MB-draft-04

1 Introduction

1.1 Background

Windsor is the one of the most important border crossing between Canada and the

United States. More than 16 million cars, trucks and buses travel through the city each

year, representing approximately 33 per cent of Canada-United States truck trade. In 2001

alone, this two-way merchandise trade totaled at over $140 billion. Windsor's economy is

intricately linked with the international border crossing. As Canadian and American trade

and tourism increase through the years, projected traffic volume is also predicted to

increase. This has made it apparent to government and commercial officials that there is a

need for an additional border crossing which will have the capacity to handle the

projected traffic volume. The privately owned Ambassador Bridge currently spans across

the Detroit River and links up Detroit and Windsor traffic through the international border

crossing facilities on each side of the bridge. One of the main concerns associated to

Ambassador Bridge border crossing is that an urban road system links up with the

Ambassador Bridge as opposed to a Highways System. This means that before a driver can

reach the border crossing they need to cross several street lights within the city core. This

causes large traffic jams and impede on the overall traffic ease of the city. This is why the

new border crossing is intended to be directly linked to the Canadian and American

highway systems, such that traffic flow within Detroit and Windsor is much more feasible.

The Detroit River International Crossing Project (DRIC) is a large scale interdisciplinary

engineering project currently valued at over one billion dollars. Construction of the New

Detroit-Windsor border crossing is intended to begin in late 2009. This border crossing will

be built in stages such that the traffic flow matches the facility capacity. Once the

preliminary design is complete, the project will be ready for a construction bid. The border

crossing is intended to be built as a showcase of leading edge innovation in: water

resource engineering, traffic engineering, environmental engineering, energy efficiency,

logistics and security.

1.2 Purpose and Scope

The purpose of this report is to develop the design of a storm water management system

for the projected Windsor Detroit International Border Crossing Plaza site. This report will

contain two parts: Firstly, a preliminary report developing and selecting alternatives

identifying the hydrological challenges of this project. Secondly, a detailed design report

dealing with the hydrological challenges of the preliminary report .In addition to that the

technical report should follow best management practices (BMPs) meeting regulated

design standards outlined in the 2003 Ministry of the Environment storm water

management guideline.

1.3 Preliminary Report Overview

2 Site Description

The western edge of the proposed site runs along the Detroit River. The most Southern East

point is located at the intersection of Ojbway Parkway and Broadway Street. The site

measures 54.3 ha. By looking at geotechnical samples and grade pictures of surrounding

site, the pre-existing site terrain inclines towards the South Eastern edge of the proposed

site. At the same time, it is fairly flat; the rough elevation difference over 1.45km is 3.5 m.

Morrison Hershfield provided design drawings which outlined the proposed site borders

and area. The calculations and design specifications will be based on those drawings. The

map below was obtained from Google EarthTM.

Figure 2.1 - Plaza Site Outlined

2.1 Existing Land Use and Vegetation

Since the percentage of the paved road is very small when compared to the landscape

area, the resulting runoff coefficient for the existing condition is assumed to be cultivated

land. So C = 0.34 and 0.47 for 5 year & 100 year storm event respectively.

2.2 Existing Soil and Groundwater Condition

Fennie

2.3 Topography and Surface Water Drainage

Preliminary Drainage Area:

According to industry standards and property law; when a new structure is built on an

undeveloped site, it is critical that the new development does not cause excess rainwater

to fall into neighboring properties and cause them flood damage. The proposed site is built

on a relatively undeveloped site. The construction of the border crossing plaza without a

storm water management system would definitely cause excess storm water to flow to

neighboring sites. There would be an excess of storm water after construction because the

run off coefficient for the soil would increase. The runoff coefficient of asphalt is 0.90, this

means that during a typical storm, 10% of the water on the asphalt will be absorbed by the

ground, 90% of the water would need to be diverted elsewhere. Therefore, the post

development coefficient will be higher than the pre-development coefficient. More water

will need to be routed properly.

