technical memorandum

Corporate Office HydraTek & Associates Inc. 216 Chrislea Road, Suite 501 Woodbridge, Ontario L4L 8S5 Canada www.hydratek.com

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TECHNICAL MEMORANDUM ____________________________________________________________________

Date: 13 December 2010

To: Oya Koc and Aimin Wang (AECOM)

From: Djordje Radulj and Bryan Karney (HydraTek)

Subject: Preliminary Hydraulic Transient Analysis of the Tullamore HLPS (Zone 6) and North Bolton Elevated Tank, Region of Peel

________________________________________________________________________________ INTRODUCTION HydraTek & Associates Inc. (HydraTek) has been retained by AECOM on behalf of the Regional Municipality of Peel (Region) to conduct a preliminary hydraulic transient analysis for two separate projects consisting of the proposed Tullamore High Lift Pumping Station (Tullamore HLPS) and the proposed North Bolton Elevated Tank (North Bolton ET); from herein together simply referred to as the “system”. Tullamore HLPS is currently in the detailed design stage and the North Bolton ET is currently at the EA stage. Since both of these components are within Peel's pressure zone no. 6, the analysis of these two projects is being combined. It is worth noting that this analysis only considers the Tullamore HLPS (Zone 6), and that the Tullamore LLPS (Zone 5) is outside of the current scope. The overall purpose of this analysis is to assess the risk in the system due to hydraulic transients and to make preliminary recommendations for reducing any such risk. The focal points of this analysis are the proposed Tullamore HLPS and the proposed North Bolton ET (including any connecting feedermain). INFORMATION PROVIDED The following is a list of the information that has been made available for this analysis:

• Tullamore PS drawings no.: P1 to P4 and P7; by AECOM and dated 14 July 2010.

• As-built plan and profile drawings for existing 750 mm and 600 mm feedermains on Mayfield Road and Coleraine Drive; by KMK Consultants and dated September 2000.

• 2011 and 2031 peak hour demand Peel system hydraulic models in Epanet2 format; by AECOM and current as of December 2010.

• 2011 and 2031 peak hour demand Peel Zone 6 Only hydraulic models in Epanet2 format; by AECOM and current as of December 2010.

• Zone 6 pumping station capacities for 2031 from Peel Master Plan; by KMK Consultants and dated December 2007.

• Current and preferred (Option 3) North Bolton ET site location and feedermain layout drawings no.: FIG1, FIG3, FIG7, FIG8; by AECOM and current as of December 2010.

Preliminary Hydraulic Transient Analysis Tullamore HLPS and North Bolton ET, Peel Region

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SYSTEM DESCRIPTION AND MODEL ASSUMPTIONS In order to undertake the hydraulic transient analysis HydraTek mostly relied on the Regions 2031 peak hour demand hydraulic model; a model which was exported and supplied in Epanet2 format by AECOM. The original Zone 6 model consisting 2500+ nodes and 3500+ links was further simplified in order to more properly suit the requirement of the transient analysis. The simplification process maintained the hydraulic integrity of the system and preserved not only all hydraulic boundary conditions, but also both looped and dead-end watermain segments. It also increased the details pertaining to the profile of existing feedermains between Tullamore PS and the Bolton and North Bolton Elevated Tanks. The steady state model layout of the system is presented below in Figure 1.

Figure 1: Model layout for simplified Peel Zone 6 system While not significant, there is a hydraulic based interaction between the East and West section of this zone, and thus the analysis considered all important boundary conditions. In addition to the Tullamore HLPS and the proposed North Bolton ET, the future Peel Zone 6 system will also include the following boundary conditions: existing Bolton ET, Zone 6 Reservoir, Snelgrove ET, North Brampton LLPS, Alloa LLPS, East Brampton HLPS and West Brampton HLPS.


