If you’re buying or redeveloping a contaminated property in Newark, an average below the soil remediation standard does not, by itself, mean the cleanup is ready to close.
In its October 21, 2026 notice, the New Jersey Department of Environmental Protection (NJDEP) reminded responsible parties and Licensed Site Remediation Professionals (LSRPs) that compliance averaging is a remedial action. Full horizontal and vertical delineation must come first. The sampling and reporting must show where contamination is, how deep it extends, and where results meet the applicable remediation standard.
For buyers, that requirement has a direct consequence: a cleanup that relies on averaging may need more investigation before the average can support a Response Action Outcome (RAO). Build the full delineation scope into your schedule and budget early.
What NJDEP’s October 21 notice changes
Compliance averaging uses a group of soil sample results to assess whether concentrations meet a remediation standard across an area. The methods discussed in NJDEP’s Attainment Guidance include the arithmetic mean, the 95% upper confidence limit (95% UCL), and spatially weighted averaging.
Averaging can be part of a remedial approach. It is not a substitute for finding the limits of contamination.
NJDEP’s notice says that using an averaging method as part of a remedial action requires full delineation first. The notice points to the Technical Requirements for Site Remediation at N.J.A.C. 7:26E-5.2(a)3, which calls for demonstrating compliance at each sampling location based on existing data, not extrapolation or modeling.
The agency’s central message is direct: “full delineation (horizontal/vertical) of contaminants is required when a compliance averaging methodology is selected as part of a remedial action at an area of concern.”
The remediation standards framework is in N.J.A.C. 7:26D. The October 21 notice addresses how the technical requirements and Attainment Guidance apply when an LSRP uses averaging during remedial action. The standard used must fit the site and applicable requirements. Don’t assume an average changes which soil remediation standard applies.
Read the October 21, 2026 NJDEP notice and consult the NJDEP Site Remediation Program for rules and guidance.
What “full delineation” means in the field
Delineation establishes the horizontal and vertical extent of contamination. In practice, the investigation must support a defensible understanding of the area of concern (AOC), using appropriate sample locations, depths, methods, and analyses.
The October 21 notice specifically calls for complete horizontal and vertical delineation using single-point compliance before an averaging method is applied. That means the investigation cannot use an average to fill gaps in the sampling data or estimate where contamination ends.
There is no one sample grid that fits every Newark property. Building foundations, former industrial operations, underground utilities, fill, access constraints, and changing soil conditions all affect the program. The LSRP must develop a sampling approach that fits the site and the contaminants of concern.
A defensible delineation program typically needs to answer:
- Where does the affected soil begin and end in plan view?
- How deep does it extend at each relevant location?
- Do sample results support the boundary at the applicable remediation standard?
- Are the sample locations and depths clear enough for a reviewer to follow?
- Does the report include the method-specific documentation for the averaging approach?
The maps matter. NJDEP directs investigators to follow the general reporting requirements at N.J.A.C. 7:26E-1.6, including AOC-specific maps and figures that show sample locations, depths, and concentrations. Appendix A of the Attainment Guidance also identifies deliverables for the selected averaging method.
Averaging cannot close gaps in the investigation
The business risk is straightforward. A low calculated average does not close an AOC if the contamination has not been fully mapped. A buyer may then face additional borings, laboratory analysis, field mobilization, report revisions, and a later RAO.
That can affect a Newark transaction in several ways:
- Closing and financing: unresolved investigation scope can complicate diligence and delay decisions.
- Construction planning: contamination with unknown boundaries can change excavation assumptions, soil management, and disposal needs.
- Budget and schedule: late sampling may require remobilization and additional review time.
- Regulatory closeout: if the documentation does not demonstrate delineation and attainment, the averaging calculation will not solve the problem.
This is relevant to ISRA NJ compliance when a transaction or facility closure brings site remediation obligations into play. It is also relevant to a Phase II environmental site assessment in NJ when the investigation identifies soil impacts that may require further characterization. Confirm the site-specific obligations with the LSRP and transaction counsel.
