Closure of Remote Historic Underground Mines in Desert EnvironmentsClosure of Remote Historic Underground Mines in Desert Environments
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
2002 SME Annual Meeting and Exhibit2002 SME Annual Meeting and Exhibit
James A. Cremeens Agapito Associates, Inc.Michael H. Rauschkolb U.S. Borax, Inc.
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
• Geotechnical solutions were developed for closure of two historic underground borate mines in the deserts of California
• The Old Borate mining district located in the Mojave Desert near Barstow California
• Mined from 1890 to 1907
• The Lila C. Mine near Death Valley California
• Mined from 1907 to 1916 and 1920 to 1926
• Geotechnical solutions were developed for closure of two historic underground borate mines in the deserts of California
• The Old Borate mining district located in the Mojave Desert near Barstow California
• Mined from 1890 to 1907
• The Lila C. Mine near Death Valley California
• Mined from 1907 to 1916 and 1920 to 1926
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
CALIFORNIA
SanFrancisco
Lila C. Mine Site
Old Borate Mine Site
DeathValley
N
LosAngeles
SanBernardino
Location of the Old Borate and Lila C. Mine Sites
Location of the Location of the Old Borate and Old Borate and Lila C. Lila C. Mine SitesMine Sites
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Big Borate CanyonBig Borate CanyonBig Borate Canyon
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Big Borate Canyon post-1898
Big Borate Canyon Big Borate Canyon postpost--18981898
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Haulage AditHaulage AditHaulage Adit
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Decline ShaftDecline ShaftDecline Shaft
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Dugout DwellingDugout DwellingDugout Dwelling
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Underground at Old Borate
(Circa 1902—from Reynolds 1999)
Underground at Underground at Old Borate Old Borate
(Circa 1902(Circa 1902——from from Reynolds 1999)Reynolds 1999)
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Closure CriteriaClosure CriteriaClosure Criteria•Prevent public access
•Protect wildlife
•Minimize impact to fragile desert landscape
•Assure environmental compatibility
•Optimize use of native materials
•Prevent public access
•Protect wildlife
•Minimize impact to fragile desert landscape
•Assure environmental compatibility
•Optimize use of native materials
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Wildlife ProtectionWildlife ProtectionWildlife Protection• Conducted by bat and desert tortoise specialists
• Daytime internal examination and night bat surveys with night vision equipment and ultrasonic detectors
• No tortoise sign found within mines
• Bats or bat sign found in most of the mine openings
• Mine openings fenced to allow bat exit but not re-entry
• Conducted by bat and desert tortoise specialists
• Daytime internal examination and night bat surveys with night vision equipment and ultrasonic detectors
• No tortoise sign found within mines
• Bats or bat sign found in most of the mine openings
• Mine openings fenced to allow bat exit but not re-entry
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Pre-Construction DesignPrePre--Construction DesignConstruction Design
•ADITS•Collapse and Regrade•Polyurethane Foam
•SHAFTS and STOPES•Pre-Cast Concrete Panel Caps
•ADITS•Collapse and Regrade•Polyurethane Foam
•SHAFTS and STOPES•Pre-Cast Concrete Panel Caps
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
31
Original Ground
Final Grade (3H:1V)
Excavation (1.5H:1V)
Shaft Opening
Precast Concrete Panels
ExtremelyWeathered Siltstone
UnweatheredSiltstone
1.51
Prepare Smooth FoundationSurface and Shim Such ThatPanel Edges are Flush andPanels are Coplanar
Panel
Foundation
Backfill with Mine WasteRock (optional)
48"Typ.
2L
12"Typ.48"
Typ.