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The above discussed steady state model was then subsequently imported into, and exercised in the TransAM software package. TransAM is a “fixed-grid” method of characteristics based simulation model that encodes a variety of numerical and physical developments undertaken at the University of Toronto over a span of two decades. The model has been extensively field tested and used in many locations throughout the world for hundreds of millions of dollars worth of pipeline systems. The key to accurate simulation is careful representation of hydraulic devices (particularly pumps, valves and surge protection devices) and the basic parameters of the pipeline system (including diameter, friction losses, pipeline profile, wavespeed and rated head). The following is a brief summary of the important system and modelling assumptions that were included as part of this preliminary analysis:

• The 750 mm and 600 mm concrete pressure pipe feedermain heading East from Tullamore HLPS on Mayfield Road and then North on Coleraine Drive was modelled with the following properties:

o Working pressure rating – 120 psi (84 m H20) - conservatively based on Class 12, although some sections have higher ratings

o Wavespeed – 1000 m/s

o C factor – as per original steady state model

o With eight (8) existing 3" (75 mm) combination air valves (for some scenarios)

• All other Zone 6 feedermains and all pipe within pumping stations were assumed to be concrete and with the following properties:

o Working pressure rating – 140 psi (100 m H20)

o Wavespeed – 1100 m/s

o C factor – as per original steady state model

o No existing air valves were included in the model

• All Zone 6 pumping station capacities were based on the most recent master plan update for 2031 and these are summarized in Table 1 below. All pump curves were assumed to be as per the Region's most recent hydraulic model.

Table 1: Zone 6 pumping station capacities

Pumping Station Minimum Total Flow

Rate in Model No. of Pumps in Operation

Mass Moment of Inertia per Pump*

Tullamore HLPS 120 ML/d (1388 L/s) 3 34.1 kg-m2

North Brampton LLPS 90 ML/d (1041 L/s) 3 4.7 to 9.0 kg-m2

Alloa LLPS 50 ML/d (579 L/s) 2 5.3 kg-m2

East Brampton HLPS 105 ML/d (1215 L/s) 3 12.5 to 39.7 kg-m2

West Brampton HLPS 90 ML/d (1041 L/s) 4 7.7 to 19.2 kg-m2

*Values were estimated using standard empirical and/or conventional equations, and a sensitivity analysis of +/- 100% to the assumed values was also subsequently conducted.


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• Tullamore HLPS assumptions:

o 1190 RPM and 85% efficiency for pumps

o Operating points as per pump curve based on a proposed ITT Flygt / Goulds Model no. 3498

o All pumps equipped with dedicated check valves

o Surge protection consisting of two proposed surge relief valves (SRVs); sizes to be determined.

• Assumptions for all other Zone 6 pumping stations:

o 1190 RPM and 85% efficiency for pumps

o Operating points as per pump curves provided in model

o All pumps equipped with dedicated check valves

o Surge protection consists of SRVs but not modelled due to local impact only

• Minor losses in the system were ignored (conservative).

• Conservative peak hour demand condition in Zone 6 with reservoir filling in North Bolton. The water levels for the existing and proposed North Bolton Elevated Tanks were set at 291 m and thus represent a low water level condition that induces the highest flow rates in the critical feedermains.

• Working pipe pressure rating assumed to represent the maximum allowable high pressure limit for analysis.


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MODELLED SCENARIOS Proper and sensible operational protocols of the Tullamore HLPS will minimize the majority of hydraulic transients associated with typical operations such as pump starts, stops, etc. Assuming that unauthorized in-line valve operations, pipe breaks and rapid bulk water withdrawals will not frequently occur, and that line filling and draining (if required) is performed in a controlled fashion, then the outstanding risk of transients in this system potentially comes in the form of a power failure at one or multiple pumping stations in Zone 6. Power failures must be considered inevitable over the long life of such a system and are by their very nature unpredictable events that can expose a weak or unprotected system. Power failures are excellent surrogate design events for many hydraulic transient risks and therefore this analysis explicitly considers the impact of power failures in this system, with the previously described system assumptions and as per the scenarios summarized in Table 2 below. Additional scenarios can be added and considered once additional details for this system are known. Table 2: Transient analysis scenarios

Scenario Event Type Surge Protection

1A Local power failure at Tullamore HLPS only No dedicated protection

1B Local power failure at Tullamore HLPS only With existing feedermain air valves

1C Local power failure at Tullamore HLPS only With proposed SRVs

1D Local power failure at Tullamore HLPS only With recommended Tullamore SRVs and existing feedermain air valves

2A Global power failure in Zone 6 No dedicated protection

2B Global power failure in Zone 6 With existing feedermain air valves

2C Global power failure in Zone 6 With proposed SRVs

2D Global power failure in Zone 6 With recommended Tullamore SRVs and existing feedermain air valves


