Water Quality Improvement at Potomac Manors

As part of Montgomery County’s responsibility to ensure the proper functioning of stormwater management facilities and reduce pollutants in our local streams and rivers, the County’s Department of Environmental Protection will upgrade underperforming stormwater management facilities and restore an eroding outfall channel in the Potomac Manors community. This area drains to Upper Rock Run, which drains to Rock Run, which flows into Potomac Direct, and eventually into the Potomac River. Together, these improvements will enhance the function of downstream receiving waters, significantly improve water quality treatment and help protect adjacent properties and resources from continued degradation and erosion.

PROJECT DETAILS

Submerged Gravel Stormwater Management System (SGSMS)

Typical SGSMS at full maturity, in the Spring/Summer.

Typical SGSMS, immediate post-construction.

Typical SGSMS at full maturity, in the Winter.

Retrofitting the existing dry pond to a Submerged Gravel Stormwater Management System (SGSMS) will add water quality treatment function while expanding the facility’s stormwater storage volume to reduce flows downstream.

  • The existing dry pond provides limited water quality treatment.
  • Various components within the existing facility are failing and in need of maintenance or replacement.
  • Structural deficiencies include sediment accumulation, failing and rusting pipes, and drains clogged with debris and sediment.
  • Retrofitting the existing dry pond facility to a SGSMS will add water quality treatment functions while increasing active stormwater storage volume.
  • Project design will include re-grading the existing sloped pond bottom and adjusting its side slopes to accommodate installation of impermeable liners and filter media on the pond bottom and embankment face.
  • Native herbaceous plant materials will be sourced specifically for this area and planted within an organic layer at the base of the SGSMS, overlaid on a gravel media. No exotic or invasive plant material will be used.
  • Flowering plants will attract and serve as habitat for pollinator species, improving plant growth and biodiversity in the region by facilitating a key step in plant reproduction processes.
  • Construction is currently scheduled to begin in Winter 2025 and will last approximately five months. Most excavation and truck traffic will occur within a 8-10-week window in the middle of construction.
  • Community members will have the opportunity to review plans before construction at various points in the planning process and will be invited to walk the site with the Greenvest team before and after construction.
  • During construction, the site will be accessed via a temporary path from the end of Bit and Spur Lane.
  • GreenVest will work to establish an additional permanent maintenance access easement from Bit and Spur Lane.
  • Parking for survey and baseline data collection is at the end of Bit and Spur Lane.

  • Limited tree removal will occur to facilitate access and construction or in cases where a tree is dying or at risk offalling. Material from trees will be primarily be used on site for in-stream structures and for wildlife habitat. Trees that are removed will be replanted. The intent of the design is to minimize tree loss to the maximum extent practicable.

  • The project must pass through rigorous review processes established by County, State and Federal agencies developed to maximize safety, minimize environmental impacts and ensure modern design standards are met.

Submerged Gravel Stormwater Management Systems are small-scale filters that mimic natural hydrologic and ecological processes to capture and treat stormwater runoff, filtering sediment and pollutants through a combination of wetland plants and gravel media. The systems are designed to capture and treat 1” of rainfall over a 24-hour period.

PROJECT DETAILS

Outfall Stabilization

Stabilizing approximately 300 linear feet of actively eroding channels conveying runoff and groundwater from the existing stormwater management facility to Upper Rock Run and the Potomac River.

  • The existing outfall channel is deeply incised and actively eroding where it meets Upper Rock Run.
  • Erosion has been exacerbated by runoff from upstream and active vertical erosion of Upper Rock Run
  • The resulting channel instability is contributing sediment and nutrients to downstream receiving waters and threatens to destabilize upstream areas including wetlands and forests.
  • Structural improvements will improve safety, reduce erosion, improve water quality and preserve upstream habitat and infrastructure.
  • This will be achieved by stabilizing outfall channels that are incised, vertically unstable and actively eroding.
  • Structural improvements will reduce erosion, improve water quality and preserve upstream habitat and infrastructure.
  • Outfall channels are major contributors to sediment and nutrient loading in downstream waters due to steep slopes, exposed and non-cohesive soils and/or inadequately controlled stormwater runoff.
  • Native vegetation, including grasses, trees and shrubs will be planted within the riparian buffer to reduce soil compaction, stabilize erodible soils, and filter storm flows. The riparian buffer will be permanently protected by an easement.
  • Construction is currently scheduled to begin in Winter 2025 and will last approximately five months. Most excavation and truck traffic will occur within a 8-10-week window in the middle of construction.
  • Community members will have the opportunity to review plans before construction at various points in the planning process and will be invited to walk the site with the Greenvest team before and after construction.
  • During construction, the site will be accessed via a temporary path from the end of Bit and Spur Lane.
  • Parking for survey and baseline data collection is at the end of Bit and Spur Lane.
  • Limited tree removal will occur to facilitate access and construction or in cases where a tree is dying or at risk offalling. Material from trees will be primarily be used on site for in-stream structures and for wildlife habitat. Trees that are removed will be replanted. The intent of the design is to minimize tree loss to the maximum extent practicable.
  • The project must pass through rigorous review processes established by County, State and Federal agencies developed to maximize safety, minimize environmental impacts and ensure modern design standards are met.

