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

DISCUSSION (?)

timothy.kelly@amec.com