Concerns about student safety have resulted in the closure of a stretch of unremediated road at the rear of Picton High School.
Wollondilly Council has blocked the unformed section of road at the end of Wonga Road due to concerns about toxicity levels on the thoroughfare and adjacent land. .
This section of road was formerly used to access an old waste disposal site.
Wollondilly mayor Matthew Deeth said the council had a "whole range of concerns" about the site prior to its use as an access point for the school during upgrade works.
"The land hasn't been remediated yet so we do not know what is actually there but there is potential for some real problems to arise," he said.
"We raised these contamination concerns with the Department of Education before [upgrade] construction began at the school but it was rushed through as a state significant development. So we've had to close the gate."
The Local Traffic Committee, which includes police, Roads and Maritime Services and council representatives, met numerous times to discuss the traffic management challenges arising from construction works at the school.
Following site inspections and consultation with the Local Traffic Committee, the council decided it was in the best interests of the school and wider community for vehicle access at the rear of the school to stop.
Council has asked the Department of Education to erect a construction fence between the road closure gate and the school's rear gates to ensure only pedestrians can access the rear of the school.
Cr Deeth said the council also suggested the department could remediate the stretch of land.
"We suggested they do their own contamination report and remediate the land but they have knocked that back," he said.
"This is a $300 million dollar development so I am not sure why the developer has decided to dig their feet in on this aspect.
"Council has been working on plans and looking into funding to remediate the site."
Cr Deeth said the council's concerns were also shared by members of the community.
“Council has been expressing concerns for two years regarding the management of the construction," he said.
“We are continuing to work with both the school and the Department of Education to try and resolve the safety issues that we have raised."