The Dive Shop in Fairfax runs the quarry.
The Dive Shop
Their next chilly willy dive at Millbrook is Sunday March 8. They have had a 100% record this year of picking chilly willy dates when I am TDY.
You need to pre-register and show up between 10:00am and 10:30am. Cost is $20.
House hunting seems to imply you are moving here. If so, the quarry will be open for the season (meaning Saturday 8am-6pm and Sunday 8am-5pm only) on April 4.
Cost is $13 per day at the Dive Shop, $15 at other dive shops in the area and $30 at the gate, so it pays to buy a pass before you show up. A season pass is $150 and is the way to go if you dive a lot.
They do allow solo diving if you have a solo cert, which helps if you like to dive a lot more than your buddies. If you drive across to beach 2, there is usually parking with some shade (nice in the summer) and it is a nice place to just dive, bring a lawn chair hang out and picnic between dives, and in general get away from the DC area crowds and grind.
There is no air on site (or food, water, etc) but Virginia Scuba is close by in Manassas. They have air and nitrox as well as equipment rentals and their weekend hours complement the quarry hours nicely.
VA Scuba
Other than Millbrook, DC is a geographic oddity where it 3 to 4 hours to anywhere else. Rawlings is 3 hours south, Dutch Spring is 3 hours north, Mt Storm is 3 hours west, Ocean City MD and Indian River DE are both 3-4 hours (depending on traffic) east and Virginia Beach is 3-4 hours (depending on traffic) south east.