The New Jersey Department of Environmental Protection (NJDEP) has updated several groundwater screening levels used to evaluate the vapor intrusion pathway at contaminated sites.
The revised values were released on February 7, 2025 and incorporated into NJDEP’s Vapor Intrusion Screening Levels tables and supporting technical documentation. The update affects three volatile organic compounds: 1,1-dichloroethene, ethylbenzene and vinyl chloride. (dep.nj.gov)
For busy environmental professionals, the main point is straightforward: projects involving these contaminants should now be assessed against the updated groundwater screening levels.
Key takeaways
- NJDEP released the updated groundwater screening levels on February 7, 2025.
- Three groundwater screening levels were revised: 1,1-dichloroethene, ethylbenzene and vinyl chloride.
- The updated levels apply when screening groundwater contamination for potential vapor intrusion risks.
- NJDEP also revised the alternate-soil-texture groundwater screening level for ethylbenzene.
- The values should be distinguished from New Jersey’s broader Ground Water Quality Standards and legally enforceable indoor air remediation standards.
What are the latest NJDEP groundwater screening levels?
The latest groundwater screening levels for the vapor intrusion exposure pathway are:
| Chemical | CAS number | Updated groundwater screening level |
|---|---|---|
| 1,1-Dichloroethene, also known as 1,1-dichloroethylene | 75-35-4 | 31 µg/L |
| Ethylbenzene | 100-41-4 | 150 µg/L |
| Vinyl chloride | 75-01-4 | 0.59 µg/L |
NJDEP also updated the groundwater screening level calculated for ethylbenzene under the alternate-soil-texture scenario. (whitmanco.com)
These values are presented in micrograms per litre, or µg/L.
The complete NJDEP master table contains screening levels for many more chemicals. However, these three values represent the groundwater screening levels changed in the February 2025 update. Other values in the table remain relevant and should still be checked when evaluating a site. (dep.nj.gov)
When were the levels last updated?
NJDEP announced the revised groundwater screening levels on February 7, 2025.
The accompanying Vapor Intrusion Screening Levels: Basis and Background document is dated February 2025. This document explains the technical basis used to derive the groundwater, soil-gas, sub-slab and indoor-air screening values. (dep.nj.gov)
The update closely followed amendments to New Jersey’s Ground Water Quality Standards, which were adopted and published in the New Jersey Register on February 3, 2025. Those wider amendments updated criteria or practical quantitation levels for numerous groundwater contaminants. (whitmanco.com)
What did NJDEP update?
The February 2025 vapor intrusion update revised the groundwater screening levels for:
1,1-Dichloroethene
The groundwater screening level for 1,1-dichloroethene is now 31 µg/L.
NJDEP’s basis document shows that the previous value was 26 µg/L, meaning the revised screening level is slightly higher. (dep.nj.gov)
Ethylbenzene
The updated groundwater screening level for ethylbenzene is 150 µg/L.
NJDEP also recalculated the ethylbenzene screening level for the alternate-soil-texture scenario. Alternate soil assumptions may be relevant where the default soil properties do not adequately represent site conditions. (whitmanco.com)
Vinyl chloride
The updated groundwater screening level for vinyl chloride is 0.59 µg/L.
Because this is a low concentration, reporting limits and laboratory sensitivity should be reviewed when planning groundwater sampling and interpreting results.
What are groundwater screening levels used for?
Groundwater screening levels help determine whether volatile chemicals in groundwater could present a potential vapor intrusion concern.
Vapor intrusion occurs when chemical vapours migrate from contaminated groundwater or soil through the subsurface and enter an overlying or nearby building. Vapours may move through cracks in foundations, gaps around utilities, sumps or other preferential pathways. (dep.nj.gov)
Where a volatile chemical exceeds its applicable groundwater screening level, the result does not automatically prove that indoor air has been affected. Instead, it generally indicates that the vapor intrusion pathway requires further evaluation.
