Evaluating Capital and Maintenance Costs for Four Low Impact Development Treatment Systems, and their Efficiency in Removing Total Suspended Solids from Storm Water Runoff

Storm water runoff is the leading source of surface water pollution. To reduce the amount of contaminants in storm water runoff, municipalities and city governments require developers to construct storm water treatment measures, or low impact development (LID) systems, as part of the development project. LID storm water treatment systems utilize a mix of sedimentation, filtration, adsorption, and phytoremediation as mechanisms that remove pollutants from storm water prior to discharging to waterbodies. Existing studies have shown that LID storm water measures are effective in reducing runoff and improving water quality, but studies that can assist decision makers in selecting the most effective practices for their water quality needs and budgets are limited. This master’s project study compared the percentage of total suspended solids (TSS) removed, and capital and maintenance costs required for each treatment measure. Data were collected from primary literature from previous studies and an analysis of variance (ANOVA) test was performed to determine any differences in TSS removal efficiencies between the four treatment types. Physical, biological, and chemical properties involved with each treatment LID were assessed to determine potential causes for differences observed in removal efficiencies. Data from primary literature were also collected for capital and maintenance costs for each treatment measure, and bar graphs were generated to visually determine the least costly LID over a 20-year time period. Maintenance requirements for each treatment measure were evaluated to provide insight into potential differences observed in treatment costs. By comparing the costs and TSS removal for each LID structure, owners and operators can now better understand and select the most cost effective and efficient solution for treating storm water runoff at their development site. Sand Filters, Porous Pavement, and Vegetated Swales were not significantly different, and achieved high removal of TSS in storm water runoff. Detention Basins were the least costly per volume of storm water runoff the LID is capable of treating due to its open-pit structural design, and minimal maintenance involved. Vegetative Swales were the most cost effective due to its high TSS removal efficiency and affordable costs relative to Sand Filter and Porous Pavement systems