“…This approach was previously used [11] to estimate annualised cost for remediation in Northamptonshire, assuming a 40-year amortisation period. At the time of our previous assessment, the UK government recommended a discount rate, based on the annual rate of inflation, of 10%, matching the assumptions of Colgan and Gutiérrez [18]. With declining inflation, the recommended value has steadily dropped, being now 3.5% for projects lasting 30 years or less, and 3% for longer-duration projects [35].…”