Post on 27-Dec-2015
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
IntroductionIntroduction
IntroductionIntroduction
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.
IntroductionIntroduction
Gaining particular interest is:Gaining particular interest is:
IntroductionIntroduction
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.
IntroductionIntroduction
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.
IntroductionIntroduction
VacuumVacuumRegenerative airRegenerative airMechanical broomMechanical broom
IntroductionIntroduction
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:
What Have We Learned?What Have We Learned?
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.
What Have We Learned?What Have We Learned?
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.
Is the Existing Dataset Flawed?Is the Existing Dataset Flawed?
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.
Is the Existing Dataset Flawed?Is the Existing Dataset Flawed?
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.
Is the Existing Dataset Flawed?Is the Existing Dataset Flawed?
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:
Is the Existing Dataset Flawed?Is the Existing Dataset Flawed?
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
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.”
An Urban MythAn Urban Myth
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.
USEPA 1982 NURP StudyUSEPA 1982 NURP Study
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
USEPA 1982 NURP StudyUSEPA 1982 NURP Study
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.
USEPA 1982 NURP StudyUSEPA 1982 NURP Study
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
USEPA 1982 NURP StudyUSEPA 1982 NURP Study
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.
USEPA 1982 NURP StudyUSEPA 1982 NURP Study
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
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
Cleaning Improves Water QualityCleaning Improves Water Quality
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
Cleaning Improves Water QualityCleaning Improves Water Quality
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
Cleaning Improves Water QualityCleaning Improves Water Quality
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.
TSS Removal CostsTSS Removal Costs
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
TSS Removal CostsTSS Removal Costs
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.
TSS Removal CostsTSS Removal Costs
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.
TSS Removal CostsTSS Removal 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
Single-Family ResidentialSingle-Family Residential
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
Single-Family ResidentialSingle-Family Residential
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.
ConclusionConclusion