Presented by: Roger Sutherland, PE Pacific Water Resources, Inc. Beaverton, Oregon Pacific Water...

Presented by:Presented by: Roger Sutherland, PERoger Sutherland, PE Pacific Water Resources, Inc.Pacific Water Resources, Inc. Beaverton, OregonBeaverton, Oregon

When Concerned About Toxic Stormwater When Concerned About Toxic Stormwater Pollutants in the Built Environment:Pollutants in the Built Environment:

Sweep Before You “Treat”Sweep Before You “Treat”

RESEARCH CONFERENCE

2007 GEORGIA BASIN PUGET SOUND

MARCH 26-29, 2007 VANCOUVER, B.C.

IntroductionIntroduction

Many water quality planners Many water quality planners recommend treating urban recommend treating urban stormwater with:stormwater with:

Wet pondsWet pondsGrassy swalesGrassy swalesSand filersSand filersWet vaultsWet vaultsOther structural devicesOther structural devices



Retrofitting drain inlets in Retrofitting drain inlets in streets and parking lots with streets and parking lots with inserts to trap litter and inserts to trap litter and contaminated sediments.contaminated sediments.


Gaining particular interest is:Gaining particular interest is:


Standard TSS testing techniques Standard TSS testing techniques and the use of automatic samplers and the use of automatic samplers have greatly underestimated the have greatly underestimated the magnitude, concentration and magnitude, concentration and average particle size of sediment average particle size of sediment in urban stormwater.in urban stormwater.


Many recent studies have Many recent studies have shown that:shown that:

IntroductionIntroductionIntroductionIntroduction

The inundation of treatment The inundation of treatment facilities with high unanticipated facilities with high unanticipated loadings of sediment and gross loadings of sediment and gross pollutants that have led to pollutants that have led to poor removal performance and poor removal performance and higher maintenance costs.higher maintenance costs.

Resulting in:Resulting in:

IntroductionIntroductionIntroductionIntroduction

Studies by Sutherland and Jelen Studies by Sutherland and Jelen clearly establish that:clearly establish that:

Street sweeping is the most Street sweeping is the most cost effective BMP from a cost effective BMP from a pollutant reduction standpoint pollutant reduction standpoint and should be considered first and should be considered first before structural treatment before structural treatment devices are used.devices are used.


VacuumVacuumRegenerative airRegenerative airMechanical broomMechanical broom


Most newer machines whether:Most newer machines whether:

are more effective at sediment and are more effective at sediment and associated pollutant pick-up.associated pollutant pick-up.

The practice should now be called The practice should now be called “Street Cleaning,” not street sweeping.“Street Cleaning,” not street sweeping.

Maestre and Pitt recently combined Maestre and Pitt recently combined nationwide stormwater quality data nationwide stormwater quality data from four major stormwater databases:from four major stormwater databases:

NURPNURP

USGSUSGS

International BMP (ASCE)International BMP (ASCE)

NSQDNSQD

What Have We Learned?What Have We Learned?

Analyses of the 10,000 individual events Analyses of the 10,000 individual events from 594 sampling locations representing 16 from 594 sampling locations representing 16 different land use categories found that:different land use categories found that:


The variability between sampling The variability between sampling locations for any land use category locations for any land use category within the same USEPA rain zonewithin the same USEPA rain zoneis greater than the variability is greater than the variability between land uses themselves between land uses themselves within that rain zone.within that rain zone.

Around 5% to 20% of the sites Around 5% to 20% of the sites

located in the same USEPA rain zone located in the same USEPA rain zone

and land use category are expected and land use category are expected

to have median concentrations that to have median concentrations that

are significantly different than the are significantly different than the

remaining sites in the group.remaining sites in the group.


Minton reports that, given the amount Minton reports that, given the amount of stormwater quality data and the of stormwater quality data and the several hundred publications, it is not several hundred publications, it is not possible to summarize what these data possible to summarize what these data are “telling us” regarding physical, are “telling us” regarding physical, chemical and biological constituents.chemical and biological constituents.

Is the Existing Dataset Flawed?Is the Existing Dataset Flawed?

There is evidence, however, that all of our There is evidence, however, that all of our past monitoring is biased and should be past monitoring is biased and should be “tossed out.”“tossed out.”

