Hijjawi Construction Labs (HCL) qualifications in the fields of soils and materials testing are based on the 
experienced staff of engineers and technicians, supported by Dr. Sami A. Hijjawi, the General Manager of HCL, who runs and supervises the testing and reporting activities. In April 2001, Dr. Hijjawi was entitled by the Council of Engineering Association – Jerusalem Center as(Engineer – Consultant) in his specialty.
Dr. Hijjawi has worked at senior positions in these fields since 1983:
- Head of Materials Testing Division – Ministry of Public Works – Yemen (1988-1990)
- Ministry of Housing & Urban Planning – Yemen – Consultant (1990-1994)
- Head of Laboratories Department , Consulting Engineering Center (1990-1992)
- Yemen Branch Manager, Consulting Engineering Center (1992-1994)
- Manager and Partner, Hijjawi Engineering Center (1994-1998)
- Lecturer of Soil Mechanics at Birzeit University – Civil Engineering Department
(1996-97).
- Lecturer of Construction Materials at An-Najah University – Civil Engineering Department (2001-2007).
- Supervisor of graduation projects in Geotechnical Engineering at An-Najah University – Civil Engineering Department (2004-2007).
Since 1983, Dr. Hijjawi has been involved in testing and QC activities for several important projects in Jordan, Yemen and Palestine and acted as geotechnical and material engineer in different projects of consultancy services.