Fifty Years of Innovation in Urban Stormwater Management

Jiri Marsalek National Water Research Institute,

Burlington, ON, Canada

Technical University of Lulea, Sweden Lulea, Sweden, Dec. 3, 2013

2

World Population: Urban and Rural Areas (UN, 2009)

Global pop. 3.5 billion

Global pop. 7.4 billion

LD rur

LD urb

MD urb

MD rur

• Swedish population: Total 9.3, urban 7.9 million (85%)(2010, CIA)

3

Urban Drainage: Systems Analysis (SA)

• Problems – unsustainable growth of urban drainage systems (UDS)

• Analytical tools – models • Solutions – BMPs and LID

and similar • Evaluations (including costs)

– mostly by modelling • Implementation –through

master drainage plans, regulations and policies

• Problem definition – evolving, the cycle repeats itself

Problem definition

Development of analytical tools

Problem solutions

Evaluation of solution alternatives

Evaluation of solution alternatives

Implementation

4

Impacts of urbanization: Surface runoff

Envelope

Return period (y)

Time

Runoff Hydrograph after urbanization

Runoff hydrograph

before urbanization

Dis

char

ge

Pos

t-dev

elop

men

t run

off p

eak

/ pre

deve

lopm

ent p

eak

5

Stormwater quality

• Discovery period (mid 1960s – late 1970s), generation of national databases (1980s) (e.g., US NURP (1983))

• Findings: – A general understanding of stormwater quality with respect to

conventionals (TSS, COD, BOD, nutrients), indicator bacteria and some priority pollutants (inorganics – trace metals)

– Occurrence of EPA priority pollutants (inorganics, some trace organics – PAHs, older pesticides) in stormwater

– Producing arguments for continuing research on stormwater pollution and its mitigation by control measures

• Current focus – priority pollutants, particularly under the EC Water Framework (recent pesticides, PCBs, plasticisers, emerging pollutants)

6

Stormwater quality (NURP) Constituent EMCs – median EMCs – 90th percentile

TSS [mg/L] 100 300

BOD5 [mg/L] 9 15

COD [mg/L] 65 140

P tot [mg/L] 0.33 0.70

P diss 0.12 0.21

TKN [mg/L] 1.5 3.3

NO2,3 0.68 1.75

Cu tot [µg/L] 34 93

Zn tot [µg/L] 160 500

Other concerns: Indicator bacteria (EC: 103 – 104/100 mL), PAHs (from traffic), waste heat (impacts cold water fisheries), priority pollutants

7

Tools for solution assessment – models Example: U.S. EPA SWMM runoff simulations

(Burlington, Ontario, 1974)

Measured runoff

Time (h)

Dis

char

ge [m

3 /s]

Rai

nfal

l int

ensi

ty [m

m/h

]

Simulated runoff

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Impacts of urban runoff on receiving waters

Factors affecting biological communities: flow regime, habitat structure, biotic interactions, food sources, chemical variables (pollution)

Seasonal effects were noted (chloride)

Log (total number/m2) Site

Sediments from all sampling sites

10 most dominant taxons

Num

ber o

f tax

ons

9

Current goals of stormwater management (SWM)

Goals Means of attaining the goals

Control of runoff peaks, preservation of water balance

BMPs, LID, Green Infrastructure, … (control of water balance and runoff )

Protection of stream geomorphology

BMPs & LID (control of runoff flow magnitude and duration)

Protection of water quality BMPs & LID (control of stormwater quality, including source controls)

Maintaining / enhancing biodiversity (ecological functions)

BMPs & LID (mimicking predevelopment water balance and water quality)

Enhancement of beneficial uses of stormwater

BMPs & LID (selected to protect aesthetics, recreational uses and ecological functions, SW use)

10

Solutions: BMPs, LID, Green Infrastructure

• BMPs (best management practices) serve to mitigate urbanization impacts on runoff quantity and quality

• Early BMPs: wet and dry ponds, infiltration trenches and basins, porous pavements, constructed wetlands, sand filters

• LID (low impact development) – a comprehensive, landscape-based approach encompassing strategies to maintain the predevelopment land hydrology and ecology (identical to “Design with nature”, Ian McHarg, 1969)

• Typical LID measures: bioretention, bioswales, green roofs, permeable pavements, box planters, naturalized drainage channels, vegetated filters/strips,

Credit: M. Dietz From Kerr, Wood, Leidal

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Hydrology of BMPs a LID: Annual water balance

S s

ewer

SW

pon

d

Dr.

ditc

h

Inf.

