Delaware

Underground storage tank (UST) compliance program

Agency Delaware Department of Natural Resources and Environmental Control

ASTM search distance Subject property and adjoining properties

The underground storage tank (UST) compliance program of the Delaware Department of Natural Resources and Environmental Control (DNREC) oversees the installation, retrofitting and removal of underground storage tank systems, to verify the work is done properly and by qualified, trained and certified individuals and companies. DNREC says the systems it regulates can be found at gas stations, manufacturing facilities, schools and hospitals. Its page, last modified December 3, 2025, says the program is responsible for ensuring the safe operation of over 400 federally regulated underground storage tank facilities and 150 state regulated heating oil underground storage tank facilities.

In a Phase I ESA

DNREC's underground tank records are the Delaware form of the state registered storage tank records that ASTM E1527-21 lists as a standard source. The general reading of a registered tank listing is on the UST / AST page. A registration says a tank system exists or existed. Releases are a separate record, the Storage Tank Corrective Action Program. Aboveground tanks have their own program, on the Aboveground storage tank (AST) program page.

Four Delaware details shape the search.

Heating fuel tanks have their own threshold. DNREC says underground tanks over 110 gallons storing petroleum or hazardous substances are required to be registered with the state and pay an annual registration fee. It states a separate line for heating fuel: heating fuel underground tank systems greater than 1,100 gallons must be registered, and those over 2,000 gallons must also pay a fee. Read the absence of a registration for a heating oil tank against that line.
Inspections run on a cycle. The program inspects facilities with underground tank systems every three years, and requires facilities to demonstrate financial responsibility for corrective action caused by accidental releases.
A red tag means deliveries are stopped. If an owner or operator does not correct the violations in a Notice of Violation, DNREC may classify the system as ineligible to receive product deliveries. Such a system is identified by a red tag attached to the fill pipe or fill pipe cap until all violations have been corrected. A red tag seen at the site visit is worth asking about.
A yearly public record. DNREC posts a Public Record Summary for each year from 2008 to 2025, which it says includes the number, sources and causes of underground tank releases, the record of compliance by owners and operators in Delaware, and data on equipment failures. Its page says federal law requires states receiving federal funds under Subtitle I of the Solid Waste Disposal Act to keep such a record.

The program's law is the Delaware Underground Storage Tank Act (7 Del.C. Ch. 74), and its rules are the Regulations Governing Underground Storage Tank Systems (7 DE Admin. Code 1351). Amendments to those regulations were approved by Secretary's Order No. 2019-WH-0047, signed December 12, 2019.

DNREC's forms for underground tanks

DNREC's Tank Management Documents page lists the forms and requirements it uses for underground tanks, among them:

the registration and notification form;
a closure notification form;
ownership transfer notifications, one for regulated tanks and one for unregulated tanks, and a foreclosure form notice;
an activity notification form for retrofits, repairs and work near a tank;
sampling requirements for removal, closure in place, change in service, change in substance stored, retrofits and cathodic protection upgrades, and over-excavation requirements.

For a tank that was removed or closed in place, the closure notification and the sampling results that go with it are the documents to ask for.

Where to look a site up

DNREC says information on underground tank facilities is available on the Delaware Environmental Navigator (DEN) and on the Delaware Open Data Portal. DNREC's open data page describes that dataset as a listing of underground storage tanks tracked and/or registered by the DNREC Tank Management Program.
Tanks Compliance is at the Lukens Drive Field Office, 391 Lukens Drive, New Castle, DE 19720, at 302-395-2500 and DNRECTanksCompliance@delaware.gov.

Getting the file

DNREC's underground tank page says a request for information may be made through the Freedom of Information Act; the route is on the DNREC FOIA Requests page. DNREC's Tank Management Documents page says select scanned facility files are available through the Delaware Environmental Navigator.

Sources

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

Underground Storage Tanks, last modified December 3, 2025.
Tanks Compliance, last modified August 25, 2025.
Tank Management Documents, last modified June 17, 2026.
Storage Tank Corrective Action, last modified June 5, 2025.
DNREC Open Data, last modified June 22, 2026.