Figure 3.03 is an elevation map outlining a rough contour of the Border crossing plaza site

and its surrounding area. This map was obtained from The National Resources Canada

website. The drainage area outlined on figure 3.03 is based on the natural flow path of

water and existence of previously built storm water structures. To illustrate, if a piece of

neighboring land has a slope facing the border crossing site, it will be considered part of

the total drainage area. However, if a neighboring storm water management pond exists in

front of the area with a slope facing the border crossing plaza site, the land will not be

considered part of the drainage area. In addition to that, if there is a piece of neighboring

land that is connected to a piece of land which will lead into the border crossing plaza area,

it will be considered part of the drainage area.

Figure 2.03: Outlined drainage area based on rough contour outline

Figure 3.04 outlines smaller drainage areas. These areas are determined based on the flow

path of rainwater. Figure 3.04 also outlines the existing flow path of water with arrows. By

following Figure 3.04 we see that water from total drainage area will naturally flow into the

Detroit River.

Figure 2.04: Existing flow path of water

The objective of this project is to create a storm water management system with a 100

year storm capacity. Water will need to be routed properly according to where it lands

relative to the border crossing plaza site. Figure 3.05 outlines how the drainage areas will

be divided:

Figure 2.05: Divided Drainage Areas

Main Drainage Area A: This area is the most important drainage area of this project. The

rainwater that lands on this area will need to be processed for quality and quantity

volumes for up to a 100 year storm. As discussed in the Preliminary report, this area will

include a main channel which will divert all rain water into the main wet ponds. The ponds

the runoff will go to will depend onthe rainfall intensity.

Secondary Drainage Area B and C: These secondary areas represent the drainage areas

outside the project area. The Runoff from these areas will simply need to be diverted into

the Detroit River as Quality requirements do not apply.

3 Stormwater Management Design

3.1 Problem Definition

Water Quality:

The Canadian border crossing site is located in an industrial area which is also connected

two major highways. This means that chemical spills can be expected in addition to that

surrounding industrial building are built with older generation construction materials

such as asbestos, lead and PCB’s. During a rainfall, theses chemicals can make their way

into the leachate and contaminate the water system i.e: the Detroit River. This will

ultimately endanger the ecosystem and drinking water source.

Sediment Control:

Water is a highly abrasive medium and with enough time, water will shape any material

to its movement. Water abrasion of roads and earth under the roads can compromise

the structural integrity of any driving surface. Earth abrasion can create pot-hole, earth

vacancies and landslides. For the safety of drivers these large driving surfaces cannot

afford to be structurally compromised, secondly it is also important to mitigate the cost

of repairing damaged driving surfaces.

In addition to this, it is important to note that, storm water from the North and the East

sides of the site may contain large amounts of sediments during the construction stage.

This sediment laden runoff can cause sewers to be filled with sediment and destroy fish

habitat in the river.

Road Safety:

The border crossing area is intended to be used as a high traffic area for vehicles of all

sizes, it is imperative that storm water be properly drained such that driving surfaces are

un-slippery and safe enough to drive on. In addition to that, we want to make sure that

during a heavy 100 year rainfall, water is properly diverted from driving surfaces and

vehicle submersion in water is unlikely.

3.2 Considerations

The Canadian Plaza is approximately 54.3 ha, consisting primarily of pavement and

commercial buildings. Stormwater management for the Plaza requires quality, quantity

and erosion controls for the peak flows from the Plaza, as the increase in impervious

area will increase the overall peak flows from the site, as well as the overall pollutant

loading. This will lead to erosion issues downstream, as well as impact the ecological

condition of the Detroit River.

The Canadian Plaza consists mostly of asphalt pavement and building rooftops. The

principle concern for large sites with a high imperiousness and vehicular traffic is

providing stormwater treatment for frequent vehicular pollutants (oil, gasoline, coolant,

etc), roadside grit and garbage (gravel, sand, and cigarette butts), infrequent pollutant

spills, and controlling increase of overland runoff to the receiving watercourses.

Enhance Quality treatment will also be required in accordance to the MOE document “

Stormwater Management Planning and Design Guidelines”, date 2003, Level 1

protection which states removal of a minimum of 80% total suspended solids (TSS). It is

to be designed based on a 100-year design flow and be controlled for all storm events

up to and including 100-year storm event.

Based on the results and the site conditions, the solutions retained were storage

SWMP’s and oil/grit separators. The storage SWMP’s will provide quality treatment,

erosion control and quantity control for the catchment area. Storage SWMP’s will be

utilized to match existing peak flow conditions to the receiving watercourses in an effort

to emulate existing conditions within the watersheds. Oil/grit separators will provide

quality treatment to the upstream catchment areas.