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RESULTS AND DISCUSSION In general, the East section of the Zone 6 system can be described as relatively long but simple, with a flat elevation profile, without significant high points, with several interconnections and with moderate peak velocity. As a result, the system is not at a high risk to hydraulic transients, with both the positive and negative transient pressures arising from the above modelled scenarios being relatively mild. The graphical results (i.e., pressure profile figures with transient pressure envelopes) are presented in the appendix of this document. These figures are plotted across different feedermain paths, and these paths (along with the reason for their selection) are presented in Figure 2 and explained in Table 3.

Figure 2: Plan view of plotting paths for pressure profile graphs Table 3: Transient analysis plotting paths

Path ID Path Description and Purpose

a From Tullamore HLPS to the proposed North Bolton ET, via the 1050 mm and 750 mm feedermains Purpose: To determine risk between Tullamore and proposed North Bolton ET

b For future North Bolton ET 1050 mm and 600 mm feedermains, from the proposed North Bolton ET to NE Bolton Purpose: To determine risk for proposed North Bolton ET feedermains

c From Tullamore HLPS to the North Brampton LLPS, via the 1050 mm and 750 mm feedermains Purpose: To determine risk between Tullamore and West part of Zone 6

Path A

Path B

Path C


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The following provides a quick summary and discussion of the transient analysis results:

• Maximum transient pressures arising from a power failure are typically below the working pressure rating of the pipe. Therefore, the traditional surge risk is quite mild, especially if coupled with the pipe’s additional surge allowance rating (i.e., additional safety factor). As a result routine pump operations and less routine power failures should not pose a risk to this system. This applies to all scenarios considered in this analysis.

• Negative (i.e., below atmospheric) pressures can be expected across many parts of Zone 6, including in the vicinity of Tullamore HLPS. Fortunately, the magnitude and duration of the sub-atmospheric pressures is limited, and the risk is further reduced if the existing combination air valves along the feedermain are considered to be in working condition (see path 'a' for Scenarios 1C, 1D, 2C and 2D). As noted earlier, the air valves for the West part of the zone were not modelled and thus path c for the above scenarios is not shown to benefit from the presence of such air valves.

• Vapour cavities at air valve locations have the potential to form and subsequently collapse, but fortunately the magnitude of the transient pressures following the collapse are predicted to be mild. Nonetheless, the scenarios with the air valves can yield slightly higher positive transient pressures than the scenarios without any surge protection.

• The local power failure at Tullamore HLPS (Scenario 1) is slightly more severe than the global power across the zone (Scenario 2), and this is mostly due to the compensating superimposition of the various positive and negative pressure waves.

• This analysis has focused on the risk at Tullamore HLPS and East part of Zone 6, and thus has not explicitly considered the risk across all of Zone 6. Similarly, the analysis has not considered the impact of existing or additionally proposed surge protection across this zone. Nonetheless, most of the additional surge protection is of the localized variety (i.e., comprised of valves) and thus is not expected to have a significant impact on the East part of the system.

• Positive transient pressures appear to be the greatest in the vicinity of North Brampton HLPS, but these pressures are below the pressure rating of the pipe and do not consider the impact of any surge protection at this specific location.

• The pressure wave return period (defined as 2 L/a) in this system is estimated to be between 20 and 22 seconds and this system property directly affects the overall duration of transient pressure fluctuation. Most system operations should take into account the need to avoid activity during the period of pressure fluctuation, and to therefore incorporate an appropriate operational standby rule. This standby period should apply to all valve operations, pump restarts following power failure, etc. In most systems, a period that is equal to 10 times the wave return period (i.e., in this system this period is almost 4 minutes) is warranted.


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• While not explicitly shown or analyzed, the greatest risk from positive transient pressures in this system likely arises if the pump start control logic is not well controlled. Fortunately, any such risk can easily be minimized if the pump valve opening and closing durations are optimized during the commissioning stage.

• A sensitivity analysis was performed on the following key model parameters:

o Wavespeed (i.e., wave velocity or celerity) o Pump moment of inertia o Vapour pressure o Elevated tank water level

The results of the sensitivity analysis indicate that the system is quite stable and not significantly impacted by a reasonable change in any of the above mentioned parameters. In other words, slight errors in the assumed model parameters do not have any appreciable influence on the results presented herein.


