appendix a hydraulic modelling report

Appendix A Hydraulic Modelling Report

Memorandum

245 Consumers Road, Suite 400

Toronto, ON, M2J 1R3

Canada

T +1.416.499.0090

F +1.416.499.4687

www.jacobs.com

Document Tracking Number (JETT) 1

Subject Hydraulic Modelling Results

Project Name Class Environmental Assessment to Plan for the Water Street Sanitary Sewage Pumping Station

(SSPS) Drainage Area

Attention Patricia Casco, Region of Durham

From Jacobs

Date June 14 2019

Copies to Aaron Christie, Region of Durham

1. Introduction

The Regional Municipality of Durham (the Region) has retained Jacobs to complete a Schedule B Class EA for the Water Street Sanitary Sewage Pumping Station (Water SSPS) to determine the preferred solution and provide the additional required capacity to meet customer demands and development needs to meet the 2031 design flow.

The Water SSPS is a critical part of an existing wastewater collection system within the Town of Port Perry along with two other stations, Canterbury SSPS and Reach Street SSPS.

The Water Street SSPS has been experiencing higher than expected inflows resulting in both pumps running simultaneously. The Region has determined that the SSPS does not have capacity for the existing flows. Additional capacity is also required for the planned future increase in flow for the Water Street SSPS catchment area.

The purpose of this Technical Memorandum is to report the preliminary results of the hydraulic analysis and modelling undertaken by Jacobs in terms of:

• System curve

• Impact of upgrading Water SSPS on Canterbury SSPS and Reach SSPS capacities

• Preliminary transient analysis

2. Methodology

An existing model built using the program AFT Fathom V10 from Applied Flow Technology Corporation

was provided by the Region and was used for the system curve analysis and analysis of the impact of

increasing the capacity of the Water SSPS on the Port Perry wastewater collection system. The AFT

Fathom model incorporates pipe length, materials and wall roughness, inside diameters, minor losses

due to elbows and valves, pump curves, elevation changes, and wet well water surface height. The

Fathom hydraulic model includes the following elements:

1) Water SSPS

Hydraulic Modelling Results

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2) Canterbury SSPS

3) Reach SSPS

4) Existing 350 mm forcemain from the Water SSPS to the Nonquon River Water Pollution Control Plant (WPCP)

5) Future twin 400 mm forcemain from Water SSPS to the WPCP

6) Existing 150 mm forcemain from the Canterbury SSPS to the connection point with the 400 mm forcemain

7) Existing 300 mm forcemain from the Reach SSPS to the connection point with the 400 mm forcemain

In addition, the Fathom model was exported/imported into the program HAMMER Connect Edition V10 from Bentley for the transient analysis. The hydraulic model was set-up in steady state mode providing the basic system information (pipe diameters, lengths, flow rates, node elevations, etc.) and was used to generate the base steady state model scenarios that were used to perform the transient analysis.

3. System Curve

The Fathom hydraulic model was used to determine the system curve at Water SSPS for the following conditions:

1) Existing conditions (single 350 mm forcemain) – good condition (C-120)

2) Existing conditions (single 350 mm forcemain) – poor condition (C-98)

3) Proposed conditions (350 mm and 400 mm forcemains) – good condition (C-120)

4) Proposed conditions (350 mm and 400 mm forcemains) – poor condition (C-98)

The system curves obtained in this way will be used to determine the required pumping capacity for Phase 1 (275 L/s at Water SSPS) and full build-out, (350 L/s at Water SSPS) as shown in Figure 1. Note full build-out condition is labelled Phase 2 on the system curve figure.

Figure 1 System Curves at Water SSPS



4. Impact of Upgrading Water SSPS on the System

The Fathom hydraulic model was also used to determine the impact of upgrading the Water SSPS on both Canterbury SSPS and Reach SSPS. As a result of increasing the firm capacity at Water SSPS and therefore the HGL, there is a reduction in pumping capacity at the other pumping stations due to the fact that the operating point moves back on its pump performance curve to higher head and lower flow.

