contractor awareness training above ground facilities part 2 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

2

Stormwater Maintenance Awareness Training

MSMD/DPWES

Course ScheduleAM session (includes two 15 minute 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 (the rest of the story….)

12:00-1:00 PM Lunch

PM session (includes two 15 minute 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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Above Ground Facilities-Infiltration Trenches (TR)

Provides some quantity control & treats runoff through filtration/infiltration

May be designed to treat surface runoff or piped drainage (downspouts)

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Properly Functioning Examples: (Typical single-family residential lot facilities)

LEFT: Picture shows a gravel infiltration trench with a cleanout and observation well, during a soil probe test. A soil probe is pushed into the underlying gravel layer to determine the topsoil depth and confirm facility is “per design”.

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Picture: VDEQ Stormwater Design Specification No. 8, Infiltration Practices, Version 1.9, 3/1/11

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Sediment Accumulation & Curb CutsTOP LEFT: Some debris and sediment on surface at curb cut

BOTTOM LEFT: Curb cut blocked (remove wheel stop)

TOP RIGHT: Surface debris & sediment accumulation

BOTTOM RIGHT: Sediment accumulation in gravel bed



Deficiencies Requiring Action:Plantings & Overgrown Vegetation

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Downed tree limb with deep-rooted/overgrown vegetation

Overgrown vegetation within the limits of a gravel bed trench may indicate sediment accumulation, as plants do not tend to grow in clean gravel.

Unauthorized plantings

MSMD/DPWES

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Turf Covered TRsSome trenches may have turf and topsoil, covering the gravel bed; however, turf is not automatically acceptable. ALWAYS refer to the approved site plan! • A soil probe test checks the gravel layer

(refer to slide 4).• Water usually reaches the gravel bed

through underground PVC pipes connected to the roof drain downspouts.

Common issues include:• Missing underground gravel beds• Disconnected roof downspouts draining

overland instead of via an underground pipe

• Bare spots/exposed soil in turf covering• Missing berms or observation wells

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Cleanouts/Observation Wells

Other common issues: • Caps stuck/not removable• Clogged cleanouts• Presence of standing water in the cleanout

Broken/damaged well cap Missing cap

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Above Ground Facilities-Infiltration Trenches (TR)• Common Remedies

– Remove all flow blockages as well as any additional trash, debris, and accumulated sediment• Special attention should be given, as required to gravel beds

(surface and within gravel pores) and may require removal/replacement of clogged sections of gravel

• Fully remove any plants growing in the accumulated sediments– Full removal includes eliminating roots and supporting

soil/sediment from the gravel bed, as spraying weed killer is not a sufficient treatment solution

– Rebuild/stabilize any areas with erosion, cave-ins, and bare spots:• Cave-ins require additional investigation to determine cause and

prevent re-occurrence

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Above Ground Facilities-Infiltration Trenches (TR)• Common Remedies

– 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 approved site plans for specific facility requirements

• For damaged/misaligned pipes:– Reinforce/repair, if possible (Internal bands and gaskets)– Slip-line pipes when possible, as this may be most cost effective– Excavate and replace/reseal, if first two options are not possible

– Cut back overgrown vegetation around facility structures to facilitate access and proper function

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Above Ground Facilities-Permeable Pavement (PP)

• Alternative paving surface which treats runoff through filtration (voids in paved surface), temporary storage (underlying stone reservoir), and infiltration– Includes permeable pavement,

pervious concrete, porous asphalt, and permeable pavers

– PP promotes a high degree of runoff volume reduction & nutrient removal

– Primarily used on commercial, institutional, & residential sites

Properly Functioning Examples:

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Key components

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Key components

Picture: VDEQ Stormwater Design Specification No. 7, Permeable Pavement, Version 1.8, 3/1/11, Figure 7.1 (as noted)

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Deficiencies Requiring ActionPervious Layer

Sediment/SiltWeeds/overgrown

vegetationDeterioration &/or cracks

in pervious layer

Asphalt Sealed?

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Outfall Structure/Underdrain

Damaged underdrains

Clogging and/or a potential blockage in the outfall structure/underdrain

Blockage in the underdrain

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

accumulated sediment• Perform a thorough restorative vacuum sweep of paved surface• Investigate the causes of any blockages to prevent re-occurrence, if

at all possible.– 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 approved site plans for specific facility requirements

• Specific to this facility type: any damaged, cracked, or failing pavers or paved sections

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• Common Remedies– Rebuild/stabilize any areas of erosion:

• Adjoining land erosion can silt in permeable pavement– Remove vegetation in permeable pavement to facilitate proper function

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

– Sealed permeable pavement requires a complete replacement

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Above Ground Facilities-Rooftop Detention (RT)• Designed to slow the flow from the

roof through short-term ponding on the roof surface

Properly Functioning Examples of Rooftop Detention Devices:

Ring with 1” holes

Slotted square detention

device

Adjustable detention

device

Custom devices

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Above Ground Facilities-Rooftop Detention (RT)Properly Functioning Examples: Scuppers convey emergency overflow off rooftop

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Above Ground Facilities-Rooftop Detention (RT)Deficiencies Requiring ActionScuppers and Adjustable Detention Devices

Scupper not providing proper water detention because it is

level with roof

Adjustable detention device opened too

wide

Detention device and debris cage

missing

Debris cage is damaged and

detention device missing

Incorrect number of drains and/or scuppers (usually too many)

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Above Ground Facilities-Rooftop Detention (RT)

Parapet Walls, Vegetation, and Detention Devices

Parapet wall missing

Debris Sediment Sediment

Tree growing on roof surface

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Above Ground Facilities-Rooftop Detention (RT)• 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 approved site plans for specific facility requirements

– Remove ANY vegetation around facility structures and on rooftop– Provide required detention flow rate

• Replace any missing or damaged detention devices and debris cages• Re-adjust detention devices, as needed• Raise scuppers that are too low or provide detention at the scupper• Repair or install any missing parapet walls• Recalculate the flow based on the actual number of drains to attain the

prescribed detention

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Above Ground Facilities-Rooftop Detention (RT)

LUNCH!Please be back & ready to start at 1:00 PM

contractor awareness training above ground facilities part 2 2016

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