The stormwater management plan consists of creating two ponds in the green spaces

south of the proposed plaza and a linear open channel/wetland feature. These green

spaces can be converted to stormwater management facilities utilizing the existing drain

to connect the facilities, discharging to the Detroit River via an outlet channel. The pond

system provides closer outlets for the sewer system, lowering the overall grading

requirements of the Plaza. The linear feature would be designed such that there would

always be an open portion to ensure that there is no restriction to the conveyance of

flow from one pond to the other. The pond system would control the release rate to

the Detroit River. In the event of a contaminant spill with the Plaza, a shut off valve or

alternative damming procedure will be required within the pond.

5 Design

5.1 Site Overview:

This section will include the technical design of the major storm water management structures

built within the border crossing plaza site. The design portion be split into two parts the design

of Storm water management system within the Main Drainage Area A and the design of the

storm water management structures outside the plaza area: Secondary Drainage Area B and C.

5.2 Main Drainage Area A:

Pond and Main Channel Positioning

From the conceptual report, the BMP’s of our storm water management system would

include ponds and a large channel leading up to the pond.

The quality and quantity pond would be located at the most western edge of proposed site

as shown on Figure 5.02 because:

1. Construction contingencies only allow the wet pond to be located at the western edge

of the site

2. Water has a much shorter distance to flow into the Detroit River if there is a larger than

expected storm that occurs.

3. Post development slope will lead water towards pond

The main storm water channel leading up to the pond will be placed along the southern

edge of the site. The channel will be in this configuration because:

1. The channel will be at the bottom of the site slope in such a way that excess rainwater

is forced to flow towards channel and does not pool in critical traffic areas

2. It will run along the greatest length of the site, catching a majority of the excess

rainwater.

3. The border crossing plaza has the greatest free space allocation along the southern

edge of the site

Figure 5.02: Channel and pond configuration

5.2 Main Channel Design

Pre-development conditions:

Based on site elevation provided by the city of Windsor, it is obvious to see that the site is

highly flat. The existing elevation difference between the highest and lowest part of our channel

is 2.72m over a 1110m span. The MOE 2003 storm water management guideline outlines that

grass swales are ideal storm water management structures for flat terrain. Thus the main

channel leading up to the pond will be a grassed swale. Grass swales also work effectively in

the quality processing of runoff.

The length of the swale was determined based on a preliminary drawing provided by Morrison

Hershfield. This length extends from the swale entrance to the projected pond entrance along

the southern edge of the site. The elevation data was obtained from the city of Windsor

corporation website.

5.2.1 Design Constraints:

The design constraints of the proposed site are mainly the flatness and ground water table

elevation. Figure 5.05 describes the design constraints of the channel. The highest elevation at

the eastern swale entrance is 178.72m. The current ground level of the pond entrance is

176.00m. This point is highly important, as it will determine the level at which the Main Swale

will enter the pond. The Detroit River Website measured that the highest water level of the

ground water table to be 3m below ground level. The MOE guideline also states that the storm

water management pond must be built 0.50m above the ground water table to prevent ground

water intrusion. Therefore the lowest point of the wet pond is 173.50m. Through shear

optimization and coordination a 2.25m allowance is required for the pond design. Thus the

channel floor cannot be lower than 175.75m. The Main Drainage Swale and Wet Pond design

will be based upon the constraints outlined above.

Figure 5.05: Existing main channel elevation profile

5.3 Channel Design using Manning’s equation:

Now that the Elevation profile for the Main swale is known, a swale height can be

determined based on the designed constraints outlined in section 5.2.1. By looking at

Figure 5.05 the height available for between the swale floor at the pond entrance and the

ground level of the most eastern point of the swale is 2.98m. The MOE also states that a

one foot clearance between the 100 year water elevation of the swale and the ground level

above the swale is required. Thus, the swale design requires that the sum of the 100 year

water level of the swale and the elevation difference due to the channel slope not exceed

2.675m. Through optimization of the manning’s equation described below it was found

that the swale would not exceed 1m in depth for a 100 year storm and that the optimal

slope is 0.125%.