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RECOMMENDATIONS The hydraulic transient analysis of the Tullamore HLPS and North Bolton ET system in Peel Zone 6 indicates that the risk due to hydraulic transients is relatively mild. This is primarily as a result of the size, scale, and type of hydraulic system in question. However, in order to minimize any other possible risk and to improve overall system operation, the following recommendations are made at this time:

1. Two moderately sized surge relief valves should be installed at the discharge header in

order to provide a reliable, fast to respond, and robust surge protection system for the pumping station components. Even though these valves are not expected to activate under most power failure conditions, the Tullamore HLPS should still be equipped with one 12" (300 mm) surge relief valve and one 8" (200 mm) surge relief valve. Both of the valves should be of the rate-of-pressure-rise variety and should be connected to the discharge header of the pumping station. The surge relief valve discharge piping should be designed for a peak velocity of 5 to 6 m/s based on 40 to 50% of the peak flow from the pumping station.

2. The 12" surge relief valve should be set to open sooner and more frequently, since it is the larger valve that opens more slowly. This larger valve would act as the primary discharge source for the fluid, thereby adequately reducing the transient pressures in the system. The 8" surge relief valve should be set to open second and therefore act as backup in the case that the larger valve does not open or is too slow to open. This smaller valve is expected to open quicker, but its discharge capacity is less. The larger (12") surge relief valve should be set to open at a pressure that is +10 psi above the maximum operating pressure and the smaller (8") surge relief valve should be set to open at a pressure that is +15 psi above the maximum operating pressure.

3. The critical combined period of pressure wave reflection in this system is estimated to be up to 4 minutes, and the numerical model predicts that in the worst case scenario most of the significant transient pressure fluctuations are dissipated within a 3 minute period. As a result, a minimum of a 4 minute standby period rule should be applied to all system operations in order to minimize the risk of multiple pressure wave interactions and potential amplification/superimposition. The standby period should be applied following any transient causing event, including but not limited to:

• Power failure of pumps;

• Pump changes, including starts and stops;

• Valve operations; and

• Bulk water withdrawals.

4. The existing air valves along the key feedermains are critical surge protection devices and should be considered as part of the surge protection system. However, air valve performance is only as good as the associated maintenance. All air valves should be inspected and flushed twice per annum. This requires a dedicated maintenance plan that


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is supported by dedicated funding allocation. The system is at a greater risk of negative transient pressures without properly functioning and/or maintained air valves.

5. Further to the above recommendation, the analysis indicates that the 1050 mm and 750 mm feedermains between Tullamore HLPS and the North Brampton LLPS can be subjected to full vacuum transient conditions without the protection of CAVs or if the existing CAVs are not in good operation condition. While outside the scope of this study, it is recommended that the Region investigate the state of CAV based protection for this feedermain.

6. A good way to confirm the performance of the recommended surge protection (including set-points) and the pump start and stop control logic (including the standby period), is to observe and record transient pressures at the pumping station discharge header during the commissioning stage. In this system, a single day of transient pressure recording at the discharge header would act to identify any risks or shortcomings of the currently proposed (trial) control logic and therefore to make the appropriate adjustments.

7. While this analysis indicates that the transient pressures in the proposed (albeit still preliminary) North Bolton ET feedermain are mild, the analysis should be revisited once the final pipe size, alignment, and profile are finalized. At that time, properly sized combination air valves should also be selected for the feedermain.

8. The transient pressures that are predicted at the existing Bolton ET through the modelled scenarios are mild, and therefore the need for the existing surge relief valve at this location (a valve which was conservatively not considered in the analysis) is currently unclear. Unless the current piping arrangement at the elevated tank is known to induce high local transient pressures, then this existing surge relief valve can likely be decommissioned and if required, relocated to the proposed North Bolton ET. The currently proposed location for the North Bolton ET is essentially quite similar to that of the existing Bolton ET, and thus this change is not expected to increase the hydraulic transient risk in the system.

