Oroville Emergency Spillway Repair Owner: CA Dept. of Water - PowerPoint PPT Presentation

Oroville Emergency Spillway Repair Owner: CA Dept. of Water Resources (DWR) General Contractor: Kiewit Drilling Subcontractor: Drill Tech Drilling & Shoring, Inc. Presented by: Brett K. Mainer, P.E., G.E. Drill Tech Drilling & Shoring, Inc.

Secant Pile Scope of Work • 605ea secant piles (5 piles per panel – 121ea panels) • 35’ to 92’ in depth • 36” diameter piles spaced 24” on center • Minimum depth into fresh rock = 15’ • Rebar cages in secondary piles

Site Settings, Geological Data

Top of Guide Wall Top of Secant Piles Wall Planned Fresh Rock Elevation Actual Drilled Tip Elevation New Plan Pile Tip Elevation

Installation Procedure • Guide Wall was excavated / formed / poured • Overburden (fill, topsoil and weathered rock) was drilled with conventional rotary drills using core barrels • Holes were flattened using a “hole flattener”, which is a modified core barrel • Magnets inserted in hole to retrieve any steel left behind • Downhole hammers (BG-50/BG-40/RTG-25) were used to punch through rock to planned depth • Hole cleaning with cleanout buckets and spin bottoms • Rebar cage placement in secondary piles • Concrete placement

Drill Equipment Summary • Overburden: • Bauer BG-40 1) • Bauer BG-24 (2ea) • Hammer: • Bauer BG-50 • Bauer BG-40 • Bauer RTG-25 (2ea) 1) Replaced with BG24 in Nov 2017 when needed on another project

BG-50 BG-24 BG-40

BG-24 RTG-25 BG-50

Hole Flattener

Hammer Drill Set Ups • 3 large air compressors per Hammer Drill • Combinations of 1300cfm, 1600cfm and 1170cfm compressors • Desired pressure to maintained = 200-225psi • Multiple hammer combinations used • Mono Hammers the primary tool • Center Rock Hammers and Bits • Atlas Copco Hammer and Bits • Cluster Drills Also used for Primary Holes only • Center Rock Cluster Drill • Keystone Cluster Drill

Hammers (Mono and Cluster) Keystone Cluster Hammer Center Rock Cluster Hammer Mono hammer

Hammer production rates • Total hammer drill rig shifts: • 552 shifts during 162 operation days. • Average production per rig shift: • 37.65 LF/rig shift. • Average production per operation day: • 128.3 LF/day.

Challenges • Rock strengths 30,000psi to 52,000psi • Rock strata was primarily composed of amphibolite • Constant destruction of tooling (Total Tooling Bill > $3M) • Concrete Placement in Hot Weather • Ground Water • Allowable Verticality Tolerance = 1.5” per 10’ = 1.25% • With only 12” of theoretical primary pile between secondary piles, piles over 40’ in depth could still be in tolerance and intersect • Rain during the winter months

Drilling Sequence • 1 st drilling sequence: • A-E-C • C-A-E • Secondary (B-D) piles • Deep Secondary Drill Holes would wander through the C piles and intersect • Sequence Revised to: • C-C-C • A-A-A • E-E-E • Secondary (B-D) piles A B C D E A B C D E

Drill Tech QC Form

Job Quantity Summary Number of Piles 605 Overburden Drilled 13,312 LF Fresh Rock Drilled 20,781 LF Total Weight of Cages 1,074,800 lbs Total Concrete Poured 11,580 CY Total Manhours Worked 61,708 Hrs Total Recordable Injuries ZERO

Final Accomplishment

Questions?