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There is no longer a need to argue the case for implementing a comprehensive storm water management strategy on new and redevelopment projects as a tool for protecting aquatic resources. The case already has been made by numerous regulatory agencies, environmental groups and academia alike. On the other hand, as storm water permit compliance becomes more a function of achieving measurable results, there is a growing debate regarding which specific elements should be included within that comprehensive strategy.
The National Academies of Sciences (NAS) report “Urban Stormwater Management in the United States” provides an in-depth review of the implementation and effectiveness of current storm water management permit programs. The conclusions include recommendations for a permit structure that gives local governments both the authority and accountability for managing storm water discharges, the need to transition to a watershed-based permitting structure and a compelling argument for rethinking storm water management technology.
It has long been considered the realm of the engineer to select, size and design structural storm water best management practices (BMPs) to meet technical criteria and, ideally, the intent of permit conditions. While the intent of the criteria may have shifted dramatically over the years—from flood control to natural channel protection to storm water quality to all of the above—the engineer still develops a site-specific design strategy that controls runoff from a single development project.
It always has been assumed that multiple site-specific strategies will lead to overall protection and improvement within a watershed. Now, as we look toward a new generation of permits and associated performance-related goals and objectives and begin to realize that this assumption may not be true, we must embark on a dramatic shift in the entire paradigm of managing storm water at the site and watershed levels.
The Need for a Shift
In Virginia, new technical criteria for managing storm water quality and quantity are being adopted. These include progressive standards for limiting pollutant loads through the use of integrated site design storm water practices. The public comment period recently was completed with an unprecedented level of interest.
Many opponents have identified the cost of implementation and the potentially marginal benefits as the reason for their opposition. To be fair, the results of the regulatory economic impact analysis (EIA) concluded: “The benefits exceed the costs for one or more proposed changes. The costs likely exceed the benefits for one or more other proposed changes.”
Further, it was noted that “uncertainties exist over the long-term cost and effectiveness of many of the storm water control practices” and “the cost of achieving additional nutrient reductions in highly urban settings and other areas with specific constraints is still uncertain but potentially high.”
It is only natural that such an assessment raises concerns and the obvious question: Why isn’t there more data to support the almost intuitive economic benefits of implementing storm water management programs and protecting aquatic resources?
There is little specific data with which to document a conventional “benefit” derived from the historical approach to storm water management. As referenced in the NAS report, the strategies of the past have not kept pace with current development patterns of ever-expanding impervious cover and over-managed turf. It has been well documented that corrective actions in urban and suburban areas using traditional structural practices are costly and that their effectiveness may take years to measure.
What the Virginia EIA and opponents failed to recognize is that the proposed criteria depends on utilizing the hydrologically functional features of the landscape in order to achieve compliance and reduce costly storm water management infrastructure. This requires a fundamental shift in how land is developed. Storm water must be considered at the very outset of the development process. For highly urban sites and on sites where there are limited options for implementing storm water site design elements, there are numerous proposals for offsets and other compensatory treatment strategies designed to encourage the most efficient approaches to management.
We have a vested interest in ensuring that the strategies being proposed are effective and can achieve the desired results. As outlined in the NAS report, storm water programs must be targeted yet adaptable in order to address specific watershed conditions over the course of time. Generally, there are two approaches to consider—one at the site level and one at the watershed level.
Site-Level Approach
The site-level approach calls for improvement in the overall effectiveness of the site-specific BMP strategy by utilizing a new design hierarchy:
- Avoidance and minimization. Reduce storm water runoff by design through strategic placement of development infrastructure so as to avoid impact to beneficial hydrologic features and minimize runoff increases.
- Runoff and pollutant reduction. Prioritize BMP selection to favor those that have been demonstrated to reduce runoff volume through attenuation, infiltration and other processes (e.g., bioretention and grass swales). Nonstructural practices that reduce the overall pollutant load available for wash-off should be considered and credited (e.g., street sweeping and pollution prevention programs).
- Capture and treat. Use structural BMPs as needed to achieve additional pollutant removal and peak-rate reduction for natural channel protection.
This strategy is referred to as the Runoff Reduction Method in the Virginia regulation and provides benefits quantified in terms of runoff quantity and quality. While the selection of appropriate practices for any given development site—along with the proper sizing, design and construction specifications—may still be up to the engineer or other qualified person, the real value is in conducting an inventory of natural resources on the property and guiding the pattern of development in order to take advantage of the site’s hydrologic features. This helps to reduce the capital and long-term operation and maintenance costs of structural BMPs.
Watershed-Level Approach
Highly urbanized localities facing legacy issues of stream channel erosion associated with increased volume and velocity of storm water and uncontrolled hot-spot sources of nonpoint source pollution have little choice but to embrace a more holistic watershed approach that incorporates a broad range of management strategies. These should include:
- Watershed-based programmatic goals (e.g., integration of multiple permit programs related to natural resource protection and enhancement);
- Comprehensive pollution prevention programs;
- Local watershed retrofit assessment and inventory;
- Updates of subdivision ordinances to minimize future impacts and foster urban retrofits as part of any redevelopment process; Illicit discharge detection and elimination; and
- Offsite, offset or pro-rata compensatory treatment mechanisms to ensure the most “bang for the buck” in implementation.
One successful example is the regional or watershed-based limitations on lawn fertilizers and the public education necessary to effectively implement such a program. The Huron River in Michigan benefitted from a 28% reduction in phosphorus levels after the adoption of a strict urban nutrient management ordinance.
It is expected that municipal governments, especially those with Clean Water Act (CWA) MS4 permits, will develop similar programs to maximize the benefits within their individual or shared watersheds. A notable element of that process in Virginia is the establishment of a BMP Clearinghouse comprised of a diverse panel of experts and stakeholders in storm water-related fields. Originally established to evaluate BMP performance, it is envisioned to serve in an agency-supporting role to review and evaluate local and watershed-based storm water programs that incorporate innovative strategies that may not fit neatly into the regulatory criteria of an equivalent program but serve to maximize the cost-benefit of implementation. The state permit authority still has the final say, but there is tremendous value in having an expert panel help evaluate program proposals and computed benefits.
Finally, in order for any storm water program to be successful, there must be an effective training and outreach component to support the entire spectrum of stakeholders. The Chesapeake Stormwater Network is an example of a regional watershed-based network focused on advancing the profession of storm water management through training, education and shared communication among thousands of industry-connected members.
The implementation of a comprehensive program at the watershed scale, rather than within political boundaries, may require a comparable level of administrative oversight and cooperation between multiple government and nongovernmental organizations. The technology of storm water and the complex research into the performance and longevity of traditional and proprietary BMPs are critical elements to achieving the goals of the CWA.
However, the biggest challenges before us are not necessarily of a technical nature. The biggest challenge is in utilizing creativity, coordination and cooperation to develop and apply an effective, comprehensive, multifaceted and multijurisdictional watershed strategy. I hope all those who live in a watershed are up to the challenge.
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