The budget for this project can be estimated based on the scope of work and industry standards. The replacement of two existing 18" HDPE culvert pipes with a precast concrete box culvert, along with the maintenance of streamflow and removal of stone headwalls, is a significant project that requires specialized equipment and labor. The cost of materials, including the precast concrete box culvert, temporary diversion or bypass pumping equipment, and stone headwalls, can range from $100,000 to $500,000. The cost of labor, including the cost of skilled workers, equipment operators, and engineers, can range from $200,000 to $1,000,000. Other costs, including permits, inspections, and contingency funds, can add an additional $50,000 to $200,000 to the total cost. Based on these estimates, the total budget for this project can range from $350,000 to $1,700,000.