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