A useful distinction: the Attainment Guidance says that actual clean-zone samples may not be necessary just to establish contaminant delineation during the remedial investigation. However, clean-zone data are required to demonstrate attainment at the conclusion of remedial action, before a remedial action permit when applicable, and before the LSRP issues an RAO. Delineation and final attainment are related, but they are not interchangeable.
Common mistakes NJDEP is seeing
NJDEP says its review of remedial-phase documents has found reports that do not fully complete or demonstrate delineation. Common avoidable problems include:
- Calculating the average too early. Averaging is used before single-point compliance has established the full horizontal and vertical extent.
- Relying on interpolation or modeling. The notice points to existing sample data, not extrapolation or modeling, to demonstrate compliance at each sampling location.
- Leaving gaps in the boundary. The investigation does not provide enough evidence to show where contamination ends laterally or at depth.
- Submitting maps without the required detail. Figures omit sample depths or concentrations, or combine areas in a way that makes the AOC difficult to evaluate.
- Leaving out method-specific deliverables. The report presents an average but does not include the documentation identified for the selected method in the Attainment Guidance.
An LSRP should check these items before a remedial-phase submission, not after a reviewer asks for clarification. See the October 21 NJDEP notice for the cited reporting requirements.
Scope the Phase II and delineation program before the deal closes
For buyers and developers, a Phase II plan should do more than confirm whether a recognized environmental condition exists. Where impacts are found, the next question is whether the sampling program can support a complete delineation and a practical path to closure.
In Newark and elsewhere in Essex County, we scope field programs around site history, known releases, site access, subsurface conditions, and the likely remedial endpoint. Our PE-led teams coordinate borings, soil sampling, laboratory analysis, field documentation, and mapping so the technical record supports the decisions that follow.
We focus on the information reviewers and project teams need: locations, depths, concentrations, data gaps, and a clear explanation of next steps. That helps the developer, LSRP, attorney, lender, and contractor work from the same picture of the site. It also helps identify investigation needs before they become a late-stage change to the budget or construction plan.
Learn more about our environmental assessment and site investigation services, NJ LSRP services, and full service offering. For New Jersey program guidance, visit the NJDEP Site Remediation Program.
Key takeaway
NJDEP’s October 21, 2026 notice does not prohibit compliance averaging. It makes the sequence clear: complete and document full horizontal and vertical delineation to the applicable remediation standard first. Then apply the averaging method with the required supporting data and method-specific deliverables.
For buyers, that means budgeting for the investigation needed to map contamination before treating an average as a path to closeout. A clear field scope can protect your schedule, support the LSRP’s work, and give your team a better basis for decisions.
Frequently asked questions
Can an LSRP use compliance averaging to close a New Jersey cleanup?
Yes, where the method is appropriate and the applicable requirements are met. NJDEP’s October 21, 2026 notice says full horizontal and vertical delineation must be completed before compliance averaging is used as part of remedial action.
Does NJDEP require clean-zone samples during the remedial investigation?
The Attainment Guidance distinguishes delineation from final attainment. Actual clean-zone samples may not be needed just to establish delineation during the remedial investigation. Clean-zone data are required to demonstrate attainment at the end of remedial action, before a remedial action permit when applicable, and before an RAO.
What must the report maps show?
NJDEP points to AOC-specific maps and figures that show sample locations, sample depths, and sample concentrations. The report must also include deliverables specific to the averaging method, as identified in Appendix A of the Attainment Guidance.
Should Newark buyers include delineation in their Phase II budget?
If initial results identify contamination and the cleanup may rely on averaging, plan for the additional investigation needed to establish the boundaries. The LSRP should determine the appropriate scope based on site conditions, contaminants, and applicable standards.
Talk with Envicon
If you’re evaluating a Newark property or planning a site investigation, get the field scope right before gaps in delineation become a closing or construction problem.
