Kathryn Wallin Bennett Trenchless. Bo Botteicher Underground Solutions. Pipe Users Group Sharing Technologies Seminar Berkeley, CA February 18, 2016

Transcription

1 Pipe Users Group Sharing Technologies Seminar Berkeley, CA February 18, 2016 Kathryn Wallin Bennett Trenchless Bo Botteicher Underground Solutions

2 Project Area

3 Existing Sewers 66-inch Dryden Trunk 60-inch Cannery Seg. Line Aban. 8, 10 & inch Abandoned Tallow Plant Dryden Golf Course 18-inch Sewer

4 Project Design Scope Awarded to O Dell Engineering and Bennett Trenchless in November 2008 Evaluate trenchless installation of new siphon Investigate rehab of existing siphon Could not assess condition of existing siphon Would require evaluation and rehab after new siphon installation Evaluate cost of twin new installations and existing siphon abandonment

5 vd Dense Very Dense md Loose Medium Dense Geotechnical Conditions B ft B-2

6 Site Restrictions Limit disruption to golf course to 2 nd fairway Long truck access route Course to remain open - winter East side had minimal restraints Truck Access Work Area Twin Siphons

7 Topography Complications Upstream sewer tie-in close to steep slope Difficult for HDD to make tight bend and reduce risk of hydrofracture Microtunneling shaft could be placed immediately adjacent 24-inch

8 Downstream Tie-in Complications Tying into 66-inch sewer Large sewers have same invert elevation Need sufficient clearance to mitigate settlement risk HDD entry angle and limited work area result in low cover MT had reduced risk inch 60-inch

9 Microtunneling Alternative Single 60-inch casing for twin 18-inch siphons Sloped 410-foot crossing Shafts close to tie-in locations Reduced hydrofracture and settlement risk

10 HDD Alternative Twin 18-inch siphons with 20-foot clearance 735-foot long bores Open-cut required for tie-ins No vertical shafts results in better hydraulics

11 Recommended Method = HDD Hydraulic characteristics had fewer O&M complications Reduced cost and schedule vs. shafts for MT Sufficient pipe layout area on east side HDD entry at golf course Increased settlement and hydrofracture risks Additional open-cut sections for tie-ins

12 Bore Geometry Steep entry and exit angles: 17 and 18 Reduce open-cut sections at entry and exit Increase depth of cover beneath sewers, river Tight bend radius: 750 feet Reduce open-cut section at exit Limited by drill pipe bend radius Bore length: 735 feet Distance between tie-ins: 675 feet

13 Settlement Risk Evaluation

14 Settlement Risk Mitigation Conductor casing at entry for bore stabilization Minimum clearance beneath sewer = 6 Extend minimum 20 beyond CSL ft 20 ft

15 Hydrofracture Risk Evaluation

16 Hydrofracture Risk Mitigation Geometry reduced risk of hydrofracture into river or riparian habitat Minimum depth of 39 feet beneath river Conductor casings at entry Hydrofracture Contingency Plan Prepare for containment and clean-up Monitor for hydrofractures Immediate notification

17 Open-Cut Sections - Profile New Manhole Existing Manhole New Trenchless Siphons New Open-Cut Existing Sewers

18 Open-Cut Sections - Plan West Side East Side ~50 ft Existing Siphon New Manhole Existing Manhole New Trenchless Siphons New Open-Cut Existing Sewers

19 Pipe Material Geometry required 18 FPVCP or 22 HDPE Pullback Load and Pipe Stress calculations recommended DR11 HDPE and DR25 FPVCP Long term hydrostatic loading conditions recommended DR9 HDPE and DR21 FPVCP Design allowed both HDPE and FPVCP 22-inch DR9 HDPE has an ID = inch DR21 FPVCP has an ID = 17.53

20 Permitting Multiple Agencies had jurisdiction: CA Dept. of Fish and Wildlife US Army Corps of Engineers CA Central Valley Flood Protection Board CA Central Valley Regional Water Quality Control Board CA State Lands Commission Largest concern: drilling fluid spills into river

21 CA State Lands Commission Rigorous and time-consuming lease application process Required both design documents and contractor submittals Submit documents > 60 days before start of construction After construction, submit testing results and stamped as-builts

22 Winning Contractor Project bid June 2014 General Contractor: Mozingo Construction, Inc. (Oakdale, CA) HDD Subcontractor: HDD Company, Inc. (Cameron Park, CA) Total project cost: $2 Million HDD Cost: $1.1 Million (~$840/foot)

23 Mobilization

24 Conductor Casings Entry pits were excavated and shored to install casings beyond tie-in locations Twin 36 conductor casings for 30 bores

25 Centralizer Casings Used during pilot bore to keep drill pipe in center of conductor casing

26 Pipe Length Issues After mobilization, Contractor discovered distance between manholes slightly longer than purchased pipe Manufacturer located additional 40 feet out of North Dakota

27 American Augers DD-210

28 Pilot Bores Used combo of walkover and wireline for guidance Pilot bore diameter = 9 7/8 Completed in 3 days, ~250 ft/day No hydrofractures in river

29 Reaming Reamed to 30 in one pass Completed in 6 days, ~125 ft/day

30 Pipe Layout

31 Pipe Support during Pullback

32 Success!

33 Summary and Conclusions Successful HDD installation of twin 18-inch siphons under the Tuolumne River No hydrofracture or settlement of overlying sewers due to use of appropriate mitigation measures (conductor casings) Impacts to golf course operations minimized Significant delays associated with CA State Lands lease application

34 Questions?