A second landslip was triggered in Rhonnda Cynon Taf and is being investigated by engineers following heavy rain across the country.
It comes as fourteen flood warnings are in place after poor weather overnight. Over the past 24 hours, Rhondda has experienced prolonged periods of rain, with a Met Office Amber weather warning in force.
The council confirmed there was movement at Wattstown Tip - a privately owned tip and situated on private land.
Both Rhondda Cynon Taf Council and the Coal Authority have been monitoring the site closely. However, in recent months the increased risk has hindered monitoring arrangements, with engineers visiting the site every 2 weeks.
A full evaluation is currently being undertaken.
Council Leader Andrew Morgan visited the site on Saturday morning and says he is in discussions with Welsh Government Ministers as one of the priority sites in Rhondda Cynon Taf. He says a long term plan and funding is needed.
The Welsh Government spokesperson said regular inspections were important and have commissioned work to ''develop options'' for the site and provide the necessary support.
Rhondda MP Chris Bryant said "everything that needs to be done will be done".
Unprecedented weather conditions have caused severe flooding in communities across the area this year.
In February, Storm Dennis cause a dramatic landslip on a former coal tip in Tylorstown following heavy rain. In July, a clear-up was underway to remove more than 60,000 tonnes of spoil from the tip.
At the time of the incident, ITV Cymru Wales spoke to people living nearby who said the incident made them fearful of another Aberfan. In 1966, 150,000 tonnes of coal waste from a colliery spoil tip collapsed into the village of Aberfan, killing 116 children and 28 adults.
Inspections have already begun across Wales as part of an urgent review of all coal tips to see if there is any risk to people or property.
Members of the public can report any hazards or get safety advice from the Coal Authority’s 24/7 helpline on 0800 021 9230 and can be contacted via firstname.lastname@example.org