Depending on the site, the next steps may include:
- reviewing the site conceptual model;
- assessing groundwater depth, flow direction and plume extent;
- collecting soil-gas or sub-slab samples;
- conducting indoor-air sampling;
- examining building construction and potential vapour entry points; or
- evaluating whether mitigation or additional monitoring is required.
Screening levels should therefore be treated as decision-making tools rather than stand-alone cleanup standards.
Groundwater screening levels are not the same as groundwater quality standards
The terminology can be confusing because NJDEP publishes several types of groundwater and vapor intrusion values.
Ground Water Quality Standards, or GWQS, establish groundwater classifications, designated uses and water-quality criteria under N.J.A.C. 7:9C. For Class II-A groundwater, the applicable standard is generally based on the higher of the groundwater quality criterion and the practical quantitation level. (dep.nj.gov)
Groundwater screening levels, or GWSLs, are used specifically to screen groundwater concentrations for the potential vapor intrusion pathway.
Vapor Intrusion Screening Levels, or VISLs, include screening values for environmental media such as groundwater, soil gas and sub-slab vapour.
Indoor Air Remediation Standards are regulatory remediation standards for indoor air under New Jersey’s remediation rules. They should not be treated as interchangeable with groundwater or soil-gas screening levels. NJDEP formally established indoor-air remediation standards for the vapor intrusion pathway through the 2021 remediation-standard amendments. (dep.nj.gov)
Environmental professionals should confirm that they are comparing each analytical result with the correct value for the sampled medium, land-use scenario and regulatory purpose.
What do the updated levels mean for environmental projects?
The revised values may affect current and historical site assessments involving the three updated chemicals.
Environmental consultants, licensed site remediation professionals, laboratories and responsible parties should consider reviewing:
- active vapor intrusion investigations;
- groundwater datasets containing 1,1-dichloroethene, ethylbenzene or vinyl chloride;
- automated exceedance reports;
- conceptual site models;
- remedial action workplans and reports;
- vapor intrusion mitigation decisions; and
- historical conclusions based on superseded screening values.
Particular attention may be needed where a reported concentration is close to one of the revised levels. A result previously classified as above or below a screening threshold may need to be reassessed against the current value.
Users should also confirm that laboratory reporting limits are sufficiently low to allow comparison with the applicable screening level, especially for vinyl chloride.
Phase-in arrangements
NJDEP provided a six-month phase-in period for certain remedial documents relying on the former groundwater screening levels.
According to the published update, the previous levels could continue to be used where an applicable remedial action workplan or remedial action report was submitted within the phase-in period and other regulatory conditions were satisfied. The stated phase-in deadline was August 3, 2025. (whitmanco.com)
That phase-in date has now passed. New assessments and reporting should therefore use the current values unless NJDEP has approved a different site-specific approach.
Using current environmental standards in ESdat
ESdat has recently compiled a range of updated standards across North America, Europe and Australia.
These updates allow users to seamlessly apply current guideline values, automate compliance monitoring, and incorporate the latest standards into reporting and decision-making workflows in ESdat.
Maintaining standards in a central environmental data management system can reduce the risk of comparing results against outdated criteria. It also helps project teams apply the correct values consistently across tables, maps, charts, exceedance reports and ongoing monitoring programs.
More information is available on the ESdat Environmental Standards page.
Final considerations
The February 2025 NJDEP update is limited in size but potentially important for projects involving 1,1-dichloroethene, ethylbenzene or vinyl chloride.
Environmental professionals should ensure that:
- the February 2025 screening values are loaded into their assessment systems;
- results are compared with the correct medium-specific values;
- historical evaluations near the revised thresholds are reviewed where appropriate; and
- the latest NJDEP master tables and technical guidance are consulted before making regulatory or remediation decisions.
The most important revised groundwater screening levels are 31 µg/L for 1,1-dichloroethene, 150 µg/L for ethylbenzene and 0.59 µg/L for vinyl chloride. (dep.nj.gov)
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