MARC BMP Manual Training Module 2

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BMP Training Module 2BMP Training Module 2

Extended Wet Detention Basin Extended Wet Detention Basin & Extended Detention Wetlands& Extended Detention Wetlands

Sponsored by: MARCSponsored by: MARCPresenters: Presenters:

Andy Sauer, P.E. (CDM)Andy Sauer, P.E. (CDM)Natalie Postel, P.E. (CDM)Natalie Postel, P.E. (CDM)

December 12, 2008

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AgendaAgenda 8:30-9:20 Lecture 1: Overview of Extended Detention and Wetlands8:30-9:20 Lecture 1: Overview of Extended Detention and Wetlands

Review Module 1 and WQv definitionReview Module 1 and WQv definition Define “Extended Detention”Define “Extended Detention” Define Extended Wet Detention and Extended Detention WetlandsDefine Extended Wet Detention and Extended Detention Wetlands

10 minute break10 minute break 9:30-10:30 Lecture 2: Design Examples9:30-10:30 Lecture 2: Design Examples

Extended Wet Detention BasinExtended Wet Detention Basin Extended Detention WetlandExtended Detention Wetland

15 minute break15 minute break 10:45 – 11:30 Design Activity10:45 – 11:30 Design Activity 11:30 – 11:45 Design Activity Results11:30 – 11:45 Design Activity Results 11:45 – 12:00 Lecture 3: Other considerations11:45 – 12:00 Lecture 3: Other considerations

ImplementationImplementation Operations and maintenanceOperations and maintenance VegetationVegetation Lessons learned Lessons learned

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Best Management Practice Best Management Practice (BMP)(BMP)

BestBest – State of the Practice – State of the Practice No definitive answerNo definitive answer Past experience, testing, research, Past experience, testing, research, Unique to siteUnique to site

ManagementManagement – Responsible Parties – Responsible Parties Improve water quality, meet NPDES Phase IIImprove water quality, meet NPDES Phase II Jurisdictional specificJurisdictional specific Meet specific requirements of a regionalMeet specific requirements of a regional

PracticePractice – Action or Implementation – Action or Implementation Practice = defined to carry out, apply, or to Practice = defined to carry out, apply, or to

do or perform often. do or perform often.

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Basic BMP PrinciplesBasic BMP Principles

PlanPlan for stormwater management for stormwater management Sustainable and “be green”Sustainable and “be green” Provide a level of serviceProvide a level of service Improve water qualityImprove water quality

MimicMimic natural hydrology natural hydrology Increase initial abstraction Increase initial abstraction Promote infiltration, retention & ETPromote infiltration, retention & ET

““Treat”Treat” the stormwater runoff the stormwater runoff Natural processesNatural processes Treatment trainsTreatment trains

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BMP Evaluation ProcessBMP Evaluation Process

Extended detention (40 hours) to increase treatment and decrease peak flows

PLAN

MIMIC

TREAT

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Detention and TreatmentDetention and Treatment

Structural BMPs Structural BMPs detain runoffdetain runoff

Extended Detention Extended Detention BasinsBasins

• WetWet

• DryDry Extended Detention Extended Detention

WetlandsWetlands Infiltration basinsInfiltration basins

Typically used as Typically used as larger, centralized larger, centralized facilitiesfacilities

Topeka KS

TREAT

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Example siteExample site

Main Channel

Bridge

Streambank Biostabilization

CulvertRoadway

Grass Swale

Wet Pond

Commercial Building

Bio-Filters

Design Documents

– APWA 5600– BMP Manual– Watershed Master Plans

TREAT

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Structural BMP ConsiderationStructural BMP Consideration

Pollutant removal efficiencyPollutant removal efficiency Water quality volumeWater quality volume Site suitabilitySite suitability Tributary areaTributary area Dimensions (depth, length-width ratio)Dimensions (depth, length-width ratio) OutletOutlet Emergency spillwayEmergency spillway Maintenance easementMaintenance easement Routine and non-routine maintenanceRoutine and non-routine maintenance

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BMP EvaluationBMP EvaluationGeneral RuleGeneral Rule

Wat

er Q

ualit

y Water Q

uantity

Aesthetics/Amenity

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BMP ManualBMP Manual

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Post Development BMP Post Development BMP SelectionSelection

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BMP Selection FlowchartBMP Selection Flowchart

Level Of Service

BMP Value Rating

Water Quality Volume/sizing

Placement, maintenance

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Water Quality Volume (WQv)Water Quality Volume (WQv)

Water Quality Volume Water Quality Volume (WQv): The storage needed (WQv): The storage needed to capture and treat 90% of to capture and treat 90% of the average annual storm the average annual storm runoff volumerunoff volume

Water Quality Storm: The Water Quality Storm: The storm event that produces storm event that produces ≤ ≤ 90% volume of all daily 90% volume of all daily storms in a year storms in a year

Extended detention and Extended detention and wetlands sizing is based on wetlands sizing is based on the WQvthe WQv

WQv

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2003 Kansas City Precip events

05

1015202530354045

0.1

0.3

0.5

0.7

0.9

1.1

1.3

1.5

1.7

1.9

2.1

2.3

2.5

2.7

Daily Precipitation (in)

# o

f d

ay

s >

or=

Kansas City Water Quality Kansas City Water Quality StormStorm

Water Quality Storm = 1.37 in

Young and McEnroe

(http://kcmetro.apwa.net)

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Why Use the WQv to size Why Use the WQv to size BMP?BMP?

