Lake Accotink Master Plan Revision

4/4/2018 Discussion with FCPA & DPWES

(updated 4/11/2018) Master Plan Objective ▪ Objective of Lake Accotink Master Plan Revision ▪ In order to meet the demand of the community for places to recreate, while at the same time protecting and preserving the county’s precious natural and cultural resources, the Park Authority has established the park master plan to guide future improvements and changes to park property and facilities. Assumption for Discussion

▪ Chesapeake Bay TMDLs require that pollutants (sediment, nutrients) levels from into (and therefore Chesapeake Bay) CANNOT increase due to agreement on TMDLs by , District of Columbia, and Delaware, , and . ▪ “Volume II Sediment TMDLs for the Accotink Creek Watershed, Fairfax County, Virginia” states: Assumption for Discussion

▪ There is absolutely no way for the dredged sediment to be landfilled within the Lake Accotink or Audrey Moore/Wakefield parks. This includes submitting for variances, compensatory payment for wetland acquisition elsewhere etc. ▪ Removal of the Lake Accotink dam will result in a wider 1% annual chance floodplain downstream of the dam. ▪ It is possible to locate the sediment forebays on the south side of Braddock Road within property owned by the FCPA. ▪ For benefit cost analysis (BCA) purposes, a 35-year life cycle is used to compare all options for Lake Accotink. Chesapeake Bay TMDL Considerations

▪ On December 29, 2010, the U.S. Environmental Protection Agency established the Chesapeake Bay Total Maximum Daily Load (TMDL). The TMDL is a historic and comprehensive "pollution diet" to restore clean water in the Chesapeake Bay and the region's streams, creeks, and rivers. ▪ As per Fairfax County DPWES, the County is ahead of its current commitments and the presence or loss of Lake Accotink and its sediment reduction does not currently “help” the County meet its Chesapeake Bay TMDLs. Local TMDL Considerations

▪ While Fairfax County is ahead of its commitments for the Chesapeake Bay TMDL, as per DPWES the County needs Lake Accotink to meet its “Local” Accotink Creek TMDL. ▪ Without Lake Accotink, Fairfax County would need to spend $86,000,000 to treat the 12 miles of Accotink Creek downstream of the Lake. ▪ Thus, currently Lake Accotink provides a value of $86M to Fairfax County. Benefit Cost Analysis – Option A (No Direct Management) Cost Benefit Financial • Yearly Dam Maintenance $13,000/yr, Major Dam Repair $4.7M/30 years • Compensatory Stormwater Quality Facility to meet TMDLs 2025-2053 = $86M Recreation • Loss of lake may lead to reduced facilities from 2025 onwards Ecological • Loss of lake by 2025 will lead to loss of (Flora/Fauna) habitat for existing Bald Eagles and Osprey. Flood • Loss of lake may lead to increased flows Protection downstream with possibly a wider floodplain affecting properties/structures. Water Quality • No sediment capture capacity from 2025 – • Capture of 47% of sediment in runoff from 2053 2019 - 2025 • Need for a compensatory Stormwater Quality Facility to meet TMDLs Benefit Cost Analysis – Option B (Continue Current Dredging) Cost Benefit Financial • Yearly Dam Maintenance $13,000/yr, Major • Avoid need for Compensatory Stormwater Dam Repair $4.7M/30 years Quality Facility from 2019 – 2053 = $86M • Dredging: $29M (initial), $29M/15 years Recreation • Assumed no change in lake recreational facilities

Ecological • No change from current conditions (Flora/Fauna) Flood • No change in flood flow attenuation and therefore, no change in floodplain downstream Protection Water Quality • Capture of 47% of sediment in runoff from 2019 - 2053

