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A Fairfax County, VA, publication
Department of Public Works and Environmental Services
Working for You!
Stormwater Mainte...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Course Schedule
AM session (includes two short breaks)
– History of S...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
• Wet Ponds (WP) and Dry Ponds...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
WET POND COMPONENTS Profile of...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Deficiencies Requiring Action:...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Water level inconsistent with ...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
DRY POND COMPONENTS - Under th...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
DRY POND COMPONENTS - Dry Pond...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Deficiencies Requiring Action ...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Dam/Berm - Erosion and Failure...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Dam/Berm - Cave-Ins and Animal...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Vegetation & Trash/Debris Accu...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Trees and Woody Vegetation on ...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Riser/Trash Rack
14
Significan...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
Outfalls
15
Undermining below ...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
• Common Remedies
– Algal bloo...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
• Common Remedies
– Repair/rep...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Ponds (WP, DP)
• Common Remedies
– Cut back o...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Wetlands (WL)
• Shallow depressions that rece...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Wetlands (WL)
• Inflow
• Forebay
• Weir wall
...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Wetlands (WL)
21
Picture: VDEQ Stormwater Des...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Wetlands (WL)
Deficiencies Requiring Action
•...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Wetlands (WL)
• Common Remedies
– Remedies ar...
Stormwater Maintenance Awareness Training
MSMD/DPWES
Above Ground Facilities-Rooftop Detention (RT)
• For more information...
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Stormwater Maintenance Awareness Training, Part II: Above Ground Facilities,October 6, 2015

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Stormwater Maintenance Awareness Training, Part II: Above Ground Facilities, October 6, 2015

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Stormwater Maintenance Awareness Training, Part II: Above Ground Facilities,October 6, 2015