Retain runoff long enough to get Retain runoff long enough to get water quality benefits water quality benefits

Reducing erosive flows from Reducing erosive flows from smaller runoff eventssmaller runoff events

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Water Quality Volume Water Quality Volume CalculationCalculation

Two methodsTwo methods Short-Cut MethodShort-Cut Method

• Sites < 10 acresSites < 10 acres• Only 1 predominant cover typeOnly 1 predominant cover type

Small Storm Hydrology MethodSmall Storm Hydrology Method• Larger or more heterogeneous drainage Larger or more heterogeneous drainage

areasareas

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WQv CalculationWQv Calculation

Short-Cut MethodShort-Cut Method

WQv = P*RvWQv = P*Rv

P = 24 hour Water Quality Storm (inches)P = 24 hour Water Quality Storm (inches) Rv = Volumetric run coefficient = Rv = Volumetric run coefficient =

0.05+0.009(I)0.05+0.009(I) I = % site Imperviousness I = % site Imperviousness

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WQv CalculationWQv Calculation

Small Storm Hydrology MethodSmall Storm Hydrology Method

WQv = P*Weighted RvWQv = P*Weighted Rv

Weighted Rv = Weighted Rv = ΣΣ(Rv(Rvii*Ac*Acii)/Total area (ac))/Total area (ac)

RvRvii = Volumetric runoff coefficient for = Volumetric runoff coefficient for

cover type (table)cover type (table) AcAcii = Area of cover type i (ac) = Area of cover type i (ac)

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Questions?Questions?

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Why the term “Extended” Why the term “Extended” Detention?Detention?

Extended: Designed to release the WQv over a period Extended: Designed to release the WQv over a period of 40 hours of 40 hours

Allows time for more particles and associated Allows time for more particles and associated pollutants to settle outpollutants to settle out

Reduces the downstream velocity and erosive Reduces the downstream velocity and erosive conditionsconditions

More closely imitates natural release rates and More closely imitates natural release rates and durationduration

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Geomorphic Effects of Geomorphic Effects of Uncontrolled Urban RunoffUncontrolled Urban Runoff

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0.1

1

10

100

1000

0.01 0.1 1 10 100

Flow Frequency for Flow Frequency for DetentionDetention

7-yr

2/yr

20/yr

Storm Return Interval more frequent than 1-yr

1-yr 10-yr 100-yr2-yr

Undeveloped

DevelopedUncontrolled

6/yr

F

low

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40-Hour Drawdown Impacts40-Hour Drawdown Impacts

Storm Return Interval

more frequent than 1-yr

1-yr 10-yr 100-yr2-yr

F

low

Undeveloped

DevelopedUncontrolled

DevelopedControlled

0.80 psf

0.26 psf

0.1

1

10

100

1000

0.01 0.1 1 10 100

•10-year control•1-year control•WQv – extended detention with 40 hr drawdown

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BMP ManualBMP ManualExtended DetentionExtended Detention

Water Quality (40-hr)Water Quality (40-hr) Pollutant removal throughPollutant removal through

• SettlingSettling• Biological uptake (more for Biological uptake (more for

wetland)wetland)• Permanent PoolPermanent Pool• WQv = Volume above the WQv = Volume above the

permanent poolpermanent pool

Stream Sustainability (40-hr)Stream Sustainability (40-hr) Mimic undeveloped Mimic undeveloped

conditions for full range of conditions for full range of hydrologyhydrology

Can meet flood control Can meet flood control objectivesobjectives

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Extended Wet Detention Basin (EWDB)Extended Wet Detention Basin (EWDB)

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EWDB Littoral BenchEWDB Littoral Bench

Littoral Bench

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EWDB Littoral BenchEWDB Littoral Bench

Provides water quality Provides water quality treatmenttreatment

Mild slope serves as Mild slope serves as safety feature around safety feature around perimeter of permanent perimeter of permanent pool pool

25% to 50% of 25% to 50% of permanent pool surface permanent pool surface areaarea

Helps control geese Helps control geese accessaccess

Topeka, KS

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EWDB Permanent PoolEWDB Permanent Pool

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EWDB Permanent PoolEWDB Permanent Pool

Water quality volume Water quality volume (WQv) mixes with (WQv) mixes with permanent poolpermanent pool

WQv released over 40 WQv released over 40 hourshours

Minimum depth of 6-ftMinimum depth of 6-ft Residence time of 14 Residence time of 14

daysdays Significantly more Significantly more

water quality benefit water quality benefit than EDDBthan EDDB

Topeka, KS

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EWDB Outlet StructureEWDB Outlet Structure

Release the WQv over a period of 40 hoursRelease the WQv over a period of 40 hours Protected by well screens, trash racks or Protected by well screens, trash racks or

gratesgrates Located as far from inlet as possibleLocated as far from inlet as possible Various outlet structure optionsVarious outlet structure options

Single OrificeSingle Orifice Perforated Riser or PlatePerforated Riser or Plate V-notch Weir V-notch Weir

Source: Hubbard Brook LTER

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Extended Detention

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EWDB VegetationEWDB Vegetation

Upland area: Native grasses Upland area: Native grasses (preferable) or turf on berms (preferable) or turf on berms and side slopesand side slopes

Littoral Zone: Native wetland Littoral Zone: Native wetland species species

Recommend 3-5 native speciesRecommend 3-5 native species

Soft Rush, Juncus effusus

Kansas City, MO

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EWDB Siting ConsiderationsEWDB Siting Considerations

Off-line, outside of stream corridorOff-line, outside of stream corridor EWDBs can be located within larger flood EWDBs can be located within larger flood

control facilitiescontrol facilities Minimum 20 feet setbackMinimum 20 feet setback Not on fill sites or steep slopes (unless Not on fill sites or steep slopes (unless

enhanced)enhanced) Use fences and landscaping to impede access Use fences and landscaping to impede access

areas to address public safety concernsareas to address public safety concerns Outflow structure shall be fencedOutflow structure shall be fenced

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Questions on Extended Wet Questions on Extended Wet Detention Basin (EWDB)?Detention Basin (EWDB)?

