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Delaware

Risk Assessment and Cleanup Standards

Agency Department of Natural Resources and Environmental Control

The Division of Waste and Hazardous Substances of the Delaware Department of Natural Resources and Environmental Control (DNREC) sets the standards for risk assessment and cleanup at contaminated sites. DNREC says cleanup is governed by the Hazardous Substance Cleanup Act (HSCA), 7 Del. C. Chapter 91, and its rules are the Regulations Governing Hazardous Substance Cleanup, 7 DE Admin. Code 1375. Among the programs HSCA governs, DNREC names HSCA enforcement and HSCA lead, brownfields, voluntary cleanup and long-term stewardship. The standards are rules and guidance, not a list of sites.

In a Phase I ESA

ASTM E1527-21 does not name cleanup standards among its standard record sources. They matter when a Delaware file says a site needs no further action or was cleaned up: the next questions are what the data were compared with and whether the outcome carries conditions. Five details from DNREC's pages help.

  • Screening levels are a first look. DNREC says the HSCA Screening Levels are set conservatively, on residential land use and on background values at uncontaminated sites, and that because HSCA requires cleanup standards based on site-specific risks, a site's cleanup standards may be higher or lower than them.
  • An initial assessment has three outcomes. DNREC's guidance uses the screening levels for an initial assessment of Phase II or facility evaluation data: the highest concentrations found at the site are compared with them. The outcomes DNREC lists are no further action whatever the site's future use, no further action if specific conditions are met, or a fuller study, usually a Remedial Investigation followed by a baseline human health risk assessment. Where a file shows no further action, check which kind; DNREC publishes Conditional "No Further Action" Guidance (Dec. 2021).
  • The cleanup goal is a risk level. DNREC says quantitative cleanup goals rest on a cumulative cancer risk of 1E-5 and a hazard index of one, except for lead, and also weigh effects on the environment and ecology. It recommends the Delaware Risk Assessment Calculator (DE RAC) for the human health calculation; other calculators need its prior approval.
  • Ecology is screened at every site. DNREC says every site is screened for potential ecological concern under its guidance for a tiered Screening Level Ecological Risk Assessment at HSCA and RCRA sites, and that where the guidance's questions call for it, results are compared with the ecological screening levels for sediment, surface water and surface soil.
  • Tank sites follow a different guide. DNREC says its HSCA risk assessment guidance applies only to sites in the HSCA program, and asks for the regulating section's approval before it is used elsewhere. For storage tank releases, DNREC uses the Delaware Risk-Based Corrective Action Program (DERBCAP) to develop cleanup goals; see Storage Tank Corrective Action Program.

How a site closes

The pages read name a no further action determination, with or without conditions, as an outcome of the initial assessment; they do not describe the document that closes a site after a Remedial Investigation and cleanup. DNREC says its cleanup regulations call for long-term stewardship (subsection 12.7.5), and that the Remediation Section recognizes institutional controls recorded in an environmental covenant. Ask for the no further action determination, its conditions, and any covenant; see Long-Term Stewardship (LTS) and HSCA State Lead and Enforcement Programs.

Where to read the rule and the numbers

  • DNREC's Risk Assessment and Cleanup Standards page links the HSCA Screening Levels, a Sortable Screening Level Table, the HSCA Human Health Risk Assessment Guidance, the ecological screening guidance, and inorganic compound tables labeled Piedmont, North Coastal Plain and Coastal Plain, for use with EPA's ProUCL software.
  • DNREC's Remediation Laws, Regulations and Guidance list, last modified September 21, 2026, dates the HSCA Screening Level Table Guidance December 2025 and links separate human health and ecological screening level tables, each as a PDF and a workbook. It also links an HSCA Reporting Level Table under its notification guidance (Dec. 2025); the pages read do not say how reporting levels relate to screening levels.
  • None of these files was opened for this handbook, so no value is stated here. The guidance list sends questions to the Remediation Section by email (DNREC_WHS_REMEDIATIONINBOX@delaware.gov) or at 302-395-2600.

Where to look a site up

DNREC's search tools for remediation sites, the Delaware Environmental Navigator and the DNREC Well Viewer, are on the HSCA State Lead and Enforcement Programs page.

Getting the file

DNREC takes records requests under the Delaware Freedom of Information Act; the route is on the DNREC FOIA Requests page.

Sources

Delaware Department of Natural Resources and Environmental Control pages, read October 13, 2026:

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