AHS H2O Mgmt Forum Vancouver 2-15

Elements to Consider in Mine Dewatering Management

Know Your Regulations And

Data Management for Optimization, Design, Troubleshooting and

Maintenance February 24, 2015

Sherry L Gaddy, Owner-Principal Hydrogeologist Aspen Hydrologic Services, LLC

Elements to Consider in Mine Dewatering Management - Agenda

•  Introduction – Sherry L Gaddy (AHS) –  Education, Experience and History

•  Know Your Water-Related Regulations –  Local and State –  Federal to International

•  Data Management –  What Data is Collected –  Accurate Data Collection –  Measuring Device Installation –  Water Balance

•  Operation/Maintenance –  Wells, Sumps, Etc: Does this affect our bottom line?

! Well Failure –  Consumption/Disposal

•  Summary

Elements to Consider in Mine Dewatering Management – Sherry L Gaddy

•  Who am I? –  Raised on a farm/ranch in South Dakota

! Raised pigs, cows, and horses !  Irrigated corn, wheat, alfalfa and oats

–  Bachelor of Science in Geological Engineering, South Dakota School of Mines and Technology, Rapid City

–  Chemist, four years of testing mine water for minerals & metals

–  Operational Hydrogeologist – 15 yrs in Nevada ! Five years dewatering Lone Tree Mine from 11,000 gpm up to 35,000

gpm •  Issues: water chemistry, water treatment plant, water disposal, aquifer recovery, high wall

stability, subsidence, high specific capacities, up to 10 wells, mine plan

! Four years dewatering Round Mountain Gold Mine from 3,000 gpm up to 8,000 gpm

•  Issues: water chemistry, water biology, high wall stability, structural subsidence, transient flows, low specific capacities, up to 25 wells, mine plan, dry miners

Elements to Consider in Mine Dewatering Management – Sherry L Gaddy

–  Operational Hydrogeologist (cont.)

! Three years in-situ mining (pumping lithium brine) at Chemetall Foote at 9,000 gpm

•  Issues: water chemistry, ash flows, salt beds (caverns), well metallurgy, pump metallurgy, ground subsidence/sink holes, high flow range, up to 60 wells

! Two years dewatering at Robinson Nevada Mine at 6,000 gpm •  Issues: structural carbonate aquifer, water biology, high wall stability, geology, water

disposal, NDEP/NDWR requirements, variable specific capacities, mine plan, dry miners

–  Consulting Operational Hydrogeologist ! Hydrologic characterization, develop hydrologic database, and EIS/

Permit/Environmental support for Mt. Hope Mine, Eureka Moly and Sumitomo Metal Mining – Pogo Mine

•  Aquifer testing, pump testing, well research, quality control of data for database import, compliance monitoring and develop digital pressure transducer array, Surface and Underground Mining

! Well Troubleshoot and Rehabilitation for Dubray Farms irrigation and Phil Henry, residential.

! Repair and maintain hydrologic GIS database for White Pine County •  Review existing GIS database for regional hydrologic study

! Water Rights reporting, training and support for Quadra - RNMC

Elements to Consider in Mine Dewatering Management - Regulations

•  Local and State (USA); Federal –  Know local requirements for City and Local Ordinances

! Will your operation affect the local water supply? Is a model required?

–  Each State regulates water rights/law differently ! CA vs. NV vs. CO

–  Do only State regulations apply or do Federal regulations apply or both? ! AK for example

–  Typical Permits !  Stormwater ! Water Quality ! Waste Water ! Clean Water Act – Water Disposal ! Process Water ! Wetlands

•  International –  How does your companies policies compare to a country’s

regulations or lack of regulation?