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Extended Detention Wetland (EDW)Extended Detention Wetland (EDW)

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EWD Permanent PoolEWD Permanent Pool

Permanent pool extends throughout wetlandPermanent pool extends throughout wetland

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Extended Detention Wetland Extended Detention Wetland (EDW)(EDW)

Forebay

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EDW ForebayEDW Forebay

Same function as EWDB Same function as EWDB Should hold at least 10% of Should hold at least 10% of

the WQvthe WQv Separated from the wetland Separated from the wetland

by a earth weir, gabion or by a earth weir, gabion or loose riprap wallloose riprap wall

Topeka, KS

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EDW MarshEDW Marsh

Marsh

Pollutant removal through plant root systemsPollutant removal through plant root systems Shallower than EWDB permanent poolShallower than EWDB permanent pool

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EDW MicropoolEDW Micropool

Micropool

Reverse slope pipe under the surface of the micropool is used to prevent clogging

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EDW MicropoolEDW Micropool

Prevents outlet clogging Prevents outlet clogging Allows further settling of Allows further settling of

sedimentsediment Should have a capacity of Should have a capacity of

at least 10% of WQvat least 10% of WQv Surrounded with a safety Surrounded with a safety

bench bench

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EDW Outlet Structure, Outfall, EDW Outlet Structure, Outfall, and Emergency Spillwayand Emergency Spillway

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EDW VegetationEDW Vegetation

Vegetation should cover 50-75% of surface areaVegetation should cover 50-75% of surface area 3-5 native species are recommended3-5 native species are recommended Select species based on stress tolerance and ability to Select species based on stress tolerance and ability to

handle variations in water availabilityhandle variations in water availability Consult local expertsConsult local experts

Topeka, KS

Lenexa, KS

Topeka, KS

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EDW Siting ConsiderationsEDW Siting Considerations

Off-line, outside of stream corridorOff-line, outside of stream corridor Perform water budget analysis to ensure Perform water budget analysis to ensure

permanent poolpermanent pool Soils should be suited for wetland speciesSoils should be suited for wetland species

Hydric soils with high phosphorous affinityHydric soils with high phosphorous affinity Not on fill sites or steep slopes (unless Not on fill sites or steep slopes (unless

enhanced)enhanced) Use fences and landscaping to impede Use fences and landscaping to impede

access areas of public safety concernaccess areas of public safety concern Outflow structure shall be fencedOutflow structure shall be fenced

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Extended Wet DetentionExtended Wet Detentionversusversus

Extended Detention WetlandsExtended Detention Wetlands

SimilaritiesSimilarities Water quality volume mixes with Water quality volume mixes with

permanent poolpermanent pool 40 hour drawdown of water quality 40 hour drawdown of water quality

volume (WQvolume (WQvv))

Differences Differences Depth of permanent pool (18 inches in Depth of permanent pool (18 inches in

wetland vs. 6 to 12 feet in basin)wetland vs. 6 to 12 feet in basin) Vegetation types and planting Vegetation types and planting

configurationsconfigurations

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AdvantagesAdvantagesandand

DisadvantagesDisadvantages

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EWDB AdvantagesEWDB Advantages

Settling of suspended solids Settling of suspended solids

Pollutant uptake by pond Pollutant uptake by pond vegetationvegetation

Flood control via peak Flood control via peak discharge attenuationdischarge attenuation

Control of channel erosion Control of channel erosion by reducing downstream by reducing downstream flow velocitiesflow velocities

Creation of wildlife habitatCreation of wildlife habitat

Recreational and aesthetic Recreational and aesthetic benefitsbenefits

Topeka, KS

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EDW AdvantagesEDW Advantages

Settling of suspended solids Settling of suspended solids Pollutant uptake by wetland Pollutant uptake by wetland

vegetationvegetation Flood control via peak discharge Flood control via peak discharge

attenuationattenuation Control of channel erosion by Control of channel erosion by

reducing downstream flow reducing downstream flow velocitiesvelocities

Creation of wildlife and aquatic Creation of wildlife and aquatic habitatshabitats

Recreational and aesthetic benefitsRecreational and aesthetic benefits Some groundwater rechargeSome groundwater recharge

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EWDB DisadvantagesEWDB Disadvantages

Potential safety concerns Potential safety concerns

Additional maintenance due to Additional maintenance due to sediment removal, floating trash, sediment removal, floating trash, scum, and algal bloomsscum, and algal blooms

Potential odor problemsPotential odor problems

Need conditions to sustain Need conditions to sustain permanent poolpermanent pool

Resident waterfowl can become a Resident waterfowl can become a source of fecal coliform and source of fecal coliform and nutrientsnutrients

Vector issues may result in Vector issues may result in additional maintenance additional maintenance requirementsrequirements

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EDW DisadvantagesEDW Disadvantages

Require more space, due to Require more space, due to shallower depth of water shallower depth of water storage storage

Additional maintenance due Additional maintenance due to vegetation overgrowthto vegetation overgrowth

Requires larger drainage area Requires larger drainage area to sustain permanent poolto sustain permanent pool

Vector issues can result in Vector issues can result in increased maintenance increased maintenance requirementsrequirements

Site limitations in urban areasSite limitations in urban areas

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Break 10 minuteBreak 10 minute

Questions?Questions?