Why biased? Two reasons.Why biased? Two reasons.

Withdrawal water velocities of older Withdrawal water velocities of older automatic samplers can’t pick up automatic samplers can’t pick up particles greater than 100 to 200 microns. particles greater than 100 to 200 microns. Hence we may have been understating Hence we may have been understating the concentrations of sediments and the concentrations of sediments and some attached pollutants.some attached pollutants.

Metals, phosphorus, petroleum and Metals, phosphorus, petroleum and related hydrocarbons and pesticidesrelated hydrocarbons and pesticidesare all hydrophobic and therefore are all hydrophobic and therefore sorb to these larger particles.sorb to these larger particles.


Standard laboratory procedures for TSS Standard laboratory procedures for TSS measurement require the split of the field measurement require the split of the field sample into aliquots for analysis.sample into aliquots for analysis.

Rapid hand mixing, pouring and use Rapid hand mixing, pouring and use of a pipette fails to properly sample of a pipette fails to properly sample larger material that may have been larger material that may have been captured resulting in an underestimation captured resulting in an underestimation of the TSS concentration.of the TSS concentration.


Others argue that we have had a bias in the Others argue that we have had a bias in the

opposite direction. Concentrations, and opposite direction. Concentrations, and

therefore loadings, may be overstated to the therefore loadings, may be overstated to the

extent that we have tended to sample larger extent that we have tended to sample larger

storms (e.g. 0.5 inches or more in depth). storms (e.g. 0.5 inches or more in depth).

But most runoff occurs from much smaller But most runoff occurs from much smaller

storms, which have lower rainfall intensities storms, which have lower rainfall intensities

resulting in lower overland and gutter flow resulting in lower overland and gutter flow

velocities and, consequently, smaller particle velocities and, consequently, smaller particle

sizes and lower pollutant concentrations.sizes and lower pollutant concentrations.


Hence, the bias of older automatic Hence, the bias of older automatic

samplers may have been counter-samplers may have been counter-

balanced by the failure to recognize the balanced by the failure to recognize the

dominance of the smaller storms.dominance of the smaller storms.

Once thing is now clear:Once thing is now clear:


Sampling in the future, done Sampling in the future, done properly, will be quite expensive.properly, will be quite expensive.

Cleaning StreetsCleaning Streets

IS NOTIS NOT

an Effective BMPan Effective BMP

An Urban MythAn Urban Myth


Nationwide Urban Runoff ProgramNationwide Urban Runoff Program(NURP) 1982 conclusion:(NURP) 1982 conclusion:

““Street sweeping is generally Street sweeping is generally ineffective as a techniqueineffective as a techniquefor improving the quality for improving the quality of urban runoff.” of urban runoff.”


What has changed by 2006:What has changed by 2006:

Improved sweepersImproved sweepers

NPDES permitsNPDES permits

TMDL complianceTMDL compliance

Public expectations are greaterPublic expectations are greater

““End-of-Pipe” treatment is very expensiveEnd-of-Pipe” treatment is very expensive

USEPA 1982 NURP StudyUSEPA 1982 NURP Study

Over $30 million was spent studying the characteristics Over $30 million was spent studying the characteristics and potential control of urban stormwater runoff quality and potential control of urban stormwater runoff quality at 28 U.S. cities between 1979 – 1982.at 28 U.S. cities between 1979 – 1982.


Street cleaning was investigated Street cleaning was investigated in the following U.S. cities:in the following U.S. cities:

CityCity SitesSites

Bellevue, WABellevue, WA

Champaign Urbana, ILChampaign Urbana, IL

Milwaukee, WIMilwaukee, WI

Winston-Salem, NCWinston-Salem, NC

22

44

22

22


The resulting runoff quality data was The resulting runoff quality data was analyzed statistically, not explicitly. analyzed statistically, not explicitly. Computer models of that era were not Computer models of that era were not considered to be reliable or accurate.considered to be reliable or accurate.

The studies used either a paired The studies used either a paired basin or serial basin approach with basin or serial basin approach with continuous sampling of end-of-pipe continuous sampling of end-of-pipe urban runoff quality occurring under urban runoff quality occurring under either either sweptswept or or unsweptunswept conditions. conditions.