ShaftOpening
Armor Finished Slopewith Cobbles and Boulders
PanelAbutmentJoint
SurficialMaterialBackfillSurvey
Monument
Pre-cast Concrete Panel DesignPrePre--cast Concrete Panel Designcast Concrete Panel Design
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
• Strength of weak siltstone and claystone did not increase with depth
• Low bearing capacity• Foundation could be easily eroded• Ground caved and grew laterally with excavation
• Excavated mine openings were larger than surface expression• Large spans for pre-cast concrete panels• Increased number of concrete panels• Would have required steel beam support for large
spans
• Strength of weak siltstone and claystone did not increase with depth
• Low bearing capacity• Foundation could be easily eroded• Ground caved and grew laterally with excavation
• Excavated mine openings were larger than surface expression• Large spans for pre-cast concrete panels• Increased number of concrete panels• Would have required steel beam support for large
spans
Field ConditionsField ConditionsField Conditions
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Final DesignFinal DesignFinal Design
•SHAFTS and STOPES•Boulder Plug
•ADITS•Collapse and Regrade with Boulder Plug•Polyurethane foam
•SHAFTS and STOPES•Boulder Plug
•ADITS•Collapse and Regrade with Boulder Plug•Polyurethane foam
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Components of a Typical Boulder Plug ClosureComponents of a Typical Boulder Plug ClosureComponents of a Typical Boulder Plug Closure
Original
Final Grade
Excavation
Boulder Plug
ExtremelyWeathered Siltstone
UnweatheredSiltstone
SurficialMaterialBackfill
SurveyMonument
(1H:2V)
Ground
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Typical Adit Boulder Plug ClosureTypical Adit Boulder Plug ClosureTypical Adit Boulder Plug Closure
Excavation
Adit
1.51
Backfill
Regraded to Original
Monument
Original
Adit Portal
Boulder
Slope or Flatter
Ground
Survey
BackfillMaterialSurficial
(1.5H:1V)(Collapse)
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Excavating a StopeExcavating a StopeExcavating a Stope
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Typical Boulder Plug Placement SequenceTypical Boulder Plug Placement Sequence
Placing Initial BouldersPlacing Initial Boulders Completed Boulder PlugCompleted Boulder Plug
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Typical Boulder Plug Placement SequenceTypical Boulder Plug Placement Sequence
Beginning Backfill and Regrade
Beginning Backfill and Regrade
Placing FinalSoil Cover
Placing FinalSoil Cover
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Summary of Old Borate ClosureSummary of Old Borate ClosureSummary of Old Borate Closure
• 120 mine openings closed in 5-week period
• Boulder plugs satisfied design criteria
• Closure costs were significantly reduced by using native materials
• Lower unit costs = more mine openings closed
• 120 mine openings closed in 5-week period
• Boulder plugs satisfied design criteria
• Closure costs were significantly reduced by using native materials
• Lower unit costs = more mine openings closed
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Lila C. Mine Site—Circa 1907
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Main Haulage Level of the Lila C. Mine—Circa 1910
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Stope at Lila C.Stope at Lila C.Stope at Lila C.
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Decline shaft at Lila C.Decline shaft at Lila C.Decline shaft at Lila C.
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Open Stope at Lila C.Open Stope at Lila C.Open Stope at Lila C.
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Wildlife ProtectionWildlife ProtectionWildlife Protection• Conducted by bat and desert tortoise specialists
• No tortoise sign found within mines
• Surveys revealed four species of bats in the mines
• Two bat “Species of Special Concern” found
• Bat accessible designs were included in closure
• Conducted by bat and desert tortoise specialists
• No tortoise sign found within mines
• Surveys revealed four species of bats in the mines
• Two bat “Species of Special Concern” found
• Bat accessible designs were included in closure
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Bat Accessible ClosuresBat Accessible ClosuresBat Accessible Closures•Bat gates and cupolas designed by specialty contractor
to protect bat access, preserve ventilation, and maintain temperature
•Underground surveys conducted to optimize bat accessible design
•Bat gates and cupolas designed by specialty contractor to protect bat access, preserve ventilation, and maintain temperature
