Methodology for Design and Optimization of Highway Detention Basins

Abstract

Detention basins store increased runoff resulting from impervious highway surfaces, treat the runoff through sedimentation and then slowly release it. Many methods exist for designing detention basins including simple design storm approaches and more complex simulation models. This paper describes a continuous simulation/optimization model that provides accurate design results but remains relatively simple to operate. The model is spreadsheet-based so virtually all engineers can understand it, and it is directly linked with Excel's Solver (and Premium Solver add-in) to determine an optimal, least cost, design. A first order reaction equation including a background concentration is used to represent the settling rate of suspended solids in the model. Conventional design methods are compared with optimized least cost designs and the results indicate that the model is relatively accurate at determining high performance, low cost designs. The comparisons showed that significant cost savings could be achieved by selecting the appropriate storage volume and release rate. The derived cost-performance relationship showed that any increased performance above 85% results in relatively high marginal costs. The significance of this study is the development of a relatively simple model that caters to a wide range of users and provides a direct link to optimization algorithms. The model has advantages over conventional design methods by including multiple storm events, antecedent conditions and cost-effective designs. Yet, the model remains much simpler to operate than more complex simulation models.