NURP concluded that street sweeping NURP concluded that street sweeping using equipment of that era was using equipment of that era was generally ineffective in reducing the generally ineffective in reducing the concentrations of pollutants concentrations of pollutants commonly found in stormwater.commonly found in stormwater.

NURP evaluated street cleaning NURP evaluated street cleaning performance as measured by the performance as measured by the percent change in the site median percent change in the site median Event Mean Concentration (EMC) for Event Mean Concentration (EMC) for each pollutant of interest.each pollutant of interest.

However, the However, the actualactual data analyses of the five data analyses of the five major pollutants (TSS, COD, TP, TKN, and Lead) major pollutants (TSS, COD, TP, TKN, and Lead) at each of the 10 sites where street sweeping at each of the 10 sites where street sweeping was investigated showed that under swept was investigated showed that under swept conditions EMCs were conditions EMCs were actuallyactually reducedreduced in in 60%of the 50 pollutant/site investigations.60%of the 50 pollutant/site investigations.

Increases in site median EMCs were reported for Increases in site median EMCs were reported for 16 out of the 50 pollutant/site investigations, 16 out of the 50 pollutant/site investigations, and 9 of those from the two North Carolina sites.and 9 of those from the two North Carolina sites.

NURP Study – Actual Data AnalysisNURP Study – Actual Data Analysis

NURP Study – Actual Data AnalysisNURP Study – Actual Data Analysis

% EMC Reduction% EMC Reduction

JOH

N S

T.

NIL

LIN

OIS

JOH

N S

T.

SIL

LIN

OIS

MA

TT

IS N

ILL

INO

IS

MA

TT

IS S

ILL

INO

IS

CB

DN

CA

RO

LIN

A

LA

KE

HIL

LS

WA

SH

ING

TO

N

SU

RR

EY

DO

WN

SW

AS

HIN

GT

ON

RU

ST

LE

RW

ISC

ON

SIN

(100)(100)

100100

5050

00

(50)(50)

RE

SID

EN

TIA

LN

CA

RO

LIN

A

ST

AT

E F

AIR

WIS

CO

NS

IN

TSS COD TP TKN Pb


We now know that these EMC increases We now know that these EMC increases resulted from the NURP era street sweeper’s resulted from the NURP era street sweeper’s inability to pick up significant amounts of the inability to pick up significant amounts of the “dirt and dust” fraction of the accumulated “dirt and dust” fraction of the accumulated street dirt (i.e. less than 1/8 inch).street dirt (i.e. less than 1/8 inch).

Intense rain storms (which occur more Intense rain storms (which occur more frequently in North Carolina) were then able to frequently in North Carolina) were then able to efficiently transport the remaining unarmored efficiently transport the remaining unarmored material which led to higher pollutant material which led to higher pollutant concentrations for the swept condition.concentrations for the swept condition.


Technology has greatly improved the Technology has greatly improved the sediment pick up performance of all types sediment pick up performance of all types of street cleaners.of street cleaners.

Because of the NURP conclusion, most Because of the NURP conclusion, most stormwater people including most stormwater people including most consultants and NPDES coordinators consultants and NPDES coordinators believe that street cleaning is ineffective at believe that street cleaning is ineffective at reducing pollutant loadings in stormwater.reducing pollutant loadings in stormwater.

Why does this matter now?Why does this matter now?

Number 1 Reason to SweepNumber 1 Reason to Sweep

Sweeping Improves Water QualitySweeping Improves Water Quality

The number 1 reason to sweep is:The number 1 reason to sweep is:

Cleaning Improves Water QualityCleaning Improves Water Quality

Box-Whisker PlotsBox-Whisker Plots


Tota

l Cop

per

Sto

rm E

MC

s (p

pb)

Before After0

20

40

60

80

100

120

Baltimore Street Cleaning Pilot StudyBaltimore Street Cleaning Pilot StudyCopper concentration declinedCopper concentration declined

Not Cleaned Cleaned


Baltimore Street Cleaning Pilot StudyBaltimore Street Cleaning Pilot StudyTotal nitrogen concentration declinedTotal nitrogen concentration declined

