The issue with developing housing around such site is compounded by such issues as the stack effect, that is warm indoor air being less dense than the exterior cold air and so creating an area of lower pressure inside a property, which will encourage the ingress of gas.
"Waste management Paper 27" from the UK Department of the Environment recommends consultation with the relevant local authority if any proposed development is to be less than 250m from the site boundary that has received waste in the last 30 years.