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Lecture 2Lecture 2Design of EWDB & EDWDesign of EWDB & EDW

Discuss key design featuresDiscuss key design features

Introduce calculations for each major Introduce calculations for each major componentcomponent

Perform example calculationsPerform example calculations

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Extended Wet Detention BasinExtended Wet Detention BasinKey Design FeaturesKey Design Features

Water quality storage volumeWater quality storage volume Permanent poolPermanent pool Outlet structuresOutlet structures

OrificeOrifice Perforated riser or plate Perforated riser or plate V-notch weirV-notch weir

Pool shapePool shape Basin shapeBasin shape ForebayForebay Littoral benchLittoral bench VegetationVegetation

Topeka, KS

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Design ExampleDesign Example

26 acre drainage 26 acre drainage Land useLand use

1.6 acres of flat roofs1.6 acres of flat roofs 8.8 acres of parking lot8.8 acres of parking lot 3.3 acres of narrow 3.3 acres of narrow

streetsstreets 12.3 acres of silty soil12.3 acres of silty soil 53 % impervious53 % impervious

Outlet Structure Outlet Structure designed for 40 hour designed for 40 hour release of WQvrelease of WQv

New Development Site

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Water Quality Storage VolumeWater Quality Storage Volume

i.i. Tributary area = 26 acresTributary area = 26 acres

ii.ii. Calculate water quality storage volumeCalculate water quality storage volume

EWDB Design Procedure Form

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Water Quality Storage VolumeWater Quality Storage Volume

ii.ii. Calculate Water Quality Storage Calculate Water Quality Storage Volume (WQv)Volume (WQv)

Two methodsTwo methods Short-Cut MethodShort-Cut Method

• Sites < 10 acresSites < 10 acres• Only 1 predominant cover typeOnly 1 predominant cover type

Small Storm Hydrology MethodSmall Storm Hydrology Method• Larger or more heterogeneous Larger or more heterogeneous

drainage areasdrainage areas

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Water Quality Storage VolumeWater Quality Storage Volume

Short-Cut MethodShort-Cut Method

WQv = P*RvWQv = P*Rv

P = 24 hour Water Quality Storm (inches)P = 24 hour Water Quality Storm (inches)P = 1.37 inches (Kansas City)P = 1.37 inches (Kansas City)

Rv = Volumetric run coefficient = 0.05+0.009(I)Rv = Volumetric run coefficient = 0.05+0.009(I) I = % site imperviousness I = % site imperviousness

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Water Quality Storage VolumeWater Quality Storage Volume

Small Storm Hydrology MethodSmall Storm Hydrology Method

WQv = (P)*(Weighted Rv)WQv = (P)*(Weighted Rv)

Weighted Rv = Weighted Rv = ΣΣ(Rv(Rvii*Ac*Acii)/Total area (ac))/Total area (ac)

• RvRvii = Volumetric runoff coefficient for cover type = Volumetric runoff coefficient for cover type

(table)(table)

• AcAcii = Area of cover type i (ac) = Area of cover type i (ac)

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Rv TableRv Table

TABLE 7VOLUMETRIC COEFFICIENTS FOR URBAN RUNOFF

FORDIRECTLY CONNECTED IMPERVIOUS AREAS

(CLAYTOR AND SCHUELER 1996)

Rainfall Rainfall (inches)(inches)

Flat roofs and Flat roofs and large unpaved large unpaved

parking lotsparking lots

Pitched roofs and Pitched roofs and large impervious large impervious

areas areas (large parking lots)(large parking lots)

Small Small impervious impervious areas and areas and

narrow narrow streetsstreets

Silty Silty soils soils

HSG-BHSG-B

Clayey soils Clayey soils HSG-C and HSG-C and

DD

0.750.75 0.820.82 0.970.97 0.660.66 0.110.11 0.200.20

1.001.00 0.840.84 0.970.97 0.700.70 0.110.11 0.210.21

1.251.25 0.860.86 0.980.98 0.740.74 0.130.13 0.220.22

1.371.37 0.870.87 0.980.98 0.750.75 0.140.14 0.230.23

1.501.50 0.880.88 0.990.99 0.770.77 0.150.15 0.240.24

Note: a reduction factor may be applied to the Rv values for disconnected surfaces, consult the BMP hydrology section

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Water Quality Control Volume Water Quality Control Volume

Cover TypeCover Type RvRv Area (acres)Area (acres)

Flat roofsFlat roofs 0.870.87 1.61.6

Parking lotsParking lots 0.980.98 8.88.8

Narrow streetsNarrow streets 0.750.75 3.33.3

Silty soilSilty soil 0.140.14 12.312.3

inP

AreaTotal

AcRvWQv ii 749.037.1

26

3.1214.3.375.8.898.6.187.

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Water Quality Storage VolumeWater Quality Storage Volume

Convert WQv from inches to ac-ft by converting Convert WQv from inches to ac-ft by converting inches to feet and multiplying by the tributary inches to feet and multiplying by the tributary areaarea

= (0.749in)*(1ft/12in)*26ac

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Permanent PoolPermanent Pool

Permanent Pool

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Permanent PoolPermanent Pool

Average pool depth 4 to 6 Average pool depth 4 to 6 feet (not to exceed feet (not to exceed 12 feet)12 feet)

A portion of the pool must A portion of the pool must be at least 10 feet if the be at least 10 feet if the pool is to contain fish pool is to contain fish

At least 5.5 acres of At least 5.5 acres of tributary area per ac-ft of tributary area per ac-ft of permanent poolpermanent pool

At least 10.3 acres of At least 10.3 acres of tributary area per acre of tributary area per acre of pool surface areapool surface area

14 day residence time14 day residence time

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

Method 1Method 1

Based on the time required for algae to uptake Based on the time required for algae to uptake sufficient phosphoroussufficient phosphorous

VVP1P1 = (C * A = (C * ATT * R * R1414) / 12) / 12

C = Runoff coefficient = 0.3 +0.6*I or APWA C = Runoff coefficient = 0.3 +0.6*I or APWA section 5602.3 section 5602.3

I = Fraction of impervious area I = Fraction of impervious area RR1414 = 14-day wet season rainfall = 14-day wet season rainfall

AAtt = total tributary acreage = total tributary acreage

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

Method 2Method 2

Based on the time required for suspended Based on the time required for suspended solids to settlesolids to settle

VVP2P2 = (V = (VBB/V/VRR * S * SDD * A * Aii) / 12) / 12

VVBB/V/VRR = ratio of design water quality volume = ratio of design water quality volume

to runoff volume (should be at least 4 for to runoff volume (should be at least 4 for adequate TSS removal)adequate TSS removal)

SSDD = mean storm depth = mean storm depth

AAii = impervious tributary acreage = impervious tributary acreage

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

Method 1Method 1

Kansas City

From APWA section 5602.3

= (0.6*26*2.2)/12

= 0.3+0.6*.53

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

Method 2Method 2~93%

VB/R=5

Figure 24

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

Method 2Method 2

= (5.0*0.6*13.7)/12

Kansas City

5.0

0.6

13.7

3.43

Correction: Step 1 should refer to Figure 24

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Permanent Pool Volume (PPermanent Pool Volume (Pvv))

1.1. Use the larger volume calculated in the Use the larger volume calculated in the previous steps and add 20% for sedimentationprevious steps and add 20% for sedimentation

2.2. Average pool depth: 4 to 6ftAverage pool depth: 4 to 6ft

3.3. Surface area = VSurface area = VPP / Z / ZPP

= 3.43*1.20

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Outlet StructureOutlet Structure

V-notch WeirSingle Orifice

Perforated Riser or Plate

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Outlet StructureOutlet Structure

Outlet sized to release Outlet sized to release WQWQvv (ac-ft) within 40 (ac-ft) within 40

hourshours Locate outlet as far away Locate outlet as far away

from inlet as possiblefrom inlet as possible Avoid short-circuitingAvoid short-circuiting

The facility must bypass The facility must bypass 1% storm event1% storm event

Provide at least 1ft of Provide at least 1ft of freeboard above WQfreeboard above WQVV

stage stage

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Single Orifice OutletSingle Orifice Outlet

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Single Orifice OutletSingle Orifice Outlet

i.i. Depth of water quality volume at outlet (ZDepth of water quality volume at outlet (ZWQWQ))

ZZWQWQ = 3 feet = 3 feet

ii.ii. Average head of WQv over invert of orifice, HAverage head of WQv over invert of orifice, HWQ WQ

(ft)(ft)

HHWQWQ = 0.5*Z = 0.5*ZWQWQ

iii.iii. Average water quality outflow rate, QAverage water quality outflow rate, QWQWQ (cfs) (cfs)

QQWQWQ = (WQ = (WQVV * 43,560) / (40 * 3,600) * 43,560) / (40 * 3,600)

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Single Orifice OutletSingle Orifice Outlet

= 0.5*3.0ft

= (1.62*43,560)/(40*3600)

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Single Orifice OutletSingle Orifice Outlet

iv. Set orifice coefficient (Co) depending on orifice plate thickness

u Do must be greater than 4 inches in the following step

u C0 = 0.66 if plate thickness is < Do

u C0 = 0.80 if > Do

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Single Orifice Outlet Single Orifice Outlet

v.v. Orifice diameter (DOrifice diameter (Doo) must be greater than 4 ) must be greater than 4 inches, otherwise use weir or riserinches, otherwise use weir or riser

WQoWQo H * g * 2 * * C / Q * 2 * 12 D

g=32.2 ft/sec2

π = 3.14

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Single Orifice OutletSingle Orifice Outlet

Do=12*2*(0.49/(0.66*π*(2*32.2*1.5)0.5))0.5

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

Photo taken by Larry Roesner

Photo taken by Larry Roesner

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

Calculate outlet area per row of Calculate outlet area per row of perforations (Aperforations (Aoo))

AAoo (in (in22) = WQ) = WQvv / (0.013 * Z / (0.013 * ZWQWQ22 + 0.22 * Z + 0.22 * ZWQWQ – 0.1) – 0.1)

Assuming a single column, calculate Assuming a single column, calculate the diameter of a single perforation for the diameter of a single perforation for each roweach row

DD11 = (4 * A = (4 * Aoo / / ππ))1/21/2

If DIf D11 is greater than 2 inches add more is greater than 2 inches add more

columnscolumns nc = 4

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

= 1.62/(0.013*3.02+0.22*3.0–0.1)

= (4*2.4/π)1/2

3.0

2.4

1.75

1

1.75

NA

9

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

Use number of columns to determine exact Use number of columns to determine exact perforation diameterperforation diameter

