Impervious surface treatment techniques and load reduction strategies are key considerations to a jurisdiction’s effective portfolio of pollution reduction strategies. Stormwater management crediting and compliance is accomplished through a wide range of methods and approaches. This webinar presented the program management considerations, general requirements of program compliance, methods of quantifying stormwater crediting through a diverse range of stormwater control types and innovative approaches, and effective methods of monitoring and inspecting the stormwater infrastructure for continued compliance.
Business needs and drivers for stormwater crediting include MS4 permits, local TMDLs, mitigation assessments and other regulatory requirements. The process must be defined at both an organizational level and at a Best Management Practice (BMP) level. Programmatic considerations include balancing cost and funding, schedule, and requirements. A cost/benefit analysis should be completed to determine the value of quantifying BMPs in a jurisdiction.
When initiating a program, managers should explore the available information that can support stormwater crediting, including ledgers/lists, GIS, as-builts and maintenance records. The foundations of the necessary analyses include impervious surface mapping, geospatial asset inventories, treatment determinations and appropriate regulatory guidelines. Assessments are completed to determine the degree of treatment for the runoff that is escaping the landscape. Quantifying BMP treatment is multifaceted in terms of the type of facility, methods for measurement (primary pollutants versus impervious treatment), performance and maintenance. Approaches can focus on impervious surface restoration through structural and non-structure methodologies as well as total maximum daily load (TMDL) reductions.
Typical challenges in stormwater crediting are wide ranging, and can include incomplete asset inventories, lack of documentation, and BMPs that are not performing as they should. It is essential to determine the business need to cost effectively perform restoration or minimize requirements that ensure the return on the investment is appropriate for a specific jurisdiction.
Components of a successful program include:
Inventory of stormwater BMPs provides the foundation for any restoration efforts. Baseline year data, such as total acreage of impervious surfaces versus percentage treated by baseline BMPs, can help set goals for retrofit. Data on individual BMPs can be compiled using existing GIS mapping, stormwater reports, design plans, inspection reports, field logs and aerial imagery. A contributing drainage area must be delineated for each facility. Field verification and coordination with adjacent jurisdictions is often required.
Innovative opportunities for credit include runoff disconnection from impervious surfaces and rooftop downspouts, as well as grass swales along roadways.
Inspection and maintenance are critical to maximizing credit. Failure to address non-performing BMPs can result in loss of water quality credit and load reductions, increased costs to retrofit or redesign the facility, safety and potential drainage issues, and degradation of receiving waters and the environment.
Monitoring of BMPs quantifies long-term results. MS4 permits call for in-stream, biological, wet weather screening and other types of monitoring. The goal is to document that BMPs are functioning as intended both individually and collectively. Results can help managers prioritize retrofit and restoration. Monitoring is resource-intensive and requires significant planning, and therefore is very useful for new or varied treatment types to determine effectiveness.
Data management and reporting creates greater understanding where BMPs are located and how the networks are treated. It can be used in site selection for new projects, for assessing information of projects as they are built, and in tracking construction of planned projects. Leveraging GIS can help in decision-making and prioritizing to maximize impacts within limited funding, as well as with long-term asset management. Investments can be targeted based on criticality, ensuring that funding forecasts and operating budgets are effective.
The key is to maximize crediting opportunities within available funding. Overarching themes for a successful program are a combination of asset management, compliance management and financial management best practices.
For more information, feel free to reach out to our presenters: