contractor awareness training vegetative practices 2016

A Fairfax County, VA, publication

Department of Public Works and Environmental Services

Working for You!

Stormwater Maintenance Awareness TrainingFor privately maintained stormwater management facilities

Maintenance and Stormwater Management Division (MSMD)

Spring 2016

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Stormwater Maintenance Awareness Training

MSMD/DPWES

Course ScheduleAM session (includes two short breaks)

– History of SWM and regulations– County inspection basics– The inspection report and MAR– Common SWM/BMP types

• Common maintenance issues-General

– Common SWM/BMP types, deficiencies, and remedies• Above Ground Facilities

12:00-1:00 PM Lunch

PM session (includes two short breaks)– Common SWM/BMP types, deficiencies, and remedies

• Below Ground Facilities• Vegetative Practices

– Closing remarks/questionsNOTE: All pictures, unless noted, are the property of Fairfax County.

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MSMD/DPWES

Vegetative Practices-Bio-Retention (BR)• Collects both piped and surface

runoff into a shallow landscaped depression incorporating pollutant removal mechanisms, filtration, and infiltration characteristics which mimic pre-development conditions– Infiltration is through a filter

bed of sand, soil and organic material.

– Filtered runoff may be returned to storm system via an underdrain and/or infiltrated into surroundings.

Properly Functioning Example:

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Above Ground Practices-Bio-Retention (BR)Properly Functioning Examples:

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Vegetative Practices-Bio-Retention (BR)Standard components • Mulch layer• Filter bed• Inflows• Ponding area• Planned plantings

Optional Components (Design Dependent) • Energy dissipators• Overflow structures (majority of facilities)• Observation wells or

underdrains• Pretreatment (Linear

BMP implementation)

Mulch Layer

PlantingsBerm

Energy Dissipator

Inflow

Overflow Structure

Pond

ing A

rea

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Vegetative Practices-Bio-Retention (BR)

Key Components

Picture: VDEQ Stormwater Design Specification No. 9, Bioretention, Version 1.9, 3/1/11, Figure 9.5 “Typical Detail of Bioretention with Additional Surface Ponding”

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Key Components

Picture: VDEQ Stormwater Design Specification No. 9, Bioretention, Version 1.9, 3/1/11, Figure 9.4 a “Typical Detail of Bioretention Basin Level 1 Design” & Figure 9.4 b “Typical Detail of Bioretention Basin Level 2 Design”

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Vegetative Practices-Bio-Retention (BR)Deficiencies/Conditions Requiring ActionOverflow/Control Structures

Overgrown Vegetation Spalling/deterioration

Sediment/debris Erosion around structure

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Vegetative Practices-Bio-Retention (BR)Ponding Area, including Mulch Layer and Vegetation

Missing, dead, & overgrown vegetation are common issues

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Vegetative Practices-Bio-Retention (BR)Ponding Area, including Mulch Layer and Vegetation Sediment and debris

Other Common Issues Include: • Inadequate mulch layer (<2-3”)• Over-mulching (mounding)• Inadequate ponding depth• Standing water after 48 hours

Check approved site plans for details

Exposed filter fabric

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Vegetative Practices-Bio-Retention (BR)Berm

Erosion and trenching

Other common issues: • Bare spots • Missing/improperly constructed berm

Animal hole

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• Common Remedies– Remove all flow blockages as well as any additional trash, debris, and

accumulated sediment– Repair/replace any damaged/missing components

• Components vary by facility type and design, and they can range from parts to structural to environmental materials (see prior noted examples)

– Check plans for specific facility requirements• Missing or inadequate mulch levels are common for this type of

facility

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• Common Remedies– Standing water after 48 hours:

• Underdrain may need to be flushed and re-checked– Rebuild/stabilize any areas with erosion and bare spots:– Cut back overgrown vegetation around facility structures to facilitate

access and proper function• Replace/replant any dead, dying, or missing vegetation per

approved site plan• Remove any non-spec vegetation, especially if it impacts the health

and function of the facility, as designed

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Vegetative Practices-Tree Filters (TF)• Ultra-urban bioretention in a

prefabricated box*, always tied into stormwater infrastructure via an underdrain– Typically implemented in large

areas of imperviousness (parking lots, schools, etc.)

– Plant provides biological pollutant and nutrient uptake

– Sometimes called Tree Box Filters

Properly Functioning Example:

* Note: While the Filterra TF (via Contech) is used here as a convenient example of commonly available/utilized technology, Fairfax County does not endorse any specific tree filter product over another.