DDperfperf = (4 / = (4 / ππ * A * Aoo / n / ncc))1/21/2

Using a 4” center to center vertical spacing Using a 4” center to center vertical spacing and Zand ZWQWQ, determine number of rows (n, determine number of rows (nvv))

nnvv = Z = ZWQWQ / 4 / 4

nv = 5

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Perforated Riser or Plate Perforated Riser or Plate OutletOutlet

= 1.62/(0.013*3.02+0.22*3.0–0.1)

= (4*2.4/π)1/2

3.0

2.4

1.75

1

1.75

NA

9

= (4/π*2.4/1)1/2

= (ZWQ*12in)/4

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V-Notch Weir OutletV-Notch Weir Outlet

Dr. Robert Pitt Source: Hubbard Brook LTER

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V-Notch Weir OutletV-Notch Weir Outlet

= 0.5*3.0ft

= (1.62*43,560)/(40*3600)

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V-Notch Weir OutletV-Notch Weir Outlet

Calculate required v-notch weir angle Calculate required v-notch weir angle (calculator in radians)(calculator in radians)

θθ = 2 * (180 / = 2 * (180 / ππ) * arctan (Q) * arctan (QWQWQ/(C/(Cvv * H * HWQWQ5/25/2))))

CV = V-notch weir coefficient = 2.5CV = V-notch weir coefficient = 2.5

If calculator is set to degrees useIf calculator is set to degrees use

θθ = 2* arctan (Q = 2* arctan (QWQWQ/(C/(Cvv * H * HWQWQ5/25/2))))

Source: Hubbard Brook LTER

θ

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V-Notch Weir OutletV-Notch Weir Outlet

If If θθ is <20º set is <20º set θθ to 20º to 20º

Calculate top width of v-notch weir Calculate top width of v-notch weir (W(WVV))

WWvv = 2 * Z = 2 * ZWQWQ * Tan ( * Tan (θθ / 2) / 2)

Source: Hubbard Brook LTER

θ

A

V-Notch Weir OutletV-Notch Weir Outlet

= 2*(180/π)*arctan(0.49/(2.5*1.55/2))

Since Since θθ < 20º set < 20º set θθ to 20º to 20º

= 2*3.0*tan(8º/2)

A

Pool ShapePool Shape

3WW

A

Water BudgetWater Budget

Recommended to Recommended to ensure permanent ensure permanent poolpool

Chapter 13 the Chapter 13 the NRCS NRCS Engineering Engineering Hand BookHand Book

outin QQtime

storage

A

ForebayForebay

Volume (VolVolume (VolFBFB) should be at least 10% of WQv) should be at least 10% of WQv

Depth (ZDepth (ZFBFB) should be at least 3feet) should be at least 3feet

Sides and bottom paved or hardenedSides and bottom paved or hardened Surface area (ASurface area (AFBFB):):

AAFBFB = Vol = VolFBFB / Z / ZFBFB

A

ForebayForebay

= 0.10*1.62

= 0.16/3.0

Topeka KS

A

Littoral BenchLittoral Bench

Serves as a planting surface Serves as a planting surface and safety feature around and safety feature around perimeter of permanent pool perimeter of permanent pool

25% to 50% of permanent 25% to 50% of permanent pool surface areapool surface area

At least 10 feet wide with a At least 10 feet wide with a max slope of 6:1max slope of 6:1

6 to 12 inches below 6 to 12 inches below permanent pool water surface permanent pool water surface

A

Littoral BenchLittoral Bench

π43,560A

2π

43,560AW

Pool

LBLB

Width of Littoral Bench (WLB):

A

Littoral BenchLittoral Bench

Min=0.25*0.82, Max=0.5*0.82

Min= (0.21*43560)/(2π*(0.82*43560/ π)1/2)

Between WLBMin and WLBMax

A

VegetationVegetation

Plant berms and Plant berms and sloped areas with sloped areas with native grasses native grasses

Littoral bench should Littoral bench should be planted with native be planted with native wetland specieswetland species

Plant trees and shrubs Plant trees and shrubs around perimeter of around perimeter of site site

Appendix A in BMP Appendix A in BMP manualmanual

A

Questions?Questions?

A

Extended Detention WetlandExtended Detention WetlandKey Design FeaturesKey Design Features

Permanent Permanent poolpool Low marshLow marsh High marsh High marsh Forebay Forebay MicropoolMicropool

Outlet structureOutlet structure Water budgetWater budget Wetland shapeWetland shape

A

Extended Detention WetlandExtended Detention WetlandPermanent Pool VolumePermanent Pool Volume

Use Method 1 or Method 2 – same as in Extended Use Method 1 or Method 2 – same as in Extended Wet Detention Basin DesignWet Detention Basin Design

Choose larger volume as permanent pool volume.Choose larger volume as permanent pool volume.

A

Extended Detention Wetland Extended Detention Wetland (EDW)(EDW)

6-18 in

0-6 in

4-6 ft

4-6 ft

A

20%

40%

20%

20%

Permanent PoolPermanent PoolDesign Volume AllocationsDesign Volume Allocations

A

= 4.1*0.2

= 4.1*0.2= 4.1*0.4= 4.1*0.2

Permanent PoolPermanent PoolDesign Volume AllocationsDesign Volume Allocations

A

Forebay ConsiderationsForebay Considerations

Pre-sedimentation at entry to EDWPre-sedimentation at entry to EDW Capacity to contain 5 years of sedimentCapacity to contain 5 years of sediment

Separated from EDW with berm, gabion, Separated from EDW with berm, gabion, or riprapor riprap

A

EDW ForebayEDW Forebay

Use VUse VForebayForebay from step II and SA from step II and SAForebayForebay from step III from step III

to find forebay depth (Zto find forebay depth (ZForebayForebay))

