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FSA Stormwater BMP Seminar
September 11, 2015
Inspection & Maintenance of BMPs
Agenda Inspection Preparation Basics
Scope of Assignment
Inspection and Maintenance ◦ Common to All Facilities
◦ Wet Detention Facilities
◦ Dry Retention Facilities
◦ Exfiltration Systems
◦ Detention w/ Effluent Filtration (Manmade Underdrains)
◦ Other Systems
Pre-Field Check List
• Inspection Binder
• Field Book/Pen/Pencil OR Tablet/Computer w/Database
• Activity Hazards Analysis /Job Safety Analysis
• Smart Phone/Camera
• Survey Rod
• Shovel
• Location Maps OR GPS Software • Sunscreen/Insect Repellent • Machete • Manhole Pick • Steel Toe Boots, Rubber Boots,
Hip Boots or Waders • Safety Equipment: Cones, Safety
Glasses, Vest, Vehicle Lights, & other PPE per your employer policy
• Last Few Days of Rainfall Data
You never know what to expect Know your system before leaving the office
Characteristics of Storm Water Facility to Inspect:
• Erosion and Sediment
• Hydrology
• Water Quality
• Structural
• Aesthetics
In Route to Site: Make observations of the drainage basin. Note any activities that could impact the drainage system associated with the facility.
Inspect Fence, Gates, and Access to Facility Accessibility Varies: • Restricted Access • Multi-Functional w/ Public Access
Overgrown Berms- Need Mowing Event and Routine Maintenance Before Inspection
Slope Vegetation Coverage - Are slopes routinely mowed or allowed to naturally vegetate?
Poor Slope Vegetation Coverage - Often from mowing activities -Add amendment to soil & seed -Resod -Engineered stabilization
Animal Burrows- Slope Stability Concern
Structures
Discharge through Grates
Control Structure Blockage
Skimmer Configurations
CHAIN LINK FENCE MISSING PANELS
Flow Area Under Skimmer Adequate?
Flow Area Under Skimmer Concerns
Better Skimmer Designs
HARD SURFACE REDUCES VEGETATION BLOCKAGE AT SKIMMER LOCATION
Better Skimmer Designs
Scour/Erosion at Structure Edges
Maintenance- Provide Scour Protection at Toe Problem typically starts at Toe
Scour/Erosion at Structure Edges
Woody Vegetation Blockage at Outfall
DOES NOT YIELD (BEND) DURING FLOWS
Sediment/ Vegetative Detritus Blockage at Outfall
Pipe Sedimentation- Source?
Pipe Joint Failure
FABRIC AROUND JOINTS
Pipe Sedimentation
Pipe Sedimentation Maintenance- Desilting
Berm Integrity Problem: Smooth surface perpendicular to water flow direction Maintenance to include blocking the flow path along structure with impervious material
BYPASS FLOW
“Smart” Structures
SMART STRUCTURE OR WEIR
OFFLINE SYSTEM
Smart Structure backing up Litter in Submerged Lines
Structure Manipulation Document 0bserved deviations from as-builted system
Structural Checks LOCATION OF CRACK WILL DICTATE NEED FOR MAINTENANCE
Structural Checks
CHECK TOE FOR SOURCE OF PROBLEM
DIRECTION OF FLOW FROM POND
Structural Checks- Failure BUBBLE UP FLOW DESIGN
DITCH PAVEMENT SECTION AND SUBGRADE IS GONE
Structural Checks- Failure
LEAKY JOINT UNDER HYDROSTATIC PRESSURE
Structural Checks- Failure MAINTENANCE WILL NEED TO RAISE EDGES OF STRUCTURES TO ELIMINATE SCOUR AT EDGES
Structural Checks- Failure
STRUCTURE SETTLED AND JOINT IS OPEN.
Structure Leakage (Flow Bypasses design path of discharge)
Leaky Structure
POSSIBLY LIFTING HOOK LOCATION FROM CONSTRUCTION
Trash Fence
EFFECTIVE AT LITTER CONTAINMENT BUT REQUIRES ROUTINE MAINTENANCE
Access Issues
ATV RACETRACK
ACCESS TO FAVORITE FISHING POND
Access Issues- Potential Liability
Safety Issues
RESET IF POSSIBLE. OTHERWISE DELINEATE WITH SAFETY DEVICE
Safety Issues
Safety Issues
DESIGNER FORGOT TO ACCOUNT FOR EASE OF ACCESS FOR CONTROL STRUCTURE INSPECTION & MAINTENANCE
Safety and ADA Concerns
Wet Detention
SCHEMATICS SOURCE: ERP STORMWATER QUALITY APPLICANT’S HANDBOOK (FDEP, WMD’S)(MARCH 2010 DRAFT) (TYP. FOR PRESENTATION)
Documenting Water Levels Stain Line Is water level range as designed?