• For Phase 1 (increase of firm capacity to 275 L/s at Water SSPS), the reduction in capacity at Reach SSPS is 10% (from 30 L/s to 27 L/s) and at Canterbury SSPS is 14% (from 22 L/s to 19 L/s) assuming a C factor of 120 as shown in Table 1. If a C factor of 98 is used instead, the reduction in capacity at Reach SSPS is 40% (from 30 L/s to 18 L/s) and at Canterbury SSPS is 40% (from 22 L/s to 13 L/s).

• For full build-out (increase of firm capacity to 350 L/s at Water SSPS), the reduction in capacity at Reach SSPS is 43% (from 30 L/s to 17 L/s) and at Canterbury SSPS is 36% (from 22 L/s to 14 L/s) assuming a C factor of 120 as shown in Table 1. If a C factor of 98 is used instead, the reduction in capacity at Reach SSPS is 76% (from 30 L/s to 7 L/s) and at Canterbury SSPS is 73% (from 22 L/s to 6 L/s).

Table 1 Impact of Upgrading Water SSPS on the System

Station

Current Firm Capacity (L/s)

Phase 1

Predicted capacity (L/s) – Based on C-Factor of 1201

Phase 1


Full Build-out


Full Build-out


Reach SSPS 30 27 18 17 7

Canterbury SSPS

22 19 13 14 6

Water SSPS 160 2752 2752 3502 3502

1. All predicted capacity considered both forcemains used.

2. Projected design capacity.

5. Preliminary Transient Analysis

A preliminary transient modelling and analysis was undertaken to determine the surge pressures (both positive and negative) through the different forcemains and understand what transient mitigation devices are required.

The assumptions for the transient modelling are listed below:

1) Power failure at Water SSPS

2) Both the 350 mm forcemain and the 400 mm forcemain were included

3) C factor of 120 for all forcemains

4) Transient wave speed of 400 m/s for all forcemains

In the absence of specific guidelines to reference for acceptable negative pressures in a sewage forcemain, a review was completed through discussions with pipe manufacturers. They indicated that the most vulnerable aspect of the pipeline system is the joints, not the pipe itself. The ASTM Standard D3139 “Standard Specification for Joints for Plastic Pressure Pipes Using Flexible Elastomeric Seals” indicates that an assembled joint is required to withstand a vacuum of -10.9 psi (-7.6 mH2O) for one hour with no leakage, while in an axially deflected position. Therefore, for this analysis the negative transient pressures were considered acceptable if they were greater than -10.9 psi (-7.6 mH2O).


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Six scenarios were modelled for transients as listed below:

1) Scenario 1: Phase 1 (275 L/s at Water SSPS) – No transient protection

2) Scenario 2: Phase 1 (275 L/s at Water SSPS) – Protection using combination air valves (CAVs)

3) Scenario 3: Phase 1 (275 L/s at Water SSPS) – Protection using a surge tank

4) Scenario 4: Phase 1 (350 L/s at Water SSPS) – No transient protection

5) Scenario 5: Phase 1 (350 L/s at Water SSPS) – Protection using combination air valves (CAVs)

6) Scenario 6: Phase 1 (350 L/s at Water SSPS) – Protection using a surge tank

The location of the CAVs included in the transient modelling were taken from the GM BluePlan Water Street Capital Need Assessment study (5 existing and 2 proposed).

1) Existing 75 mm CAV on the 400 mm forcemain at the Reach Street connection

2) Existing 75 mm CAV on the 400 mm forcemain north of Cell 1

3) Existing 50 mm CAV on the 300 mm Reach forcemain at the high point approximately 150 m east of Sherington Drive

4) Existing 50 mm CAV on the 150 mm Canterbury forcemain at the high point approximately 50 m north of the intersection of Waterbury Crescent and Coulter Street

5) Existing 75 mm CAV at the discharge header of Water SPS

6) Proposed 75 mm CAV at the 350 mm forcemain approximately 125 m west of Simcoe Street

7) Proposed 75 mm CAV at the 400 mm forcemain south of Cell 5

5.1 Transient Results

The results of the preliminary transient modelling are shown in the graphs below. The following parameters are displayed in the graphs: pipe profile (green), static HGL (black), maximum envelope HGL (red), minimum envelope HGL (blue), full vacuum HGL (grey), acceptable negative pressure HGL.

