GeoInsight®

Environmental Strategy & Engineering

Asset Management and Wells

David Maclean, P.G. GeoInsight

Agenda

Source Related Assets:

Pumps/Wells/Aquifers

Determining/Extending Asset Life

Expectancy:

Contingencies: What if things go

wrong?

Pump Types

Submersible Pumps

Vertical Turbine Pumps

Types of Wells

Aquifer Types

Life Expectancies

Consultant:

Pump:

Well:

Aquifer:

40-50 years

10-15 years

25-30 years

Indefinitely ?

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?

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;

Biofouling

Biofouling

Evaluating Pumps & Wells: Tools

Factors of interest include:

Discharge (Q)

Drawdown (s)

Specific Capacity (SC = Q/s)

Well Efficiency & Well Loss Coefficient

Geochemistry & Microbiology

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”

Operator Tip: Pump Curves

Worn Pump

Clogged Pump

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

)

Well Efficiency

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.

Maintenance

Cost/Methods for Routine

Maintenance?

Frequency of Maintenance Costs?

Contingencies: Replacement Wells

• Must be hydrogeologically

similar

• not appropriate for

contamination

Contingencies: New Wells

Contingencies: New Wells

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;