Outfall Stabilization is the practice of implementing a stable channel that extends from an upland stormwater pipe outfall to a receiving stream channel. It provides a permanently stable stormwater conveyance through engineering practices such as grading, step-pools, cascades and/or rock stream bank protection.

Typical outfall at full maturity, in Spring/Summer.

Typical outfall, immediate post-construction.

Typical outfall at full maturity, in the Fall/Winter.

PROJECT UPDATES

News & Updates

Check back regularly for up-to-date project news and information, including construction alerts and opportunities to meet with the project team.

12/11/23 Community Meeting Recap
GreenVest hosted a second virtual public meeting on December 11th to provide residents with updates on stormwater management work in the Potomac Manors community,
November 2023 Community Update
PROJECT UPDATES Upcoming Virtual Community Meeting Join the Greenvest team on Monday, December 11, at 7 p.m. for a virtual meeting with Potomac Manors
Virtual Community Meeting with GreenVest, 12/11 @7pm
Join us for an opportunity to learn more about water quality and stormwater management improvements in the Potomac Manors Community. Community Meeting Details Date:  

PROJECT RESOURCES

Learn More

Frequently Asked Questions

Montgomery County holds a Municipal Separate Storm Sewer System Permit (“MS4 Permit”) issued by the Maryland Department of the Environment under authority delegated from the U.S. Environmental Protection Agency which imposes several water quality improvement requirements and goals on the County. This project will support the County’s efforts to achieve water quality requirements by addressing failing stormwater infrastructure, retrofitting an existing dry stormwater management pond, and stabilizing eroding outfall channels.

  • The facility has various structural deficiencies and does not address water quality. By updating the facility to meet modern standards, the proposed work will expand the facility’s active stormwater storage volume.
  • Additionally, an existing outfall channel is deeply incised and actively eroding where it meets Rock Run. The resulting channel instability is contributing sediment and nutrients to downstream receiving waters and threatening the stability of upstream areas including wetlands, forests, and the existing stormwater management facility.
  • The project will enhance the geomorphic and hydraulic function of the stabilized stream reach to improve water quality and help protect adjacent properties from continued bank erosion and storm flows. Specifically:
    • Retrofitting the existing stormwater management facility to a Submerged Gravel Stormwater Management System (SGSMS) will treat sediment, nutrients, and other pollutants, thereby improving water quality.
    • Increasing active stormwater storage volume will reduce storm flows.
    • Stabilizing approximately 300 linear feet of actively eroding channels conveying runoff and groundwater from the existing stormwater management facility will reduce erosion, improve water quality and preserve upstream habitat and infrastructure.
  • Construction is currently scheduled to begin in Winter 2025 and will last approximately five to six months. Most excavation and truck traffic will occur within an 8-10-week window in the middle of construction.
  • During construction, the site will be accessed via a temporary path from the end of Bit and Spur Lane.
  • GreenVest will work to establish an additional permanent maintenance access easement from Bit and Spur Lane once the project is complete.
  • Parking for survey and baseline data collection will occur at the cul-de-sac at the end of Bit and Spur Lane.
  • All project work will follow strict soil erosion and sediment control requirements set by both the State and the County to minimize dust during construction.
  • Techniques such as wetting throughout the day, street sweeping, dust screens, and a stabilized construction entrance will be utilized to minimize dust and dirt during construction.
  • There will be some noise disruption during construction. In addition to compliance with standards set forth in the Montgomery County DEP’s Noise Control Law, GreenVest will use noise mitigation techniques to minimize impacts to adjacent property owners. Night work is not anticipated.
  • Most of the excavation work will occur below foundation elevations, which will make vibration unlikely for adjacent residents. However, it is possible that homeowners within 50 feet of the project could feel minimal vibration during excavation.
  • GreenVest provides a 1-year guarantee on the completed project which includes providing required maintenance. After this time and into the future Montgomery County will be responsible for structural maintenance of the SGSMS facility, including:
    • Removal of sediment accumulation and debris, if necessary, after major storms.
    • Semi-annual removal of sediment, invasive plant species and replanting in any poorly established areas.
    • Removal of accumulated vegetation and replanting, if necessary, every 2-3 years.
  • Outfall stabilization is designed to be maintenance free.
    • The County will monitor and maintain if needed the streams for a period of five years. This includes ensuring that riparian and floodplain plants are successful and established.
    • After five years, the County will only perform limited maintenance to address concerns that may impact the function of the project.
  • The HOA will continue to be responsible for non-structural maintenance in this area, as it is currently.

For a full list of FAQs, click here.

PROJECT CONTACTS

Contact the Project Team

Residents can sign up to receive email updates and/or text alerts and ask questions of the project team through the contact information below and the form to the right.

Email :

info@GreenPotomacManors.com

Translation Services :

If you would like project information in another language or format, or if you require the services of an interpreter, please contact hilary@GreenPotomacManors.com.