Elements to Consider in Mine Dewatering Management – Data Management

•  Optimize Water Management Through Accurate Data Management

–  Data Collection – Water Flow is a Balance ! Accurate and consistent with Quality Assurance (QA) – Develop SOP’s ! Most common instrumentation: Flowmeter/Totalizer and Flumes ! Must measure every point of diversion (source of water)

•  Wells •  Surface Water Inflows (considered MIW) •  Operational Sumps (considered MIW) •  Pit Lakes (considered MIW)

•  Fun Fact: NV is considering requiring a water right to account for evaporation (SB 173) ! Must measure every point of consumption or disposal

•  Dust Control - Water Truck Loadouts and Crusher •  Mill Freshwater Makeup •  Mill Reclaim via Tails •  Water Treatment Plants – MIW and Waste •  Potable Water •  Municipal •  Irrigation •  AMD •  Injection Wells •  Rapid Infiltration Basins •  Discharge to Surface waters

•  Quality Data Collection

–  Bad Data is worse than No Data ! Why?

–  Accuracy – proper installation of measuring devices ! Totalizers/Flowmeters

•  Requirements for accurate Flow Readings •  Must have Laminar Flow

–  Flow that is essentially straight or flat –  Spool ahead is 5 to 10 times diameter in length

–  Spool following is 2 to 5 times diameter in length

•  Minimize turbulent Flow –  Flow that is curved, circular or bent (swirling) –  All valves are located after the meter and spools (not before!) –  All elbows, ‘T’s, laterals, etc. are located either ahead or following the spools

(not next to the meter)

•  Must have a full pipe –  Magmeters will measure any and all fluids including air (false flow or negative

flow) –  Paddle meters will measure partial flows as full flows and turbulence will also

cause inaccuracy


Well Discharge Head Assembly

Motor Controller

Bu,erfly Valve Check Valve

Air Relief Valve

Flowmeter/Totalizer

Pressure Gauge Sample Port

Water Level Pressure Transducer

Spools


Well Discharge Head Assembly

Check Valve Air Relief Valve

Flowmeter/Totalizer

Pressure Gauge

Bu,erfly Valve

Sample Port


What is wrong with this picture? Saddle Valves located too close to meters.

No spools following the meters.

Check & Bu=erfly Valves immediately following meters.



–  Accuracy – proper installation of measuring devices !  Stream Gages

•  Requirements for accurate Flow Readings •  Must have Laminar Flow

–  Relatively straight section of the stream –  Flow measured at regular intervals perpendicular to flow in the centroid

of flow.


Discharge Measuring Equipment-Klamath.ppt, USGS, 9-22-11


–  Accuracy – proper installation of measuring devices !  Flumes

•  Requirements for accurate Flow Readings •  Upstream conditions need to be straight and nearly flat for laminar flow

•  Crest of the flume needs to be level longitudinally and transversely •  Downstream conditions need to prevent submerged conditions


Tracom – Parshall Flume and H-Flume


–  Accuracy – proper installation of measuring devices ! Weirs

•  Requirements for accurate Flow Readings •  Eliminate water circumventing the weir

•  Flow over the crest should have air pocket (beveled edge) •  Excess sedimentation in the throat or approach minimizes accuracy •  Throat or approach needs to be straight for a distance of 20X max head and little to

no slope

•  Stilling pond may be required to slow velocity at the weir to <0.5ft/sec •  Weir needs to be level and material impervious to water


“What is a Weir and How does it Work?”, Hubbard Brook, T. Siccama and E. Denny, 1-2001

Parshall Flume and V-Notch Weir used in conjunction for high flow variation.

