Technical Bulletin 22-06 is now available and describes a new policy regarding runoff and detention on single-family detached building sites. Please see our Stormwater Management Design for Residential Infill Lot Grading Plans for related information and new design tools for infill lot stormwater detention. 

This policy clarifies that Minimum Standard 19, and the Stormwater Management Ordinance where applicable, require evaluation of sheet flows from land disturbing activities.  Plans proposing increases in stormwater flows upstream of known inadequate channels must provide detention as required by this Technical Bulletin. Plan preparers are also directed to Technical Bulletin 22-26, regarding known inadequate outfalls in Fairfax County. 

This Technical Bulletin also introduces the Simplified Infill Detention Method (SIDM) to aid plan preparers in designing on-site detention systems. The SIDM provides designers template detention designs intended to simplify plan preparation, review, and installation by standardizing facilities for use in Fairfax County. These SIDM designs may be used instead of other practices. Use of SIDM standards is encouraged but not required; applicants may continue to submit custom designed detention systems.  

Technical Bulletin 22-06 provides more background information, details, and the SIDM description. The Stormwater Management Design for Residential Infill Lot Grading Plans website now includes much of this content, along with the SIDM design guidelines, a SIDM User Manual, and design tools for infill lot plan preparers. 

Please contact Yosif Ibrahim, PE, in the Site Development and Inspections Division at 703-324-1720 with any questions.