Tren

ch

Bio

rete

ntio

n

Gre

en R

oof

ETINF

RUNF0

1020

30

40

50

60

70

80

90

100B

alan

ce fr

actio

nFr

actio

n [%

]

Surface runoff

Infiltration Evapotranspiration

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International Stormwater BMP Database: Performance in removal of TSS

Bioreten-tion

Green roofs

Wet ponds

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Life-cycle costs of removing 1 kg of TSS by SWM (from Urbonas)

0

2

4

6

8

10

12

14

16

18

sand filer basin wet pond porousconcerete

pavers

porouslamndscape

detention

oil & gritseparator

inlet inserts

Annu

al c

ost o

f rem

ovin

g 1

kg o

f TSS

[$/k

g/y]

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SWM Implementation

• Understanding of technical-scientific issues of SWM has greatly advanced during the last two decades

• Yet, there is a tendency of promoting “idola fori” (idols of the market) defined by Sir Francis Bacon (1561-1626) as “fallacies arising from the imperfections and the abuse of language”.

• Examples include the thoughts that pavements should be excluded from cities (ignoring their function), all stormwater is a resource (this would include catastrophic rainfalls), etc.

• This needs to be corrected by public education

Source: Wikipedia

Francis Bacon

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Smart Cities

• There is realization that the city’s performance in meeting end-users needs does not depend just on hard infrastructure, but also on the availability and quality of knowledge communication social infrastructure

• These concepts were introduced into urban planning as “smart”, “intelligent” or “liveable” cities featuring attractive built and natural environments

• It is of interest to note how these concepts are viewed by the economists (The Economist magazine, EM)

• EM asserts that these concepts follow the “hype cycle”, characterized by a period of inflate expectations leading to some lower level of sustained productivity

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The Hype Cycle (after Gartner)

• A discussion model, but based on past experiences

• The plateau of productivity is hard to predict (but experts try)

• For smart cities, EM expects to see some benefits in late 2013 or in 2014

Visibility

Time

Peak of inflated expectations

Trough of Disillusionment

Plateau of productivity

Technology trigger

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UDS Innovation • Growing cities create pressure on existing

water systems, solutions require innovation • Past innovation in SWM – adopting /adapting

existing concepts from catchment hydrology and wastewater management (low hanging fruit)

• Uptake of innovation is impaired by technological lock-in (long design life) and monopoly in service delivery

• Near future innovation of sewers, BMPs will proceed slowly (limited incentives)

Source: The Economist

18

Innovation (cont. 1)

• Other aspects involving private enterprise and research – e.g., updating UDS problem definition, software for planning, design and operation, and environmental technologies will keep evolving, because of incentives

• Environmental technologies - proliferation of devices treating SW, but their full (life-cycle) costs including maintenance may be prohibitive - need to be assessed

• A further impediment may be ambiguous terminology - often introduced by vendors of SW equipment wishing to distinguish their products from others already on the market by implying superiority

19

Evolution of UD Problem Definition

• Common understanding of urbanization impacts is fairly advanced, but a number of issues require further research:

– building materials as in-situ pollutants, – priority pollutants, – climate change impacts on UD, and – drainage in special climates

• Building materials – progress has been made, but concerns are continuing (plasticisers and biocides in industrial paints and building materials

• Municipalities have limited control options • Positive effects – e.g. self-cleaning concrete

with embedded TiO2 nanoparticles (may remove pollutants at street level)

