Incorporation of LID Cost Estimating Functionality into the National Stormwater Calculator
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Project Objective

The United States Environmental Protection Agency (USEPA) engaged Geosyntec to help develop a tool to estimate costs for stormwater control measures; this tool will be integrated into the agency’s National Stormwater Calculator (SWC). While the USEPA’s SWC is a useful tool for estimating stormwater runoff during planning, it lacked a comprehensive and up-to-date cost-estimation tool for stormwater control. The objective of this project was to allow planners and managers to evaluate the capital and life-cycle costs of low-impact development (LID) controls. The tool considers user-identified size configuration of LID-controlled infrastructure, whether the project is being applied as part of new development or redevelopment, existing sites and construction feasibility constraints, and other variables.

Geosyntec's Scope of Services

Geosyntec and the USEPA developed reliable cost-estimation procedures and programmed these features into the SWC. This included the following steps:

  • Review and Research. Our team thoroughly reviewed existing cost-data sources, cost-estimation tools, models, and literature related to the costs of LID construction and maintenance. We synthesized and compared regional and national project-planning-level cost estimates, including both capital and operation and maintenance (O&M) costs.
  • Cost-Curve Development. We developed a sophisticated cost-curve estimation procedure that is easy to use and simple to update and maintain. These curves leveraged a unit-cost estimation procedure, eliminating the need for users to navigate itemized unit costs, varying LID sizes, and the complexities of physical site constraints and construction feasibility during project planning.
  • Real-Time Data Acquisition. To support ongoing accuracy and relevance, we designed and programmed a real-time data acquisition procedure that mines data from the Bureau of Labor Statistics to account for inflation and cost variability of stormwater-control capital and O&M costs at national and regional scales. The procedures help the tool remain up to date with recent-year economic variables and integrate with existing tools like the USEPA Storm Water Management Model (SWMM).

Notable Accomplishments

The novel and innovative approach we developed for cost estimation in the SWC accounts for both inflation and regional cost variability and was well received. In fact, the USEPA and Geosyntec coauthored and published a paper on the approach in the Journal of Sustainable Water in Built Environment in December 2020. The SWC continues to be a key resource for the stormwater management community, providing efficient workflows to access meteorological and site data, define and evaluate model scenarios, and understand the potential effects of climate change. By incorporating life-cycle cost estimating procedures into this tool, we helped increase its usefulness to support effective management decisions.

Learn More

Check out the tool and learn more: National Stormwater Calculator (SWC)

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Project Summary

  • Location: United States
  • Client: US Environmental Protection Agency Office of Research and Development
  • Project Practice Areas: Water and Natural Resources
  • Services Provided: Cost estimation tools; LID, cost-variables analysis; algorithm development; GUI programming; stormwater control; bureau of labor statistics CPI; regional cost variability