•  Collection

–  Keep hand written records for auditing purposes ! Data is required to prove water pumped/consumed/disposed ! Consistency is KEY

–  Data collected daily –  Data required:

! Name of person collecting data ! Date and time for each location ! Volume in gallons or acre-feet ! Multiplier (x1, x10, x100, x1000) !  Flow in gpm or cfs

–  Pump/Motor Data (wells, booster stations, sumps, etc.) !  Electrical current in amps, average of three phases !  Electrical current balance (unbalance) !  For high speed submersible motors – must be less than 5% ! Discharge head pressure in psi, Inlet psi (booster) ! Water Levels in Pumping Well (Weekly Collection) Note Method of Sounder or

Pressure Transducer, etc. ! Comments


EXAMPLE DATA COLLECTION SHEET


•  Water Balance

–  All data collected will be entered into a digital file –  The data will be used – be detailed and accurate –  A detailed water balance is just like a budget

! Accounting ! A ledger of water pumped from all source locations (income) ! Compared to water consumed and disposed (expenses) ! Water applied to the Dewatering Water Rights is considered disposed

back to the basin and not consumed or used ! All water income should equal all water expensed


Elements to Consider in Mine Dewatering Management – Operation/Maintenance

•  Wells, Sumps, Etc: Does this affect your bottom line?

–  How does all this data help you? ! Moving water is expensive!! An efficient system saves money.

•  Move only enough water to get the job done – how much freeboard is required by the mine plan? How much water is required for process?

! Determine well, pump and pipeline efficiencies

•  Redesign and/or rehabilitation may be required as systems age and water levels drop

! Enhance Preventative Maintenance with Trends over Time

•  Catch pump/well failures before they become catastrophic

! Failure Analysis/Troubleshooting – Simplified with Data

•  Quicker and more accurate determination of failures with solutions

–  Example – Well Failure September 2007, Southeastern Copper Mine NV

Elements to Consider in Mine Dewatering Management – Well Failure

•  Well Failure September 2007, Southeastern Copper Mine NV

•  What did we know? – Original Flow of ~1,200 to 1,400 gpm –  Last Recorded Flow of ~800 gpm –  Pump was shut down in response to mill fresh water

needs – At restart, no water made it to surface and motor

controller shut pump off. Repeated starts produced the same results, until the motor/pump no longer engaged

– Motor megged bad – No pumping water level data collected during

operation – No amperage or discharge head pressure data had

been collected


•  Well Failure September 2007, Southeastern Copper Mine NV

•  Additional data gathered with further investigation: – Nearby monitoring well water level data was

available through consultant (not kept onsite) – Well had been producing sand for over a year (not

reported until review meeting) –  Flow had been dropping for over a year –  Pump curve was made available through

consultant (not available on-site) – Well Driller’s Report Log for Pumping Well

Drawdown (dd) is the difference in water level caused by pumping stress (pwl-‐swl).

StaOc water level (swl) is the water level at atmospheric pressure.

Pumping water level (pwl) is the water level during pumping.

Recovery is when the water level returns to staOc.

Specific Capacity (SC) is flow (gpm) per foot of dd.


Well Pump Curve 2006

Design Point

600

1,400

675

800

Expected Water Level

442

Pump Condition?


•  Well Failure September 2007, Southeastern Copper Mine NV (cont.)

–  Now what do we know? ! Flow declined for over a year from 1,400 gpm to 800 gpm

! Repeated starts burned up the motor

! Drawdown in the nearby monitoring well slowed and then began to recover while the pumping well was in operation

! Pump curve shows severe decline in pump condition

•  Drop in flow while pumping water level recovered rather than drawing down



–  Theoretical Conclusions based on Data: ! Decline in pump condition caused motor to fail

! Pumping sand caused decline in pump condition

! Potential sources of sand or well casing failures caused by the following:

•  Ground movement

•  Screen slots widening overtime due to consistent erosion

•  Gravel pack too small for screen slot size

•  Hole in casing or screen



–  Action required due to data-based conclusions is to pull the pump and determine additional information or damage

! Based on weight of pumping system and column pipe, Carson Pump was hired to pull the system

! Pump rig mobed to site and attempted pull.

! Pumping system was too heavy for the rig!

! Why?

! Bring in Boart Longyear and a much larger rig.


Pump Pulled in Dec 2007 by Boart Longyear.

Size and quantity of Gravel Pack confirmed with Well Driller’s Report Log.