The Manning’s equation is industry recognized and will be used to determine the water

level of our channel for a 100 year storm. The water elevation is a key parameter of

determining the main swale cross-sectional dimensions. The equation is as follows:

V= kn∗R

23∗S0.5

By multiplying both sides by the area of the channel the modified Manning’s equation is:

Q=1.49n

∗A R( 23 )S0.5

Where n is the roughness coefficient, A is the cross sectional area of the channel, R is the

Hydraulic radius and S is the slope.

Q: 100 year Post Development flow m3/s. For our site area it is 9.3305m3/s

n: Mays Water Resources Engineering defines n = 0.03 for grass channels

A: MOE 2003 STMWTR Guideline specifies that the swale will need a trapezoidal form thus

area is defined as:

A=(B+Zy) y

B is defined as the Base of the swale. MOE 2003 STMWTR Guideline specifies 6m. However

due to the fact that the site is very flat we will use a swale base of 7m

Z is defined as the horizontal distance per meter of the side slope MOE 2003 STMWTR

Guideline specifies 2.5m

y is the height and water level of the trapezoid for a 100 year storm it is the unknown we

are solving for

Figure 3.06 swale

R:Hydraulic radius for a trapezoid defined as:

R=¿

S: Channel Slope, after optimization the best slope to use given the site constraints is

0.125%. This is a very minor slope however given the water table depth, site elevation and

resulted channel depth this value is the most optimal.

Now that all values are defined we solve for y in the following equation:

0=(B+Zy ) y ( (B+Zy ) y

B+2∗y (1+Z2 )0.5 )23−Q∗n/(1.49∗S0.5)

Due to the fact we will be designing many channel in this project we have created a

manning’s equation worksheet on Excel to solve for Y. The 100 year Main Drainage Swale

Depth is YMDS=1.00m

6m Base (MOE 2003)

2.5:1m Side Slope

Unknown: Y

Foot Clearance

For a 5 year storm we use Q=4.4675m3/s

Y5MDS=0.67m

Now that the water level is found, figure 3.07 outlines the profile view of the section

Figure 3.07: Post Development Swale Profile

Figure 3.08: Main Drainage Swale Cross sectional Dimensions in Meters

Section 6.00 Secondary Drainage Channels:

Figure 3.04 and 3.05 demonstrates there is a considerable amount of runoff that will find itself draining unto the border crossing plaza site due to the pre existing drainage pattern discussed in Section 2.3 . By official standards and law, the natural flow pattern of neighboring sites cannot be interfered with. However, even though the water must pass through the bordercrossing site, the runoff does not need to be processed to meet provincial quality standards as opposed to the runoff landing on the border crossing plaza site which do.

This design section will consider all runoff predicted to enter the site from Secondary Drainage Areas B and C, refer to Figure 2.05. Figure 6.09 is an illustrative diagram of the secondary drainage channels and swales of the site which will route the runoff for up to a 100 year storm directly into the Detroit River.

There will be 4 channels which will need to be designed:

-The Minor Drainage Swale represented by P6-P5-P4-P3-P2 will route runoff from Secondary Drainage Area B into Major and Minor Drainage Swale MMDS.

-The Major Drainage Swale represented by P6-P7-P8-P9-P10-P11 will route runoff from Secondary Drainage Area C into the Major Drainage Culvert MajDC.

-The Major Drainage Culvert represented by P2-P7 will route runoff from MajDS into the Major and Minor Drainage Swale MMDS. The culvert will be placed under ground such that it does not mix with the runoff expected to land on the main border crossing plaza site. The culvert will be underground and incased with cement.

-The Major and Minor Drainage Swale represented by P1-P2 will route runoff from MajDC and MinDS into the Detroit River.

Figure 6.09 Secondary Drainage Channel Layout

Figure 6.091 Will outline this Drainage pattern more clearly

Figure 6.091: Secondary Drainage Channel Outline

1. Minor Drainage Swale MinDS:

The line representing P6-P5-P4-P3-P2 will collect the water from Secondary Drainage Area B and route it to point P2. Figure 6.10 is pre existing elevation profile of Line P6-P5-P4-P3-P2. This line will represent the Minor Drainage Swale MinDS

Figure 6.10: Pre existing elevation profile of Line P6-P5-P4-P3-P2, MinDS

2. Major Drainage Swale MajDS:

The line representing P6-P7 will collect the water from Secondary Drainage Area C and route it to point P7 which is the entrance of the major drainage culvert MajDC. In addition to that, the line representing P7-P8-P9-P10-P11 will collect the water from Secondary Drainage Area B and route it to point P7 which is the entrance of the major drainage culvert MajDC aswell.Figure

6.11 is the pre existing elevation profile of Line P6-P7-P8-P9-P10-P11 which will represent the Major Drainage Swale MajDS.

