DeMarr Logo
pro rata development fee and stormwater management

Fairfax County’s Pro Rata Development Fee

When embarking on a new home or pool construction project in Fairfax County, it is important to be aware of the Fairfax County Pro Rata Fee, a development fee imposed by the county for the increase in impervious area resulting from the construction. The purpose of this fee is to contribute to the funding of public storm drain infrastructure.

The amount of the fee is determined based on the extent of the impervious area increase on the property.

Calculating Pro Rata Fee for Land Development Projects

To calculate the Pro Rata Fee for land development projects, let’s consider a scenario. If you currently have a house on your property and intend to demolish it to build a new house with a 1,000 square feet larger footprint, your impervious area increase would be 1,000 square feet. Based on Fairfax County’s Pro Rata Fee rate of $26,713.59 per increase in impervious acre, your Pro Rata Fee would be ($26,713.59 / Acre) * (1,000 SF / 43,560 SF/Acre) = $613.26. It is important to note that impervious area also includes increases from driveways, patios, walkways, and other structures. The example provided simplifies the calculation by focusing solely on the increase in house footprint, but in reality, all impervious area increases are considered during the design process.

In another scenario, if you purchase a vacant lot and decide to build on it, your Pro Rata fee will be higher compared to a tear-down and rebuild project. For instance, if you plan to construct a house with a 2,500 square feet footprint and an associated impervious area of 2,500 square feet (including driveway, patio, pool, etc.), your impervious area increase would be 5,000 square feet. In this vacant lot example, the Pro Rata Fee would amount to $3,066.30, five times the fee in the tear-down and rebuild example. It is worth noting that a vacant property may not always be a more cost-effective option compared to a lot with a tear-down house on it.

In addition to the Pro Rata Fee, there are additional Stormwater Management costs based on the extent of the increased impervious area. This means that the more impervious area you plan to develop on your property, the higher the cost will be to mitigate the impact on downstream properties and infrastructure.

You can read more about this Pro Rata Fee in Fairfax County’s Letter to Industry.

erosion damage caused by excessive stormwater runoff
Figure 1: Example of erosion damage caused by excessive stormwater runoff from upstream properties.

If you are ready to start on your next Land Development project, or have questions, please contact us for a quote.

Related Blogs