Virginia Nutrient Credits: A Plain-English Guide for Developers and Builders
If your site plan can't meet Virginia's post-construction phosphorus requirement on site, the law gives you another route: buy nutrient credits from a state-certified bank. Here is how that works, when you're allowed to use credits, and what to have ready before you call.
What a nutrient credit is
A nonpoint source nutrient credit is a certified, permanent reduction in phosphorus and nitrogen runoff. It's created when land changes to a use that sheds less pollution, such as cropland planted to forest or an eroding stream restored. The Virginia Department of Environmental Quality certifies credits under 9VAC25-900 and only then places them on the state registry, where they can be sold.
Credits used for stormwater compliance have to be perpetual, which means the land generating them is protected for good. When you buy phosphorus credits, the nitrogen credits generated alongside them are retired at the same time, and the bank's certification documents both.
When the law lets you use credits
Under Va. Code § 62.1-44.15:35, your local stormwater authority must allow nutrient credits for water quality compliance when any one of these is true:
- The project disturbs less than five acres.
- The phosphorus reduction requirement is under 10 pounds per year.
- You show the requirement can't practically be met on site. The law treats this as satisfied if you control at least 75 percent of the required phosphorus reduction on site.
Localities may allow credits more broadly than that. What credits can't do is satisfy water quantity requirements: runoff volume and flood protection need their own solution, on site or through another offsite option your authority allows.
Where your credits have to come from
This is the part that trips up most buyers. Credits must be generated in the same or an adjacent fourth-order subbasin (the HUC 8 watershed) as your land disturbance. If none are available there when the authority accepts your final site design, credits from elsewhere in the same tributary can be used.
Since January 1, 2021, 9VAC25-900-91 adds another test. If your runoff reaches a water with a local nutrient TMDL, the bank has to sit upstream of the point where your discharge meets that water. If the water is impaired for nutrients but has no local TMDL, the rule sets an order of preference that starts with upstream banks. A bank can be in your watershed and still not work for your site. Spotsylvania County's guidance page walks through how one locality applies the rule.
Credits come before dirt moves
The authority has to see the reductions secured before land disturbance starts. Phased projects can buy credits for each phase before that phase begins, which keeps cash from sitting in credits years ahead of construction.
The typical sequence looks like this:
- Your engineer calculates the phosphorus requirement and how much is met on site.
- You request a letter of credit availability from a bank that serves your site.
- The authority reviews that letter with your stormwater plan.
- You complete the purchase and receive the affidavit of sale and bill of sale for your file.
The ratio is one to one: each pound of required reduction met by credits takes one credit.
Why buyers choose credits when they could build on site
Land is the obvious reason. Every acre given to a stormwater facility is an acre you can't build, lease or sell. Maintenance is the less obvious one. Onsite facilities come with maintenance agreements that run with the property. The same statute lets an owner substitute perpetual credits for existing onsite controls when the credits cover 10 or fewer pounds of phosphorus, or when the controls aren't working after reasonable attempts to maintain them, and the owner is then released from those maintenance obligations.
Credits aren't free, and supply is local. Some watersheds in fast-growing counties sell out. That's why it pays to check availability during design, not after the plan is approved.
What to send us
Potomac Mitigation Bank is based in Hamilton, in Loudoun County, and operates nutrient banks in Loudoun and Westmoreland counties. To get an answer quickly, send:
- Project name and address or coordinates
- The receiving water or HUC, if your engineer has it
- Pounds of phosphorus you need to buy
- Your permit and construction timeline
We'll confirm which of our banks can serve your site and come back with availability and pricing. Request pricing or call (540) 251-1321.
