Evaluation of Etobicoke Exfiltration System in The City of Barrie • Parto Peyvandisani • MEng student, Environmental Engineering, Ryerson University • Toronto, Ontario • BEng, Civil Engineering, University of Birmingham, 2013 1
Evaluation of Etobicoke Exfiltration System in The City of Barrie
• Parto Peyvandisani• MEng student, Environmental
Engineering, Ryerson University• Toronto, Ontario• BEng, Civil Engineering, University of
Birmingham, 2013
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Evaluation of Etobicoke Exfiltration System in the
City of BarrieParto Peyvandisani
Prof. James Li and Dr. Darko Joksimovic
Ryerson University, Toronto, Canada
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Presentation Outline
• Background• Aim of the study• Modelling Scenarios• Validation• Screening for retrofit opportunities• Conclusions
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Background• Etobicoke exfiltration system (EES)
was constructed as a conveyance system control in 1993 in the City of Etobicoke (now Toronto)
• Runoff/Capture of 15mm storm• Perforated pipe conveys flows to
the void space provided by granular trench
• Exfiltration to the surrounding soil• Recharge the groundwater
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Advantages
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FOUR SEASONS RECHARGE GROUNDWATER
FLOODING, WATER QUALITY, EROSION,
ETC.
NO SURFACE SPACE WITHIN THE RIGHT-
OF-WAY
ECONOMICAL
Limitations
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PERCOLATION RATE > 15 MM/HR
GROUNDWATER LEVEL > 1M BELOW BEDDING
LOCAL RESIDENTIAL ROADS
Aim of this studyEvaluate the runoff control performance of EES retrofit• focus on quantity control • Kidd’s Creek watershed area in the City of Barrie Methodology:• develop a SWMM model to simulate the EES retrofit• validate the modelling approach using flow test data• screen for retrofit opportunities in the Kidd’s Creek drainage area• apply the EES model and analyze results
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EES Modelling Approaches
Orifice – storage – pump (older version of SWMM)SWMM LID module (infiltration trench)This study:
- Scenario 1: storage unit with seepage- Scenario 2: conduit with seepage
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Scenario 1:Storage Unit with seepage
MH2: Upstream manholeMH3: Downstream manholeC1: Storm sewerOrifice 1 & 2 : Connections to perforated pipesSU: Storage UnitC2 and outfall: Dummy conduit
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Exfiltration Storage Model
Exfiltration from a storage unit
• Equation 1. Green Ampt Infiltration Rate
• 𝑓𝑓 = 𝐾𝐾(𝜓𝜓𝜓𝜓𝜓𝜓𝐹𝐹 𝑡𝑡
+ 1)
• Equation 2.The Cumulative Infiltration
• 𝐹𝐹 𝑡𝑡 = 𝐾𝐾𝑡𝑡 + 𝜓𝜓𝜓𝜓𝜓𝜓ln(1 + 𝐹𝐹 𝑡𝑡𝜓𝜓𝜓𝜓𝜓𝜓
)
Where • K= hydraulic conductivity• Ψ= Suction head• θ= Soil moisture content
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Scenario 1:Storage Unit with seepage
Storage Curve:
• Tabular Curve• Trench depth: head difference of MHs + Inlet offset of the conduit
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0102030405060708090
100
0 0.2 0.4 0.6 0.8 1 1.2 1.4
Surf
ace
Area
(m2)
The depth of Water(m)
Tabular Curve, between two manholes
Wedge storage
Scenario 2: conduit with seepage
MH2: Upstream manholeMH3: Downstream manholeC1: Storm sewerOrifice 1 & 2 : Connections to perforated pipesC2 and outfall: Dummy conduitC3: Conduit with seepageJ1: Dummy manhole
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Scenario 2: conduit with seepage• It is suitable to represent
perforated pipes or natural channel
• The seepage loss rate would depend on:
1- The flow depth in the conduit
2- The hydraulic conductivity for the surrounding soil
3-The variation in moisture content of the soil
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Leaky Conduit Modeling
Scenario 2: conduit with seepage
• It does not present continued exfiltration into the surrounding soil
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Validating the Modelling approach
• Fire hydrant test on the original EES
• Flow and level measurements between MH2 and MH3
• Duration of the flow test was about 110 minutes
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Monitoring Location & Equipment• Pressure
Transducers in the upstream and downstream of the stone trench
• Data logger in manholes
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Validation Result
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
Wat
er D
epth
(m)
Time(min)
Water Depth in the Stone Trench
Measured Data Simulation Result
ValidationResult
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28
11
31
0
5
10
15
20
25
30
35
Exfiltration loss (m3) Final stored Volume (m3)
Volu
me
(m3)
Exfiltration Loss AnalysisExperimental Result Simulation Result
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Sensitivity Analysis
0
50
100
150
200
250
0
5
10
15
20
25
30
Sand LoamySand
SandyLoam
Loam Silt Loam SandyClay Loam
Clay Loam Silty ClayLoam
SandyClay
Silty Clay Clay
Hydr
aulic
Con
duct
ivity
(mm
/hr)
Exfil
trat
ion
loss
(m3)
Sensitivity Analysis
Exfiltration loss(m3) in SU Hydraulic Conductivity(mm/hr.)
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Seepage Properties Sensitivity Analysis
Pros and Cons
The exfiltration rate is compatible with Green Ampt method
Flooding occurs when the inflow rate to the manhole > inflow to the main storm sewer in case of large event or when there is a deficiency in the conventional system
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Flooding News, Barrie
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Screening for retrofit opportunities
• All local public roads
• Wellhead zone A-B is excluded
• The groundwater > 8 ft is considered
• Storm sewer installed before 1998 are considered
• Pavement installed before 1993 are considered
• Soil group A and B have been selected
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Kidd’s Creek Watershed Area• Area 26-ha
• 47% imperviousness
• 33 EES retrofit
• Required trench depth achieved for 25 mm design storm
• SCS-5 year-6 hours design storm event (present and future conditions)
• Peak flow analysis for 72 hours
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EES locations throughout Kidd’s Creek watershed area
Results
0%
20%
40%
60%
80%
100%
120%
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33
Max
imum
Per
cent
Util
ized
Link ID
Maximum Storm Sewer Utilization
Conventional EES
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Results
0
10
20
30
40
50
60
70
SU1 SU2 SU3 SU4 SU5 SU6 SU7 SU8 SU9 SU10 SU11 SU12 SU13 SU14 SU15 SU16 SU17 SU18 SU19 SU20 SU21 SU22 SU23 SU24 SU25 SU26 SU27 SU28 SU29 SU30 SU31 SU32 SU33
Max
imum
Per
cent
Ful
l
Trench Storage ID
Maximum Utilization of Trenches
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ResultsOutfall flow rate to the creek :
• Conventional system: 2,612 L/s
• With EES: 1,499 L/s
• 42 % reduction in outlet to the creek
• Exfiltration loss: 2,542 m³
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Outfall flow rate (L/S) to the creek
Conclusions
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Kidd’s Creek watershed would benefit from significant capacity improvements through
EES retrofit
Storage node with seepage appropriately models EESLimitations due to HGL simplification (horizontal) in the trench: overestimate levels, possible node flooding
Recommendations and Further Studies
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New experimental data needed to validate the modelling approach
Enhance SWMM to explicitly model buried, exfiltrating stone trench hydraulically
Acknowledgement: City of Barrie
Thank you
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