Least Cost Method for Sewer Design

Engineers have achieved significant reductions in construction costs of wastewater collection systems by the use of computers. Still greater cost savings can be achieved by improving the method of integrating pipes into a collection system with the technique of dynamic programming. With the method proposed in this paper, the conventional design constraints of minimum ground cover, critical invert elevations and minimum and maximum velocities are used to establish a region of feasible solutions for each pipe. The integration, then, of each pipe into one collection system is achieved by the dynamic programming algorithm. Not only is the least cost design generated but a range of alternative discharge elevations and associated costs are made available to the engineer, allowing him maximum flexibility in exercising his judgment. Solutions of realistic sewer design problems show that the least-cost design is produced by this system.