Long Branch at Arlington Boulevard and Robin Ridge Court - Concept Design and Community Meeting
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Restore streambed and banks, ~4,500 linear feet Reduce sediment and nutrient inputs into stream system Installation of grade control structures, improve/correct channel dimension and alignment Improve floodplain connectivity and ecological processes Reduce force and volume of water within the channel during storm and flood events Naturally process nutrients and sediments on the floodplain and within the streambed Improve habitat for biological community Native landscaping Floodplain wetlands Streambed and flow diversity In-stream structures Protect Infrastructure – Sanitary Sewer Lines Channel Relocation away from sanitary sewer lines when possible Armoring channel banks and bottom where relocation is not an option
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Long Branch at Arlington Boulevard and Robin Ridge Court - Concept Design and Community Meeting
- 1. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Housekeeping and Logistics PLEASE MUTE YOURSELF ASK QUESTIONS FOR US IN THE CHAT SLIDES WILL BE AVAILABLE ON OUR WEBSITE Q/A WILL BE AT THE END
- 2. A Fairfax County, VA, publication Department of Public Works and Environmental Services Working for You! Long Branch @ Arlington Boulevard and Robin Ridge Court Concept Design Community Meeting December 7, 2021
- 3. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Who Are We? 3 Department of Public Works and Environmental Services Capital Facilities Solid Waste Stormwater Stormwater Planning Division Maintenance and Stormwater Management Division Wastewater
- 4. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Agenda 4 • Program Drivers • Vicinity Map • Project and Social Goals • Project Background • Existing Conditions • Concept Design • Typical Structures • Completed Projects • Next Steps • Contact Information
- 5. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Stormwater Program Drivers 5 In response to The Clean Water Act of 1972… • Municipal Separate Storm Sewer Permit (MS-4) • Chesapeake Bay Total Maximum Daily Loads (TMDL) – Regulates amount of pollutants in waterways • Other Local TMDLs = Local Stream Health • Maintenance of Existing Stormwater Infrastructure • Dam Safety Regulations • Public Safety /Emergency Response
- 6. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Vicinity map 6
- 7. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Project Goals 7 • Restore streambed and banks, ~4,500 linear feet • Reduce sediment and nutrient inputs into stream system • Installation of grade control structures, improve/correct channel dimension and alignment • Improve floodplain connectivity and ecological processes • Reduce force and volume of water within the channel during storm and flood events • Naturally process nutrients and sediments on the floodplain and within the streambed • Improve habitat for biological community • Native landscaping • Floodplain wetlands • Streambed and flow diversity • In-stream structures • Protect Infrastructure – Sanitary Sewer Lines • Channel Relocation away from sanitary sewer lines when possible • Armoring channel banks and bottom where relocation is not an option
- 8. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Social Goals 8 1. Maintain open dialog and share information. 2. Coordinate with all the stakeholders and the community. 3. Build partnerships with local organizations such as homeowners associations.
- 9. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Project Background 9 Design Winter 2019 - Fall 2022 Construction - TBD Inspection Survey Fall 2018 Revegetation Design Team: • Wetland Studies and Solutions, Inc • Stormwater Planning Division • Utilities Design and Construction Division
- 10. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Channel Evolution Model 10
- 11. Long Branch @ Arlington Boulevard and Robin Ridge Court Existing Conditions 11
- 12. Long Branch @ Arlington Boulevard and Robin Ridge Court Existing Conditions 12
- 13. Long Branch @ Arlington Boulevard and Robin Ridge Court Existing Conditions 13
- 14. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Proposed Design 14 • Concept Design Plan • Multiple Construction Access Points • Tree Inventory • Optimizing floodplain connectivity
