UST Release Response

UST Release Response guidance

Please follow the applicable guidance in the DOH HEER TGM, DOH HEER EAL guidance, and other guidance documents on the DOH HEER website including Multi-Increment (MI) soil sampling, monitoring well installation, Low Flow groundwater sampling, soil vapor (SV) sampling, use of appropriate EALs, and preparation of the Environmental Hazard Evaluation (EHE) and Environmental Hazard Management Plan (EHMP) for UST release response.


Five decision units (DUs) are requested for multi-increment (MI) soil sampling of UST excavations for USTs 6,000 gallons or larger. For USTs less than 6,000 gallons, the four walls and floor may be combined into one DU and MIS soil sample to be sent to the lab. Additional DUs are requested for pipe runs and beneath fuel dispensers. For piping runs 90 feet or less, one DU is recommended with additional DUs for additional lengths of 90 feet or less. Dispensers should have their own DUs.

On neighbor islands, consultants may use alternative methods described in Section 5.6.3 of the HEER TGM to avoid the use of methanol for analyses of volatile organic compounds (VOCs) in soil samples. These include: freezing of samples in collectors and extraction into methanol at the laboratory, or soil vapor (SV) site assessment.

Soil vapor (SV) site assessments differ from sub-slab intrusion investigations as the purpose is to detect a release of any quantity vs. the potential for SV intrusion thru the foundation slab of a building. For SV site assessment of in-place USTs, please locate an area at the edge of the concrete or other cap over the USTs. Following the general guidance of a sub-slab SV intrusion investigation (HEER TGM Section 7), advance the SV probe into the pea gravel surrounding the USTs. Two SV samples (and one QA) sample collected from different locations in the pea gravel of in-place USTs should be able to determine if a confirmed UST release has taken place.

For piping, the SV probe should also be advanced into the pea gravel or directly adjacent at the estimated depth of bottom of piping. SV samples should be obtained every 20 linear feet of piping. For both methods, the UST or piping must be under pavement or asphalt. If removing USTs or piping, then multi-increment (MI) soil sampling should be performed instead of SV site assessment. If native soil is not present, contact DOH-UST Release Response at 808-586-4226.

See Table 9-5 in DOH HEER TGM for required petroleum constituent analyses by fuel type. Unknown USTs need TPH-g, TPH-d, TPH-o and sub-analytes on Table 9-5.

Formats for the UST Initial Release Response report and Quarterly Release Response reports may follow the format of Site Investigation reports in DOH HEER TGM 18.5.9. If you have any questions or comments, please contact DOH UST Release Response Section at 808-586-4226 or email.