The paper describes the development and implementation of a methodology enabling remote, real-time monitoring of a contaminated industrial site that may pose risks to the environment. The methodology, in this paper called `continuous contaminated site monitoring' (CCSM), consists of several stages, such as: real-time physico-chemical data acquisition and analysis; maintenance and supervision of in situ sensors and analysers in order to evaluate the measurements' validity; and determination of the state and evolution of the contaminated site so as to make decisions with respect to optimal site decontamination and recovery methods.The project is applied to a post-industrial contaminated site, located in the north of France: a former coking plant which was active between 1906 and 1950. The installations were dismantled in 1976, but significant quantities of different polluting substances have been left in the soil (e.g. polycyclic aromatic hydrocarbons - PAH, benzene/toluene/ethyl benzene/xylene - BTEX, as well as ammonium, etc.).The CCSM project will deal with real-time pollutant concentration monitoring in a few strategic points, so as to follow the evolution and transfer in the saturated and unsaturated zones. Pollutant diffusion modelling and simulation are considered. The methodology that has been developed aims at an interactive and convenient access to the data, using an integrated decision-making support tool. Polluted-site managers should be able to access any aspect of the information and identify the relevant indicators, which can then be compared with weather data and/or complementary simulation results for diffuse pollution plumes at different time scales.