- 15. Stormwater Planning Division Crook Branch @ Mantua Elementary School Stream Restoration Stream Structures and Bed Reinforcement 15 Reinforced Bed Step Pools Cross Vanes
- 16. Stormwater Planning Division Crook Branch @ Mantua Elementary School Stream Restoration Stream Reinforcement – Using Wood 16 Toe Wood Type I Woody Debris Riffle Log Rollers In-Stream Habitat Log Sill
- 17. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Proposed Design 17 • Adding sinuosity to create a longer meander path to slow down water • Implementing trees back into the stream as woody debris • Utilizing the floodplain • Protecting trees of value • Building grade control structures to stabilize stream banks
- 18. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Tree Survey 18 • # of Trees Surveyed (> 12”) = 528 • # of Trees to be removed (>12”) = 232 – Poor/Dead Trees = 56 • Trees that are removed are used in the stream design as woody habitat • Careful consideration goes into tree removal, with evaluation from the County’s Urban Forester on tree prioritization • Trees of lesser value are targeted for removal
- 19. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Strategies for Successful Revegetation • Pre-Construction – Non-Native Invasive Plant Management • Establish clear zone so that natives can re-establish • Final Phase of Construction – Stabilize with native seed – Plant native shrubs and trees – Minimum 1-year warranty • Minimum 3-year monitoring – For Native Vegetative Cover – Less than 20% Invasive – Zero % Highly Invasive 19
- 20. Stormwater Planning Division Long Branch @ Arlington Boulevard and Robin Ridge Court Completed Restoration Examples – Dead Run Segment 1 20
- 21. Stormwater Planning Division Long Branch @ Arlington Boulevard and Robin Ridge Court Completed Restoration Examples – Dead Run Segment 1 21
- 22. Stormwater Planning Division Long Branch @ Arlington Boulevard and Robin Ridge Court Completed Restoration Examples – Dead Run Segment 1 22
- 23. Stormwater Planning Division Long Branch @ Arlington Boulevard and Robin Ridge Court Completed Restoration Examples – Dead Run Segment 1 23
- 24. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Temporary Infrastructure to Restore the Stream 24 Access road and tree protection area Construction staging and stockpile
- 25. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Large Construction Equipment is Required 25 Track truck Excavator
- 26. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Schedule 26 • Concept design – May 11, 2021 • Community meeting - Fall 2021 • Final Design – Fall 2022 • “Pardon Our Dust” Community Meeting – prior to construction • Construction – Fiscal Year 2024 • pending approval of future funding
- 27. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Contact Information 27 Vivian Bui– Project Manager 703-324-5609 Vivian.Bui@fairfaxcounty.gov Stormwater Planning Division 703-324-5500, TTY 711 12000 Government Center Parkway Suite 449 Fairfax, Virginia 22035 www.fairfaxcounty.gov/publicworks/stormwater To request this information in an alternate format call 703-324-5500, TTY 711
- 28. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division Online Resources 28 • Stormwater Planning Division Website • https://www.fairfaxcounty.gov/publicworks/stormwater/ • Northern Virginia Soil and Water Conservation District • http://www.fairfaxcounty.gov/nvswcd/newsletter/planning.htm • Long Branch North @ Arlington Blvd and Robin Ridge Rd Stream Restoration • https://www.fairfaxcounty.gov/publicworks/stormwater/plans-projects/long-branch-north- arlington-blvd-and-robin-ridge-court-stream-restoration-sd-000031-219
- 29. Long Branch @ Arlington Boulevard and Robin Ridge Court Stormwater Planning Division 29 Questions?
Editor's Notes
- use the raise hand feature if you would like to
- We are the Stormwater Planning Division, that takes care of capital improvement projects such as stream restoration and other stormwater improvement projects. Our sister agency, MSMD, handles the maintenance of infrastructure such as pipes, outfalls, and existing ponds, and much more. Together we are one of the four business areas of the department of public works.