Documenting Water Levels
Low water level fluctuation that should be documented
Orifice/Drawdown Device
Orifice/Drawdown Device
Small openings are easily clogged
Orifice/Drawdown Device
Orifice/Drawdown Device- Blockage
Orifice/Drawdown Device- Blockage
REDUCED CLOGGING DEVICE
STANDPIPE FOR PLUNGING CLEAN
PERMITTED BLEED DOWN OPENING
NUMEROUS DRILLED OPENINGS EQUAL TO 4-5X THE CONTROL BLEED DOWN OPENING AREA
CAPS ON ENDS
Vegetation Coverage
PERMIT MAY OR MAY NOT REQUIRE CERTAIN % VEGETATION COVERAGE ON WET DETENTION POND
Vegetation Coverage
Vegetation Coverage Becomes storage volume loss concern Represents large nutrient sink/source
Vegetation Removal due to Volume Loss - Document nutrient load
removal - Laboratory analyses required: mg TN/kg mat’l Or mg TP/kg material of detritus/vegetation mix
Vegetation Coverage- Sediment Deltas
Vegetation Coverage- Maintenance: Sediment Delta Removal
INITIAL CLEARING
Vegetation Coverage- Sediment Delta Removal
SUMP EXCAVATION PLUG OLD PREFERENTIAL FLOW PATH
Sediment Delta Removal Maintenance Completion
NEW FLOW PATH OVER DESIGNED SEDIMENT SUMP
Dry Retention
SCHEMATICS SOURCE: ERP STORMWATER QUALITY APPLICANT’S HANDBOOK (FDEP, WMD’S)(MARCH 2010 DRAFT) (TYP. FOR PRESENTATION)
Sediment Sump Capacity Loss - No capacity left - Backs up water levels in storm sewer
Sediment Sump Capacity Loss Sizing: Total suspended solids (TSS) load estimate on an annual basis times 25-50 years Geometry per expected particle size in TSS
Extent & Characterization of Sedimentation is Important -Relatively light spread of organics with good tilth
Extent of Sedimentation THIS SEDIMENT IS FULL OF FINE PARTICULATES THAT GREATLY REDUCE INFILTRATION RATE
NEED TO STOP THE MOVEMENT OF FINES THROUGHOUT THIS SMALL SYSTEM
Extent of Sedimentation- Throughout Pond Accumulating Layer of Fine Sediments Preferred removal method is by scraping (Long Stick Excavator)(Do not disk in)
Sinkhole Report immediately for proper closure
Dry Retention Recovery -treatment depth of system affects recommendations -is standing water level equal to the design control elev.?
Dry Retention Recovery -treatment depth loss (to standing water) of system affects recommendations -compare relative to total treatment depth
“Upwell” Design Sediment level around upwell inlet must be of allowable height to not cause flooding of system
Documenting Water Levels Rack Line -Are water levels staging where expected?
Linear Dry Retention/Swales/Ditchblocks
POOR DESIGN- DITCH CLEANING COMPROMISED GRADE ON EACH SIDE OF BLOCK
BETTER DESIGN- PROTECTION AT FLOW CONCENTRATION POINTS
Failed Linear Dry Retention -Standing water -Vegetation type Must determine if this is a perched condition (from sediments) or due to high water table and/or poor soils
Exfiltration (a.k.a. French Drain)
SUMP “PRE-TREATS” STORMWATER. THIS SHOULD BE THE VERY MINIMAL PRE-TREATMENT ELEMENT CONSIDERED FOR THIS HIGH MAINTENANCE TYPE OF SYSTEM. CONSIDER BAFFLE/SEDIMENT CAPTURE PRE-TREATMENT SYSTEMS AS WELL.
French Drain
SEDIMENT ALLOWED TOO HIGH IN SUMPED INLET -SEDIMENT ENTRY INTO SYSTEM
SEDIMENT/DEBRI MIX ALLOWED TOO HIGH IN SUMPED INLET-SEDIMENT & DEBRIS ENTRY INTO SYSTEM
#1 MAINTENANCE ITEM FOR THESE SYSTEMS IS PREVENTATIVE MAINTENANCE- KEEPING THE SUMP/PRE-TREATMENT SYSTEM CLEAN. DESILTING PIPE SHOULD NOT BE RELIED ON AS “FIX”.
