It is well known that three quarters of the world contain saline water. The saline water contains amounts of salt dissolved in water to a concentration of parts in per millions (ppm) includes sodium chloride, Sodium sulfate and magnesium sulfate. Compaction of Base coarse layer is usually done by water which is considered tap water. Cites near shores often need coastal roads to act as service roads parallel to shore lines. For this matter, the use of saline water in compaction is considered a main objective in this situation due to the decrease in transportation cost of Tap water used in hauling and compaction of base coarse layer. This research studies the effect of saline water on the mechanical properties of the unbounded granular material used in base coarse layer. The study compares the results between the use of saline water and standard tap water by subjecting both samples to different lab tests such as California baring ratio (CBR) and modified proctor. The results showed that saline water could be used successfully in the operation of constructing base coarse layer with good results concerning the amount of absorbed water content and maximum dry density of the base coarse layer which will result in good compaction. In addition, the CBR test results showed high evaluation of strength for samples contained saline water. The study used Dolomite material for base coarse layer from Jabal Ataqa as one of the most used aggregate types in Egypt through construction.