Evaluation of Long Term Performance of Stormwater Controls
Research Idea Scope
TERI Administrator Note: Selected as FY12 NCHRP Project 25-40; estimated completion is April 2014
As the surface transportation systems of the nation expand and transportation agencies continue to meet the growing demand of the traveling public, they are also faced with the challenge of growing with environmental awareness and regulation of stormwater (rainfall-runoff and snow-snowmelt runoff). National and state regulations require transportation agencies to provide a more directed effort towards control of constituent concentrations, loads and receiving water impacts associated with transportation projects and transportation land use operations that generate such constituents; such as daily traffic operations. Highway, and more generally, transportation land use loadings are a coupled hydrologic, sediment transport and water chemistry phenomena that represent a significant control concern. These transportation systems are linearly-extensive systems, whose geometry represents a design, resource, operation and maintenance challenge for many structural-type stormwater controls (commonly as best management practices, BMPs). Surface transportation systems such as highways, with a significant amount of paved surface area and compacted soils impacts receiving waters and ecosystems through changes in water quality and hydrology. These water quality changes are chemical, thermal, hydrologic, and have micro- to macro-biological impacts. Loads from sediment material and the oxygen demand of the runoff impacted by traffic activities on inter state and major arterial roadways are equivalent to those of untreated domestic wastewater for an urban area. Changing regulatory requirements compound the challenge as compliance with the National Environmental Policy Act, National Pollutant Discharge Elimination System (NPDES) – Phase II, Total Maximum Daily Loads (TMDL), and the Endangered Species Act require mitigation of stormwater discharges in order to acquire permits. Public concerns and regulatory requirements pose significant challenges in planning, design, construction and funding for transportation agencies. In response to public concern, knowledge advancement and regulatory directives, transportation agencies implement some form of structural BMP that becomes a component of the transportation system.
However, implementation of structural BMPs that address regulatory directives, function to mitigate public concern, and perform as intended, represent a very challenging unknown for transportation agencies. Ignoring the uncertainty associated with the initial load-response benefits of BMPs, the uncertainty associated with the long term performance, operation and maintenance of a BMP are essentially unknown. While the behavior or misbehavior of BMPs as a function of maintenance in the highway environment can be envisioned, there is no compilation or analysis of the response difference between maintained and un-maintained BMPs. The economy associated with installation and capitol costs do occasionally exist, but need compilation and updating. Despite such significant unknowns, most transportation agencies have no option other than implementing BMPs whose long term performance have not been determined; yet in the process are allocating significant amounts of their budgets for such BMP systems.
Literature Search Summary
Numerous local studies of BMPs performance have been accomplished but we are unaware of any national studies compiling performance, long term cost, and regional variations due to
hydrology and climate.
The objectives of this research are:
- Identify appropriate selection of BMPs or BMP systems for transportation land use categories, hydrology and constituent properties
- Identify and quantify what is known about BMP performance and behavior; performance that is defensible
- Examine the maintenance of BMP systems and provide assessment of how to quantify maintenance and maintenance economics, including assessing how these costs vary with regional geographic and climate variability
- Examine operation and management of BMP systems in surface transportation systems
- What is known, in a quantifiable manner regarding the restoration of BMP systems
- Quantify the economics (whole life costs) of BMPs and BMP systems
- Quantify the capital costs of BMP systems
- Identify the site constraints for BMPs based on the linear extended nature of transportation systems
- Provide guidance for selection, design, operation and maintenance of BMP systems for the highway environment
- Provide recommendations for integration of hydrology, water quality, treatment performance and maintenance of BMP systems
- Provide recommendations for estimates of the design life of a BMP system subject to surface transportation loadings in order to establish design standards for transportation agencies
The research may be based field data collection or on data obtained from the professional literature, use of numerical, physical models or analytical tools.
To accomplish the research objectives, the following work phases are recommended.
PHASE I: Literature search and evaluation of conflicting issues for integrating BMP and BMP systems into surface transportation land use systems. Evaluations and reviews will need to examine the linkage between hydrology and water quality for designs, and development of design considerations/procedures for integrated designs.
PHASE II: Development a guidance manual based on compilation of existing information, databases, analytical and modeling tools so that the manual is a comprehensive document for transportation agencies on long term performance aspects of BMPs.
Urgency and Payoff
Current and promulgated federal and state regulations such as the NPDES and TMDLs, citizen concerns and also advances in knowledge of stormwater and interactions of stormwater with the environment, have created significant challenges for transportation agencies. As TMDLs are established for impaired waterways, numerical pollutant reduction requirements are being established by states and/or by EPA; transportation agencies are finding increasing challenges in addressing stormwater beyond traditional drainage concerns. It is very important for the transportation agencies to be prepared for a future of more and comprehensive environmental requirements, environmental monitoring of transportation discharges, the requirements of load reduction, and also source controls in order to protect the environment for future generations. Without proper tools and knowledge, the economics of many transportation projects will become unsustainable both in terms of capitol costs and whole life costs. The current situation where a BMP system is installed as a prescriptive or presumptive solution is ineffective and uneconomical. Maintaining the current situation will result in the non-sustainability of stormwater control solutions. Transportation agencies must begin to examine stormwater control solutions, whether structural BMPs or non-structural controls in a rigorous and scientific method in order to know what long term performance can or cannot be provided and the costs of such long term performance. For these reasons, the benefits of a planned research project as described will provide significant benefit to transportation agencies.
Transportation Research Board AFB60 Subcommittee on Water Quality (John J. Sansalone, P.E., University of Florida, Environmental Engineering Sciences Department)