LID Changes Everything!

The New Stormwater M i t P diMaintenance Paradigm

Agenda

• LID and Maintenance: • The Changing Local Maintenance Paradigm.• Bioretention Case Study • Managing Your Existing BMP Inventory to Maximize

Performance

BUDGET25% T d Mainten nce

BUDGET25% Toward a New MaintenanceMaintenanceModel

Vegetation management

ESD

SEDIMENT CLEANOUTS

ESD

WAYS TO REDUCE WAYS TO REDUCE YOUR MAINTENANCE BURDEN in 6 WEEKS

Technical Bulletin # 10Maintenance of LID Practices: Guidance for Designers Maintenance of LID Practices: Guidance for Designers

Inspectors, and Local Stormwater Managers

• Design criteria to reduce future maintenance burden• New roles for ESC inspectors and landscape

contractorscontractors• Construction sequencing and inspection• Performance bonding g• Certifying LID performance • LID maintenance inspections and work triggers

L l LID t ki t • Local LID tracking systems

* Draft to be released early in 2012 Draft to be released early in 2012

Why Stormwater Maintenance?

P t t t lit• Protects water quality• Improves longevity of

stormwater BMPsstormwater BMPs• Maintains BMP pollutant

removal rates over time• Physically transfers trapped

stormwater pollutants to safe upland areassafe upland areas

• Ensures facilities are safe, attractive and functional

• Helps meet Bay TMDL

The Old Pond Maintenance Model

One big pond

The New LID Maintenance Model

24 disconnections18 swale sections18 swale sections14 rain gardens5 bioretention areas4 tree planting areas

l 6 sheet flow credits

Stormwater Manager Survey

• 50% not sure how to document LID compliancedocument LID compliance

• 70% report concerns about LID maintenance and longevity

• 90% report that it will have a moderate to major have a moderate to major impact on their maintenance programs

The Changing Maintenance ParadigmConventional Practices LID PracticesConventional Practices LID Practices

Example of Practice Pond Disconnects/rain garden

Number of practices? A few at each site DozensSize of practices? Large drainage area Micro-drainage areaWhen to construct? During site construction After site is stabilized

Wh i ibl ? H i ti HWho is responsible? Homeowner association HomeownerWho does inspection? Public sector engineer Trained contractorWho does maintenance Specialized contractor Landscape contractor

How long does it take? Hour or more 10 minutesWhat is the goal? Prevent dam failure and

and public nuisancesMaintain hydrologic function and landscapingand public nuisances function and landscaping

Sediment cleanouts? On a 30 to 50 year cycle (if ever)

Annual cleanouts at pretreatment devices

Maintenance Tri ers After catastr phic failure When it l ks like crapMaintenance Triggers After catastrophic failure When it looks like crap

The Dirty Little Secrets of the Old Maintenance Model:The Dirty Little Secrets of the Old Maintenance Model:

•Apart from cutting the grass, we only maintain to prevent catastrophic failure•No triggers for pollutant cleanouts, and no money to pay for it if we didgg p , y p y•We do have fancy inspection checklists

How will the shift to LIDHow will the shift to LIDreshape local stormwater maintenance programs ?

Increased Role for Erosion and Sediment Control Inspectors During LID constructionp g

• Protect areas during site construction• Authorize LID constructionAuthorize LID construction• Inspect and Accept LID credits• Certify Vegetative Stability and Soil Amendments

Oth rs ? • Others ?

At what point is a LID practice ready for final inspection and acceptance ?

• Perform final inspection at end of establishment phaseend of establishment phase

• Usually 6 to 12 months after inst ll ti n f r m st installation for most vegetative LID practices

• Developer or builder responsible for this first year of maintenanceof maintenance

What exactly does an LID as-built look like?

• Engineered surveys ?• Digital photo and GPS coordinates ?• Depends on type and scale of LID Depends on type and scale of LID

practices

Verifying Disconnection and Buffer Credits

• Look for signs of Look for signs of concentrated flow

• Verify distance• Verify distance• Vegetative density• Screwdriver test • Exposed soilp• Digital photo

As-builts for micro LID practices (CDA less than 5000 sf)( f)

• Digital photo and Digital photo and GPS coordinates

• Vegetative cover and • Vegetative cover and stability C fi di • Confirm ponding elevation and flow

thpaths• No survey work

Larger LID Practices (CDA more than 5000 sf)( m f)

•Limited survey work to confirm inlet and •Limited survey work to confirm inlet and outlet elevations, flow paths and ponding depths

f d d d h d fl•Confirm underdrain depth and outflow

•Ensure landscaping meets design objectivesobjectives

•Verify boundaries of stormwater easement

•Check overflow to downstream conveyance system

•Digital photo after establishment phase

Maintaining On-lot Practices

Disconnections and dry wells are OK

Rain gardens OK if there is h i ti a homeowner association

that can enforce private maintenance

May want to shift them to expanded street right of way

May want to avoid use in id d b k dside and backyards

Where to Locate Residential LID Practices

On – lot• Front yard• Back yard ?y• Side yard ?