5.1.1 Scenario 1: Phase 1 (275 L/s at Water SSPS) – No Transient Protection

For Scenario 1, a transient event is generated when Water SSPS pump stops suddenly due to a power failure. This causes a negative surge that reaches -10.0 mH2O or full vacuum conditions along 47% of the forcemain and returns as a positive surge. This negative pressure results in the formation and collapse of a vapor pockets at the high point followed by the development of an additional positive surge ranging from 5 mH2O to a maximum of 20 mH2O in the last 1.5 km of the forcemain (10 mH2O more than the static conditions). Refer to Figure 2. There is very little attenuation of positive and negative surges under these conditions.



Figure 2. Scenario 1 - Water SSPS Phase 1 (275 L/s) - HGL Envelope – No Protection - Profile from

Water SSPS to WPCP along the 400 mm forcemain

5.1.2 Scenario 2: Phase 1 (275 L/s at Water SSPS) – Protection Using Combination Air Valves (CAVs)

For Scenario 2, a transient event is generated when Water SSPS pump stops suddenly due to a power failure, but the system is protected using 7 CAVs as described in the previous section. This causes a negative surge that reaches -10.0 mH2O or full vacuum conditions along 14% of the forcemain and returns as a positive surge. This negative pressure results in the formation and collapse of a vapor pockets at the high point followed by the development of an additional positive surge ranging from 5 mH2O to a maximum of 16 mH2O in the last 1.5 km of the forcemain (6.6 mH2O more than the static conditions). Refer to Figure 3. There is reduced attenuation of positive and negative surges under these conditions.


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Figure 3 Scenario 2 - Water SSPS Phase 1 (275 L/s) - HGL Envelope – Protection through CAVs -

Profile from Water SSPS to WPCP along the 400 mm forcemain

5.1.3 Scenario 3: Phase 1 (275 L/s at Water SSPS) – Protection Using Surge Tank

For Scenario 3, a transient event is generated when Water SSPS pump stops suddenly due to a power failure, but the system is protected using a 6,000 L bladder type surge tank. This protects the system and full vacuum conditions are completely eliminated. Only a short section of the FM near the WPCP remains negative but above the acceptable negative elevation. The surge tank also protects the system against the formation vapor pockets and the positive surge in the last 1.5 km of the forcemain is reduced. Refer to Figure 4. There is a significant attenuation of positive and negative surges under these conditions.



Figure 4 Scenario 3 - Water SSPS Phase 1 (275 L/s) - HGL Envelope – Protection through Surge

Tank - Profile from Water SSPS to WPCP along the 400 mm forcemain

5.1.4 Scenario 4: Full Build-out (350 L/s at Water SSPS) – No Transient Protection

For Scenario 4, a transient event is generated when Water SSPS pump stops suddenly due to a power failure. This causes a negative surge that reaches -10.0 mH2O or full vacuum conditions along 72% of the forcemain and returns as a positive surge. This negative pressure results in the formation and collapse of a vapour pockets at the high point followed by the development of an additional positive surge ranging from 5 mH2O to a maximum of 22 mH2O in the last 1.5 km of the forcemain (12.6 mH2O more than the static conditions). Refer to Figure 5. There is very little attenuation of positive and negative surges under these conditions.


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Figure 5 Scenario 4 - Water SSPS Full Build-out (350 L/s) - HGL Envelope – No Protection - Profile

from Water SSPS to WPCP along the 400 mm forcemain

5.1.5 Scenario 5: Full Build-out (350 L/s at Water SSPS) – Protection Using Combination Air Valves

(CAVs)

For Scenario 5, a transient event is generated when Water SSPS pump stops suddenly due to a power failure, but the system is protected using 7 CAVs as described in the previous section. This causes a negative surge that reaches -10.0 mH2O or full vacuum conditions along 28% of the forcemain and returns as a positive surge. This negative pressure results in the formation and collapse of a vapor pockets at the high point followed by the development of an additional positive surge ranging from 5 mH2O to a maximum of 16 mH2O in the last 1.5 km of the forcemain (10.1 mH2O more than the static conditions). Refer to Figure 6. There is reduced attenuation of positive and negative surges under these conditions.