Figure 6.11: Pre existing elevation profile of Line P6-P7-P8-P9-P10-P11, MajDS

3. Major Drainage Culvert MajDC:

The line representing P2-P7 will collect the water from MajDS and route it to point P2 which is the entrance of the Major and Minor Drainage Swale MMDS. Figure 3.12 is the pre existing elevation profile of Line P2-P7 which will represent the Major Drainage Culvert MajDC.

Figure 3.12: Pre existing elevation profile of Line P2-P7, MajDC

4. Major and Minor Drainage Swale MMDS:

The line representing P1-P2 will collect the water from MinDS and MajDC and route it directly into the Detroit river. Figure 3.13 is the pre existing elevation profile of Line P1-P2 which will represent the Major and Minor Drainage Swale MMDS.

Figure 3.13: Pre existing elevation profile of Line P1-P2, MMDS

Section6.2 Secondary Drainage Channels Design Constraints:

As described in the Main Channel Design, the Border crossing plaza area is very flat, elevation is a primary design consideration. In the main channel design section 5.2.1 the Ground Water Table was the elevation constraint, however for the secondary drainage channels, the Detroit River water level is the design constraint. The channel floor must be higher than the highest Detroit water elevation. The highest water level report of the Detroit River is 175.00m. Thus the channel floor cannot be lower than 175.00m.

The manning equation parameters will be determined based the River Water Level and slope elevation difference. The design begins by looking at the longest path runoff will have to travel before reaching the river. By investigating Figure 3.09 that path is obviously P11-P10-P9-P8-P7-P2-P1. By combining the elevation profile of MMDS, MajDC and MajDS. Figure 3.14 Displays the P11-P10-P9-P8-P7-P2-P1 elevation profile.

Figure 3.14 Elevation Profile For P11-P10-P9-P8-P7-P2-P1.

Figure 3.14 clearly outlines there is a 3.30 meter difference between the highest and the lowest point of the Secondary Drainage Channels. In design it is important to consider that any swale design must have a minimum of a 30.5cm clearance. We will also use a 0.125% slope similarly to the Main Channel Design. The elevation difference due to the slope at 0.125% is 2.16m. Thus the remaining elevation availability for the 100 year storm water level in the swales and culvert is 83.25cm.The 0.125% slope was obtained by optimization using the manning equation excel worksheet. Displayed in the appendix.

Section 6.3 Secondary Drainage Channel design using Manning’s equation

The following section will explain the inputs of the Manning’s equation

3. 06.01 Minor Drainage Swale (MinDS):

The MinDS will route all the excess rainwater from Minor Secondary Drainage area to MMDS at point P2. The Minor Secondary drainage area was determined to be 77642m2, with 15695m2 paved with concrete (C=0.95) and 619500m2 with grass (C=0.47). The intensity of a 100 year storm is 75mm/h for 35 minutes. By using Rational method (Q=CiA) the resulting flow is 2.3107m3/s. by using approached outlined in Section 3. 05.03 inputs in the Manning’s equation are as follows: Q=2.3107m3/s, n=0.03, S=0.125%,Z=2.5m, B=6m. After applying Manning’s formula, we solve for y=0.50m

Figure 3.11 outlines the MinDS cross section

Figure 3.11: MinDS cross section

3. 06.02 Major Drainage Swale (MajDS):

The MajDS will route all the excess rainwater from Major Secondary Drainage area to MMDS, P7.The Major Secondary drainage area was determined to be 434983m2, with 109285m2 paved with concrete (C=0.95) and 325698m2 with grass (C=0.47). The intensity of a 100 year storm is 75mm/h for 35 minutes. By using Rationnal method (Q=CiA) the resulting flow is 5.3521m3/s. by using approached outlined in Section 3. 05.03 inputs in the Mannings equation are as follows: Q=5.3521m3/s, n=0.03, S=0.125%,Z=2.5m, B=6m. After applying Manning’s formula, we solve for y=0.79m

