Rapid and accurate in-situ measurement of soil properties is still a challenge facing the construction industry and there is a need for new and advanced devices and methods. Dynamic cone penetration test (DCPT) is an effective device used for field exploration and quality assessment of subsoil. DCPT could be used to predict the engineering properties of sand because it is difficult to perform conventional density tests, such as the sand replacement method, especially when loose or submerged sandy soil is encountered. Two cases of DCP field testing were conducted in Al-Jubail and Ras Al-Khair, eastern Saudi Arabia, where the major petrochemical industries are located. These tests were utilized to evaluate the potential use of DCPT to assess the density during the construction of backfills, whereby the nuclear gauge was also used to accurately measure the in situ soil density and water content. The DCP-nuclear gauge data clearly indicated that there is a good correlation between the dry density obtained from the nuclear gauge and the dynamic cone penetration (DCP) readings, which proves that the DCPT is an effective and reliable tool in the assessment of in situ compaction of sand backfills.