New 3rd Party Construction Inspection Checklist and Certification: Underground Detention Chamber (Detention Only)

The Department of Land Development Services (LDS) developed a new 3^rd Party Construction Inspection Checklist and Certification form for underground detention chambers submitted to meet the detention requirements for development plans. This checklist supplements the existing 3^rd Party Construction Inspection Checklist and Certification forms tailored to other stormwater Best Management Practices (BMP) already available in the LDS Forms library.

The 3^rd Party Construction Inspection Checklist and Certification forms are required for underground detention chambers installed in Fairfax County. A checklist must be certified and submitted before issuance of the occupancy permit and release of the conservation deposit. Previously, underground detention chambers were certified using checklist forms not tailored specifically for this facility type. This new checklist form is specifically written for small detention-only facilities.

On August 5, 2022, LDS issued Technical Bulletin 22-06 “Localized Flooding Mitigation Policy for Residential Infill Development Detention Requirements.” The policy also published new county-approved BMP designs, including an underground detention chamber. This new checklist is suitable for certifying the as-built information for these underground detention chambers and for similar facilities even if not designed using the Simplified Infill Detention Method.

Please contact Yosif Ibrahim, Residential Infill Development Branch Chief, with general questions, or your assigned site inspector, if you have questions related to using this checklist for a specific project.