- AECOM
- AirLiquide
- All American Pipeline Company
- American Air Liquide Inc.
- Anadarko Petroleum Corporation
- Axis Midstream Holdings
- Bay Ltd.
- Black Lake Pipe Line Company
- Bridgetex Pipeline Co
- Buckeye Partners
- Cavern Solutions Inc.
- CenterPoint Energy
- CH2M
- Chenier
- Chevron Pipe Line Company
- CIMA
- ConocoPhillips
- Contanda
- Contract Land Staff LLC
- Denbury Onshore LLC
- Diamond Shamrock
- Diamond-Koch
- Dow Chemical Company
- Driver Pipeline Company
- Easton Energy
- EnCana Oil & Gas (USA) Inc.
- Energy Specialists Consulting LLC
- Energy Transfer Company
- EnsiteUSA
- Enterprise NGL Pipelines LLC
- Enterprise Products Operating Company LP
- Equilon Enterprises LLC
- Equistar Pipeline
- ETC Tiger Pipeline Company
- Explorer Pipeline Company
- ExxonMobil Pipeline
- Fairway Energy Partners LLC
- Farnsworth Group
- Flint Hills Resources
- Florida Gas Transmission Company
- Fluor Daniel Inc.
- Greene's Energy Group LLC
- Groundwater & Environmental Services Inc.
- Hanson Professional Services Inc.
- Harvest Pipeline Company
- Houston Fuel Oil Terminal Company
- Houston Pipe Line Company LP
- INEOS
- Intercontinental Terminals Company
- Jacobs Engineering
- John Griffin Surveyors
- JTAM Engineering
- Kaneka North America LLC
- KEGroup Inc.
- Keyera Energy
- Keystone Engineering Inc.
- Kinder Morgan
- Kleinfelder
- Langan Engineering & Environmental Services Inc.
- LBC Terminals
- Liberty Pipeline Group
- Lloyd Engineering Inc.
- Lubrizol Corporation
- LyondellBasell
- Magellan Pipeline Company LLC
- Marathon
- Mitchell Energy Corporation
- MODA Midstream LLC
- Motiva
- Natural Gas Pipeline Company of America LLC
- Navitas Midstream Partners LLC
- Next Wave Energy Partners, LP
- Occidental Chemical Company
- ONEOK
- Onshore Pipeline Services (OPS)
- Paragon Engineering Services Inc.
- PetroLogistics Olefins LLC
- Phillips 66
- Piling Inc.
- Pond Engineering
- Praxair
- Primoris Energy Services Corporation
- Project Consulting Services Inc. (known as PCS)
- Regency Gas (purchased Eagle Rock)
- Rover Pipeline LLC
- S&B Engineers and Constructors Ltd
- Sabine Pipe Line Company
- Sanchez Oil & Gas Corporation
- SAW Construction Corporation
- Sealevel Construction Inc.
- Seaway Products Pipeline Company
- SemGroup Corporation
- Shell
- South Texas Pipeline Company
- Square Mile Energy LLC
- Summit Industrial Construction LLC
- SWCA Incorporated
- Targa Resources
- Tarsco Construction Corporation
- Tellepsen
- Tetra Tech, Inc.
- Texas Brine
- Texon LP
- TexStar Midstream Logistics Pipeline LP
- Total
- Transwestern Pipeline Company LLC
- Umicore Catalysts USA
- Universal Pegasus International (UPI)
- URS Corporation
- Valero
- Vintage Petroleum Inc.
- Vopak Moda Houston LLC
- WCM Group
- Wildcat Midstream Operating
- Willbros
- Williams
- Wood.
- Zachry Industrial Inc.