  1. 1. A Fairfax County, VA, publication Department of Public Works and Environmental Services Working for You! Stormwater Maintenance Awareness Training For privately maintained stormwater management facilities Maintenance and Stormwater Management Division (MSMD) Fall 2015
  2. 2. Stormwater Maintenance Awareness Training MSMD/DPWES Course Schedule AM 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/questions 2 NOTE: All pictures, unless noted, are the property of Fairfax County.
  3. 3. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) • Wet Ponds (WP) and Dry Ponds (DP) are both depressed basins providing temporary storage for stormwater runoff. – WP are designed to have a permanent pool. – DP basins are designed to usually be dry, except when handling runoff. • Some DP basins may have permanent wet features, including deep cells, micropools, or sediment forebays. 3
  4. 4. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) WET POND COMPONENTS Profile of a typical WP Plan view of WP with sediment forebay and WL 4 Pictures: VDEQ Stormwater Design Specification No. 14, Wet Pond, Version 1.9, 3/1/11, Figure 14.1 “Wet Pond Design Schematics”
  5. 5. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Deficiencies Requiring Action: Algae/Turbidity (WP only) 5 Trash rack crushed/damaged, requires replacement BELOW: High turbidity caused by suspended materials (soil, sediment, microbes, etc.) can harm aquatic life, create clogging concerns, and cause build-up. ABOVE: Algal bloom and growth can create significant water quality issues, impacting plant and wildlife, as well as creating visual and odor concerns.
  6. 6. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Water level inconsistent with plans (WP only) 6 s
  7. 7. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) DRY POND COMPONENTS - Under the new Virginia SWM regulations, Extended Detention Ponds constructed after July 1, 2014 must include, at a minimum, the following components: • Sediment Forebay • Micropool 7 Pictures: VDEQ Stormwater Design Specification No. 15, Dry Pond, Version 1.9, 3/1/11, Figure 15.1 “Typical Extended Detention Pond Details”
  8. 8. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) DRY POND COMPONENTS - Dry Ponds constructed prior to July 1, 2014 are likely to have a simpler profile: 8 LEFT Picture: Page 62, http://www.novaregion.org/DocumentCenter/Home/View/1679
  9. 9. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Deficiencies Requiring Action (continued): Trickle Ditches (DP only) 9 TOP RIGHT: Erosion and trenching along the trickle ditch, with some overgrown vegetation BOTTOM RIGHT: Significant spalling and deterioration of concrete in trickle ditch TOP LEFT: Obstruction or blockage in trickle ditch BOTTOM LEFT: Trickle ditch with some significant sediment and debris accumulation
  10. 10. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Dam/Berm - Erosion and Failure NOTE: Remaining slides apply to both WP and DP 10 BELOW: Erosion of the dam face has led to significant piping (formation of water channels throughout embankment interior) and blockage, requiring immediate attention RIGHT: (Both pictures are from same site) Significant erosion and sloughing of the dam/berm, requiring immediate attention as this can lead to dam failure with increasing area damage
  11. 11. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Dam/Berm - Cave-Ins and Animal Holes 11 LEFT: Dam/berm cave-ins, possibly caused by pipe joint separation, seepage, and/or problems with the interior dam fill RIGHT: Animal holes on top and side slope of dam/berm
  12. 12. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Vegetation & Trash/Debris Accumulation 12 RIGHT BOTTOM: Sediment accumulation and debris reduces the holding capacity of the pond and its ability to treat the designed volume of stormwater runoff. BELOW: Large appliance dumping and other trash/debris accumulation from upstream can critically impact facility function & create problems downstream. RIGHT TOP: The riser structure has overgrown vegetation around it.
  13. 13. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Trees and Woody Vegetation on Dam/Berm 13 Back Face Control Structure No trees or woody vegetation should be on any side of the dam/berm embankment (face, back, top, etc.) *Check site plans for specifics. Pond Floor
  14. 14. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Riser/Trash Rack 14 Significant sediment & debris accumulation and trash rack damage-requires cleaning and trash rack replacement Trash rack & low-flow orifice plate, if required by site plans, must be installed flush with the riser structure, with no gapping. Here, debris must be cleared, then low-flow orifice plate & trash rack properly re- installed. Missing low-flow orifice plates are a common issue. Inside riser blockage
  15. 15. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) Outfalls 15 Undermining below outfall pipe (can be related to separation at last joint of PSP, etc.) Downstream blockage or impending blockage within 20 feet of outfall structure (potential back up and impact to water flow from the PSP) Erosion at curb cut inflow area, needs repair
  16. 16. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) • Common Remedies – Algal bloom, turbidity, and water level inconsistent with plans (WP only) • Investigate and resolve cause(s), if at all possible – 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 (trash racks, well caps, etc.) to structural (walls, concrete, etc.) to environmental materials (soil, gravel, etc.) – Check approved site plans for specific facility requirements 16
  17. 17. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) • Common Remedies – Repair/replace any damaged/missing components (continued) • For damaged/misaligned pipes: – Reinforce/repair, if possible (Internal bands and gaskets) – Slip-line pipes when possible, as this may be more cost effective – Excavate and replace/reseal, if first two options are not possible – Rebuild/stabilize any areas with erosion, cave-ins, and bare spots: • Cave-ins require additional investigation to determine cause and prevent re-occurrence • Fill-in/stabilize any animal holes, per plan maintenance guidelines, to discourage occupancy and re-occurrence 17
  18. 18. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Ponds (WP, DP) • Common Remedies – Cut back overgrown vegetation around facility structures to facilitate access and proper function (WP/DP/WL have special requirements, as noted below) • Remove all trees and woody vegetation from the entire dam embankment: face, back, top, etc. – Check plans for a ‘Planting Plan’ which may have allowed plantings on the dam embankment • Remove overgrown vegetation – Within 10’ of control structure – Within 5’ of all other structures – Within inflow/outlet channels – Other areas, as needed, for facility access 18
  19. 19. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Wetlands (WL) • Shallow depressions that receive stormwater for water quality treatment by providing an ideal environment for: – Long residence time – Gravitational settling – Biological uptake – Microbial activity • Stormwater management benefits: – Nutrient load removal and reduction • Nitrogen • Phosphorus • Sediment 19 – Runoff volume reduction – Channel protection – Flood mitigation Properly Functioning Example:
  20. 20. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Wetlands (WL) • Inflow • Forebay • Weir wall • Permanent pool • Low flow orifice • Riser • Embankment • Outfall • Emergency spillway • Micro-topographic features • Tree peninsulas • High and low marshes • Micropools • Deep pools 20 Picture: VDEQ Stormwater Design Specification No. 13, constructed Wetlands, Version 1.9, 3/1/11, Figure 13.1 “Plan and Cross Sections of Constructed Wetland Level 1 and Level 2 configurations”
  21. 21. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Wetlands (WL) 21 Picture: VDEQ Stormwater Design Specification No. 13, constructed Wetlands, Version 1.9, 3/1/11, Figure 13.1 “Plan and Cross Sections of Constructed Wetland Level 1 and Level 2 configurations”
  22. 22. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Wetlands (WL) Deficiencies Requiring Action • Clogging of pipes from sediment, vegetation and debris – If low flow orifice is clogged, it can result in a rapid change in wetland water elevations. • Sedimentation accumulations in forebays and micropools • Erosion and braiding (channel separation and intermixing, sometimes with formation of deposited bars or islands) • Vegetation Issues – Growth over access points – Invasive species – Dead, dying, missing vegetation – Bare spots – Trees and woody vegetation on dam embankment 22
  23. 23. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Wetlands (WL) • Common Remedies – Remedies are the same as for WP/DP (please refer to slides 16-18) – Additional vegetative concerns specific to wetlands: • Remove any non-spec vegetation, especially if it impacts the health and function of the facility, as designed • Replace/replant any dead, dying, or missing wetland vegetation per approved site plans 23
  24. 24. Stormwater Maintenance Awareness Training MSMD/DPWES Above Ground Facilities-Rooftop Detention (RT) • For more information call 703-877-2800 TTY 711 • Maintenance and Stormwater Management • Department of Public Works and Environmental Services • Fairfax County, Va. • www.fairfaxcounty.gov 24

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