Some specifications call for the contractor to grub the road or compound area from three to six inches deep and place a sub base course to the top of the existing rough grade elevation. The sub base is occasionally described as a compacted base course without organic materials, allowing engineered fill material, but most often, there will be a requirement for crushed stone, which prevents the intrusion of sub grade soils and provides greater surface stability in addition to contributing to drainage. Some rock-based and heavily compacted conditions will not require a sub base course.
If a crushed aggregate base is called out in the specifications it is typically #57 stone, a mixture of 1” to No. 4. Pricing for this stone ranged from $6.00 to $12.95 per ton at the pit with an average cost of $8.87. The default pricing used in the road and compound pricing in "My Estimator" includes the cost that would be charged by the excavating or site development contractor to furnish, deliver and grade the sub base.
We recommend that you contact our valued excavators and site development companies to obtain additional information about your project-specific sub base requirements.