Indiana Groundwater Published Levels - Volatile Organic Compounds (VOCs)

Overview

These are Indiana’s Published Level Table 1 groundwater standards for volatile organic compounds (VOCs), from the IDEM Risk-based Closure Guide (WASTE-0046-R2, “the R2”), effective March 28, 2025. IDEM renamed these values from “Screening Levels” to “Published Levels” in the 2022 R2 update.

Risk basis: Indiana’s published levels are derived at a 1E-05 cancer risk (1 in 100,000) and a hazard quotient (HQ) of 1.0. This is 10 times less conservative than EPA’s default 1E-06 risk level. For carcinogenic VOCs such as benzene, TCE, and vinyl chloride, Indiana’s groundwater published levels are approximately 10 times higher than default EPA Regional Screening Levels for the residential tap water pathway.

Residential values only: IDEM does not publish commercial/industrial groundwater screening levels. Per the R2 (Section 3.3), groundwater is evaluated under a single residential use scenario regardless of current or planned land use. This differs from Ohio’s VAP, which offers residential, restricted potable use, and non-potable classifications.

Qualifier key:

• C = Carcinogenic - value is cancer risk-based
• N = Noncarcinogenic - value is hazard quotient-based
• M = Based on the Maximum Contaminant Level (MCL) - the MCL governs when it is more restrictive than the risk-based value
• D = Detection limit-based

Blank cells indicate no published level for that chemical - not a level of zero.

MCL note: When qualifier M appears, the published level equals the Safe Drinking Water Act MCL. For chemicals with M-qualified values, the MCL is more protective than the risk-based calculated level at Indiana’s 1E-05 target risk.

Groundwater Published Levels - VOCs

Practical Notes

Benzene is the primary risk driver at petroleum UST sites and most petroleum spill sites. Indiana’s benzene groundwater published level is set by the MCL (5 µg/L). Concentrations above this level require corrective action under the IDEM UST program regardless of the land use scenario.

Chlorinated solvents (TCE, PCE, vinyl chloride) are common at dry cleaner sites, metal degreasing facilities, and industrial operations. Vinyl chloride is a TCE/PCE reductive dechlorination product and often has the most stringent standard of the chlorinated solvent family. Always include it in your analyte suite at chlorinated solvent sites.

1,4-Dioxane is increasingly evaluated at sites with chlorinated solvent contamination because it was used as a stabilizer in 1,1,1-trichloroethane (TCA) formulations and co-occurs with TCA and its degradation products. It is highly mobile in groundwater and resistant to natural attenuation. Check whether 1,4-dioxane is in your analyte list if TCA is a site contaminant.

MTBE is common at petroleum UST sites. Indiana’s MTBE published level reflects its taste and odor threshold rather than a toxicological endpoint - even low concentrations can render drinking water unpalatable.

Groundwater-to-indoor-air pathway: Dissolved VOCs in groundwater can volatilize and migrate into overlying buildings through the vapor intrusion pathway. Groundwater results should be compared to both the groundwater published levels on this page and Indiana’s Indoor Air Published Levels using the applicable attenuation factors.

Sampling method: For VOC groundwater samples, collect in 40 mL glass VOA vials with zero headspace and HCl preservative. Low-flow sampling is the standard method for most IDEM programs. See also our guide on bailer sampling for appropriate applications.