Off - lot I d d i h f • In expanded street right of way

• HOA open space

Localities should clearly define the Localities should clearly define the appropriate conditions under which LID practices can be located within a residential lot.

Is there a superior legal instrument to l i t f ll LID compel maintenance of smaller LID

practices that an owner can really understand ?

• Depends on whether it is to be maintained by homeowner, HOA or property managerHOA or property manager

• Key is an owners /maintenance guide w/ LID

map with digital photo of installed practicesnsta pract c s

Key Issues in Maintenance Agreements

• Identify specific parties responsible for maintenancep

• Identify landscape contractor or other party to perform maintenance maintenance

• Require annual self-inspection• Reference the specific annual

i t t k th t t b maintenance tasks that must be performed

• Provide LID locator map to find ppractices

• Provide photos of the established LID practicesestablished LID practices

Moving beyond Checklists to Punchlists

Maintenance Task Order Clean out curb cuts and inlets for accumulated grit Clean out curb cuts and inlets for accumulated grit,

leaves, and debris that are blocking inflow

Spot weeding, trash removal, and mulch raking Prune trees at SE corner Add reinforcement planting to cell 3Add reinforcement planting to cell 3 Remove invasive plants and dead yellow poplar at point B Stabilize and reseed the exposed soils on bioretention

buffer at point D Supplement mulch in devoid areas to maintain a 3 inchpp m m m

layer Prune trees and shrubs Remove sediment in pre-treatment cell

Clear “triggers” to compel maintenance tasksmaintenance tasks

How Does LID Change Performance Bonds?

• ESC and SWM Bonds ensure the design is properly installed

• Price bonds for LID practices and credits based on landscape contractor Front end load the ESC Bonds• Front end load the ESC Bonds

• On-lot LID (builder) Off-lot LID (developer)

Training Landscaping Contractors on LID

Many crews may not realize the Many crews may not realize the stormwater objectives of the landscaping areas they are maintaining landscaping areas they are maintaining

How do we do visual inspections to rapidly assess LID performance?assess LID performance?

5 or 10 minutes max5 or 10 minutes max

Schedule within 24 hours after a decent storm

Visual indicators

CBSTP Training in 2012

LID i ti t i i f t t d ESC • LID inspection training for stormwater and ESC inspectorsFi ld d l t i i t l l BMP i • Field and classroom training at local BMP campuses in the watershed

• Certificates of proficiency • Certificates of proficiency • Video training materials for landscape contractors

How do we track LID in our local database ?How do we track LID in our local database ?

Each site would provide data to Each site would provide data to store in the system:

• Site map with LID LocatorSite map with LID Locator• Responsible party for

maintenance• BMP design info for larger • BMP design info for larger

LID practices• Maintenance and inspection

reportsreports• Digital photos of accepted

LID practices• Nutrient and runoff • Nutrient and runoff

reduction credit

Linking Maintenance Inspections to state permit and TMDL trackingpermit and TMDL tracking

• Maintain a project file for each ll LID project installed.

• The file should be maintained for th lif ti f hi h th t i t the lifetime for which the nutrient removal credit will be claimed.

• The typical duration for the credit • The typical duration for the credit will be approximately 25 years

• Locality required to conduct a Locality required to conduct a performance inspection at least once every five years to verify that the system is being d l i i d d adequately maintained and

operating as designed.

Certification of Hydrologic Performance

Post-construction field evaluation of LID practices to pensure they are operating properly and are achieving nutrient reduction nutrient reduction

Local BMP Reporting to state f B id TMDL d MS4 for Bay-wide TMDL and MS4 Permits

Bay BMP credits are tied to periodic recertification (5 years) years)

Questions?

Bioretention Maintenance

Performance Issues Observed in Field

General Performance Problems with Bioretention (n = 40)

25%

33%

No Pre-Treatment

Need Maintenance

18%

23%

Short-Circuiting of Treatment

Inadequate Vegetation

No Pre Treatment

15%

18%

Excessive Vegetation

Sediment Deposition

8%

8%

Clogged Soil Media

Inappropriate Media

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Maintaining the “Bio” in Bioretention

• Prune woody matter, remove invasive plants, and manage vegetative growth to maintain landscape.• Add reinforcement planting to maintain desired vegetation density.

