At present, there is a significant need to develop decontamination agents that can be used effectively after detonation of a radiological dispersal device (RDD) in an urban environment. There is also a need for the development of reproducible test surfaces to be used to determine the efficacy of the agent being developed. Researchers at Lawrence Livermore National Laboratory (LLNL), under the auspices of the US Department of Energy (DoE), conducted a field study to evaluate the deposition of an explosively dispersed radionuclide surrogate (CsCl) on grime-bearing and non-grime-bearing urban surfaces. The goal was to investigate the preparation and contamination of urban surfaces that closely mimic what one would expect to encounter following the detonation of an RDD. Migration of Cs into concrete surfaces was investigated in detail. Many non-proliferation, security and response organizations that have modeled RDD scenarios use cesium-137, as well as cobalt-60, strontium-90, americium-241 as the most likely RDD agents. Cesium-137 is an isotope of concern for possible use in an RDD due to its potential availability resulting from its widespread legitimate use in construction, geotechnical and medical industrial devices. In some Cs-containing instruments the Cesium-137 is present as the highly dispersible and water soluble salt, cesium chloride more » (CsCl). In this form Cs is able to rapidly disperse in the environment, as witnessed in the 1987 Goiania accident in Brazil, when inadvertent dispersal of a radiotherapy source resulted in fatalities and injuries. « less