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Priority Pollutants

• Recent studies of priority pollutants were motivated by the EU Water Framework Directive

• Such data are useful for assessing the pathways and fate of priority pollutants, but their control is likely outside of municipal mandate – will be achieved by policy instruments, as done e.g., in the case of lead

• Municipal “ownership” of the PP issue would be costly and require special removal of disposal of contaminated materials (e.g., pond sediment disposal might increase two orders of magnitude)

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Example of Policy Control Instruments: Phasing Pb out of Gasoline

• Phasing Pb out of gasoline was highly effective

• Highway runoff data indicate reduction of Pb in runoff about 30 times

• This is actual prevention, not just a diversion, or immobilization

• There are other similar opportunities

US Highway Data (1970s)

CDN Highway Data (1990s)

10

1

.01

.001

Pb (mg/L)

Z score-2 -1 0 1 2

Reduction 97%

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UDS: Climate Change

• Excellent monograph produced under the leadership of IWG on Urban Rainfall • The problem of producing quantitative assessment of

impacts is highly challenging and complicated by the dynamic nature of urban areas

• Global or regional climate model outputs need to be downscaled to few km and resolution in minutes

• Uncertain results depend on the downscaling process, standard procedures need to be developed

• So far, focus on flooding, but the performance of the stormwater management infrastructure in a changing climate should be of interest as well

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Cold climate issues

• Stormwater management research in cold climate is more challenging than in temperate climate, yet not receiving adequate attention

• Some issues: higher rates of pollutant releases, shock wave pollutant transport (producing toxicity), reduced effectiveness of BMPs

• More research needed

0

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10-Jan 24-Jan 07-Feb 21-Feb 07-Mar 21-Mar 04-Apr 18-Apr

Date

Cum

ulat

ive

Mas

s C

hlor

ide

(kg)

Snow storage runoff treatment train

Chloride runoff from snow storage site

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Some UD Research Challenges

• Models vs. prototypes: While the value of studying processes under controlled conditions is indisputable, most lab studies ignore some important field process conditions, and field proofs are needed (example: boundary conditions in lab studies of porous pavements)

• Site vs. catchment: Vast majority of BMP/LID studies investigates mass balance of single facilities

• Water management goals are much broader – how such measures protect the whole catchment and its resources; what is the minimum uptake of BMPs to achieve these goals?

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Study Duration

• Much of the BMP/LID research is of short duration, may miss gradual deterioration of performance due to:

– Reduction in percolation rates due to clogging, or biofilm growth – Reduction in sorption sites – Chemical transformation processes – Reduction in treatment volume by sediment accumulation

• Need triggers for maintenance operations, going beyond cost-benefit analysis – including environmental risks

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Frequency of BMP maintenance

BMP Facility Frequency of maintenance

Large maintenance

Curb inlet screens 2-4 times per month

Cartridge sand filters

2-3 times per year

Hydrodynamic separators

Once a year

Rain gardens Several times per year

Detention ponds 2-3 times per year Sediment removal 10-30 years

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Measuring SWM Research Accomplishments

• Different criteria, e.g., biological community assessment, return of critical species, or DCIA

• In research, papers proliferating in great numbers (interest in the urban environment, general availability of funding)

• For many papers, it is becoming challenging to identify how they serve the end-users

• The gap between the end users and researchers grew to the point that we need “knowledge translation” providers

• Scientific journal revenue estimated at $6 billion annually, With high profit margins

• The business model is unusual – the valued product (new knowledge) is provided free, the quality control depends on engaging volunteers and competitors

• Changes are occurring in the form of open-access publishing; which depends on paper fees for financing, hence a potential conflict of interest

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Conclusions

• Remarkable progress in stormwater management has been achieved during the past 50 years,

• Requirements on SWM are changing as a result of: – Dynamic nature of urban areas – Climatic changes (particularly precipitation) – Changing releases of pollutants, and – Changing objectives of UD operation arising from changing

expectations of the urban population

• Thus, demands on innovation and research will continue