Cost analysis methodology for advanced treatment of stormwater: The Los Angeles case

Cities in the United States can expect to be affected by proposed stringent stormwater treatment plans and standards set to be triggered by existing Federal policy-making requirements. In Los Angeles, these standards require three levels of treatment of all stormwater before it is discharged into a public body of water. This work presents a methodology for conceptual cost budgeting for these new required treatments, and describes methodologies and cost modeling tools needed for assessment of city and regional economic impacts associated with construction and operation of these plants. The research is case-study based, and presents nine different cost analysis scenarios based on different strategies for determination of rainfall, locations of plants, and size of plants. The cost and size of the new collection and treatment facilities increases substantially if they are designed to accommodate a larger share of expected annual rain events. It will cost about six times more to build a system that can treat storm flows from 97% of the region's annual average storm days than it would to build to a 70% sta additional cost achieves about nine additional days of storm flow coverage. In addition, if stormwater treatment facilities are financed locally and constructed over a twenty-year period, most communities in the greater Los Angeles area would experience very significant employment and net economic losses.