Soil Contamination Calculator

The Contamination Index (CI) is the ratio of the measured contaminant concentration to the background concentration (CI = Measured / Background). A CI of 1 means the site matches natural background levels. Values above 1 indicate contamination, with higher values representing greater degrees of pollution relative to natural conditions.

The Hazard Quotient (HQ) is the ratio of the measured contaminant concentration to the regulatory screening level (HQ = Measured / RSL). An HQ below 1.0 suggests that concentrations are within acceptable risk thresholds. An HQ above 1.0 indicates potential human health or ecological risk and typically triggers further site investigation or remediation.

Screening levels vary by contaminant and land use. For residential land, EPA Regional Screening Levels (RSLs) include approximately 400 mg/kg for lead, 0.39 mg/kg for arsenic, and 70 mg/kg for cadmium. Commercial and industrial sites generally have higher screening thresholds. Always verify current values from EPA or your local environmental authority.

The Enrichment Factor compares the measured concentration to background levels and indicates the degree of anthropogenic (human-caused) enrichment. An EF near 1 suggests natural origin; EF between 2–5 indicates moderate contamination; EF above 10 signals severe anthropogenic pollution requiring remediation action.

The number of samples depends on site area, variability, and regulatory requirements. As a general guideline, at least 5–10 samples per hectare are recommended for initial screening. Larger or heterogeneous sites may require systematic grid sampling or statistical sampling designs to achieve acceptable confidence levels in the assessment.

Surface contamination (0–15 cm) typically results from atmospheric deposition, direct spills, or agricultural practices and poses higher exposure risk to humans and ecosystems. Subsurface contamination may indicate deeper infiltration, historical dumping, or groundwater interaction, which can affect aquifer quality. Both depths are assessed differently under most regulatory frameworks.

Remediation is generally required when the Hazard Quotient exceeds 1.0 for non-carcinogenic contaminants, or when cancer risk exceeds 1 in 100,000 for carcinogens. Trigger thresholds vary by jurisdiction and land use. Residential sites typically have stricter cleanup standards than commercial or industrial properties due to greater human exposure pathways.

This calculator is designed for chemical and heavy metal contaminants. Radioactive soil contamination requires specialized tools such as the NUREG-1507 methodology, which calculates Minimum Detectable Concentrations (MDC) using parameters like background count rates, survey instrument type, and index of sensitivity. For radiological assessments, consult ORAU or NRC-approved calculators.