Drilling work to assess the status of a caved-in mineshaft, which could lead to the demolition of houses in a Cumbria town, is due to begin.
The hole appeared overnight and quickly filled with water
The 30ft (9m) hole appeared in back gardens in Greenmoor Road, Egremont, last summer.
Nine homes were initially evacuated and four residents remain unable to return home amid safety fears.
Specialist engineers working on the site are due to drill the first borehole on Thursday.
The properties are owned by Home Housing, part of the Home Group.
Sean Reed, from Home Housing, said: "We have a drilling rig on site.
"At the moment we are hampered by the fact that we don't know where the rock head is.
"Once we find out where it is, that will help us identify what the engineering solution will be."