ISO 21365:2019

Overview

ISO 21365:2019 - Soil quality - Conceptual site models for potentially contaminated sites provides guidance for developing and using conceptual site models (CSMs) during site investigation, remediation (if required), and subsequent construction or engineering works. The standard defines what a CSM is, outlines its constituents, and stresses an iterative and dynamic approach to CSM development. It applies to potentially harmful substances whether naturally occurring or anthropogenic and covers all environmental media (soil, groundwater, surface water, sediments, soil gas, air, biota, subsoil and built structures).

Key topics and technical requirements

• Definition and purpose of a CSM: A synthesis of all relevant site information, with interpretation and stated uncertainties, structured around source–migration pathway–receptor linkages.
• Iterative development: CSMs are updated as new data are collected; they guide investigation design and focus intrusive work on data gaps.
• Step-wise procedure: Key steps include defining objectives and spatial/temporal boundaries; identifying contaminants and sources; characterizing contaminated media; mapping migration pathways; identifying receptors, exposure pathways and points of exposure; and considering foreseeable events.
• Investigation phases: Guidance is provided for CSM development across preliminary assessment, exploratory investigation, detailed and supplementary investigations, and links to remediation and construction planning.
• Representation and communication: Emphasis on clear, multi-audience presentation so regulators, technical teams and non-technical stakeholders can understand assumptions and uncertainties.
• Data quality and QA: Recommendations for appropriate data collection, sampling strategies and quality assurance to make CSMs robust and defensible.

Practical applications

• Designing focused, cost-effective site investigations by prioritizing sampling where it will reduce key uncertainties.
• Supporting baseline human health and ecological risk assessments by documenting exposure pathways and receptors.
• Informing feasibility studies and remediation planning, including selection and monitoring of mitigation measures.
• Guiding construction and engineering works on previously contaminated land by identifying residual risks and required controls.
• Serving due diligence, environmental audits and stakeholder communication for redevelopment projects.

Who should use ISO 21365:2019

• Environmental consultants and site investigators
• Remediation and geotechnical engineers
• Regulators and permitting authorities
• Landowners, developers and construction project managers
• Risk assessors, auditors and public stakeholders involved in contaminated land management

Related standards

• ISO 11074 (Soil quality - Vocabulary) - referenced for terminology
• ISO 18400 series (Soil quality - Sampling) - linked for investigation and sampling methods

Keywords: ISO 21365:2019, conceptual site model, CSM, soil quality, potentially contaminated sites, site investigation, remediation, risk assessment, groundwater, soil gas, environmental media, contaminated land.