EP A/600/S-22/124 Summary of Radiological Stormwater Modeling Research Overview After the Chernobyl nuclear disaster, stormwater played a role in transport of radionuclides. High concentrations of 137Cs were found around houses where rain transported radioactive materials from roofs, secondary contamination of sewage systems/sludge storage areas was caused by washoff from roads, and decontamination activities included watering streets to move radionuclides into the sewer system.1 In some locations, stormwater runoff from streets was contaminated by 137Cs for up to seven years.2 After the Fukushima nuclear disaster, 137Cs associated with soil particles was mobilized during periods of high rainfall, and hydrogeological maps were used to assess mobilization pathways and recontamination routes when planning decontamination.3 EPA's Homeland Security Research Program (HSRP) within the Office of Research and Development conducts research to aid in the response to and recovery from radiological disasters. EPA is leading stormwater modeling studies that investigate how to simulate transport of radiological contamination in urban stormwater. This has resulted in several publications and an active research portfolio described in more detail below. Together, the ongoing body of work can be leveraged to make more informed decisions after a radiological disaster. Publications Model Reviews Stormwater modeling software can offer decision makers insights on where to focus sampling and decontamination efforts based on transport after rainfall events. While a wide variety of stormwater tools are actively used in the urban planning and regulatory sectors for flood water control and water quality management, the use of water modeling tools during emergency response and recovery is relatively rare compared to atmospheric modeling. Existing water modeling tools are often sub-sector specific, and most need modification from their original formats to serve the needs of the radiological emergency response and remediation community. The following two publications outline the unique needs for stormwater models when used in emergency response and provide 1-page summaries of 26 common models. • Journal Publication: Urban Fate and Transport Modeling of Contaminants: The Unique Needs of Emergency Response and the Potential for Adapting Existing Models • EPA Report: Survey and Assessment of Fate and Transport Models for Use Following a Wide-Area Urban Release to Inform Mapping. Characterization, and Site Clearance 1 Environmental consequences of the Chernobyl accident and their remediation : twenty years of experience / report of the Chernobyl Forum Expert Group 'Environment'. — Vienna : International Atomic Energy Agency, 2006. 2 U.S. EPA. Particle Transport of Radionuclides Following a Radiological Incident. U.S. Enviromnental Protection Agency, Washington, DC, EPA/600/R-15/113, 2015. 3 JAEA Model project report (Remediation of Contaminated Areas in the Aftermath of the Accident at the Fukushima Daiichi Nuclear Power Plant: Overview, Analysis and Lessons Learned Volume 1: A Report on the "Decontamination Pilot Project" Fukushima Enviromnental Safety Center, Sector of Fukushima Research and Development Japan Atomic Energy Agency Sakae, Fukushima 960-8031, Japan). 4Shireman, J., Ratliff, K., & Mikelonis, A. M. (2022). Modeling radionuclide transport in urban overland flow: a case study. Urban Water Journal, 19(2), 130-140. ------- EP A/600/S-22/124 Model Construction There are unique aspects required to develop and adapt a stormwater model to support radiological remediation actions such as sampling, waste staging, and installation of treatm ent technologies. EPA researchers have demonstrated the model construction process for a 2D overland flow model in a case study involving a hypothetical dirty bomb detonation (Figure 1). The paper discusses considerations for modeling non-traditional pollution, including selecting and testing various washoff parameters for 13 7Cs, In partnership with local utilities and academia, EPA researchers have also modified two combined sewer overflow models to contain finer scale components that facilitate higher resolution modeling of surface transport of13'Cs. These models are used to support ongoing research studies that may better inform incident support and are available for use in table- top training exercises. Maximum Load Curies Discharged * <0.003 0 0.003- 0.03 O 0.03 - 0.3 O 0.3-3 * >3 O Not Detected ** % VV A A £ I j « r v v -i I: \ •t t ¦ ~ \v ... - -=vr s \ >* !L 4 % \ ~ s ./ ••'v r Jf ¦/ ¦£ ¦*' *7 s?' :^x - m > f'i :F (t* K < ^ \ 0 1,000 2,000 4,000 Feet Soirees; Esri, HERE, Gsrmin. USGS, Intefmep,•)NC REf/1 ENT P, qO NRCen, Esri Japan, MET1, Esri Chirrs [Hcng Kong), EsriKcres, ® Esri iThailsrcj. NGCC. 'cj .GpenStreetMap contributors. and the GIS User Community Figure 1.137Cs contaminated drainage pathways predicted by stormwater model.4 • Journal Publication: Modeling radionuclide transport in urban overland flow: a case study • Technical Summary: Stormwater Modeling Response to a Wide Area Radiological Dispersal Device Incident Stormwater Emergency Response Framework EPA researchers recognize that detailed stormwater models take time to develop for any particular site. Still, many web resources are publicly available to assist in visualizing stormwater runoff flow paths, and simple calculations may be utilized to estimate peak flows and storage volumes necessary to respond to imminent precipitation events. • Journal Publication: Emergency response to stormwater contamination: A framework for containment and treatment ------- EP A/600/S-22/124 Ongoing Research EPA researchers are leading work in the following areas related to radiological fate and transport in stormwater: • Development of stormwater modeling table-top exercises • Research in the impact of model structure (e.g., ID vs. 2D vs. dual drainage modeling) on spread of contamination in simulations • Development of modeling scripts to optimize resource placement (e.g., inlet seals, inflatable dams) to stop the spread of contamination Disclaimer This document has been reviewed in accordance with U.S. Environmental Protection Agency policy and approved for publication. ------- |