Nutrient credits are a tool to protect our waterways and offset the negative impacts of development on stormwater runoff. A nutrient credit is a single quantifiable unit of improvement to the environment and represents a specific amount of nutrient absorption within a watershed. Nutrient credits are offered by nutrient credit banks, which are regulated by the Virginia Department of Environmental Quality (DEQ).
Nutrient credit banks are projects or pieces of land that follow an approved practice of nutrient reduction that has been certified by the DEQ. Examples of approved practices include converting farmland from crop or hay production to a forest, stream restoration projects, and construction of best management practices (BMPs) such as constructed wetlands.
Nutrient credits are quantified and approved by the DEQ then available to developers for purchase to address post-construction stormwater management. There are certain requirements that govern which projects can utilize nutrient credits and which banks they can be purchased from.
Why are Nutrient Credits Important?
As the landscape is altered to expand our built environment and roadway infrastructure, more impervious cover and concrete is placed on the ground. This process makes the area more susceptible for runoff and erosion. It leads to harmful nutrients, largely from nitrogen and phosphorus fertilizers used in agricultural practices, seeping into natural waterways since water doesn’t percolate into impervious ground as easily. Nutrient-laden stormwater runoff flows off concrete into the waterways, overloading the water with nutrients and causing the subsequent depletion of dissolved oxygen. A lack of oxygen in the water can result in the death of plants and animals and an overall decline in water quality.
Nutrient credits are a way to mitigate the impact of our projects on our local waterways and protect the health of our aquatic ecosystems.”
Jeni Swenson
What Projects Can We Purchase Nutrient Credits for?
Projects are eligible to use nutrient credits to satisfy stormwater management requirements if less than five acres of land will be disturbed or the phosphorus control requirement is less than 10 pounds per year. If the previous two requirements are not met, a developer may utilize nutrient credits to satisfy a maximum of 25% of the phosphorus control requirement while achieving 75% of the required treatment onsite through the construction of BMPs that provide nutrient removal. Nutrient credits can be used for a larger portion than 25% of the treatment requirement in extenuating circumstances and with demonstration that alternatives were considered.
How Do You Purchase Nutrient Credits?
The DEQ’s Nutrient Trading Data Viewer can be used to search for nutrient credit banks near your project and view how many credits they have available, though this information needs to be verified upon contacting the bank. Nutrient credits are purchased by first contacting nutrient credit banks to verify price and availability of credits. Upon project plan approval, the purchase and credit transfer will be finalized.
The Accotink Creek Stream Restoration in Fairfax County, Virginia, is an example of a project that can serve as a nutrient credit bank.
What Hierarchy is in Place?
When purchasing nutrient credits, the location of the nutrient credit bank in proximity to the project is an important factor. Credits should be purchased from a bank as close to the project as possible, ideally from a bank within the same hydrologic unit code (HUC) as the project. However, there is a hierarchy of purchase that must be followed if credits are not available. A HUC is a hierarchical land area classification system that consists of multiple smaller drainage areas (12-digit HUCs) that nest within a 10-digit HUC, and multiple 10-digit HUCs that nest within a larger drainage area known as an 8-digit HUC.
- The first aspect you would consider is if the nutrient credit bank is upstream of where the discharge reaches impaired waters, meaning a body of water contaminated by pollutants. This information is shown on the DEQ’s Nutrient Trading Data Viewer.
- If there are no credits available, then you would check if there are credits available anywhere within the same 12-digit HUC as your project is located
- If there are no credits in that HUC, you would zoom out to 10-digit and then 8-digit HUCs to see if there are credits available
- If there are no credits available in the same HUC as your project, you would check an adjacent 8-digit HUC within the same tributary
- If there are no credits available within an adjacent HUC, you would then check in any HUC within the same tributary
As we continue to develop and expand the built environment, nutrient credits provide benefits to both communities and developers. They help developers to meet stormwater management requirements while expanding and building the infrastructure we rely on, provide a monetary incentive for landowners to engage in conservation or environmentally beneficial practices on their land, and help protect water quality and the health of our aquatic ecosystems.