Figure 3.12 outlines the MajDS cross section

Figure 3.11: MajDS cross section

3. 06.03 Major Drainage Culvert (MajDC):

The Culvert will route all the excess rainwater from MajDS to the MMDS. The culvert will be designed to go underneath the border crossing plaza’s roads and buildings it will be incased in reinforced concrete with strength able to sustain the weight of the largest truck multiplied by a safety factor of 3. The culvert will be trapezoidal as all of our other channels are trapezoidal: The inputs of the Manning’s equation are as follows: Q=5.3521m3/s, n=0.017 (for Sewer Concrete), S=0.125%, Z=2.5m, B=6m. After applying Manning’s formula, we solve for y=0.52m

Figure 3.12 outlines the MajDC cross section

Figure 3.12: MajDC cross section

3. 06.04 Major and Minor Drainage Swale (MMDS):

The Swale will route all the excess rainwater from surrounding sites, P2, to the Detroit River. The flow value is simply the sum of the 100 peak flow for MinDS and the MajDS which is Q=7.6628m3/s. The culvert will be trapezoidal as all of our other channels are trapezoidal: The rest of the inputs of the Manning’s equation are as follows: n=0.03 (for Grass) , S=0.125%,Z=2.5m, B=8.5m (minimum width given elevation constraints). After applying Manning’s formula, we solve for y=0.68m

Figure 3.13 outlines the MMDS cross section

Figure 3.13: MMDS cross section

3.07 Post Development Storm Water routing

In Figure 3.10 we see that the total drainage area has been split into 3 main areas: Our site

are, The Major Secondary Drainage Area and the Minor Secondary Drainage.

Using rational method we have found that the

4 Stormwater Management Ponds

1.0 Water Quantity Control

Rational method was used in determining for the peak flows of both pre-development

and post-development along with storage volume.

Qpeak = C*i*A

where Q - the peak flow (m3/s)

C - runoff coefficient

i - intensity of rainfalls (mm/hr)

A - the drainage area (ha)

The drainage area to be used in the design should include all those areas which will

reasonable or naturally drain to the storm system. The area term in the Rational Method

formula represents the total area tributary under consideration. For this proposed site,

the drainage area is 63.8965 ha (see Figure X).

As noted in Section 2.1, the runoff coefficients used to determine pre-developed flows

are C = 0.34 for 5 year event, and C = 0.47 for 100 year event. For the post-development

conditions, as depicted in FigureX, approximately 29 ha of proposed site will be covered

in asphalt, with a further 1.7 ha of building area. The remaining 33.2 ha of the site is

proposed to be landscaped area. The proposed site has a composite runoff coefficient

value of 0.5472 for 5 year and 0.7009 for 100 year (please refer to calculation in

Appendix X) and has an increase runoff potential compared to existing conditions. The

final drainage area breakdown for the post-development condition, along with their

coefficients is shown in Table 3.1.

Table 3.1 – Drainage Areas, Land Covers and Runoff Coefficients for Post-development

Description Area (m2) Area (ha)Runoff Coefficient

5 year 100 year

Building 16629 1.6629 0.8 0.97

Paved Area 290083 29.0083 0.77 0.95

Landscape 332244 33.2244 0.34 0.47

Source: Water Resources Engineering by Larry Mays 2005

The rainfall intensity and time of concentration were determined from intensity

duration-frequency curve (IDF curve).

Under the requirement of City of Windsor, 5-year and 100 year storm events are needed

to be taken into account. Time of concentration is the time required for flow to reach

the pond from the most remote part of the drainage area. Upland method was used.

As stated in the “Water Resources Engineering” by Larry Mays 2005, upland method is

based on defining the time of concentration as a ratio of the hydraulic flow length to the

velocity.

Tc = L / (3600 * V)

where Tc - time of concentration (hrs)

L – hydraulic flow length (ft)

V – velocity (ft/s)

The velocity can be estimated by knowing the land use and the slope (see Fig. 3.1 in

appendix 1.)

