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RVISL User's Guide

PDF of User's Guide

Welcome to the EPA's Radon Vapor Intrusion Screening Level (RVISL) Calculator User's Guide for Radionuclide Contaminants at Superfund Sites. This guide contains descriptions, equations, and default exposure parameters used to calculate cancer risk and dose-based RVISLs. Additional guidance is also provided on sources of parameters and proper RVISL use. It is suggested that users read the RVISL Frequent Questions page before proceeding. The User's Guide is extensive, so please use the "Open All Sections" and "Close All Sections" links below as needed. Individual sections can be opened and closed by clicking on the section titles. Before proceeding through the User's Guide, please read the Disclaimer below.

This tool provides screening level (SL) concentrations of radon (Rn) for groundwater, soil gas (sub-slab and exterior), and indoor air to assist Agency staff with making a RVISL determination based on limited, initial data. In addition to calculating SLs, this tool can calculate indoor air concentrations from radon in soil gas and groundwater concentrations entered by the user. The cancer risk and dose from calculated indoor air concentrations and user-provided indoor air concentrations can also be calculated. The equations for these features are presented in the following sections. For Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remedial actions, dose assessment is generally done only to show compliance with a dose-based Applicable or Relevant and Appropriate Requirement (ARAR). In addition, the calculator presents the option to compare the indoor air concentration, entered by the user or derived from groundwater or soil gas activities, to state standards or Uranium Mill Tailings Radiation Control Act (UMTRCA) standards, which also may be potential ARARs. For more information on when UMTRCA indoor radon standards are potential ARARs, see the guidance document "Establishment of Cleanup Levels for CERCLA Sites with Radioactive Contamination" Attachment A: Likely Federal Radiation (AEA, UMTRCA, CAA, CWA, SDWA) ARARs, page 3 (OSWER Directive 9200.4-18, August 1997). Users should note that since background radon levels are typically outside the risk range, the RVISL calculator is likely to be used primarily for ARAR compliance. For example, the UMTRCA indoor radon standards 40 CFR 192.12(b)(1) and 192.41(b) were identified as likely Federal ARARs for Rn-222 and Rn-220 in Attachment A of the EPA guidance document "Establishment of Cleanup Levels for CERCLA Sites with Radioactive Contamination." There are some state standards expressed in pCi/l or mrem/yr that, if more stringent than the UMTRCA standards, may be selected as ARARs.

RVISLs are a type of preliminary remediation goal (PRG) and both are a specific variety of the broad SL category. The RVISL calculator provides updated guidance for developing SLs), for indoor Rn-222, Rn-220, and Rn-219 that are risk- or dose-based and for showing compliance with the UMTRCA indoor radon standards for Rn-222 and Rn-220. The RVISL, therefore, supersedes the risk assessment approach in Preliminary Remediation Goals for Radionuclides in Buildings (BPRG) electronic calculator, the dose assessment approach in ARAR Dose Compliance Concentrations Goals for Radionuclides in Buildings (BDCC) electronic calculator, and Q17 of the guidance document "Radiation Risk Assessment At CERCLA Sites: Q & A" issued on May 2014. Computer codes such as the RVISL, which were developed to predict hazards from potential human exposure to radon concentrations in indoor air, are based on simplified equations and protective assumptions. While RVISLs may be imprecise for an individual house or structure they are protective in nature for screening a wide variety of buildings. EPA would recommend, where possible, Regions use measurements of radon indoors rather than rely on the transport portions of the RVISL. In particular, testing of groundwater or soil gas is not required to demonstrate compliance with RVISL WL, pCi/L, risk, or dose targets.

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1. Introduction

2. Understanding the RVISL Website

3. Understanding Your Superfund Site

4. RVISL Equations

5. Predicting WL, ELCR, and Annual Dose from Indoor Air Concentration

6. Modifications of Standard Equation Inputs

7. Recommended Default Exposure Parameters

8. References