water system management new england
TRANSCRIPT
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GeoInsight®
Environmental Strategy & Engineering
Asset Management and Wells
David Maclean, P.G. GeoInsight
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Agenda
Source Related Assets:
Pumps/Wells/Aquifers
Determining/Extending Asset Life
Expectancy:
Contingencies: What if things go
wrong?
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Pump Types
Submersible Pumps
Vertical Turbine Pumps
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Types of Wells
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Aquifer Types
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Life Expectancies
Consultant:
Pump:
Well:
Aquifer:
40-50 years
10-15 years
25-30 years
Indefinitely ?
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Inventory: Importance
Remaining Useful Life: ?
Consequence of Failure:
• Do I have another pump ?
• Do I have another source ?
• Do I have a back up well ?
• Do I have access to other
promising spots for
prospecting?
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Evaluating Wells: Potential
Problems
Biofouling: Biologic Activity causing
Iron and Manganese Encrustation;
Chemical Encrustation: Chemical
Precipitation;
Siltation: Mechanical problem with
screen and aquifer;
Contamination: from a point or non-
point source;
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Biofouling
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Biofouling
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Evaluating Pumps & Wells: Tools
Factors of interest include:
Discharge (Q)
Drawdown (s)
Specific Capacity (SC = Q/s)
Well Efficiency & Well Loss Coefficient
Geochemistry & Microbiology
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Transducers and Monitoring Wells
2005 In-Situ Inc.
Measures:
• Level, Depth, Pressure
• Temperature
• (Open channel flow, derived from pressure)
• (Barometric Pressure – Baro TROLL)
Only 18.3mm
(0.72 in) OD
Now Shorter at 216mm (8.5 inch) in length
All Titanium Design!
Polly the consultant says:
“use monitoring wells and
transducers”
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Operator Tip: Pump Curves
Worn Pump
Clogged Pump
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Specific Capacity Q/s
Specific Capacity - PW7
0
1000
2000
3000
4000
5000
6000
May-93 Feb-96 Nov-98 Aug-01 May-04 Feb-07
Date
Sp
ecif
ic C
ap
acit
y (
m3/d
ay/m
)
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Well Efficiency
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Red Flags
Specific Capacity drops by 25% from initial value;
Water levels in well significantly lower from closest monitoring well;
Pump performance falling off the pump curve;
Water level approaches the top of the well screen; (gravel pack wells)
Water level lower than important fractures (bedrock wells);
Static water takes a long time (or never) to reach original static.
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Maintenance
Cost/Methods for Routine
Maintenance?
Frequency of Maintenance Costs?
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Contingencies: Replacement Wells
• Must be hydrogeologically
similar
• not appropriate for
contamination
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Contingencies: New Wells
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Contingencies: New Wells
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Thoughts to Take Away
• Wells are an expensive asset that can be
difficult to replace;
• Most New England wells are beyond their
typical life expectancies;
• Monitoring wells and transducers are needed
to interpret well performance;
• Install back up wells;
• Practice conservation and develop
contingency plans;