2000

VegetationManagementManagementIs Key Maintenance T k

2003Task

Many Future Maintenance Problems are Rooted in Poor Designin Poor Design

• Lose the filter fabric on • Lose the filter fabric on the bottom

• Max 12 inch ponding depthp g p• Flat slope• Max Contributing Drainage

A (CDA)Area (CDA)• Maximize Flow Path and

Length to Width RatioLength to Width Ratio• Turf cover

Provide Pretreatment

• Nature of pretreatment d d i f depends on size of bioretention area and type of flow it experiencesp– Concentrated flow: two

cell design with a small trapping “forebay” and trapping forebay and level spreader

– Sheet flow: grass filter gstrip, stone diaphragm, stone ring berm

No Pre-treatment: Maintenance Problem

Maintenance Considerations During Installationg

• Protect bioretention during gsite construction

• Don’t install until site is st bili d stabilized

• Make sure the original design still worksdes gn st ll works

• Excavate from the side• Make sure ponding depth

meets design• Water and maintain

plantingsplantings

Construction Inspection

• Under drain and stone sump installationinstallation

• Verify the actual contributing drainage area b dboundaries

• Confirm inlet and outlet elevationselevations

• Side-slope stabilization

b l h d * Subtle changes in grading, paving and drainage can really screw up an otherwise fine designdesign

The establishment phase through first growing season

Make sure vegetatively Stabilized

Landscaping contract covers first year after installation Landscaping contract covers first year after installation Regular watering first few months Spot re-seeding and remove/replace dead plants R di t l ti t i l tRemove sediment accumulation at inletsRepair erosion on side-slopes

Maintenance ConsiderationsMaintenance Tasks Frequency

Mow grass filter strips and bioretention with turf cover Check curb cuts and inlets for accumulated grit leaves and At least 4 times a Check curb cuts and inlets for accumulated grit, leaves, and

debris that may block inflowt least t mes a

year

Spot weeding, trash removal, and mulch raking Twice during growingseason

dd f l d d h Add reinforcement planting to maintain desired the vegetationdensity

Remove invasive plants using recommended control methods Remove any dead or diseased plants

b l h b d

As needed

Stabilize the contributing drainage area to prevent erosion

Conduct a maintenance inspection Supplement mulch in devoid areas to maintain a 3 inch layer Prune trees and shrubs AnnuallyPrune trees and shrubs Remove sediment in pre-treatment cells and inflow points

y

Remove sediment in pre-treatment cells and inflow points Remove and replace the mulch layer

Once every 2 to 3years

Review current BMP inventory and code them by design era and performance design era and performance.

•Our BMP inventory is lousy

•We are missing all the BMPs installed before 1995 (well, we really just have paper files, somewhere) p p , )

•When I finally merge my BMP inventory with my GIS system, I find that 50% of all drainage areas have more than one all drainage areas have more than one BMP

Maintaining Your Traditional BMPs

• Inventory BMPs

• Perform Stage 1 BMP triage inspection to categorize problems

• Safety issues

• Dysfunctional

• Out-dated technology, not worth fixing

• Needs routine maintenance ASAP

Dealing with the Local BMP Legacy

Thirty Years of BMPs. The BMP Inventory in a Maryland County (2006)

g g y

Potentially High Performers Known Low Performers

Bioretention/Dry Swales 49 Underground 270y gDetention

Sand Filters 279 Dry Ponds 528

Wet pond 212 Oil Grit Separators 805p p

Pond Wetland 98 Proprietary Practices 239

Infiltration Basin 58 Flow Splitter 321

Infiltration Trench 459 Other (plunge pools) 30

Grand Total 3350

James River Basin BMP type (n=3112)James River Basin BMP type (n=3112)

0%0%

Level SpreaderWet Swale

0%0%0%0%

Filter PracticePermeable Pavement

Dry SwaleLevel Spreader

2%2%

1%0%

Proprietary DeviceBioretention

Constructed WetlandUnderground Storage

12%7%

2%2%

InfiltrationOther

Pond, Water Quality DetentionProprietary Device

43%17%

14%

Wet PondPond, Unidentified Detention

Grass Channel

0% 10% 20% 30% 40% 50%

Developing a Preventative Maintenance Programg m

Identify maintenance levels: • Routine maintenance – garbage pickup • Routine maintenance – garbage pickup,

underground cleanouts, weeding, mulch replacement, exercising valves on pond drains, etc.

• Minor maintenance – removal of top layer of medium forebay dredging etcmedium, forebay dredging, etc.

• Major maintenance – total medium replacement; total dredge, replacement of replacement; total dredge, replacement of failed risers, etc.

