Preliminary Engineering Analysis and Design Foxcroft Colony and Mosby Woods Condominiums Prepared for: City Council Work Session November 3, 2015

Project History and Timeline City allocated additional funds to continue Initial Feasibility Study to address flooding issues. Preliminary Engineering Analysis and Design Initiated May 2014 Recommendations to address flooding issues presented to City and HOAs. Fall 2014 Public Meetings to discuss recommendations. Spring 2015 Completed Preliminary Design of recommended options. October

Impacted Areas  Based on the FEMA Flood Insurance Rate Maps (FIRMs) for the City of Fairfax: -There are 28 condominium units in 7 buildings at the Foxcroft Colony Condominium complex that are located in the 100-year floodplain and are at risk of future flooding -There are 28 condominium units in 7 buildings at the Mosby Woods Condominium complex that are located in the 100-year floodplain and are at risk of future flooding -Several commercial properties in the vicinity are also located within the floodplain and affected during large storm events 3

Impacted Areas – Foxcroft Colony 4

Impacted Areas – Mosby Woods 5

Work Completed  Continued Feasibility Analysis -Evaluated potential options for improvements -Conducted initial Benefit to Cost Analysis -Held stakeholder outreach meetings  Selected recommendations for improvements  Prepared preliminary plans  Developed preliminary cost estimates 6

Flood Protection System and Pump Station Flood protection system consists of a concrete floodwall and earthen levee in height between 1 ft. – 5 ft. Wall height designed for 25-year storm -Partially located within Pickett Road right-of-way -1 pump station to remove water behind system -New portions storm drain system on property Estimated Construction Costs are about $2.3-$2.7M -Land acquisition is not included FEMA funding is unlikely due to project having a low benefit –to–cost analysis Foxcroft Colony – Recommended Design 7

Foxcroft Colony - Proposed Flood Protection System and Pump Station 8

Concrete Floodwall and Earthen Levee Concrete Floodwall in height between 8 ft ft. Portion on upstream end is earthen levee Designed to meet the 100-year flood elevations -No freeboard provided New storm drain system to bypass flow Scour protection – grouted rip-rap Estimated Construction Costs are about $2.8-$3.3M -Land acquisition not included – City owned land Potential for FEMA funding due to benefit-to-cost analysis near/above 1 Mosby Woods – Recommended Design 9

Mosby Woods – Proposed Concrete Floodwall and Earthen Levee 10

Mosby Woods – Proposed Concrete Floodwall and Earthen Levee 11

Mosby Woods – Proposed Concrete Floodwall and Earthen Levee 12

 Finalize Design -Design Documents o 30%, 60%, 90%, final documents -Construction Permitting -USACE Permitting (Mosby Woods) -Land use agreements -FEMA grant application (Mosby Woods)  Construction -Construct Flood protection systems -Construction Administration/Management Next Steps… 13