A summary of the assessment of Commonside said the identification of potentially unacceptable risks “does not mean that harm or pollution is occurring” but that “further assessment would be needed to understand the significance of the risks”.
The assessment said the potential risks to human health “are associated with possible exposure to impacted soils, water and sediments in Foxhill Brook and drainage ditches, as well as vapours and landfill gas”.
The brook had “a strong chemical odour in places” and testing found contaminants from the landfill were present, the assessment said.
It said the “moderate to high” risks to the brook and surrounding drainage ditches were a “priority risk for further investigation”.
The consultants said the risks to shallow groundwater from the site were “moderate” but would also be a priority for further investigation.
The risks to deeper groundwater under the site, used as a source for local drinking water, were low but “further information and evidence is needed to better understand this risk”, the report said.
Water provider United Utilities has previously said routine testing of the water quality from its borehole was “consistently good” and enhanced testing also produced “clear” results.