Duff's Dog Park in Stafford County, 4 acres, 2 parks for big dogs and small dogs

https://www.tourstaffordva.com/attraction/duff-mcduff-green-memorial-park/

For members that can't always come into Arlington and DC and for DC, Maryland and Alexandria, Arlington and Falls Church members that want to try something different, let's go to Duff's Dog Park.
Thanks to Gabriel and WallE for the suggestion

Dog Run area is roughly 4 acres of open field. Open to both small and large dogs. A great area for agility training and exercise, it also has access to the Rappahannock River.

Small Dog Park is for dogs 30 lbs and under.
Large Dog Park is for dogs 31 lbs and up.

Duff’s Dog Park will be open to the public and their dogs during regular business hours.