help.
There are fears that if levels continue to rise it could lead to pollution of the River Carnon and the Fal Estuary.
Levels are being monitored by the Environment Agency who are working with the Coal Board and plant operations to relieve the situation. The Public Health and Protection Agency is also assisting while Maritime Services are working with local oyster fishermen.
More top news
A dead whale - believed to be a minke whale - has washed up on a Devon beach between Dawlish and Dawlish Warren.
Controversial plans to axe maternity services in North Devon have led mothers to protest on social media.
Senior druid, King Arthur Pendragon, is taking legal action over a parking charge at Stonehenge because he's being forced "to pay to pray".