• Retrofit or replacement

Triage Condition 1: Reconstructive BMP Surgery

Failed infiltration basin to Wet Swale

Failed infiltration basin to Extended Detention with Micro-pools

BMP Triage System

Condition 3: Condition 2:

g y m

Condition 3: Notify Owner to Perform

Routine Maintenance

Condition 2: Major Repair/Functional

Enhancement

Using the Design Era Approach to Evaluate the Local BMP Inventory

Era 1: Pre-1986. BMPs installed prior to 1984 Maryland Stormwater law that provide detention and peak shaving

y

Stormwater law that provide detention and peak shaving.

Era 2: 1986 to 2002. These practices reflect an era where water quality was incorporated into design, although sizing and q y p g g gdesign standards were not as great.

Era 3: 2002 to 2009. These were built to the greater water quality and channel protection sizing requirements and more quality and channel protection sizing requirements and more stringent design standards in the 2000 Maryland Stormwater Manual

Era 4. 2010 and Beyond. New ESD Sizing, these are “nutrient neutral” and fully treat impervious cover

Performance Code Example1

Code 0: Pretreatment BMPs2 Proprietary pretreatment Code 0: Pretreatment BMPsNot intended to provide runoff reduction or significant pollutant removal

Proprietary pretreatment practices, Oil/grit separator, Plunge pool, vegetated pool

Code 1: Non-performing BMPs Detention or other practices with no runoff reduction and no long

Underground detention vaults Pond-dry quantity control , dry ED ponds

term pollutant removal Code 2: Under-performing BMPs No runoff reduction and low p ll t nt m l

Infiltration basin with extended detention, infiltration basin St mfiltpollutant removal Stormfilter

Code 3: Effective BMPsNo runoff reduction but moderate to high pollutant

Wet ponds, Wet ED ponds Sand filter, Pond-wetland

moderate to high pollutant removalCode 4: LID BMPsHigh runoff reduction and

Dry swale, BioretentionInfiltration trench, Green Roof, High runoff reduction and

moderate to high pollutant removal

Infiltration trench, Green Roof, permeable paving

BMP Coding can identify retrofit potential, and ability to improvesystem performance through maintenance upgrades

Composite Runoff Reduction, Impervious Treatedand Pollutant Removal by BMP Code

Code Description RR1

(%)IAET2

(%) TSS (%) TN(%)

TP(%)

Non1 Non-performing 0 0.05 5 0 0

2 Under-performing 5 0.15 20 5 5performing

3 Effective 10 0.75 80 40 504 ESD Practices 60 1.0 90 65 65

RR: percent annual reduction in post development runoff volume for storms2 IAET: Fraction of contributing impervious acres effectively treated to the Water Quality Volume, and is multiplied by contributing impervious area to track IC acres treated in the watershed area to track IC acres treated in the watershed

Example for BMP Conversion Retrofit

• Contributing Drainage Area: – Same as Previous Example

• Existing BMP– Dry Detention Pond

• Conversion to Sand Filter – Forebay and five sand filter cells – Treats an inch of rainfall – Traditional design criteria

CBP Approved BMP Removal Rates: Incremental MethodBMP TP Removal TN Removal D D t ti P d 10 5Dry Detention Pond 10 5Sand Filter 60 40Incremental Rate 50 35

Example for BMP Conversion

• Retrofit Removal Rate Retrofit Removal Rate – For TP: 50– For TN: 35– For TN: 35

• Nutrient Load Reduction Achieved F TP 50 * 0 50 25 d– For TP: 50 * 0.50 = 25 pounds

– For TN: 335 * 0.35 = 117 pounds

Example for BMP Enhancement• Contributing Drainage Area:

– Same as Previous Example • Existing BMPg

– 20 year old Wet Pond, designed to treat half inch of rainfall

• Enhanced Wet Pond Design gLevel 2 Design (RR:0; TP:75; TN:40)

TV = 1.5(Rv) (A) Multiple Cell DesignPool of 4 to 8 feet

CBP Approved BMP Removal Rates: Incremental Method

Pool of 4 to 8 feetFlow path 1.5:1 or moreAdequate water balance

CBP Approved BMP Removal Rates: Incremental MethodBMP TP Removal TN Removal Existing Wet Pond * 45 20Level 2 Wet Pond Design 75 40I l R 30 20Incremental Rate 30 20* CBP-approved rate

Example for BMP Enhancement

• Retrofit Removal Rate Retrofit Removal Rate – For TP: 30– For TN: 20– For TN: 20

• Nutrient Load Reduction Achieved F TP 50 * 0 30 15 d– For TP: 50 * 0.30 = 15 pounds

– For TN: 335 * 0.20 = 67 pounds

Questions and AnswersQuestions and Answers

Session Resources

R1. Pond and Maintenance GuidebookR2 Pdf of this presentationR2. Pdf of this presentation