April 4,, 2017 Parks Operations Bldg Working Group Meeting Arts Districts Overview Stormwater/RPA/Stream Considerations First Principles
Agenda 7:00pm 7:05pm 7:10pm 7:40pm 8:30pm 9:40pm 9:45pm Welcome General Business Presentation: Arts Districts Overview Presentation: Stormwater, RPA & Stream Valley Management Considerations Working Group Discussion: First Principles Meeting Review / Next Steps Public Comment 10:00pm Adjournment 2
Process Timeline 3
4MRV Park Master Plan Resource Protection Area, Stormwater, and Stream Valley Management Considerations 4MRV Working Group Meeting April 4, 2017 Parks Operations Building
Outline Resource Protection Area (RPA) Purpose and Requirements Existing RPA Conditions in Park Areas Overview Stormwater Management Ordinance Requirements Addressing RPA and Stormwater Management Requirements Together (and recent park project examples) Stormwater Master Plan Priorities Q&A Main purpose of the presentation: Frame how RPA and stormwater management compliance requirements and policies as currently applied would shape redevelopment of Park areas Summarize how study area relates to Stormwater Master Plan priorities Frame some questions for workgroup to consider in developing recommendations looking beyond a master plan to future design and regulatory compliance
Resource Protection Areas Established under Chesapeake Bay Preservation Ordinance (Chapter 61) Environmentally sensitive buffer areas that provide critical ecosystem functions and protect the health of adjacent streams and wetlands from upland land uses. Minimum width is 100 feet from the streambank edge, expanded to include steep slopes 25% or greater. Desired condition is forest with mix of trees and shrubs, as well as an herbaceous layer.
Why are RPAs protected? Filter and absorb upland runoff Stabilize soil and streambanks Provide wildlife habitat Provide shading for streams
Condition of RPAs varies widely throughout Arlington, ranging from areas with 100 or more of natural buffer to many locations with impacts from existing private and public development and activities that pre date the ordinance Long term objective is RPA improvement through redevelopment and restoration
Approach to Reviewing Development Activity in RPAs Very site specific Balance continuing existing uses with net buffer improvement concept trade offs Higher intensity use/impact more mitigation Stormwater compliance Activities that increase RPA footprint require exception through CBORC* Bluemont Park baseball field Berkeley apartments Woodlawn park playground *Chesapeake Bay Ordinance Review Committee appointed by County Manager
RPAs and Park Study Area
Existing RPA Conditions Jennie Dean Park Limited riparian buffer Nutrient runoff and potential for soil compaction; but active turf and nutrient management programs in place
Existing RPA Conditions Parking area Minimal riparian buffer Stormwater runoff from paved areas petroleum, metals, sediment, and other pollutants
Existing RPA Conditions Shirlington Dog Park Minimal riparian buffer Exposed soil and soil compaction Upper bank erosion in places High pollutant load potential (bacteria and nutrients; sediment)
Passive recreational activity Varying buffer widths wider and narrower areas Some pollutant and runoff impacts from park areas (trail and grass surfaces) Road impacts beyond park area Existing RPA Conditions Four Mile Run Trail along south bank
Stormwater Management Ordinance Triggered by land disturbance of 2,500 square feet or more Runoff from impervious (pavement and rooftops) and other surfaces (e.g., grass, dirt, mulch) must be managed State provides a menu of SWM facilities that can be used Generally, 10% to 20% net pollutant reduction required relative to existing conditions Compliance must be considered at beginning of design Like RPA management, long term objective is incremental and cumulative water quality and flood protection improvements through redevelopment process
Addressing RPA and Stormwater Management Requirements Together A context sensitive approach is taken SWM facilities can only be located in areas of existing impact Strategies that mimic purpose and function of natural buffers are prioritized Less compatible strategies require extensive grading and drainage piping that can conflict with protection and enhancement of riparian buffer Net buffer improvement also achieved
Vegetated filter strip compliance option Most compatible RPA option Creates a forested buffer and meets stormwater requirements State specified minimum width of 35 consistent with research on buffer pollutant removal functions No excavation, piping, or conflict with high water tables Requires a physical barrier to prevent foot traffic from damaging vegetation and soil Cost effective way to meet both RPA and SWM requirements
Bluemont baseball field 35 to 60 wide forested buffer area Four Mile Run RPA boundary
Woodlawn Park Playground replacement with ADA improvements in RPA Created expanded forested buffer area (8,000 SF) to comply with ordinance requirements Includes requirement for 5 year invasive management plan Lubber Run Forest area RPA boundary
Berkeley Apartments redevelopment Current RPA consists largely of turf, hardscape and rooftop Redevelopment reduces footprint in RPA and enhances buffer width and composition RPA boundary Four Mile Run RPA boundary Four Mile Run
Stormwater Master Plan Adopted by County Board September 2014 Incorporates 3 technical needs assessment studies that identified priorities and led to current CIP project proposals: Stream inventory Watershed retrofit plans Storm sewer capacity analysis Provides comprehensive framework for managing stormwater, streams, and watersheds for next 20 years. 22
Stream inventory prioritizes severe erosion as well as infrastructure damage Regulatory credits for stormwater permit require active erosion and Donaldson Run comprehensive stream restoration Four Mile Run along Park study area: Floodplain and adjacent uses limit comprehensive stream restoration But there are opportunities to improve the riparian zone, address spot bank erosion, and naturalize streambanks, and provide stable public access points
Some Questions for Workgroup to Consider in Developing Recommendations Looking beyond a master plan to future design and regulatory compliance. What are the impacts of the plan on RPA condition? Positive? Negative? Which concept is most consistent with RPA management requirements and objectives? Has stormwater compliance been considered? Does the plan require significant stream related resources not aligned with Stormwater Master Plan priorities?
Q&A and Discussion