Tota

l Nitr

ogen

Sto

rm E

MC

s (p

pm)

Before After0

2

4

6

8

10

Not Cleaned Cleaned


Tota

l Pho

spho

rus

Sto

rm E

MC

s (p

pm)

Before After0

0.4

0.8

1.2

1.6

2

Baltimore Street Cleaning Pilot StudyBaltimore Street Cleaning Pilot StudyReduction of higher concentrations for total phosphorusReduction of higher concentrations for total phosphorus

Not Cleaned Cleaned


Cross Israel Highway (CIH)Cross Israel Highway (CIH)Stormwater Quality StudyStormwater Quality Study

0

0.2

0.4

0.6

0.8

1.0

1.2

Cleaned

Comparison of Not Cleaned to Cleaned Pavement

Zin

c (

mg

/L)

Not Cleaned

In the built environment:In the built environment:

OOne half to two thirds of the rain that falls on ne half to two thirds of the rain that falls on impervious surfaces is falling on pavementimpervious surfaces is falling on pavement

Pavements contribute half, if not more, of the Pavements contribute half, if not more, of the toxic pollutants found in stormwatertoxic pollutants found in stormwater

Unlike most other BMPs, sweeping can have an Unlike most other BMPs, sweeping can have an immediate impactimmediate impact

Pavement cleaning is the most cost-effective BMP Pavement cleaning is the most cost-effective BMP based on dollars per pound of pollutant removed based on dollars per pound of pollutant removed from the stormwaterfrom the stormwater

Benefits of CleaningBenefits of Cleaning

TSS Removal CostsTSS Removal Costs

Working with data from 46 individual Working with data from 46 individual

stormwater treatment devices located in stormwater treatment devices located in

Snohomish County, Washington, Minton Snohomish County, Washington, Minton

and Ewbank (2002) reported the following and Ewbank (2002) reported the following

costs per pound of TSS removed.costs per pound of TSS removed.


TreatmentDevice

Number of Projects

Cost Range $/lbTSS Removed

AverageConstruction Cost

MedianCost

Wet pond

Wet vault

O/W separator

Sand filter

Swale (New)

StormFilterTM

Vortex separator

5

7

6

3

5

1

1

$2.0 - $15

$4.3 - $61

$2.8 - $24

$4.0 - $26

$0.5 - $4.4

$7.8

$4.4

$7.0

$22

$10

$14

$1.5

$7.8

$4.4

$4.3

$10

$5.9

$13

$0.9

$7.8

$4.4

Excludes costs of engineering, permitting and land


Minton and Ewbank (2002) also Minton and Ewbank (2002) also

estimated the cost effectiveness of estimated the cost effectiveness of

retrofitting roadside ditches to retrofitting roadside ditches to

function as treatment swales to be function as treatment swales to be

$5.5 to $28 per pound of TSS removed.$5.5 to $28 per pound of TSS removed.


Data from a study of structural Data from a study of structural

stormwater treatment devices by stormwater treatment devices by

CALTRANS indicates that TSS removal CALTRANS indicates that TSS removal

costs ranged from $10 to $60 per costs ranged from $10 to $60 per

pound, not including land costs.pound, not including land costs.


Sutherland, Myllyoja and Jelen (2002) studied street Sutherland, Myllyoja and Jelen (2002) studied street

cleaning practices in Livonia, Michigan and computed cleaning practices in Livonia, Michigan and computed

TSS removal costs for regenerative air sweeping of TSS removal costs for regenerative air sweeping of

residential streets that ranged from $1.80 to $3.20 residential streets that ranged from $1.80 to $3.20

per pound of TSS removed depending on cleaning per pound of TSS removed depending on cleaning

frequency, which ranged from once every two months frequency, which ranged from once every two months

to twice each month.to twice each month.

Similar TSS removal costs were computed during a Similar TSS removal costs were computed during a

study of street cleaning practices in Jackson, Michigan.study of street cleaning practices in Jackson, Michigan.

