only a bit
an environmental risk assessment for soil contamination requires taking samples of top and sub soil from a number of sites over the area to be tested .these are then analyzed for lead cadmium etc etc ,for organic toxins such as pcb's and dioxins ,etc asbestos is also on the list of tests iirc
there will also be an inspection for "evil"plant life such as Japanese knotweed which has to be treated as hazardous waste
cost depends on size of area and the detail required
the eho might be able to give advice to compliment that of planning .
might be worth looking into the history of the site .if it is "number one smelter lane "you probably dont need to check