Not finish yet

1.1 Water Quantity Control

1.1.1 Design Criteria

The Esssex County Conservation Authority requires that post-development peak flows

from the proposed development will not exceed their pre-development levels for

rainfall events up to and including the 1:100 year return period storm. Detention must

therefore be provided for any increase in post-development run-off.

The rational method was used in the determining pre- and post-development flows

along with storage volumes. Calculations are enclosed in Appendix x. Table 3.3.1

provides a summary of flows and storage volumes.

4.1 Design Details of Proposed Pond

The proposed quantity control pond is indicated on Drawing X. The tributary area of the

pond will be 63.9 hectares of which 33.2 hectares will be undeveloped. Drainage will

enter the pond via a 900mm diameter piped splitter storm sewer and via an overland

flow swale. Outlet control will be provided by means of a 650mm orifice placed within

the 875mm outlet pipe. The pond bottom will be graded at 0.50% to reduce the

possibility of ponding during low flow run-off events. The pond invert (174.7 m) is above

the level of the local water table (173.5 m), and the side slope gradient has been

reduced to 4:1 to ensure slope stability during water level fluctuations.

The proposed pond was calculated into the 5 and 100 year post-development and the

results were compared to pre-development peak flows. The pre-developed flows are

2.7759 m3/s and 6.2564 m3/s for 5 year and 100 year storm events respectively with an

existing runoff coefficient of 0.34 for 5 year and 0.47 for 100 year storm events and a

time of concentration of 35.3 mins. The post-development flows are 4.4675 m3/s and

9.3305 m3/s for 5 year and 100 year storm events respectively with calculated post-

development composite runoff coefficient of 0.5472 for 5 year and 0.7009 for 100 year

storm events and a time of concentration of 35.3 mins.

Table 3.3.1 – Summary of Quantity Volume and Peak Flows

Design Parameters

The design events used in the analysis were as follows:

5 Year City of Windsor Storm

100 Year City of Windsor Storm

Time of Concentration : 35.3 mins

Summary

Storm Events Storage Volume (m3)Peak Flows (m3/s)

Pre-development Post-development

5 yr 4783.6521 2.7759 4.4675

100 yr 8693.129 6.2564 9.3305

The maximum water level during the 1:100 storm event will be approximately 175.4 m.

Maximum water depth will therefore be 2.05 m. The detention storage is 8693.13 m3.

Detailed calculation can be found in Appendix 1. An emergency overland outlet from

the pond to the adjacent Detroit River will be available at the downstream end of the

pond at an invert of 174.3 m. Existing topography at this location will direct pond

overflow to the Detroit River.

ItemsPre-development Post-development

5 yr 100 yr 5 yr 100 yr

Area (ha) 63.8956 63.8956 63.8956 63.8956

Runoff Coefficient 0.34 0.47 0.5472 0.7009

4 Water Quality Control

4.2 Design Criteria

As indicated on Drawing X, the proposed development will discharge into Detroit River.

The report entitled “Practical Alternatives Evaluation Working Paper, Natural Heritage”

dated July 2007, was conducted to determine potential impacts on vegetation, wildlife,

and fish habitat, as well as fishery habitat classification. Information on fish habitat for

the receiving watercourses is integrated with the design of stormwater management

facilities, as adequate stormwater quality treatment from the proposed development

will be required for watercourses with sensitive fishery habitat. From this report,

Detroit River is classified as coldwater fish habitat.

Design criteria for water quality control features are included in “Stormwater

Management Practices Planning and Design Manual 2003” from Ministry of

Environment. This manual presents a method for determining the level of water quality.

Level 1 protection is the most stringent and involves the highest degree of stormwater

quality control, while Level 4 is least stringent. Due to the presence of a cold water

fishery, stormwater quality features for this project were designed using the Level 1

criteria.

Based on the above information, and with reference to Table 3.2 in the “Stormwater

Management Practices Planning and Design Manual 2003”, the following criteria apply:

210 m3/ha of permanent storage (dead storage)

40 m3/ha of active storage (live storage)

All storm runoff should be conveyed through an oil/grit separator prior to discharge into

the storm sewer system to remove suspended solids and oils. (see Appendix X for sizing

chart)

Appendix

Data Collection

The data information was gathered from MNR, DRIC draft environmental assessment reports and

discussion with Morrison Hershfield engineers.