ZZForebayForebay = V = VForebayForebay/SA/SAForebayForebay

Depth should be 4-6feetDepth should be 4-6feet

A

EDW ForebayEDW Forebay

A

Micropool ConsiderationsMicropool Considerations

Prevents clogging of outlet Prevents clogging of outlet 4-6 feet deep4-6 feet deep Should be surrounded by a safety shelfShould be surrounded by a safety shelf

A

EDW MicropoolEDW Micropool

Using the same method used to calculate the forebay:Using the same method used to calculate the forebay:

ZZMicropoolMicropool = V = VMicropoolMicropool/SA/SAMicrpoolMicrpool

Depth should be 4 to 6 feetDepth should be 4 to 6 feet

Safety bench should be Safety bench should be ≥ 12 feet≥ 12 feet

A

EDW EDW Water Quality OutletWater Quality Outlet

Depth of water quality volume above permanent Depth of water quality volume above permanent poolpool Consider survivability of plant species Consider survivability of plant species Maximum depth should be 2 feet or lessMaximum depth should be 2 feet or less

Single Orifice, Orifice Plate or Standpipe, and V-Single Orifice, Orifice Plate or Standpipe, and V-notch outlet examples in Manualnotch outlet examples in Manual

Sized for 40 hour drawdownSized for 40 hour drawdown

A

ShapeShape

Flowpath length (L) to permanent pool width (W) Flowpath length (L) to permanent pool width (W) ratio must be greater than 3:1ratio must be greater than 3:1

Place berms or high marsh wedges at 50-foot Place berms or high marsh wedges at 50-foot intervals perpendicular to the flow direction to intervals perpendicular to the flow direction to increase dry weather flowpath lengthincrease dry weather flowpath length

Wedge-shaped, narrowest at the inlet and widest Wedge-shaped, narrowest at the inlet and widest at the outletat the outlet

L

W

A

VegetationVegetation

Wetland vegetation should occupy 50-75% of surface Wetland vegetation should occupy 50-75% of surface areaarea

Develop a landscaping plan, which places appropriate Develop a landscaping plan, which places appropriate species in each EDW zone and the surrounding area species in each EDW zone and the surrounding area

For plantings, use soil from an existing wetland or a For plantings, use soil from an existing wetland or a designed wetland planting mixdesigned wetland planting mix

Kansas City, MO

A

Questions?Questions?

15 minute break15 minute break

A

Design ActivityDesign Activity

UMKC Rain Garden Project

A

Activity Activity

Design an extended wet detention basin to capture Design an extended wet detention basin to capture runoff from a 42 acre drainage area with mixed land runoff from a 42 acre drainage area with mixed land use. Size the permanent pool and WQv of the basin use. Size the permanent pool and WQv of the basin using a v-notch outlet structure that will release the using a v-notch outlet structure that will release the WQv over a period of 40 hours.WQv over a period of 40 hours.

A

Activity - Design an EWDBActivity - Design an EWDB

A

Activity ResultsActivity Results

A

Lecture 3Lecture 3Other ConsiderationOther Consideration

Vegetation Vegetation Operations and maintenance Operations and maintenance ImplementationImplementation

PlanningPlanning DesignDesign ConstructionConstruction

Lesson’s learned Lesson’s learned

A

Vegetation

Process Design Review Standards Construction Adaptive Management &

Maintenance Buy-in

Project Sponsor Public/Stakeholders

Education Aesthetics Establishment Benefits and challenges

Success Realistic

A

VegetationVegetation Use plants listed in the BMP Manual Appendix A Use plants listed in the BMP Manual Appendix A

“Recommended Plant Materials for BMPs”“Recommended Plant Materials for BMPs” Narrow down from this list by:Narrow down from this list by:

Treatment only, habitat creation / biodiversity, Treatment only, habitat creation / biodiversity, aesthetics?aesthetics?

• If treatment is most important, then a wetland seed If treatment is most important, then a wetland seed mix may be sufficient. mix may be sufficient.

• If habitat creation and biodiversity is desired, specific If habitat creation and biodiversity is desired, specific species with habitat benefits are recommendedspecies with habitat benefits are recommended

Evaluating site conditions - soil quality, climate, Evaluating site conditions - soil quality, climate, wetness, pollutionwetness, pollution

• Hardier plants would work better in areas with poorer Hardier plants would work better in areas with poorer site conditionssite conditions

A

VegetationVegetation

Narrow down from this list by (cont):Narrow down from this list by (cont): Speaking with local nursery or botanistsSpeaking with local nursery or botanists

• What plants are available for purchase?What plants are available for purchase?• Which plants have the best survivability?Which plants have the best survivability?• Which plants would be best candidates for wet areas, Which plants would be best candidates for wet areas,

variable moisture, poor soils, etc.?variable moisture, poor soils, etc.? Visit at natural wetland in the areaVisit at natural wetland in the area

• What plants are naturally favored in local area?What plants are naturally favored in local area?• Are there specific invasive species that need to be Are there specific invasive species that need to be

managed?managed? Check municipal codes to ensure all plant materials Check municipal codes to ensure all plant materials

are approved for the areaare approved for the area

A

Wetland Species

A

Nuisance Species

A

Nuisance Species

A

Native versus Non-native Native versus Non-native PlantsPlants

Native plants are Native plants are recommendedrecommended Larger root systemLarger root system Increase infiltrationIncrease infiltration More drought More drought

toleranttolerant Disease resistantDisease resistant Adapted to Adapted to

environmentenvironment

A

Native Plants-Advantages and Disadvantages

Advantages Indigenous to the area and able to thrive in the local climate with

less maintenance. Deep roots enhance stormwater infiltration into the soil. Able to withstand flooding events as well as extended dry

periods. Reduces flow velocity of stormwater runoff. Wide range of application (restoration of native prairie, woodland,

wetlands, & riparian areas) Attracts wildlife and improves biological diversity. Requires little to no fertilizer or chemical maintenance Requires less water to survive. Provides attractive and natural vegetative scenery.

