Design of a Minor System Using XPSWMM Software

Prepared for Dr. Imtiaz Shah, CEE 9632 Advanced Storm Water Management

Prepared By: Fatima Elkhair

Aronne De SouzaMuhammad UmarStewart Handrahan

Rongtian FengJM Rakibul Hasan

December 2, 2014

Content• Introduction• Advantages of XPSWMM• Site Plan• Objectives• Design Requirements• Design Methodology• Layout and Design of Conduit Network• Modelling Details• Results & Discussion• Alternatives & Value Engineering• Conclusion

Introduction

• The Site– Next Phase of a residential subdivision in London Ontario. – Approx. 4.6 ha of total drainage area

• Scope of Work– Design of a minor system to meet City of London design guidelines for a 2

year storm – Briefly discuss some value engineering/LID alternatives (concept level only)– End of pipe is a wet pond designed for 250 year storm– Flows greater than 2 year storm event will be carried by the major system

Introduction

• Minor System• Collects Stormwater runoff of 2 to 10 years return period

– Urban minor system consists of • curbs, gutters, catch basin inlets, storm sewer, swales, ditches

– Rural minor system consists of• roadside ditches, minor drainage swales

Introduction

• XPSWMM

– Comprehensive strorm, sewer and flood modeling software– Create dynamic hydrologic or hydraulic modeling– Calculates 1D and 2D hydraulic performances– Simulates natural runoff to design drainage system– Does water quality analysis

Advantages of XPSWMM

• Physical reality• Regulator approval• Easy sharing of model • Integration of GIS systems• Time Saving• Economical Solution

Site PlanArea No. Area (ha) c

A1 0.514 0.55

A2 0.928 0.55

A3 0.341 0.55

A4 0.109 0.55

A5 0.29 0.55

A6 1.073 0.75

A7 0.767 0.75

A8 0.62 0.55

A9 0.022 0.55

Objectives

• Determine the most economical and sustainable design of the minor system

• Meet requirements given by regulatory authorities for the site

Design Requirements• From City of London SWM Guidelines :

– Manholes must not flood during a 2-year storm event.– Capacity > Flow– Velocity of flow must be between min & max

• Vmin 1.0 m/s• Vmax

– 4.5 m/s (300 mm to 825 mm)– 6.0 m/s (> 825 mm)

– Minimum slope • 0.54% (300 mm)• Slope based on velocity (>300mm)

– Min embedment depth = 1.5m– Wet pond permanent pool elevation = 314.75m

• Standard OPSS conduit and catch basins must be used

Design Methodology

• 2 Year Storm, City of London parameters • Catchment Areas based on economical grading, provided by others• Run-off for each catchment area generated by Rational Method – Q = 0.0028*C*I*A– C: runoff coefficient ranges from 0.55 to 0.75 (provided by others)– I: generated from IDF parameters provided by City of London SWM

Guidelines– A: catchment area (provided by others)

• Standard OPSS concrete CB/CBMH/MH and circular conduit

Layout of Conduit Network

Design of Conduit Network• Layout based on grading plan (lengths and routing provided)• Network input into XPSWMM model (nodes & links) • Flows manually input into catch basins (nodes) in XPSWMM model• Flow simulation performed by software, given initial conduit sizes and inverts. Size

and slope (inverts) adjusted downstream if upstream manholes flooding during a given simulation. (iterative process)

• Capacity of each conduit based on Manning’s Equation for flow– Q = (1/n)*A*Rh2/3*S1/2

• Once the system is not flooding, velocity for each conduit section is checked against min/max velocity requirements. Conduit size and/or slope adjusted accordingly by iterative process

Defining Nodes and Conduit Profile

Flow Route 1

Dynamic Long Section 1

Flow Route 2

Dynamic Long Section 2

Flow Route 3

Dynamic Long Section 3

Results (Running The Model)

Results Area No. Q (m3/s)

A1 0.051196

A2 0.092431

A3 0.033964

A4 0.010857

A5 0.028885

A6 0.145736

A7 0.104175

A8 0.061754

A9 0.002191

Discussion of Results

• Manholes do not flood during 2 yr storm event• Capacity > Flow• Velocity between min. & max. guidelines• Min. slope achieved on all but one conduit section• Min. ground cover (1.5m) could not be achieved for – 0810, 2010, 30PD– Grading should be altered to achieve min. cover over these conduit

sections, or alternatively provide insulation

Design Alternatives / Value Engineering

• Conduit 1232 & 3230 require 500mm conduit size– The minimum size is 300mm – Q = CIA; therefore Q is directly proportional to C– LID methods should be evaluated to attempt a reduction in the 2 yr

run-off so that 300mm conduit sizes can be used– Possible LID options include lot-level conveyance (roof water barrels

or cisterns), permeable pavements, bio-swales, infiltration trenches, etc.

– Cost benefit analysis should be performed

Conclusion

• An effective design of the minor system is presented, from the XPSWMM modelling.

• The design presented meets the objectives required by the City of London SWM Guidelines.

• Alternatives should be evaluated to reduce cost of the minor system while leading to an overall system that better resembles the natural hydrologic cycle.

THANK YOU

Questions?