The subsurface conditions in the Windsor area are characterized by flat-lying soils including:

Native deposits of sand and silt

Extensive deposits of clayey silt to silty clay beneath the sand

Bedrock is encountered at depths of 20 to 35 metres.

Beneath the existing pavement structures, topsoil and / or surficial fill materials, granular materials

consisting of sand and gravel, sands and silty sands were identified at a depth of approximately 0.3

metres below existing ground surface. Groundwater levels are expected to be located about 3 metres

below ground surface in the clayey silt and silty clay materials. The silty clay, clayey silt, sand and gravel

and sands are considered to be slightly erodible and the silty sands are considered to be moderately

erodible.

Qpre = Cpre * I * A

Qpost = Cpost * I * A

S = 0.5(Qpost * Tbase) – 0.5 (Qpre* Tbase)

Post-development Peak Flow, Qpost

Flow

Pre-development (100 years)

Area : 52.97 ha

Coefficient: 0.5 (assumption)

Tc : 10 mins

Intensity: 161.5 mm/hr

Qpre100 = 1/360 * 52.97 * 0.5 * 161.5 = 11.88 m3 /sec

Post-development (100 years)

Area Coefficient

Commercial Buildings: 1.66 ha 0.95

Paved Area: 33.67 ha 0.90

Landscape Area: 17.64 ha 0.25

Coefficient got from Water Resources Engineering by L. Mays

Cpost = (1.66 * 0.95) + (33.67 * 0.90) + (17.64 * 0.25)

52.97

= 0.6851

Qpost100 = 1/360 * 52.97 * 0.6851 * 161.5 = 16.28 m3/sec

5 years storm

Area : 52.97 ha

Coefficient: 0.5 (assumption)

Tc : 10 mins

Intensity: 102.8 mm/hr

Qpre5 = 1/360 * 52.97 * 0.5 * 102.8 = 7.563 m3 /sec

Qpost5= 1/360 * 52.97 * 0.6851 * 102.8 = 10.363 m3/sec

Orifice

Qo = c * A * sqrt(2 * g * H)

The smallest diameter orifice to ensure that clogging does not occur in a stormwater system is 75 mm.

The preferred minimum orifice size is 100mm where the effects of freezing are a concern. 5 year storm

was used to control the size of the orifice. Therefore,

Qo = Qpre5

Pond Design

Water table: 3 m below surface

Length to width ratio: 4 to 1

Permanent Pool Depth: Max. depth 2.5m mean depth: 1 – 2 m

Active Storage Depth: Water Quality and erosion control max 1.0m total 2m

Figure 5.03: Ground water table is at 173.00m. The MOE 2003 guideline specifies that a 0.50m

clearance is required between the ground water table and the pond floor. The pond floor is thus at

an elevation of 173.50m. The 175.00m elevation was determined as the lowest channel floor

elevation since the pond water surface must be lower than the swale floor. The predevelopment

ground elevations the pond is 176.00m.The current ground conditions at the swale entrance is

178.72m

In this design section we will consider the runoff predicted to enter our site from neighboring lands. Figure 3.04 and 3.05 demonstrate that there is a considerable amount of runoff that will find itself onto our site due to the pre existing drainage pattern. Because we cannot interfere with the natural drainage pattern this area and so we must let the water pass through our site. However there are no quality requirements, meaning that water does not need to be processed by us to meet provincial quality standards. So we will simply route the water flow from surrounding sites directly into the Detroit River because we have assumed that it is the neighbor’s responsibility to process their own water for quality.

In Figure 3.10 we see that the total drainage area has been split into 3 main areas: The Plaza site area, The Major Secondary Drainage Area and the Minor Secondary Drainage. Ultimately the water from outlined secondary drainage area will be routed directly into the river through the large Major and Minor Drainage Swale (MMDS). The Minor Drainage Swale (MinDS) will have a slope of 0.20% and lead directly in to the MMDS. The Major Drainage Swale (MajDS) will have two design components the design of the grassed Major Drainage Swale leading up to the Major which will have a 0.02% slope towards the culvert entrance, and the Major Drainage Culvert

(MajDC) which will lead directly into the MMDS.In design of the following 4 channels we are using a 100year peak flos as the guiding design parameter.