Safety, code compliance and cost effectiveness should all be central considerations when upgrading a facility.
By Evan Williams

Converting a fleet to compressed natural gas (CNG) can make a lot of sense to reduce fuel costs. Typical considerations toward making this decision include the cost of the new vehicles as well as the fueling infrastructure. An often-overlooked component, that is essential for a fleet CNG conversion, is the cost to modify the existing shop facility to ensure those new vehicles can be serviced in a safe and code compliant environment. It is essential to understand the activities that occur in the shop as they have a direct impact on the CNG retrofit building modifications.

Existing Shop Typical Improvements
As the existing shop is assessed, the first question should be about what might be required for it to be CNG compliant. While a qualified engineer or specialty consultant should be engaged to perform the detailed analysis and scoping, there are several elements that will likely need to be provided, as well as several items to avoid.

The existing ventilation system will likely need to be upgraded to afford more air changes per hour. The shop (if it is heated) is likely heated with a gas-fired unit or radiant tube heaters. These are typically not compatible with a CNG shop and will need replacement.
Shop Height
The height of the shop has a direct impact on the ventilation requirements. If the shop is shorter than 20′-0″, it may not be entirely viable for a CNG retrofit.

Gas Detection
It is likely that the existing facility does not have a gas detection system. One may be required by the local Authority Having Jurisdiction (AHJ).

Fire Separation
The walls that separate the shop from the administration offices will be required to be two-hour rated for a CNG Shop. If the current walls are not rated, upgrading these can be costly and disruptive to operations.

Look up at the ceiling and down at the floor. If there is any wiring or conduit in the areas within 18″ of the roof or the floor, it will need to be upgraded to Class 1, Division 2 rated.
This is not an exhaustive list of where all changes need to be made, but it is meant to help illustrate how the CNG retrofit work can impact many different areas of the shop. With a better understanding of areas where upgrades will likely be necessary, the next step will be to work with a consultant to perform a detailed analysis of the facility to better define which of the potential upgrades the facility will need to begin servicing CNG vehicles.

Major shop upgrade requirements.
Photo courtesy of Marathon Technical Services (CNG fueling station and CNG garage facility upgrade design experts;

Existing Shop Classification
The assembled team should start the shop conversion analysis with a detailed review of the existing shop and what activities are performed there. The goal will be to determine whether the facility will be classified as a Minor Repair Shop or Major Repair Shop The terms ‘Minor Repair Shop’ and ‘Major Repair Shop’ are designations in the code that determine the standards the shop needs to meet, depending on the work that will be performed there:
• Minor Repair Shop: This includes service activities that do not impact the fuel system or generate heat in excess of 750° F (welding, grinding, etc.). It does include brake repairs, tire work and PM activities.
• Major Repair Shop: These include areas where there will be welding, vehicle body work or engine overhauls. Fuel system work may also be performed here.

There are different building requirements for minor versus major shop upgrades, so understanding clearly what operations need to be performed can help define the level of improvements needed in order to operate safely. Alternatively, it may be determined that while completing only some tasks would make the facility a Major Shop Upgrade, the costs of the higher-level retrofit might not make sense and will classify a shop as a Minor Repair Shop and that certain tasks could be farmed out to a third-party. With this in mind, pricing options should be obtained to retrofit the shop as either a Minor or Major Repair Shop and see what the costs end up being. At a minimum, this can be a part of the cost benefit analysis and a component of ROI. To make sure the proposed improvements will align with code requirements and industry best practice(s), the architect or engineer should perform a detailed code check of the building to establish the code requirements that will need to be addressed. Codes vary by State and jurisdiction, but the most common are:
• International Building Code (check for State/Local amendments)
• International Mechanical Code (check for State/Local Amendments)
• International Fire Code (check for State/Local Amendments)
• National Electric Code
• NFPA 30A – Motor Fuel Dispensing Facilities and Repair Garages

Major Versus Minor Shop Upgrades
The type of shop and the applicable codes should help create a code-minimum list of required building improvements. Keep in mind that the overlapping codes do not always offer the same requirements. Where disconnects are noted, contact the local AHJ for their interpretation. It is much better to get the clarification while in the scoping and design development phase, rather than when the upgrades are complete and the AHJ will not allow operations to begin. Note: Tables 1 and 2 are subject to State/local code amendments, as well as future changes to codes.



Addressing Considerations

Converting a facility to accommodate a CNG fleet is not a simple task. From complex overlapping code requirements that vary by jurisdiction, existing facilities that may not be ideal candidates for retrofitting, and investments in staff training and procedures, there are many considerations that need to be addressed. Working with a team that has a familiarity with these requirements and the needs of the waste industry can help sort out the “must haves” from the “nice haves” to realize a final product that is practical, code-compliant, safe and cost-effective. | WA
Evan Williams is a Design Project Manager at Cambridge Companies (Griffith, IN), a design-build firm working with the waste industry for more than 20 years. During this time, more than 100 solid waste design-build projects have been completed, including new build, repairs, upgrades and/or modifications at transfer stations, recycling centers/MRFs, hauling companies, landfill facilities, office buildings and more. Cambridge continually monitors the industry to determine any new needs, changes or improvements that will benefit their clients and improve their design-build solutions. Evan can be reached at (219) 972-1155, via e-mail at [email protected] or visit


You may also like:

Facilities Planning and Design: Making Way for CNG

Telematics for CNG Vehicle Fuel Management