Twining is accredited by, inspected by, affiliated with, or an active member of the following organizations.
American Association of State Highway and Transportation Officials (AASHTO)
AASHTO Materials Reference Library (AMRL)
American Concrete Institute (ACI)
American Concrete Institute Southern California Chapter (ACI)
American Concrete Pavement Association (APCA)
American Council of Engineering Companies (ACEC)
American Public Works Association (APWA)
American Society of Civil Engineers (ASCE)
American Society for Nondestructive Testing (ASNT)
American Society for Testing and Materials (ASTM International)
American Welding Society (AWS)
California Council of Testing and Inspection Agencies (CCTIA)
California Department of Transportation (Caltrans)
California Geoprofessionals Association (CalGeo)
Cement and Concrete Reference Laboratory (CCRL)
City of Los Angeles Department of Building and Safety (LADBS)
City of San Diego Development Services
Division of the State Architect (DSA)
International Accreditation Service (IAS)
International Code Council (ICC)
Office of Statewide Health Planning and Development (OSHPD)
US Army Corps of Engineers (USACE)