March 2019

Volume 4, Issue 1

Topic: CNG

Focus: CNG Conversion at Existing Facilities,

            CNG Example,

            New Staff Biographies


Making Sure Your Facility is Properly Equipped for a CNG Conversion

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

Evan Williams

This article appeared in the February 2019 edition of Waste Advantage Magazine

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.

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.

Read more.

CNG at Waste Facilities

Our client needed a new facility with a CNG compliant shop to meet local contract requirements. The new facility has (6) maintenance bays, (1) lube equipment & storage bay, (1) wash bay and an office area to accommodate all the drivers, training, locker rooms and operations team. It also has a second floor for storage and future expansion.

Read more.



Lisa RedmondProject Coordinator

Lisa began working for Cambridge in January 2019. She attended South Suburban College for her Construction Management & Technology Certificate. Lisa’s experience includes management of rental properties; monitoring profitability on all properties; invoicing and collection; executing necessary accounting functions; organizing and managing monthly budgets; …

Click here to read more about Scott!


Zerina VilaAssistant Project Manager

Zerina started with Cambridge Companies in March 2019. She has worked as a Project Coordinator, Construction Administrator, and Office Manager. Zerina’s experience includes being the interface between the engineering and design teams; attending client meetings; preparing scopes of work; proposing creative solutions to resolve conflicts to best serve client’s needs; …

Click here to read more about Bob!

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