Design and Construction of the Lake St. Martin Emergency Outlet

Transcription

1 Design and Construction of the Lake St. Martin Emergency Outlet

2 Background 2011 was the largest flood event experienced in the last 200 years Flood Fighting required some difficult decisions by the Manitoba Government Assiniboine River runoff was high in peak flow rates and unprecedented in volume and duration All Assiniboine River flows greater than 18,000 cfs had to be diverted into Lake Manitoba to prevent disastrous flooding between Portage la Prairie and Headingley Resulted in unprecedented volumes diverted into Lake Manitoba through the Portage Diversion and highest levels in over 100 years Page 2

3 Flood Protection Works in Manitoba Page 3

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5 Resulting 2011 Water Levels Lake Manitoba Crested at ft (249.1m) 4.7 ft (1.43m) above the desirable range of ft to ft Lake St. Martin, Crested at ft (245.4m) 5.5 feet (1.68m) above the desirable range of 797 to 800 ft Page 5

6 Project Objective (from MIT mid-june 2011): Identify: Emergency flood relief options from Lake St. Martin and Lake Manitoba Required flow rates to significantly reduce water levels Required earthwork volumes and construction costs Biophysical and socio-economic impacts The recommended options were presented to Manitoba within 5 weeks Page 6

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10 Summary of Options Examined Page 10

11 Recommendations KGS & AECOM recommended the following course of action to Manitoba: Begin immediate construction of an additional emergency channel from Lake St. Martin to address the hydraulic flow restrictions in the Dauphin River and accommodate additional Lake Manitoba outflows over the winter; and Allow unrestricted outflow of water from Lake Manitoba through the Fairford River Water Control Structure through the winter of 2011/2012, allowing several times more outflow than past winters. If in service by of the Fall 2011, both lakes could be 2 to 3 feet lower by spring than without emergency channel Page 11

12 Lake St. Martin to Lake Winnipeg Channel Context Page 12

13 Lake St. Martin Emergency Outlet Channel Channel construction from Lake St. Martin approximately 6 km northeast towards Big Buffalo Lake Flow allowed to follow natural flow path to Buffalo Creek which re-enters the Dauphin River approximately 4.5 km upstream of the river mouth June/July 2011: Route investigations, survey, seismic investigations August 2011: Site preparation, layout, securing tugs and barges, developing barge access etc. September 2011: Channel construction, under difficult construction conditions (1.0 to 1.5m wet peat underlain by hard basal till) Page 13

14 Lake St. Martin Emergency Outlet Channel Construction of Outlet Channel: Presented significant timing and constructability challenges Extremely wet and isolated conditions Remote construction access Page 14

15 LSM Outlet Channel Early Access Page 15

16 LSM Outlet Channel Construction Excavating Barge Channel Page 16

17 LSM Outlet Channel Transportation Challenges Page 17

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19 At its peak the project had: Over 100 pieces of heavy equipment 3 construction camps 3 tugs, 4 barges, 10 support boats 2 helicopters 2 AECOM field offices and A multitude of AECOM personnel for office and field duties Page 19

20 Channel & Spoil Pile Section Illustration Lake St. Martin Channel Construction Page 20

21 Outlet Control Section approx location Page 21

22 Outlet Control Structure 2-D Velocity Model Outlet Control Structure Barge Channel Page 22

23 Lake St. Martin Emergency Outlet Channel Looking North Page 23

24 Lake St. Martin Emergency Outlet Channel Staff and Construction Equipment Over 100 pieces of Equipment Over 150 Construction Staff Over 50 AECOM Staff worked on project 41 from Manitoba Page 24

25 Lake St. Martin Emergency Outlet Channel Approach Channel Construction Page 25

26 Lake St. Martin Emergency Outlet Channel Approach Channel Page 26

27 Lake St. Martin Emergency Outlet Channel Approach Channel Page 27

28 Lake St. Martin Emergency Outlet Channel Big Buffalo Lake Page 28

29 Lake St. Martin Emergency Outlet Channel Big Buffalo Lake Page 29

30 Lake St. Martin Emergency Outlet Channel Big Buffalo Lake Page 30

31 Resulting Water Levels Page 31

32 Lake St. Martin Outlet Channel Looking Downstream Page 32

33 Questions?? Page 33