Figure 6 Scenario 5 - Water SSPS Full Build-out (350 L/s) - HGL Envelope – Protection through

CAVs - Profile from Water SSPS to WPCP along the 400 mm forcemain

5.1.6 Scenario 6: Full Build-out (350 L/s at Water SSPS) – Protection Using Surge Tank

For Scenario 6, a transient event is generated when Water SSPS pump stops suddenly due to a power failure, but the system is protected using a 6,000 L bladder type surge tank. This protects the system and full vacuum conditions are completely eliminated. Only a short section of the FM near the WPCP remains negative but above the acceptable negative elevation. The surge tank also protects the system against the formation vapor pockets and the positive surge in the last 1.5 km of the forcemain is reduced. Refer to Figure 7. There is a significant attenuation of positive and negative surges under these conditions.


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Figure 7 Scenario 6 - Water SSPS Full Build-out (350 L/s) - HGL Envelope – Protection through

Surge Tank - Profile from Water SSPS to WPCP along the 400 mm forcemain

5.1.7 Transient Modelling Results Summary

The transient results are summarized in Table 2.

Table 2 Transient Modelling Results Summary

6. Conclusions and Recommendations

The following conclusions can be derived from the transient analysis and modelling:

• The positive surges are not as critical as negative surges (full vacuum in a large section of the FM)

• The CAVs reported by GMBP (5 existing and 2 new) help mitigate/reduce the transient but not to eliminate it completely and there are still some sections of the FM subjected to full vacuum both for

7 locations as

reported by GMBPat Water SSPS mH2O

x -

x 9.8 Full Vacuum (-10.0) 47% of the length of the FM


x 6.0

x -



x 8.2

CAV at

Ultimate

350 L/s

2.3

-6.4

mH2O

Phase 1

275 L/s

2.3

-5.4

Condition Pressure

Static No Protection

Surge TankMAX MIN

6000 L



Phase 1 and full build-out. It is recommended that the location and size of the CAVs is investigated further to determine is these devices can provide a better protection against transient.

• The 6,000 L bladder type surge tank completely eliminates the full vacuum (-10 mH2O) and only a short section of the FM near the WPCP remains negative but above the acceptable negative elevation (-7.6 mH2O). It is recommended to further investigate the option of protecting the system using a surge tank at the Water SSPS. Moreover, the type and size of the tank should also be further investigated.

7. References

GM BluePlan. Water Street SPS Capital Needs Assessment, Port Perry – Appendix B Water Street Transient Analysis Memorandum, Feb 2016

Appendix B Proposed Pumping Station Layouts for the

Alternative Sites

GENERATOR

PUMPING STATION

TRANSFORMER

LIFTING GATE

LIFTING GATEPARKING SPOTS

CURB

CURB

N

SCALE 1:40020151050

SITE 1-A

PRIVATE ACCESS AREA

GE

NE

RA

TO

R

PUMPING STATION

TRANSFORMERLIFTING GATE

ACCESS EASEMENTLIFTING GATE

CURB

CURB

PARKING SPOTS

N

SCALE 1:40020151050

SITE 1-B

PRIVATE ACCESS AREA

GENER

ATO

R

4 m A

CCESS R

OA

DPUMPING STATION

TRANSFO

RM

ER

CHAIN LINK FENCE AND GATE


NSITE 2

SCALE 1:40020151050

PRIVATE ACCESS AREA

GENERATOR

4 m A

CC

ES

S R

OA

D

PUMPING STATION

TRANSFORMER


N

SCALE 1:40020151050

SITE 3-A

GE

NE

RA

TO

R

4 m A

CC

ES

S R

OA

D

PUMPING STATION

TR

AN

SF

OR

ME

R

N

SCALE 1:40020151050

SITE 3-B

1.2 m W

AL

KW

AY

PUMPING STATION

GENERATOR

TRANSFORMER

4 m A

CC

ESS R

OA

D


NSITE 4

SCALE 1:40020151050

PRIVATE ACCESS AREA

appendix a hydraulic modelling report

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