•Underground surveys conducted to optimize bat accessible design
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Closure DesignClosure DesignClosure Design
•SHAFTS and STOPES•Rock Mattress – AAI innovation
•ADITS•Collapse and Regrade with Boulder Plug•Polyurethane foam
•SHAFTS and STOPES•Rock Mattress – AAI innovation
•ADITS•Collapse and Regrade with Boulder Plug•Polyurethane foam
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
NativeGround
NativeGround
OriginalGrade
Partially Collapsedand Backfilled Stope
Pre-closure Daylighted Stope Configuration
PrePre--closure closure Daylighted Daylighted Stope Stope ConfigurationConfiguration
Limits of
Mattress
Excavation
BackfilledStope
(1H:1V)
GabionsBackfill
Final Grade
NativeGround
Rock
Rock Mattress Excavation and Construction of a
Daylighted Stope Closure
Rock Mattress Excavation Rock Mattress Excavation and Construction of a and Construction of a
Daylighted Stope ClosureDaylighted Stope Closure
Lila C. Mine—Typical Profiles
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Open StopeExisting
GabionsBottom Layer
GabionsTop Layer
Gabions In PlaceBottom and Top Layer
CL
Rock Mattress Construction for a Daylighted Slope
Rock Mattress Construction for a Daylighted Slope
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
a) Pre-constructiona) Pre-constructionattress Construction for a Daylighted Stopeattress Construction for a Daylighted Stope
b) Grading Hanging Wallb) Grading Hanging Wall
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Daylighted StopeRock Construction for a Daylighted Stopec) Wheel Roll Compactionc) Wheel Roll Compaction
d) Gabion Constructiond) Gabion Construction
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Daylighted StopeRock Construction for a Daylighted Stopee) Filling Gabions withNative Rocke) Filling Gabions withNative Rock
f) Backfilling OverGabion Rock Mattress
f) Backfilling OverGabion Rock Mattress
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Daylighted StopeRock Construction for a Daylighted Stopeg) Partially BackfilledRock Mattressg) Partially BackfilledRock Mattress
h) Final Grade and Armored Slope
h) Final Grade and Armored Slope
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Shaft ClosureRock Construction for a Shaft Closure
a) Shaft after Surface Preparation for Rock Mattressa) Shaft after Surface Preparation for Rock Mattress
Plywood Barrier to Keep Debrisout of Shaft During Excavation
Rock Debrison Plywood Barrier
ShaftPerimeter
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Shaft ClosureRock Construction for a Shaft Closure
b) First Layer of Gabions of Shaftb) First Layer of Gabions of Shaft
ShaftPerimeter
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Shaft ClosureRock Construction for a Shaft Closure
c) First and Second Layers of Rock-filled Gabions—Completed Rock Mattress at Shaft
c) First and Second Layers of Rock-filled Gabions—Completed Rock Mattress at Shaft
First Layerof Gabions
Second Layerof Gabions
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Rock Construction for a Shaft ClosureRock Construction for a Shaft Closure
d) “Load Test” on a Rock Mattress at Shaftd) “Load Test” on a Rock Mattress at Shaft
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Backfillover L26a
L26b
Rock Construction for a Shaft ClosureRock Construction for a Shaft Closure
e) Backfill over Rock Mattresse) Backfill over Rock Mattress
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Typical Foam Seal ConstructionTypical Foam Seal ConstructionTypical Foam Seal Constructiona) Preparing Backing Latticea) Preparing Backing Lattice
b) Applying Foamb) Applying Foam
c)Completed FoamApplication
without Backfill
c)Completed FoamApplication
without Backfill
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Bat GateBat GateBat Gate
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Construction and Final Configuration of Bat CupolaConstruction and Final Configuration of Construction and Final Configuration of Bat CupolaBat Cupola
a) Landing Ring and First Course Concrete
Pipe in Place
a) Landing Ring and First Course Concrete
Pipe in Place
b) Completed/Backfilled
Shaft ExtensionAnd Bat Cupola
b) Completed/Backfilled
Shaft ExtensionAnd Bat Cupola
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Cost Comparison (USD-2000)Cost Comparison Cost Comparison (USD(USD--2000)2000)
•Gabion Rock Mattress with concrete $21,920
•Plastic Grid $21,712
•Foam Plug $20,890
•Gabion Rock Mattress $18,880
•Gabion Rock Mattress with concrete $21,920
•Plastic Grid $21,712
•Foam Plug $20,890
•Gabion Rock Mattress $18,880
AGAPITO ASSOCIATES, INC.Consulting EngineersAGAPITO ASSOCIATES, INC.Consulting Engineers
Thank-YouThankThank--YouYou