Trucking Impact: 35,000 truck trips = 8.4 trucks/hour (Assuming 2 year dredging-trucking, 5 day work week, 8 hour work day) Benefit Cost Analysis – Option C (Major Dredge & Forebays) Cost Benefit Financial • Yearly Dam Maintenance $13,000/yr, Major • Avoid need for Compensatory Stormwater Dam Repair $4.7M/30 years Quality Facility from 2019 – 2053 = $86M • Dredging: $45M (initial), $776K/year Recreation • Assumed no change in lake recreational facilities

Ecological • Deeper lake with less sediment will support (Flora/Fauna) area wildlife and increase biodiversity (especially aquatic life). Flood • No change in flood flow attenuation and therefore, no change in floodplain downstream Protection Water Quality • Capture of 47% of sediment in runoff from 2019 - 2053

Trucking Impact: 50,000 truck trips = 12 trucks/hour (Assuming 2 year dredging-trucking, 5 day work week, 8 hour work day) Benefit Cost Analysis – Option E (Single Channel no dam) Cost Benefit Financial • Project Establishment $11M, $26K/year • Compensatory Stormwater Quality Facility to meet TMDLs 2019-2053 = $86M • TBD costs for trails and nature observation areas. Recreation • Loss of lake may lead to reduced facilities • Opportunities for trails and nature from 2018-2019 onwards observation areas increased. Ecological • Loss of lake by 2025 will lead to loss of • Wetland habitat to support area wildlife (Flora/Fauna) habitat for existing Bald Eagles and Osprey. and increase biodiversity. Flood • Loss of lake will lead to increased flows • Eliminates concerns for dam safety and Protection downstream with a wider floodplain potential impact if dam were to be potentially affecting properties/structures. breached. (Structures in no dam FP?) Water Quality • No sediment capture capacity from 2019 – 2053 • Need for a compensatory Stormwater Quality Facility to meet TMDLs Benefit Cost Analysis – Option F (Single Channel, Small Lake) Cost Benefit Financial • Project Establishment $13M, $26K/year • Compensatory Stormwater Quality Facility to meet TMDLs 2019-2053 = $86M • TBD costs for trails and nature observation areas. Recreation • Loss of large lake may lead to reduced • Opportunities for trails and nature facilities from 2019 onwards observation areas increased. Ecological • Loss of lake by 2025 will lead to loss of • Wetland habitat to support area wildfire (Flora/Fauna) habitat for existing Bald Eagles and Osprey. and increase biodiversity. Flood • Loss of lake will lead to increased flows • Eliminates concerns for dam safety and Protection downstream with a wider floodplain potential impact if dam were to be potentially affecting properties/structures. breached. (Structures in no dam FP?) Water Quality • No sediment capture capacity from 2019 – 2053 • Need for a compensatory Stormwater Quality Facility to meet TMDLs Financial Summary – Benefit Cost Analysis

Option Cost Benefit Net

Option A (No Direct Management) $90,713,000 - ($90,713,000) Option B (Continue Current Dredging) $92,538,000 $86,000,000 ($6,538,000) Option C (Major Dredge & Forebays) $77,374,980 $86,000,000 $8,625,000 Option E (Single Channel no dam) $98,086,815 - ($98,086,815) Option F (Single Channel, Small Lake) $99,842,706 - ($99,842,706)

Note: 35-years used for period of analysis Forebays at Braddock Road

▪ Lyle C. (Chet) McLaren ▪ Former member of Fairfax County Park Authority Board ▪ Former member of Fairfax County Environmental Quality Advisory Council ▪ Former member of Fairfax County Tree Commission ▪ Resident of the Ravensworth Farm neighborhood ▪ Mr. McLaren shared that the need for Forebays at Braddock Road to capture sediment coming into Lake Accotink had been discussed in the 1980s but not implemented due to cost ▪ Fairfax County DPWES informed that Forebays not possible South of Braddock Road due to wetlands but are possible North of Braddock. Alternative Option C-2

