1 module 2: enhanced systems when it’s more than a straight pipe from the catch basin to the...

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Module 2: Enhanced Systems

When it’s more than a straight pipe from the catch basin to the waterbody

Stormwater System Maintenance: A 4-Part Workshop Series

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Today we will review

• How we identify & describe structural BMPs

• How we inspect, clean & repair structural BMPs

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We will

• Review the goals as written in the General Permit

• Clarify or expand as needed

• Review what we are doing now

• Review how we report our activities

• Look for ways to improve our effectiveness and/or efficiency

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O&M Program

Required Goal– Identify, locate & describe all structural BMPs

owned or operated by the MS4 operator

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What are Structural BMPs?

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Why do we have them?

• In response to the changes in stormwater runoff as land use changed from undeveloped to developed

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What are they supposed to do?• First generation: flood control

– Late 1970’s, early to mid-80’s– Requirement incorporated into subdivision regulations

• Second generation: water quality benefits (treat pollutants)– Mid to late 1980’s– Modified basin designs– Proprietary structures– Focus on total suspended solids (TSS)

• Current emphasis: improved treatment and volume control– Low Impact Development (LID)– Small scale controls

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The Smart Development for a Cleaner Bay Act of 2007

• Amend Stormwater Design & Installation Standards Manual

• Regulatory programs require use of low-impact design techniques

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Runoff from our watersheds

Flows to city/town system

Flows to other MS4s

Flows to State system

Flows to private system

Flows directly to stream, pond, etc.

(Chart for illustrative purposes only, based on Best Professional Judgment of Southern RI Conservation District)

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Our stormwater system

Pipe directly to surface water

Flow to private BMP or other MS4

Flow to MS4 BMP

(Chart for illustrative purposes only, based on Best Professional Judgment of

Southern RI Conservation District)

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Private Structures

• Municipality permitted development based on some level of water management

• Municipal system now dependent to some degree on BMPs functioning properly

• Therefore, need to know where they are & what condition they are in

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Private Structures

• Post-Construction Minimum Measure requires us to identify private BMPs, inspect and enforce O&M

GoodHousekeeping

Post-Const Runoff

Const. Runoff

Illicit Discharge

Pub. Part.

Pub. Info & Ed

SWMPP

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Ideal

• You know where & how stormwater runoff flows in the watersheds of your MS4

• You know who’s responsible for the performance of each system

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You know:

•Where structures are

•What condition they’re in

•Who is responsible

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Problems?

• Records of what’s gone on the ground in the past thirty years may have slipped through the cracks– May not know where all structures are– May not have designs/as-builts– May not know who’s responsible for

maintenance– May not have O&M plans

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Our Structural BMP Inventory

• Maps

• Database

• Update

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Why a Database?

• Track maintenance and inspection• Streamline processes

– Scheduling inspections/maintenance– Sending notices to private owners– Reporting

• Provide documentation• Develop program cost estimates• Identify retrofit opportunities• Evaluate program effectiveness

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RIGL 45-61.1-3.(b)

• “A regulated small MS4 shall designate…those storm drainage systems that are prone to street flooding and/or contribute significantly to storm water management problems.”

• Structural BMPs included in definition of “storm drainage system”

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Updating Required

• Update– As new structures are installed– As forgotten structures are found– As maintenance is performed

• Report– Include in MS4 Annual Report

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What if I find “something” that’s not on the map, or an error in the map?

• Note the location on a copy of the map

• Describe the structure and its condition, or note what the error is

• Submit the map and note to the Engineering office

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O&M Program

Required Goal– Procedures for inspections, cleaning & repair of

detention/retention basins and related storm sewers, catch basins

Inspection & maintenance schedule BMP-specific as approved, modify based on reports Maintain records

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How is a BMP supposed to work?

Runoff from a given area (catchment) is directed to a structure

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• Design peak flow is over

• Water infiltrates

• Solids settle out

• Pollutants are filtered or taken up by vegetation

A structural BMP holds the water back until at least one of the

following occurs

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Performance depends on

• ENVIRONMENTAL CONDITIONS– Actual climate &

catchment conditions are similar to design conditions

• BMP CONDITIONS– Well-designed– Built as designed– Maintained

MAINTENANCE IS REQUIRED

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Common Performance Problems

• Structure volumes are insufficient for the amount of water they receive– May have been sized/built wrong– Catchment may have changed (size and/or

land use)– Volume may be reduced by sediment,

vegetation and/or litter

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Swale completely filled with sediment, vegetation and debris

(Inlet buried)

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Common Performance Problems

• Outlet controls don’t function as intended– Design errors– Installation errors

• Especially compaction of infiltration systems

– Controls are clogged by sediment, vegetation and/or litter

– Mechanical controls are broken– Cumulative impact

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What is cumulative impact?

• Multiple structures, each slowly releasing increased runoff

• Results in increased volume of water moving downstream

• Timing of releases can increase flooding

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How do we know if a structure is performing well?

• INSPECT

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Our Inspection Procedures

• Schedule– Routine inspections

– Non-routine inspections

• Inspection forms

• Post-storm checks

• Reports

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RIGL 45-61.1-2.

• “…systems prone to flooding or contributing significantly to storm water management problems shall be inspected at least once per year…”

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Ideal Inspection Schedule

• Routine– Two times per year– After every big storm

(blockage of inlets or outlets)

• Non-routine to be scheduled based on– Physical condition

noted in routine inspection

– Tendency to flood – Watershed address

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Routine Inspections

• Unexpected ponding• Obstructions of inlet

or outlet• Cracking or settling• Excessive erosion or

sedimentation• Signs of dumping or

vandalism• Encroachment

• Healthy vegetation under control

• Pipes, fences, etc. in good condition

• Stability of sideslopes & downstream channel

• Emergency spillway in good condition

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Non-routine inspection• Need original design/as-built for

comparison– Check structure volume– Check size, types of inlets, outlets– Check elevations

• Dam/top of structure• Inlets• Outlets

– Verify catchment assumptions

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BMP Maintenance

• Customized O&M Plan

• Permit requirements

• Inspection results

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Routine maintenance

• Vegetation control by mowing or removal of undesired plants

• Debris & litter control

• Minor bank stabilization & erosion control

• Access to inlets & outlets maintained

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Non-routine maintenance

• Mechanical components

• Sediment removal

• Recondition soils for infiltration

• Replacement/retrofit

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Remember Safety!!

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Waste Disposal

• Trash & litter to landfill

• Vegetation to compost or chipper

• Dewater sediments – Use as daily cover or– Test for use as fill

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Using results of maintenance records

• Revise inspection & maintenance schedules

• Improve design, site plan review for ease of maintenance

• Evaluate opportunities for retrofit

• Improve program cost estimates

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Enhanced Systems

• Structure purpose:– Reduce flooding– Improve water quality

• Good Housekeeping purpose:– Enable structures to

perform adequately

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Stormwater System Maintenance: Employee Training

Brought to you by:

This program was developed by the Southern Rhode Island Conservation District in partnership with the URI Cooperative Extension RI NEMO Program and the Rhode Island T2 Center. Funding was provided by the RI Department of Environmental Management and the RI Department of Transportation under the Phase II Stormwater Education and Outreach Project.