LID MAINTENANCE –BEGIN WITH THE END IN MIND

2011 Philadelphia Low Impact Development

September  28, 2011

Andy Sauer, P.E.Principal

Today’s Presentation

• LID, BMPs, Green Infrastructure Basic Principles• Good design begins the end in mind• What can we do better?• Typical maintenance activities• Maintenance schedules and forms• Lessons learned

Basic BMP Principles

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PLAN: Minimize Development Impacts, Low Impact Development (LID): Preserve open space, stream buffers,

reduce impervious area, disconnect impervious surfaces, filter strips, narrow streets

MIMIC: Collect & treat runoff nearest the sourceRain gardens, bioretention cells, swales,

bioswales, infiltration trenches, pervious pavements, dry wells,

green roofs, rain barrels/cisterns

TREAT: Collect & treat runoffat centralized facilities:

Extended detention,wetlands, wet

ponds

Level of Maintenance Increases

Costs Increases

BMP EvaluationGeneral Rule

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Aesthetics/Amenity

Maintenance

Myth Buster

BMPs and/or Green Infrastructure does NOT mean NO Maintenance! 

Green vs. Gray

Green Infrastructure• Weakest Day 1• Dynamic system• Maintenance Activities

– Make it stronger– Improve the look– Living system– Seasonal

• Improve function• Proactive and regular 

(especially the 1st 1‐3 years) 

Gray Infrastructure• Strongest Day 1• Static system• Maintenance Activities

– Maintain structural integrity– Public doesn’t see it– Cleaning to design capacity– When needed/time allows

• Maintain function• Reactive and/or emergency 

maintenance

LID/BMP Maintenance (Real World)

• Too infrequent • Only major maintenance (costly)• Not completed, particularly when the BMP is 

privately owned• Improper maintenance decreases the efficiency and 

can in some cases increase pollutant loading • Lack of maintenance reduces aesthetic qualities • Operation and maintenance language not specified 

in stormwater ordinance• Lack of stormwater easements for maintenance• Level of maintenance varies widely

How can we do better?

• Starts with better designs– Reduce maintenance needs– Provide access– Reduce chance of failure– Technical reviews

• Requires ordinances to enforce– Who is responsible for maintenance– Warranties– Maintenance agreements– Schedule of maintenance activities– Inspections

• Provide training and education

Better LID/BMP Designs

• Need to consider both short and long term maintenance during design

• Larger facilities– Forebays with maintenance access– Vegetation selection & water need– Trash capture and removal

• Smaller facilities– Vegetation selection & water need– Soils and subsurface conditions– Size relative to who is maintaining– “The Look” (Gardner vs. Wild)

Large Facilities

Forebay

MaintenanceAccess

Large Facilities

Transition Zones

Planting Zones

Small Facilities

Rain Gardens & Bioretention

• Infiltration capacity– Test over time– Stabilize upstream area– Water need

• Plants– Hand weeding– Replace– More gardens than lawns

• Irrigate– Especially the 1st year

• Repair erosion• Underdrains• Overflow

Bioretention Infiltration Rate vs. Time Impacts Design & Long‐Term Sustainability

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1

2

3

4

5

6

7

8

9

10

0 60 120 180 240

Infiltration Ra

te  (in/hr)

Time (min)

0.3

0.5

1

1.5

3

Manage Concentrated Flow

• Sheet flow best for treatment• Concentrated flows cause erosion• Inspect and repair

Topeka KS

Swales and Linear Bioretention

• Mowing– Select areas– Sightline issues

• Weeding– Remove invasive 

species• Pruning• Irrigate• Replace plants• Repair erosion• Remove trash and 

floatables16

Topeka KS

Vegetation

• Mowing• Burning• Spot herbicide or hand 

weeding• Seeding or plantings• Repair areas of erosion• Educate adjacent land owners• Aesthetic value

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Kansas Biologic Survey (www.kbs.ku.edu/)Miami County, KS

Infiltration BMPs (Non‐Vegetated)

• Stabilize upstream• Remove sediment• Mature trees‐leaf matter• Remove and replace 

infiltration media• Underdrains• Stilling wells

I’Lan Park, Leawood, KS

Pervious Pavement

• Street sweep (4‐8 times per year)

• Limit snow removal activities

• Replace failing sections• Inspect underdrains• Test infiltration capacity• Tree maintenance of 

overhanging limbs

Other Systems – Hydrodynamic devices, media filters, baffle boxes

• Large equipment (e.g. Vac Truck)– Trash/Floatables– Sediment

• Retro‐fits• Remove, Clean, Replace• More routine• Below grade

– Confine space certification

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Shawnee, KS

Ordinances, Enforcement & Inspections

• Reference local BMP design manual/standards• Specify required easements• Clearly identify responsible parties