9. Another hydraulic transient risk worth considering in operation is the one arising during the period of filling. Line filling is problematic in that the leading edge of the water column is accelerating against very little resistance. The drastic changes in velocity and the continuous and sudden expulsion of air can create very high positive transient pressures. Since the numerical models do not take this into account very well, filling protocols must follow standard practice. The typical recommendation is to keep filling velocities below 1 ft/s (0.3 m/s).

10. All flow control valve operations should be performed during periods of steady flow. The valve operation should be performed in a smooth and gradual manner. More specifically, the last 10% of a closure or the first 10% of the opening should be performed over 90% of the overall closure/opening time. For example, if it takes 3 minutes (180 seconds) to fully close or open a butterfly valve, then the last 10% of the closure (or the first 10% of the opening) should be performed over a period of ~160


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seconds. The key point is that the last 10% of a closure or the first 10% of an opening is most critical, and patience is required in order to allow the system to reach equilibrium.

11. This preliminary hydraulic transient analysis and report have been completed based on

the information available at this point in time, and should be revisited once additional details for the North Bolton ET (and associated feedermain) are available. Barring any drastic system change, any minor change in this part of the system should not affect the surge protection requirements for Tullamore HLPS. Lastly, this Zone 6 analysis has been focused on Tullamore HLPS, North Bolton ET and the associated parts of the Zone 6 East system. As a result, this analysis cannot be considered complete and/or comprehensive for any other pumping station or the West part of the Zone 6 system.


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APPENDIX: GRAPHICAL TRANSIENT ANALYSIS RESULTS This appendix incorporates graphical transient analysis results for the Tullamore HLPS and North Bolton ET system in Peel Zone 6 through the use of pressure (head) versus distance (i.e., pressure profile and envelope) figures. The pressure profile figures should be read from left to right, with the left side corresponding to the boundary condition that is listed first for the corresponding plotting path (i.e., a, b, c, or d) in Table 3. All of the pressure profile figures can be deciphered using the following legend: Red Line: Pipe’s rated working pressure (estimated)

Light Blue Line: Steady state hydraulic grade line (HGL)

Blue Lines: Maximum and minimum transient pressure envelope

Green Line: Existing and proposed pipe profile The “general” goal of the analysis is to keep the Blue Lines between the Red Line and the Green Line, therefore ensuring that the transient pressures are within an acceptable range.

Figure 3: Scenario 1A – Local power failure; no dedicated protection; path a


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Figure 4: Scenario 1A – Local power failure; no dedicated protection; path b

Figure 5: Scenario 1A – Local power failure; no dedicated protection; path c


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Figure 6: Scenario 1B – Local power failure; proposed SRVs; path a

Figure 7: Scenario 1B – Local power failure; proposed SRVs; path b


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Figure 8: Scenario 1B – Local power failure, proposed SRVs; path c

Figure 9: Scenario 1C – Local power failure; existing feedermain CAVs; path a


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Figure 10: Scenario 1C – Local power failure; existing feedermain CAVs; path b

Figure 11: Scenario 1C – Local power failure; existing feedermain CAVs; path c


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Figure 12: Scenario 1D – Local power failure; existing CAVs and recommended SRVs; path a

Figure 13: Scenario 1D – Local power failure; existing CAVs and recommended SRVs; path b


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Figure 14: Scenario 1D – Local power failure; existing CAVs and recommended SRVs; path c

Figure 15: Scenario 2A – Global power failure; no dedicated protection; path a


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Figure 16: Scenario 2A – Global power failure; no dedicated protection; path b

Figure 17: Scenario 2A – Global power failure; no dedicated protection; path c


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Figure 18: Scenario 2B – Global power failure; proposed SRVs; path a

Figure 19: Scenario 2B – Global power failure; proposed SRVs; path b


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Figure 20: Scenario 2B – Global power failure; proposed SRVs; path c

Figure 21: Scenario 2C – Global power failure; existing feedermain CAVs; path a


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Figure 22: Scenario 2C – Global power failure; existing feedermain CAVs; path b

Figure 23: Scenario 2C – Global power failure; existing feedermain CAVs; path c


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Figure 24: Scenario 2D – Global power failure; existing CAVs and recommended SRVs; path a

Figure 25: Scenario 2D – Global power failure; existing CAVs and recommended SRVs; path b


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Figure 26: Scenario 2D – Global power failure; existing CAVs and recommended SRVs; path c

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