Street Cleaning Programs Can ControlStreet Cleaning Programs Can Control

Type of sweeper usedType of sweeper used(pick-up performance is most important)(pick-up performance is most important)

Forward speed of the sweeperForward speed of the sweeper(4-to-6 miles per hour is recommended)(4-to-6 miles per hour is recommended)

Parked car interferenceParked car interference(requires a political will, ordinances and (requires a political will, ordinances and enforcement; however, fines can be used to enforcement; however, fines can be used to support the cleaning program)support the cleaning program)

Frequency of street cleaningFrequency of street cleaning(usually varies by land use or street categories)(usually varies by land use or street categories)

Establishing the Most Cost-Effective OperationEstablishing the Most Cost-Effective Operation

But how does a street cleaning program But how does a street cleaning program determine the most cost-effective or best determine the most cost-effective or best program for reducing stormwater program for reducing stormwater pollutant washoff?pollutant washoff?

For accurate estimates, computer For accurate estimates, computer modeling must be used.modeling must be used.

Pacific Water Resources has available a Pacific Water Resources has available a model they developed called SIMPTM.model they developed called SIMPTM.

Benefits of SIMPTM ModelingBenefits of SIMPTM Modeling

SIMPTM estimates stormwater pollutant SIMPTM estimates stormwater pollutant loadings for both NPDES reporting and loadings for both NPDES reporting and TMDL planning.TMDL planning.

Can establish the relationship between Can establish the relationship between frequency of cleaning by land use or street frequency of cleaning by land use or street category and the amount of pollutant that category and the amount of pollutant that would have been removed from the urban would have been removed from the urban runoff washoff over a historic rainfall runoff washoff over a historic rainfall record of unlimited length.record of unlimited length.

SIMPTM Modeling ResultsSIMPTM Modeling Results

BMP Production FunctionsBMP Production Functions

Single-Family ResidentialSingle-Family Residential

Livonia, MI Case

Study

SIMPTM Modeling ResultsSIMPTM Modeling ResultsLivonia, MI Case

Study

BMP Total Cost CurvesBMP Total Cost Curves


SIMPTM Modeling ResultsSIMPTM Modeling Results

Lbs. of loading Lbs. of loading

reduction/acre/yearreduction/acre/year

As related to …As related to …

$ and $ and MMaximum aximum EExtent xtent PPracticableracticableM

arg

inal

Co

stM

arg

inal

Co

st$

/las

t p

ou

nd

re

mo

ve

d$

/las

t p

ou

nd

re

mo

ve

d

SIMPTM Modeling ResultsSIMPTM Modeling ResultsLivonia, MI Case

Study

BMP Marginal Cost CurvesBMP Marginal Cost Curves


Newer Mech. Sweeping No CB

CleaningNewer Mech. Sweeping Annual CB

CleaningHigh Eff Sweeping No CB

CleaningHigh Eff Sweeping Annual CB

CleaningRegen Air Sweeping No CB

CleaningRegen Air Sweeping Annual CB

CleaningTandem Sweeping No CB

CleaningTandem Sweeping Annual CB

Cleaning

New developmentNew developmentCertain retrofits where:Certain retrofits where:

ConclusionConclusion

Stormwater Treatment Devices Stormwater Treatment Devices are best suited for:are best suited for:

Street sweeping is not practicalStreet sweeping is not practical

Toxic pollutant loadings are elevatedToxic pollutant loadings are elevated

Higher level of pollutant removal Higher level of pollutant removal is neededis needed

No one has considered or evaluated the No one has considered or evaluated the integration of sweeping with structural integration of sweeping with structural treatment, whether new or redevelopment.treatment, whether new or redevelopment.

With effective sweeping, it is possible to use With effective sweeping, it is possible to use much smaller structural treatment systems much smaller structural treatment systems or possibly eliminate the use of structural or possibly eliminate the use of structural controls in some situations.controls in some situations.

The monies saved could be used (fee-in-lieu) The monies saved could be used (fee-in-lieu) to support the sweeper program.to support the sweeper program.



When dealing with the built environment:When dealing with the built environment:

Sweep Before You TreatSweep Before You Treat

Presented by: Roger Sutherland, PE Pacific Water Resources, Inc. Beaverton, Oregon Pacific Water...

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Transcript of Presented by: Roger Sutherland, PE Pacific Water Resources, Inc. Beaverton, Oregon Pacific Water...