Over 80 T of Gravel Pack in Column Pipe and Pump.


The hole in the column pipe caused water to jet a hole in the well screen allowing ~700 ft of well gravel to pour into the well and/or be pumped to the mill.

Column Pipe Failure at connecOon immediately above the Pump.


•  Well Failure September 2007, Southeastern Copper Mine NV (cont.) –  Results in pulling the pumping system

!  80 ft of well gravel in column pipe and pump

! Gravel locked up pump and caused motor to burn up under repeated starts

! Well had 200 ft of fill (well gravel) in the bottom of the well

! Hole in the column pipe located immediately above the pump

–  Downhole Camera Survey Performed ! Needed to see exact location and size of hole in the casing

!  Located and marked visually on camera with sounder tape

! Visually confirmed lack of gravel pack behind the screen above the hole

–  Repair well casing and removal of fill required ! Bill Longmire swaged the hole in the well casing with thin crimped steel

! Boart Longyear returned with bailer to remove fill and redevelop well via air-lifting

! Perform Air-Lift/Recovery Test to determine new well specific capacity for pumping system design


Bill Longmire Swaging Pumping Well

Crimped Steel Pipe SecOons for well Casing Repair


•  Well Failure September 2007, Southeastern Copper Mine NV (cont.) –  Cost incurred in Catastophic Failure of Well and Pump

!  Carson Pump to Pull Pumping System - $14,000 !  Boart Longyear to Pull & Set Pumping System & Bail Well - $100,000 !  Boart Longyear to Camera Survey Well Before & After Swage - $3,000 !  Bill Longmire to Swage Hole in Well Casing - $8,000 !  New Pump, Motor, Downhole Cable and Column Pipe - $252,000 !  Total Cost of Failure - $377,000 !  Lost Production to Mill from Reduced Production & Well Down - 852,048,000 Gals

–  Estimated Cost with Data Tracking and Preventative Maintenance !  Carson Pump to Pull and Set Pumping System - $22,000 !  Boart Longyear to Camera Survey Well Before & After Swage - $3,000 !  Bill Longmire to Swage Hole in Well Casing - $8,000 !  New Pump and Column Pipe - $96,000 !  Estimated Cost of Preventative Maintenance - $129,000 !  Potential Cost Savings - $248,000 !  Lost Production to Mill from Reduced Production & Well Down - 43,920,000 Gals !  Potential Gallon Savings - 808,128,000 Gals


•  Consumption/Disposal

–  How does all this data help you? ! Properly manage consumptive use to minimize dewatering well

downtime ! Properly manage dewatering disposal to minimize dewatering

well downtime ! Maximize efficiency of the overall system ! Coordination with mine operations and mill process ! Lost dewatering time is never made up

•  Don’t get behind! It can seriously affect or delay your mine plan!

–  Cannot sump your way to success ! Potential geotechnical issues (high wall instability and failure) ! Safety setbacks such as MSHA ordered pit shutdown ! Wet ore increases cost of blasting due to emulsifiers, cost of

digging due to unstable dig face & getting stuck in the mud, and cost of haulage due to high water content (added weight with no benefit) and slippery, uneven surfaces.

! Wet ore also increases maintenance costs, such as, tire wear, etc.

Elements to Consider in Mine Dewatering Management – Operation/Maintenance

Elements to Consider in Mine Dewatering Management - Summary

•  Know Your Water-Related Regulations –  Local and State –  Federal to International

•  Data Management –  What Data is Collected –  Accurate Data Collection –  Measuring Device Installation –  Water Balance

•  Operation/Maintenance –  Wells, Sumps, Etc: Does this affect our bottom line?

! Well Failure

–  Consumption/Disposal

Elements to Consider in Mine Dewatering Management

QUESTIONS?!SHERRY L GADDY!

[email protected]!

AHS H2O Mgmt Forum Vancouver 2-15

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