▪ Attributes of alternative ▪ Install forebays in north side of Braddock Road with large sediment drying areas with access from Braddock Road ▪ Initial dredge of 500,000 cubic yards ▪ Pumping of dredged “slurry” to large sediment drying area of Forebays. Dried sediment is trucked away without truck traffic in neighborhoods. ▪ Existing dam structure will require yearly maintenance and repair. ▪ Existing dam structure will require significant repair and upgrades on estimated +/- 35-year cycle ▪ Benefit Cost Analysis ▪ Benefits and cost of this option will be similar to Option C with the exception that the truck traffic is Note: Red stars indicate location of forebays removed from the neighborhoods. Alternative Option C-3

▪ Attributes of alternative ▪ Install forebays in north side of Braddock Road with sediment drying areas with access from Braddock Road ▪ Initial dredge of 500,000 cubic yards ▪ Pumping of dredged “slurry” to Audrey Moore / Wakefield park where a parking lot is used as a sediment drying area. Dried sediment is trucked away without truck traffic in neighborhoods. ▪ Existing dam structure will require yearly maintenance and repair. ▪ Existing dam structure will require significant repair and upgrades on estimated +/- 35-year cycle ▪ Benefit Cost Analysis ▪ Benefits and cost of this option will be similar to Note: Red stars indicate location of forebays Option C with the exception that the truck traffic is removed from the neighborhoods. Additional Considerations

1. Stormwater Service District Funding ▪ Lake Accotink while owned by the Fairfax County Park Authority is more than just a recreational lake, it is a significant stormwater management facility trapping 47% of sediment that flows into it. ▪ As a stormwater management is also a function of Lake Accotink, funding from the Stormwater Service District budget may also be appropriate to fund the Lake’s dredging. ▪ Understanding that the DPWES Stormwater Service District funding ▪ 2015 - $0.0225/$100 assessed value, resulting in $56M ▪ 2018 - $0.0275/$100 assessed value ▪ https://www.fairfaxcounty.gov/publicworks/stormwater/stormwater-service-district ▪ While the Stormwater Service District Funding cannot fully cover the cost of Lake Accotink’s Option C, it may provide an additional source of funding that can reduce the amount needed via a bond referendum. Additional Considerations

2. Streambank Erosion ▪ As per ”Lake Accotink Sustainability Plan” (WSSI, 2017) the primary source of sediment in Lake Accotink is due to streambank erosion. ▪ The sedimentation rate is 22,750 cubic yards or 13,800 tons of sediment annually. ▪ 22,750 cubic yards of sediment is equivalent to 2,275 dump truck loads of sediment being deposited in the lake annually. Additional Considerations

3. Streambank Sediment Loads and Virginia DEQ Report ▪ Commonwealth of Virginia report, “Volume II Sediment TMDLs for the Accotink Creek Watershed, Fairfax County, Virginia“ (http://www.deq.virginia.gov/Portals/0/DEQ/Water/T MDL/drftmdls/Vol_II_Draft_SED_TMDL_12-20-17.pdf_) ▪ Report appears to indicate that a substantial amount of the sediment to Lake Accotink comes from Long Branch. ▪ It would be useful to understand the specific reaches of Accotink Creek and it’s tributaries that account for a majority of the sediment that enters Lake Accotink. Source: Volume II Sediment TMDLs for the Accotink ▪ With knowledge of such key reaches it may be Creek Watershed, Fairfax County, Virginia possible to prioritize stream restoration projects which will result in significant reductions in sediment entering Lake Accotink. Additional Considerations

4. George Mason University 4th Year Design Project ▪ The 4th year engineering design project is also to develop alternatives for the Lake Accotink. The presentations on their projects will be presented by end of April. It may be useful to see if they come up with some innovative solutions. ▪ The professor overseeing the 4th year projects is Dr. Joe Manous ([email protected]). Additional Considerations

5. Harnessing Public Involvement ▪ A significant number of Fairfax County residents are aware of the issues facing Lake Accotink and are galvanized to take action. ▪ Would it be possible for a group under direction of the FCPA to undertake streambank restoration projects? Thanks