– Reviews required– Prior to issuance of permit

• Maintenance plan• Maintenance agreements

– Short term: 1‐3 years (Contractor)– Long term: 3+ years (Owner, HOA, City, or Other)

• Inspections– Document & enforce

Training & Education

• Planning Level– Preliminary plat– Watershed Plan or Comprehensive Plans

• Design Level– Adapt designs to meet the site– Build on local and regional examples

• Implementation Level– Contractors & Inspectors– Initial start‐up

• Long Term O & M Level– Property Owners, HOA, Neighborhoods– Non‐Profits, City Crews

BMP Maintenance Types

• Routine Maintenance– Annual– Semi‐Annual– After each rainfall event     

> 0.5 inches– Document and fix– Less costly

• Non‐Routine Maintenance– Major repairs– Overgrown vegetation– Poor drainage– Removal and replacement– Programmed (CIP)– More costly

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BMP Maintenance – Responsible Parties

• Private Property– Annual inspection submittals– Tied to HOA– Title restriction

• Public Property– Part of stormwater infrastructure O&M program– Inspection crew(s)– Maintenance crew(s)– Seasonal (April – Oct.)– Vegetation Management– Signage

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Post Construction BMPs–Inspection & Maintenance Tools

• BMPs as Infrastructure– How to bring BMPs into an 

agency’s maintenance schedule 

• Inspection and acceptance guidelines

• Inspection checklists

BMP NumberBMP TypeDesigned ByInstallation DateScheduled 3 Month Inspection Date: Actual 3 Month Inspection Date:Installed By

PhoneEmail

Maintenance Bond or Escrow Account? Number:Date of Expiration:Final InspectionAdded to Agency Maintenance Schedule?

1st Fall Inspection Scheduled Actual 1st Fall Inspection Date:1st Fall Maintenance Completed1st Spring Inspection Scheduled Actual 1st Spring Inspection Date:1st Spring Maintenance Completed2nd Fall Inspection Scheduled Actual 2nd Fall Inspection Date:2nd Fall Maintenance Completed2nd Spring Inspection Scheduled Actual 2nd Spring Inspection Date:2nd Spring Maintenance Completed

BMP Construction Record

Inspection for First Two Growing Seasons:

Post Construction BMPs–Inspection & Maintenance Tools

• BMPs as Infrastructure– Who is responsible for short / long term maintenance

• Developer / Contractor / Design Professional / Public Entity / Volunteer

9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8Project site/Building ConstructionProject site StabilizationTemporary Stormwater Control at BMP SiteBMP Installation & Veg. Establishment

Post Wet-Weather ChecksAnnual Key Milestones-BMP

Fall Bi-annual Inspection/MaintenanceSpring Bi-annual Inspection/Maintenance

Indicates inspection and/or Maintenance Activity (See corresponding checklist)

Example Construction ScheduleMonth of Year

Long Term ScheduleMonth of Year

Post Construction BMPs –Inspection & Maintenance Tools

• BMPs as Infrastructure– What are short / long term 

maintenance responsibilities• Vegetated and non‐vegetated BMPs

– Short Term• Prior to/during install & establishment

• 3‐months post install– Long Term

• Fall & Spring Inspection

Short Term Vegetated BMP Maintenance Prior to and During Installation and Establishment of BMP

Task Explanation Encourage phased construction of development surrounding BMP

Utilize staged construction to limit erosion potential of land exposed

Provide temporary stormwater control Stormwater runoff shall be routed around facility until vegetation is established (generally 2-3 months)

Provide site stabilization Utilize erosion control during construction and until facility is established

Protection from foot traffic and BMP education through signage

Use fencing and signage to prevent damage from animal and human foot traffic and to initiate public interest and education

Planting of native vegetation Optimum planting window depends on location in KS; For seeding rates and other assistance contact local NRCS

Mulching Use mulch made from native hay or native plants to reduce potential competition for resources

Fertilization Typically with native vegetation fertilization is not required, however consult local NRCS for fertilizing suggestions after soils test

Irrigation/Watering Watering schedule must be established for upkeep of vegetation

Lessons Learned

• Don’t bring the BMP on‐line until vegetation is established (60 – 90 growing days)– Green is not gray

• Separate construction contracts for general civil and landscaping contractors– Warranties need to be separate– More control over final product– Saves money

• Stabilize drainage area• Manage concentrated flow• Adaptive maintenance plan• Don’t be afraid to ask questions

Questions?

Andy Sauer, P.E.PrincipalCDM

9200 Ward Parkway, Suite 500Kansas City, MO 64114

(816) 412‐3116saueran@cdm.com