Explosive and Flammable Facilities


There are inherent potential dangers associated with locating HUD-assisted projects near hazardous facilities which store, handle, or process hazardous substances of a flammable or explosive nature. Project sites located too close to facilities handling, storing or processing conventional fuels, hazardous gases or chemicals of an explosive or flammable nature may expose occupants or end-users of a project to the risk of injury in the event of an explosion.

To address this risk, regulations at 24 CFR part 51 subpart C require HUD-assisted projects to be separated from these facilities by a distance that is based on the contents and volume of the aboveground storage tank, or to implement mitigation measures.

HUD Guidance

When considering explosive and flammable facilities in the context of HUD-assisted projects, two lines of inquiry are appropriate:

1. Aboveground stationary storage tanks near the project

Does this project include any of the following activities: development, construction, rehabilitation that will increase residential densities, or conversion?

If so, within 1 mile of the project site, are there any current or planned stationary aboveground storage containers:

  • Of more than 100 gallon capacity, containing common liquid industrial fuels OR 
  • Of any capacity, containing hazardous liquids or gases that are not common liquid industrial fuels?

For a list of common industrial fuels, consult Appendix I of the Regulation and HUD’s guidebook “Acceptable Separation Distance.” Stationary aboveground containers that store natural gas and have floating tops are excluded from 24 CFR 51, Subpart C as well as underground storage containers, mobile conveyances (tank trucks, barges, rail road tank cars), and pipelines, such as high pressure natural gas transmission pipelines or liquid petroleum pipelines.  Aboveground storage tanks that are part of a 1-4 unit single-family FHA-insured property are also excluded.

Aboveground storage tanks containing liquified petroleum gas (“LPG” or propane) are also excluded from coverage when they are 1,000 gallons or less in volume and comply with the National Fire Protection Association Code 58, in a version no earlier than 2017 (NFPA 58 (2017)).  Further guidance on the exclusion for LPG and propane is provided in the fact sheet H1, FR-6054-F-02 Conforming the Acceptable Separation Distance (ASD) Standards for Residential Propane Tanks to Industry Standards.

Is the Separation Distance from the project acceptable based on standards in the regulation?

For proposed development activities in proximity to aboveground storage tanks (ASTs) that are not excluded by the exceptions listed above, the Acceptable Separation Distance (ASD) can be calculated based on the volume of the container, the contents, and whether or not the container is diked. Once the volume of the container (gallons), dike dimensions, and phase of state of the product (liquid or gas) are known, the ASD can be calculated using the electronic calculator.

The ASD is measured from the center of the assessed container to the perimeter of the proposed HUD–assisted project site. If the ASD is not met, mitigation is required, or another site must be considered. Mitigation options are discussed in the HUD guidebook Acceptable Separation Distance.

If the separation distance is not acceptable, mitigation is required. Otherwise, the project should be moved to a different location. A technical evaluation by a licensed engineer must be conducted to determine whether an existing barrier (natural or man-made) is sufficient mitigation or to design a barrier. For more guidance on barriers and mitigation, contact Nelson Rivera, a licensed engineer at HUD, at nelson.a.rivera@hud.gov or 202-402-4455. 

2. Hazardous facilities included in the project

Does the proposed HUD-assisted project include a hazardous facility (a facility that mainly stores, handles or processes flammable or combustible chemicals such as bulk fuel storage facilities and refineries)?

If so, is the hazardous facility located at an acceptable separation distance from residences and any other facility or area where people may congregate or be present? See guidance above on calculating the ASD.

Compliance and Documentation

The environmental review record should include:

One of the following on aboveground storage tanks in proximity to the proposed HUD-assisted project site:

  • A determination that the project does not include development, construction, rehabilitation that will increase residential densities, or conversion
  • Evidence that within one mile of the project site there are no current or planned stationary aboveground storage containers except:
    • Containers less than 100-gallons capacity containing common liquid industrial fuels
    • Containers that are 1,000 gallons or less water volume capacity and in compliance with NFPA 58 (2017)
  • For all other containers within the search distance, a determination along with all supporting documentation that the separation distance of such containers from the project is acceptable
  • Documentation of mitigation verified by a licensed engineer

AND one of the following on hazardous facilities that are proposed for development using HUD assistance:

  • A determination along with all supporting documentation that the hazardous facility is located at an acceptable separation distance from residences and any other facility or area where people may congregate or be present
  • Documentation of the existing or planned barrier that would serve as sufficient mitigation, including correspondence with a licensed engineer

View Explosive and Flammable Facilities - Worksheet.

View Explosives - Partner Worksheet.