Site MU1 - situated between Pogmoor, Higham and Barugh Green along the M1 corridor - is subject to planning applications lodged by Strata Homes and Sterling Capitol, who make up the Barnsley West Consortium (BWC).
Outline approval for the development of 1,760 homes, a new 420-space primary school and ‘community facilities’ is being sought - but campaigners and local residents whose homes neighbour the site have expressed doubt over its stability.
Having a number of underground coal seams, it was home to opencast sites named Craven I, Craven II, Hunters Cottage and Farm House Lane - all of which were backfilled.
Craven II, which sat in the centre of the 122-hectare site’s northern-most half, was excavated to depths of almost 45 metres from 1957 to 1963, records show.
The Coal Authority subsequently stepped in due to the site’s past and carried out groundworks recently - with a Barnsley Council report revealing concerns have now been lodged by the public body.
The report, from the local authority’s head of planning, Joe Jenkinson, said: “The application falls within a defined development high-risk area and the site contains coal mining features and hazards.
“These need to be considered in relation to the determination of the planning applications.
“The Coal Authority raised concerns on the basis that intrusive site investigations need to be undertaken in advance of a detailed scheme being approved.
“They would expect that those investigations should inform the detail of the site layout.
“It is my understanding that the full and detailed site investigation report is likely to be submitted by late February, together with a remediation strategy.”
Campaigners hope the findings will reshape the site’s so-called masterplan framework - a blueprint which developers must adhere to - after the applicants conceded there are areas on MU1 where development would be ‘restricted’ due to ex-mining.
MU1 has been at the centre of stern opposition from campaign group Keep It Green, whose members have called on the council to protect the borough’s green spaces and listen to those who lived by the site in its mining heyday.
A spokesperson added: “The matters upon which the concerns are focused have an all too familiar ring about them - they are all points our supporters have been making ever since the proposals were first mooted.
“These have been reiterated during the various ‘consultations’ carried out by the council and the developer.
“Yet, rather than refuse the applications outright as advocated by Keep It Green, the council still endeavour to work with a developer whose current proposals show scant regard for this valuable area of countryside and the quality of life enjoyed by the many residents who live close to or alongside the land.
“Perhaps the only thing we can take heart from at this stage is that the council are not simply lying down and immediately acquiescing to the whims of the developer.
“They appear to have acknowledged that many of the points made by those who have objected to the development, including Keep It Green, are valid and weighty and warrant further consideration.”
A statement from the BWC said the two firms are ‘committed’ to bringing the development forward - and assured residents that further investigations into the ground will commence.
“We believe the site gives a fantastic opportunity to deliver this investment,” it said.
“The comments received are not unusual for a site of former mining activity and residents should be assured that we are undertaking further ground investigations.”