French Drain
French Drain- Details
3/8” ± 1/32” OPENING SLOT
Manmade Effluent Filtration (a.k.a. sidebank filters or underdrains)
Sidebank filters or Underdrains Examples
Sidebank Filters– Lack of Maintenance
Effluent Filtration- Strength of Flow
Sidebank Filters- Maintenance
24 INCH SAND LAYER DEPTH ALLOWS FOR REPEAT REMOVAL OF SEVERAL INCHES OF FILTER ENVELOPE SURFACE
Sidebank Filters- Maintenance For Drainage Basins with limited particulate sedimentation on filter field, Herbicide control of vegetation on filter bed may be sufficient for longer service life
Sidebank Filters- Enhancing Service Life
SEDIMENTATION SUMP DEFLECTION BAFFLE
Underdrain Filters Maintenance mistake- Cutting vegetation left to remain in place
Underdrains are somewhere under all of this
Underdrain Filters-Retrofit
DEEP SUMP FOR DEPOSITION
Underdrain Filters-Retrofit
UNDERDRAIN RELOCATION AWAY FROM INFLUENT STORMWATER
INFLOW
Underdrain Filters-Retrofit
BAFFLE
LONG FLOW PATH FOR DEPOSITION
Effluent Filtration-Iron Ochre/Sludge Deposits
Common in Fine Sands, Silty Soils, Soils with Organic Hardpan, Organic Soils
Iron is reduced under flooded conditions in the overlying soils with bacteria present therefore key is to keep system aerated through sufficient water drawdown in system.
Effluent Filtration- Cleanout Damage
PERMIT COMPLIANCE ISSUES- SHORT CIRCUITING OF TREATMENT SYSTEM
Effluent Filtration- Filtration Bed Issues
DEPOSITION OF MATERIAL IN INSPECTION BOX. SOURCE?
LOSS OF MATERIAL AROUND C/O
Effluent Filtration- Filtration Bed Issues
FILTER BED MATERIAL LOSS
Effluent Filtration- Manipulation
HOLES DRILLED TO PRESUMABLY HELP DRAW DOWN WATER INTO UNDERLYING UNDERDRAIN SYSTEM
Other Systems and Issues
Exfiltration/Effluent Filtration Chamber
LONG EXFILTRATION TRENCH PARALLEL TO EFFLUENT FILTRATION WITH 2’ SAND FILTER IN BETWEEN
INFLUENT SUMP IS FULL OF SEDIMENT
TO EXFILTRATION PIPE
RAW STORMWATER IN
Dry Detention
LINEAR SYSTEM W/ BLEED DOWN DEVICE
Dry Detention
Trench Drains Form of dry retention (open on bottom) -Typically subject to frequent cleaning due to shallow design depth
Drainage Wells Ensure skimmer devices and approach channels are clear of debris, litter, vegetation
Gross Solids Separation Units CDS - Remove litter & check sediment level quarterly(±) - Remove sediments biannually (typ)
CDS Maintenance
DEWATERING SCREEN EXPOSED
CDS Maintenance
SCREEN PRESSURE WASHING SUMP SEDIMENT REMOVED
Baffle Box- Second Generation
SOURCE: SUNTREE TECHNOLOGIES, INC.
Baffle Box- Second Generation
LIFTING HOOKS FOR INSPECTING BASKET
TAILWATER IN RECEIVING DITCH IMPACTS EFFECTIVENESS OF DEBRIS BASKET CHECK SEDIMENT IN BOTTOM (3 CHAMBERS (TYP))
Backflow Preventers
CHECK TO ENSURE THERE IS NO BLOCKAGE OR FUTURE VEGETATIVE BLOCKAGE POTENTIAL HINGES NEED TO MOVE FREELY
Illicit Discharges/Illegal Dumping
-OBSERVE -REPORT
Illicit Discharges from Construction
SOURCE?
SOURCE!
Illicit Activity FOLLOW EMPLOYER’S PROTOCOL IN ADDRESSING HOMELESS CAMPS
Looking for Pollutant Load Reduction Opportunities
RAW STORM WATER IN
TREATED WATER OUT
SEPARATOR BAFFLE
Looking for Opportunities to Increase Treatment
RAW STORM WATER IN
RAW STORM WATER IN
VERTICAL VOLUME RECOVERY SYSTEM (TYPE OF EFFLUENT FILTRATION SYSTEM)
ADDITION OF SMALL BERM INCREASES TRAVEL LENGTH TO OUTLET & INCREASES NATURAL INFILTRATION
SHORT CIRCUIT PATH TO HIGH MAINT. SYSTEM & OUTFALL
VIEW TOWARD OUTFALL VIEW TOWARD TREATMENT SYSTEM
Unexpected Findings
DELTAS IN MIDDLE OF POND IMPERVIOUS LINER RISING DUE TO GASES UNDER LINER