Disadvantages Can be difficult to establish if some circumstances. Can be expenses if planted from nursery stock plugs. Can be considered “weedy” by some people.

A

Vegetation – Design Consideration

Local and regional planning initiatives Public involvement/public relations Visibility-Aesthetics Height of vegetation Financial (funding source, budget, property values) Regulatory requirements Function/risk Utility-stormwater management Recreation

A

Vegetation ResourcesVegetation Resources

Appendix A in the MARC BMP manualAppendix A in the MARC BMP manual Local nurseriesLocal nurseries www.kansasnativeplantsociety.org www.grownative.orgwww.grownative.org

http://plants.usda.gov

A

Other Sources

Tallgrass Restoration Handbook for Prairies Savannas and Woodlands (Packard & Mutel, 1997)

The National List of Plant Species that Occur in Wetlands-Region 3 (USFWS, 1988)

The Flora of Missouri (Steyermark, 1963; 1996)

Steyermark’s Flora of Missouri, Volume I, II,…; Yatskeievych; 1999…)

The Flora of the Great Plains (McGregor et. al.)

Ecologist; Landscape Architect

A

Vegetation Examples Vegetation Examples

BanksBanks Butterfly Milkweed, Butterfly Milkweed,

Asclepias tuberosaAsclepias tuberosa

Littoral BenchLittoral Bench Blunt SpikerushBlunt Spikerush, ,

Eleocharis obtusaEleocharis obtusa

Clarence A. Rechenthin @ USDA-NRCS PLANTS Database

Robert H. Mohlenbrock @ USDA-NRCS PLANTS Database

A

Vegetation – Other Design Consideration

Setting Urban Rural

Built Environment Commercial Residential Mixed Use

Stormwater Utility – Stormwater Management Recreation

CONTEXT

A

Vegetation – Installation & Maintenance

Installation Oversight Contractor Experience Plant availability

Maintenance Measures Has a maintenance program/budget been established? What type of adaptive management will be implemented?

• Burning or mowing

• Herbicides

• Transplanting Who will do the management-establishment?

• Lawn maintenance crews

• Native Landscape specialists

A

General MaintenanceGeneral Maintenance

Event Inspection (> 0.5 inches)Event Inspection (> 0.5 inches) Inspect facility operation, especially outlet structureInspect facility operation, especially outlet structure Remove trash & debrisRemove trash & debris Document potential problemsDocument potential problems

Monthly InspectionMonthly Inspection Inspect & repair erosionInspect & repair erosion Water plant material during dry periods (1Water plant material during dry periods (1stst Year) Year) Perform routine plant maintenance (pruning, weeding, etc.)Perform routine plant maintenance (pruning, weeding, etc.)

Semi-Annual InspectionSemi-Annual Inspection Remove and replace dead or diseased vegetationRemove and replace dead or diseased vegetation Re-landscape/re-mulch any area areasRe-landscape/re-mulch any area areas

Annual InspectionAnnual Inspection Inspect inlet & outlet structure conditionInspect inlet & outlet structure condition Record assessment of planted species & evidence of invasive Record assessment of planted species & evidence of invasive

plant speciesplant species Perform comprehensive safety inspectionPerform comprehensive safety inspection

A

Other MaintenanceOther MaintenanceConsiderationConsideration

Maintenance access - 15 Maintenance access - 15 feet wide strip around feet wide strip around the perimeter of the sitethe perimeter of the site

May need to harvest May need to harvest excess plantsexcess plants

Erosion issuesErosion issues Sediment removal from Sediment removal from

forebay when 50% fullforebay when 50% full Sediment removal from Sediment removal from

micropool and marsh micropool and marsh area when 10 to 15% fullarea when 10 to 15% full

Design Phase

– Erosion and sedimentation controls– Post-construction BMPs– Flood control improvements

Construction Phase

– Inspect and maintain BMPs for construction activities

– Construct Post Construction BMPs

– Maintain agreements for post-construction BMPs

DesignerDesigner

Planning Phase

– Environmental Site Assessment– Select Post Construction BMPs– Flood Control Study– Establish Long-term Maintenance Agreements

Review Team

PlanningEngineering

Parks & RecreationEnvironmental Specialists

Attorney Review Team

PlanningEngineering

Parks & RecreationEnvironmental SpecialistsOperations & Maintenance

Review Team

PlanningEngineering

Code ComplianceInspectors

Plat Approval

Occupancy Permit

Building Permit

A

Upcoming Training SessionsUpcoming Training Sessions

Module #3 – Rain Gardens & BioretentionModule #3 – Rain Gardens & Bioretention Date: January 23, 2009Date: January 23, 2009 Location: Helzberg Auditorium, KCPLLocation: Helzberg Auditorium, KCPL

Module #4 – Extended Dry Detention & Infiltration Module #4 – Extended Dry Detention & Infiltration (Pervious Pavements)(Pervious Pavements) Date: February 20, 2009Date: February 20, 2009 Location: Helzberg Auditorium, KCPLLocation: Helzberg Auditorium, KCPL

A

Questions?

Comments.

Suggestions.