- Now that we took care of the WHO, I will next go over the WHY, our overarching program drivers that facilitate our work Next I’ll go over general project information and goals and existing conditions I’ll take us through the concept plan that has been developed, showing some typical structures that been successful on completed projects and will be used again in this one I’ll end with example photos of completed projects, and what is to come next, along with my contact information for those who would like to reach me
- There are multiple federal, state and local regulations that we must comply with in regards to water quality In general, they all have different ways of saying we need to reduce pollutants into our waterways, specifically the Chesapeake Bay Erosion is common in urban streams due to development and the reduction of pervious areas. The ground is a natural sponge, and when we build roads, schools, our homes and other buildings, we remove that sponge effect, and instead of water soaking into the ground, it goes rushing downhill and eventually firehoses into our streams. That unusually high velocity of water is one cause of erosion, and that sediment dissolves into the water and we start to get an excess amount of nitrogen, phosphorus and total suspended solids into our waterways which suffocates aquatic life and pollutes our water. Stormwater as a business area of Public Works is relatively new, we just turned 20 last year, and we exist for other reasons such as maintenance of our infrastructure as I had mentioned, and also to regulate local dams and be prepared for emergency response, specifically for major hurricanes or tropical storms
- This drainage area that flows into our project area consists of nearly 50% impervious area. What’s unique about this reach down here is that has a large existing floodplain that is relatively empty of trees, extremely high in non-native invasives and has great potential for stream revitalization. To note, there are existing storm water and floodplain easements through this entire stream valley which gives the County permission to enter and restore the stream channel
- Ultimately, mass erosion, as we often experience in developed communities is bad. If we can reduce this mass erosion, we reduce how much sediment is falling into the water, which is a source of the excess nutrients found in the stream valley/Potomac River and ultimately the Chesapeake Bay, as we saw in that NASA photo As mentioned, there is 50% impervious area in this drainage area which means half of this area is asphalt, concrete, roofs, buildings, where water cannot infiltrate into the ground and instead rushes through pipe systems and later fire hosing into Long Branch during large storm events. With that large quantity of fast moving water in mind, a lot of design effort has been made to make sure we design a stream that conveys water efficiently Allowing water to escape out of the channel and into the floodplain is an extremely important concept of a healthy stream restoration In a natural, healthy stream valley, there is always an activated floodplain, where water can reside to infiltrate slowly as opposed to be rushed downstream By doing so, there is less force and volume within the channel which is what often leads to erosion. Also, utilizing the floodplain allows us to design the streams more naturally with less heavy “engineered” solutions such as gabion baskets or massive boulders to protect the stream The floodplain acts a natural filter for nutrients and sediments that would normally be washed downstream. From a landscaping perspective, the moist nature of the floodplain allows for ecological diversity with wet loving plants. That then segways to improving the ecological habitat, to introduce back wildlife that have been absent, and remove the invasives that are currently taking over As we get further into the design, an extensive native landscaping plan will be developed to encourage species diversity, and these native plants will be another source of natural filters for water entering the stream valley We want to protect our sanitary infrastructure by either relocating the channel away from them, or armoring the banks and bottom when that is not an option The last thing anybody wants is a broken pipe with sewage spilling into our stream.
- We plan on holding more of these community meetings as we continue through the design process, and keep that open dialog going and get feedback We don’t want to surprise anyone when the project goes under construction and make sure that we set realistic expectations with the community, you all, that will be directly impacted by this project. We understand that this is your home and want to respect that and encourage participation
- We have taken this design through review by ecologists, urban foresters, residents, and engineers. Design Team includes engineers, ecologists, arborists, landscape architect, technicians, and other field staff to help pull this project together. A TEAM effort with many different backgrounds and expertise
- This graphic here is my last “Stream 101” slide, and it is the Channel Evolution Model that most urban streams go through. In an ideal circumstances, there is a constant base flow within the channel, and it can escape to a small bench or floodplain during larger events However when there is land use change, whether it is neighborhoods or roads, that bench starts to wash away and is now more incised with shear stresses from lots of water flowing through Eventually there is this downcutting effecting until the sides start to cave in, or if bedrock is hit, and then we have this widening effect. Overtime, the stream will heal itself by naturally forming benches again, but at the expense of widening and eating up land, which in this case, is a lot of people’s backyards and in extreme cases, into people’s homes. That is why we’re here to restore the stream. We are trying to prevent further movement of the stream because of these outside factors and instead design a stream that will convey water in a healthy and natural fashion Conduct Geomorphic and Watershed (HH assessment). CEM Incision (also know as downcutting or headcutting) can occur independently or simultaneously with meander migration. The bed is eroded and the base level of the stream is lowered. Downcutting increases bank height, which can eventually lead to bank failure and channel widening. Widening and downcutting continue until equilibrium is regained. Aggradation occurs when sediment supply exceeds transport capacity and the stream deposits sediment in the channel. Aggradation can be triggered by an increase in sediment supply due to upstream channel erosion or land development, or by a decrease in discharge, which reduces the transport capacity of the system. Deposition continues until a new state of dynamic equilibrium is achieved.
- Access path/staging areas are placed in areas of surveyed dead trees
- What questions can I answer for you?