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Vegetative Practices-Tree Filters (TF)

Standard Components• Plant (shrub or tree)• Mulch• Filter media• Underdrain• Throat• Overflow structure Overflow Structure

PlantTree Frame and Grate

Flow

Gutter & Curb

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Vegetative Practices-Tree Filters (TF)Key Components (Typical Tree Filter Section View-Filterra 2007)

www.conteches.com

Fairfax County BMP Fact Sheet

http://www.conteches.com/

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Vegetative Practices-Tree Filters (TF)Deficiencies/Conditions Requiring ActionThroat Opening/Mulch Layer

Common Issues:• Trash, debris, and sediment

accumulation, usually at the throat• Inadequate mulch layer• Missing surge stone at throat• Spalling and deterioration

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Vegetative Practices-Tree Filters (TF)Plants/Vegetation

Dead Vegetation

Missing Vegetation Damaged Vegetation

Overgrown/Crowded

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Vegetative Practices-Tree Filters (TF)Outfall/Overflow Structures

OTHER COMMON ISSUES:

• Blockages• Sediment/debris• Separation/misaligned

joints

Spalling and concrete deterioration

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accumulated sediment– Rebuild/stabilize any areas with erosion and bare spots– Repair/replace any damaged/missing components


– Check approved site plans for specific facility requirements• Missing or not to spec media and mulch levels are common for this

type of facility• Missing pre-treatment devices, per approved plans

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• Common Remedies– Standing water after 48 hours:

• Underdrain may need to be flushed and re-checked– Cut back overgrown vegetation around facility structures to facilitate


approved site plan• Remove any non-spec vegetation, especially if it impacts the health

and function of the facility, as designed

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Above Ground Facilities-Rooftop Detention (RT)

Is there a need for a short

BREAKor shall we just GET IT DONE?

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Vegetative Practices-Green Roof (GR)• Captures, temporarily stores, &

reduces runoff, while also reducing pollutant loads through biological nutrient uptake– Extensive Roof systems have

shallow soil media (2-6”), with drought tolerant plants such as sedums, and are primarily functional

– Intensive Roof Systems have deeper soil media (6-12”), more extensive plantings, and also act as public green spaces

Properly Functioning Examples:

Intensive Roof SystemIntensive Roof System

Extensive Roof SystemINTENSIVE ROOF SYSTEM

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MSMD/DPWES

Vegetative Practices-Green Roof (GR)• Key Components

– Deck layer– Waterproofing layer– Insulation layer– Root barrier– Drainage layer and drainage

system– Root-permeable filter fabric– Growing media– Plant cover– Roof drains– Emergency overflow

VDEQ Stormwater Design Specification No. 5, Vegetated Roof, Version 2.3, 3/1/11, Figure 5.2 “Typical Section-Extensive Vegetated Roof (Source: Northern VA Regional Commission)”

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Vegetative Practices-Green Roof (GR)Key Components

Aluminum curb, filter fabric, & drainage layer(VDEQ Stormwater Design Specification No. 5 Vegetated Roof, Version 2.3, 3/1/11, Figure 5.1 “Photos of Vegetated Roof Cross Sections (Source: B. Hunt, NCSU)

Roof drain Rooftop access (hatch, door, or ladder)

Roof drains and scuppers help to drain off any excess water to avoid accumulation

Multiple downspouts can drain to the GR (from other roof sections)

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Vegetative Practices-Green Roof (GR)

Deficiencies/Conditions Requiring Action– Dead/dying vegetation– Invasive species– Weeds– Waterproof membrane

• Leaks• Cracks

– Clogged roof drains or scuppers

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Vegetative Practices-Green Roof (GR)• Common Remedies

– Remove all flow blockages as well as any additional trash, debris, and accumulated sediment

– Repair/replace any damaged/missing components • Components vary by facility type and design, and they can range

from parts to structural to environmental materials (see prior noted examples)

– Check plans for specific facility requirements– Rebuild/stabilize any areas with erosion and bare spots– Cut back overgrown vegetation to facilitate proper function

• Replace/replant any dead, dying, or missing vegetation per approved site plan

• Remove any non-spec vegetation, especially if it impacts the health and function of the facility, as designed

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Vegetative Practices-Vegetative Swales (VS)

• Similar to BR in form and function, though typically configured as a shallow linear channel– Primarily stormwater conveyance– Pollutant removal provided via temporary storage/filtration– VS typically lined with turf or other non-turf vegetation to protect

against bank shear stress due to greater runoff velocities

• Check site plans for proper vegetation type

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Vegetative Practices-Vegetative Swales (VS)Standard components • Vegetated banks• Filter media• Inflows• Ponding area• Overflow structureOptional Components (Design Dependent)

