Pembrokeshire County Council is to undertake a full assessment of the old landfill site at Narberth's Town Moor.
The investigations on the site - previously used for commercial and industrial waste - will comprise of drilling bore holes to attain full gas level readings.
The work has been requested by County Clr. Wynne Evans.
He said: "I regret that while the work is being carried out, part of the area will have to be cordoned off.
"I am meeting various multi-agencies involved in this work programme on site this week as the remains of the landfill site are directly near the stream in Cardingmill Lane where other county council schemes are already underway."
Full details and reports are available from Clr. Evans's office at the Span Building.