stream restoration project update february, 2020 · • 2,800+ ferns & perennials • native...
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Donaldson Run Tributary BStream Restoration Project Update – February, 2020
Project area map
• Project length is 1,355 linear feet
• N. Upton St to Tributary A confluence
• NC Approved Project - 2007
• Stormwater Master Plan
• Protect existing infrastructure
• 30” water main
• Sanitary sewer
• Trail
• Repair storm infrastructure
• Address active stream erosion
• Control invasive plants
• Provide for improved long-term forest health
• Improve water quality- Bay cleanup
• Addresses key, regulated pollutants – sediment & nutrients
Project Description
Exposed
water main
2010 2019
2010
2019
2010 2019
2010
2019
2010 2019
Stream stabilization tools
• Step pools
• Stacked stone walls
• Floodplain benches
Step pools
Stacked stone wall
& floodplain bench
Stream stabilization tools
• Plunge pools
• Live staking
Plunge pools
Live staking
Site-specific
Challenges
• EXTREMELY tight space to work within
• Steep slopes
• Elevation change
• Approximately 44’ of change from upstream to downstream end of project
• Infrastructure
Infrastructure
Challenges
• Protect 30" water main
• Repair N. Upton Street outfall
• Repair two additional eroded stormwateroutfalls
• Improve trail
• Provide for adequate slope and under trail drainage
• Protect sanitary crossings and main
Recent Work
• Stormwater pipe outfall repair
design for N. Upton street
• Final stream design coordination
o Outfall protection
o Grading revision
o Protect sanitary sewer
• Design QA/QC
• Tree preservation plan review &
update
• Planting plan revised
• Additional easement acquisition
• Re-authorization – U.S. Army Corps
of Engineers
• Local and state permitting
Tributary B’s final bend before joining
Tributary A
Design QA/QC
• Update survey
✓ Review tree preservation plan.
✓ Review grading plan.
✓ Computations for design are conservative.
✓ Improve structures
• Plant down further into stream channel and use more erosion control matting
✓ Review stormwater pipe orientations
✓ Model 100-yr storm
Trees
• Tree inventory completed in
2015, reviewed October 2019
• 21 trees dead since 2017
o Erosion & storm damage
• 10 of those trees >24 in dbh
• Tree removals – 86 trees
• Potential removals – 16 trees
• More realistic evaluation of impacts
• Grading revisions
Trees
Tree impacts
• 86 total trees
• 12 trees >24 inches
• 44% less than 12 in
• 14 in poor condition*
• 60% tulip poplars
• TBD tree removals near
confluence
*trees <12 in, no condition rating
Sanitary
sewer
Planting plan
Trees required
• 161 Trees
Diverse, Native Plantings
• 332 Trees
• 150 Live Stakes
• 120 Shrubs
• 2,800+ Ferns & Perennials
• Native Seed Mix
Post-construction
• Maintenance – 5 years
• Supplemental planting in
Yrs 3 and 5
• Tree watering
• Deer protection
• Invasive control
Arrowwood
Viburnum dentatum
Christmas fern
Polystichum acrostichoides
Schedule
• Local permitting (in process)
• Additional survey
• Outreach
• Companies bid on construction
• Board awards contract
• Construction begins Fall 2020
Construction Impacts
• Trail closure along Tributary B
• Anticipated to last 6 months
• Construction staging
o Material & equipment
storage on N. Vermont
Trib A vs. Trib B Tributary B
Tributary A
June 2010
Christin Jolicoeur
Cjolicoeur@arlingtonva.us
703-228-3558
Aileen Winquist
Awinquist@arlingtonva.us,
703-228-3610
http://projects.arlingtonva.us/projects/donaldson-run-stream-restoration-tributary-b/
Contacts
Additional slides
Tributary A: Before and After
Tributary A Outfall from Utah St. – before restoration
After restoration
After restoration – looking downstream from outfall
Tributary A - Rip rap
and erosion of trees
above confluence
before restoration
After restoration
Tributary A and
B Confluence
with rip rap, before
restoration
After restoration
Broken sanitary sewer pipe and steep eroded banks – DS of confluence
Tributary A
before
restoration.
Note person in
photo –
Banks are over 6
feet high
After restoration
Tributary A
before restoration
Old stone wall, rip rap, and erosion below. Near location of current ped bridge.
After restoration
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