• Check dams• Pretreatment• Planned plantings• Underdrains• Observation wells

Overflow Structure

Flow Observation Well

Ponding Area

Vegetated Berm

Flow

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Vegetative Practices-Vegetative Swales (VS)Key Components

Picture: VDEQ Stormwater Design Specification No. 10, Dry Swales, Version 1.9, 3/1/11, Figure 10.2 “Typical Detail s for Level 1 and 2 Dry Swales”

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Vegetative Practices-Vegetative Swales (VS)Key Components

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Vegetative Practices-Vegetative Swales (VS)Deficiencies/Conditions Requiring ActionCheck Dams and Overflow/Control Structure

Undermining/erosion Spalling & deterioration

Sediment and debris

Overgrown vegetation

Internal blockages are also common (not shown)

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Vegetative Practices-Vegetative Swales (VS)Vegetated Banks/Ponding Area/Vegetation

Common Issues (Clockwise from TOP LEFT): • Overgrown vegetation

(see plans, amount varies)• Clogging/poor drainage

(ponding water after 48hrs of dry weather)

• Sediment accumulation (plant growth in gravel often a sign of sediment)

• Erosion, bare spots• (Not shown) Trash & debris

Upper-right photo is from VDEQ Stormwater Design Specification No. 3, “Grass Channels”,

Version 1.9, 3/1/11

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Vegetative Practices-Vegetative Swales (VS)Cleanouts/Observation Wells

LEFT: Broken/damaged RIGHT: Trash/debris

Other Common Issues:• Unable to locate (possibly overgrown vegetation)• Cap stuck, broken, or missing

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Vegetative Practices-Vegetative Swales (VS)


accumulated sediment– Repair/replace any damaged/missing components


– Check approved site plans for specific facility requirements– Rebuild/stabilize any areas with erosion and bare spots:– Cut back overgrown vegetation around facility structures to facilitate


approved site plan• Mow per plan maintenance guidelines

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Closing Remarks/Questions

Questions?

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Additional Resources

• Fairfax County– Public Facilities Manual (

http://www.fairfaxcounty.gov/dpwes/publications/pfm/)

– Stormwater Management Website (http://www.fairfaxcounty.gov/dpwes/stormwater/)

– Stormwater Best Management Practices Fact Sheets (http://www.fairfaxcounty.gov/dpwes/stormwater/factsheets.htm)

• Virginia Department of Environmental Quality– Stormwater Management Website (

http://www.deq.virginia.gov/Programs/Water/StormwaterManagement.aspx)

– Virginia Stormwater BMP Clearinghouse (http://www.vwrrc.vt.edu/swc/)

http://www.fairfaxcounty.gov/dpwes/publications/pfm/

http://www.fairfaxcounty.gov/dpwes/publications/pfm/

http://www.fairfaxcounty.gov/dpwes/stormwater/

http://www.fairfaxcounty.gov/dpwes/stormwater/

http://www.fairfaxcounty.gov/dpwes/stormwater/factsheets.htm

http://www.fairfaxcounty.gov/dpwes/stormwater/factsheets.htm

http://www.deq.virginia.gov/Programs/Water/StormwaterManagement.aspx

http://www.vwrrc.vt.edu/swc/

http://www.vwrrc.vt.edu/swc/

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Additional Resources

• Virginia Department of Transportation– N. VA Fairfax & Arlington Counties Permits (

http://www.vdot.virginia.gov/business/fairfax-permits-main.asp)

– Manuals Guides and Informational Instructions (http://www.virginiadot.org/business/manuals-default.asp)

• Includes BMP Design Manual, Drainage Manual, ROW Manual, etc.– Virginia Work Area Protection Manual: Temporary Traffic

Control (http://www.vdot.virginia.gov/business/resources/wztc/Virginia_WAPM_2011_web.pdf)

http://www.vdot.virginia.gov/business/fairfax-permits-main.asp

http://www.virginiadot.org/business/manuals-default.asp

http://www.vdot.virginia.gov/business/resources/wztc/Virginia_WAPM_2011_web.pdf

Additional Information

For additional information, please contact

www.fairfaxcounty.gov/dpwes

39MSMD/DPWES

Department of Public Works and Environmental ServicesMaintenance and Stormwater Management Division

703-877-2800


Thanks for attending! Don’t forget to fill out a course evaluation and to pick up your certificate of attendance!

contractor awareness training vegetative practices 2016

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