The City of Redwood City Completes Trenchless Sewer Installation under Highway 101

Transcription

1 The City of Redwood City Completes Trenchless Sewer Installation under Highway 101 By Nick Lazarakis, PE, Kennedy/Jenks Consultants Special Thanks to: James Bowland, PE, Kennedy/Jenks Consultants Brad Moore, PE, Staheli Trenchless Ahmad Haya, PE, City of Redwood City James O Connell, PE QSD/P, City of Redwood City Twenty-Sixth Annual Sharing Technologies Seminar

2 Existing Site

3 Purpose of Project Increase capacity to move raw wastewater under Highway 101 Service areas include Redwood City (excluding Redwood Shores, Pacific Shores, and Seaport) and San Mateo County-run Sewer Districts: Fair Oaks, Kensington, Oak Knoll and Emerald Lake Hills The 2008 Sewer Master Plan reported flow then of PWWF of 38 MGD, but would grow to 41 MGD. PDWF was reported then as 12 MGD but would grow to 15 MGD Correct a problem existing 48-inch pipe that had a 0.7-foot reverse slope

4 Site and Geotechnical Background Tidal flats area before developed Tannery prior to the highway being built in the 1960 s Artificial Fill from Highway, Young Bay Mud, then Quaternary-age basin deposits (stiff, lean to fat clay with varying amounts of sand).

5 Geotechnical Borings

6 Summary of Design Started in 2010 with conceptual design by RMC and McMillen Jacobs Associates KJ/Staheli team was selected in 2013 to perform final design, bidding and ESDC. Major Design Elements: 60-inch diameter Sewer Interceptor Two diversion structures

7 B-1 B-2

8 Walnut Street

9 Trenchless Design Selecting the tunneling method Carrier pipe needed to be designed as jacking pipe and sewer pipe Include grout ports in carrier pipe

10 Selected Open Shield Pipe Jacking B-1 B-2

11 Tunneling Pipe Design RCP Jacking Pipe Steel Joint Rings Grout Ports Double Gasketed T-Lock Lined Two Rebar Cages

12 Tunneling Pipe

13 Diversion Structure Design Local geology of bay mud, concerns of settlement due to weight. Resulted in a robust subbase wrapped in geofabric. Provide simple robust design with no moving parts, ability to divert flow through either pipe, and perform maintenance on existing 48-inch SS resulted in aluminum stop logs being used to isolate sections of the diversion structure. The large size of the structures required relocation of some existing utilities. Bypass were necessary and set up during construction, so sewer could keep flowing.

14 Diversion Structures Walnut Street Side

15 Diversion Structures Maple Street Side

16 Caltrans Encroachment Permit Direct pipe jack without a casing, not Caltrans standard Submitted permit, accepted on first submittal Extended permit two times before project started

17 Existing Utilities Moved interceptor to north of existing 48-inch SS for clearance Very tight clearance to old 48-inch SCVW FM Installed Steel Plate in Trench Tight grade control very important SVCW water service on Maple side relocated without issue PG&E gas line on Walnut side relocated without issue AT&T telephone Line on Walnut side conflicting with jacking shaft

18 Settlement Monitoring Plan

19 Bidding Results and Schedule Bidder Bid Total Engineer s Estimate $2,512,604 JMB KJ Woods Construction Construction $2,708,000 $1,200 per LF of tunnel pipe installed $20/ diameter inch per LF Schedule: Bid May 2016 NTP July 2016 Final inspection May 2017 $3,138,000 Ranger Pipelines $3,255,000

20 Sewer Bypass Walnut Street Excavate and expose existing 48 RCP line Cut out section of 48 RCP and install plug and bypass pump to downstream manhole Reroute existing 48 piping

21 Tunnel Boring Machine 72 ID 14 Length 100,000 ft. lbs. cutting torque 0-12 rpm cutting speed 55 gpm oil supply

22 Tunnel Boring Machine Cont.

23 Tunneling Rates 6-10 feet per day 2-3 week tunneling schedule went to two months

24 Spoils

25 Grout Ports in Tunneling Pipe 2-inch ports, performed annular space grouting 7 CY

26 Construction Considerations Slow Production Sewage Backups Existing Utilities Field repairing existing RCP after bypassing

27 Conclusions and Lessons Learned Pipe material specification important Keep it simple if possible Permits

28 QUESTIONS?