Leesburg Pike townhomes approved, addressing potential Pimmit Hills flooding

A townhome development planned for 7700 Leesburg Pike will include stormwater facilities intended to address flooding concerns in the nearby Pimmit Hills neighborhood.

The Fairfax County Planning Commission approved the more stringent plan for the site currently occupied by a circular office building on Nov. 10, determining that developer EYA met the county’s new standards to help prevent flood damage to nearby properties.

“We don’t want to have this development impact the downstream,” Commissioner Mary Cortina, who represents Braddock District, said during a Nov. 3 public hearing.

She noted that the property is not a big runoff producer today, but commissioners don’t want the proposed development to make flooding any worse.

The Board of Supervisors voted on Oct. 19 to adopt a comprehensive plan amendment allowing a residential project to proceed if it exceeded certain stormwater management standards to mitigate downstream flooding, among other factors.

Located on a hill, the four-story office was built in 1976 and includes professional and medical offices as well as a private college of nursing.

EYA is seeking to replace the office building with 104 townhomes, nine of which would be affordable dwelling units. The townhomes could be three stories high with optional fourth-story additions.

“Pimmit Hills has experienced a lot of problems with stormwater through the Pimmit Run watershed and through some of their sub watersheds,” said Dranesville District Commissioner John Ulfelder, who serves as the planning commission’s vice chair. “People have had flooded basements many times, and there’ve been lots of complaints.”

An engineer for the project conceded that the proposed development would make the site 12% more impervious, meaning it will have surfaces that produce runoff as opposed to vegetated areas that absorb water.

But the developer is pursuing several solutions to address stormwater issues, according to a county staff report.

That includes reducing possible discharges of phosphorous, which can be harmful to people and animals. EYA will provide two water treatment facilities to improve worst-case scenarios for different levels of flooding, including a 100-year-flood, which isn’t required.

According to the county report, the developer has committed in a proffer to meeting certain targets for stormwater runoff reduction:

The applicant proposes to reduce the 1-year site peak runoff rate to a minimum of 5% below the allowable release rate determined using the energy balance equation for sites draining to a natural stream. The site peak runoff rates for the 2-year event will be reduced below the peak runoff rates of the site as it exists prior to the current development by a minimum of 20%. The 10-year site peak runoff rate will be reduced to the peak runoff rate that would drain off the site if it has a forested condition. The 100- year site peak runoff rate will also be reduced a minimum of 10% below the peak runoff rate that would be released from the post-development site if it did not have any stormwater measures.

The Board of Supervisors will still have to give the final approval to the townhouse project, which Ulfelder said might not be scheduled this year.