A Tale of Two Wells: Reconstruction of Two Hand Dug Caisson Well Stations. Joe Foote, PE May 2017 PNWS AWWA Kennewick WA

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1 A Tale of Two Wells: Reconstruction of Two Hand Dug Caisson Well Stations Joe Foote, PE May 2017 PNWS AWWA Kennewick WA

2 Outline Introduction Background Project Drivers Challenges Investigation / Assessment Design / Construction Summary 2

3 Background Well 4 Modern Electric Water Company Located in the Spokane Valley Constructed 1906 Hand dug, with wood cribbing Concrete caisson (~6 x 7 ) Perforated steel lower section Depth 113 feet Capacity Well Test 3,900 gpm with 2.5 foot of draw down (Specific capacity 1,500 gpm/foot of drawdown) Two pumps installed (1 3,000 gpm, 2 2,000 gpm) 3

4 Background Continued 4

5 Background Continued

6 Background Central Avenue Well No. 1 City of Spokane Located in north central Spokane Constructed 1959 Hand dug Brick lined caisson (8 diameter) Perforated steel lower section Depth 271 feet (215 feet is upper portion, 56 feet lower section) Capacity Estimated specific capacity 1,400 gpm/foot of drawdown Two submersible pumps installed (1 Offline, 2 3,500 gpm) 6

7 Background 7

8 Background 8

1 Wellhead relocated above ground Convert to vertical line shaft turbine pump from

9 Project Drivers Well 4 Upgrading an old facility Building structure Mechanical equipment Electrical equipment Capacity Improved operations Central Avenue Well No. 1 Wellhead relocated above ground Convert to vertical line shaft turbine pump from submersible pumps Replacement of electrical equipment Improved operations and access Capacity 9

10 Challenges Construction of new facility over existing caisson well Maintaining existing well surface seal Structural integrity and load-bearing capacity Caisson Pump pedestal Retrofitting pump pedestal Protection of well from contaminates Site limitations Fixed well location Setback requirements Zoning ordinances 10

11 Investigation / Assessment As-builts Geotechnical investigation Structural evaluation Visual inspection Ground Penetrating Radar (GPR) Estimate on concrete thickness and existence of reinforcing Schmidt hammer Estimate on concrete strength 11

12 Ground Penetrating Radar (GPR) GPR Electromagnetic radio wave Defines different materials Immediate results StructureScan Mini XT by GSSI 12

13 Well 4 Design Approach Demo Existing Building Isolate Well Caisson Setback / Clearance Existing Plan View of Pump Pad Plan View of Pump Pad And Caisson Improvements 13

14 Well 4 Setback Wellhead E Valleyway Avenue 14

15 Well 4 Address Field Changes 15

16 Well 4 Facility Upgrades Retrofit Pump Pedestal Protect existing beams 16

17 Well 4 Facility Upgrades Maintaining some of the old 17

18 Central Avenue Well No. 1 Design Approach Demo Existing Vault Isolate Well Caisson Saw cut Concrete Section Plan 18

19 Central Avenue Well No. 1 Design Approach Integrate with existing structure 19

20 Central Avenue Well No. 1 Setback & Clearances Proposed Well Building 16 x 29 4 Property Boundary Overhead Power 24 E Central Avenue 30 20

21 Central Avenue Well No. 1 OHP Clearances Coordination with power utilities Building clearance Construction clearance and protection 21

22 Central Avenue Well No. 1 Demo Protection of well Installation of barrier Requirements for cleaning and disinfection 22

23 Central Avenue Well No. 1 Pump Pedestal Upgrade 23

24 Central Avenue Well No. 1 Facility Upgrades 24

25 Summary Well 4 Existing: Capacity 5,000 gpm (1-3,000 gpm, 1-2,000 gpm pumps) Update: Capacity 3,750 gpm (1-2,500 gpm, 1-1,250 gpm pumps) 25

26 Summary Central Avenue Well No. 1 Existing: Capacity 3,500 gpm (1-0 gpm, 2-3,500 gpm pumps) Update: Capacity 8,000 gpm pump 26

27 Existing Well Retrofit Considerations Availability of as-built information Visual inspection Field measurements Accommodating new equipment Space/clearance Available power Retrofit/demolition impacts Impacts to surface seal Structural Permitting Start early Zoning ordinance requirements Meeting current standards 27

28 Acknowledgements Modern Electric Water Company City of Spokane Project Team LSB Consulting Engineers Budinger & Associates ZBA Architecture GeoEngineers 28

29 Questions? Joe Foote, PE 421 W Riverside Ave, Suite 762 Spokane, Washington Joe.Foote@murraysmith.us

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