COMPONENTS & BENEFITS of PROPERLY CONSTRUCTED WELLS
Transcript of COMPONENTS & BENEFITS of PROPERLY CONSTRUCTED WELLS
COMPONENTS & BENEFITS of
PROPERLY CONSTRUCTED
WELLS
STEVE SCHNEIDER – BSME, MGWC
2011, 2012, 2013 President – National Ground Water Research & Educational Foundation
Figure 1 – Hydrologic Cycle pg.3
Non-Porous Earth and Confining Rock
Fresh Ground Water Zone Ocean
Water Vapor
Rain
Snow
Hail
HYDROLOGIC CYCLE
Septic
System
Salty/Brackish
Water Zone
Water
Well
Soil/Porous Earth
Infiltration &
Percolation
Sun’s Heat
Causes Evaporation
WATER: Same amount
yesterday, today & tomorrow
ROLE OF GROUNDWATER
World’s most extracted raw material (600 to 700 billion m3/year).
Less than 1% of all water is liquid freshwater (not ice).
Fresh liquid: >100X SW
Fresh GW:
>99% of all liquid freshwater
WHY WELL GUIDELINES?
‘WHY PROPER WELL CONSTRUCTION?’
“... in Bangladesh, …half of the countries 12 million … wells have unacceptable levels of arsenic due to the wells not being dug deep enough...” Wikipedia
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“It is not enough to drill a well and walk away,” says … Jamie Skinner of the London-based International Institute for Environment and Development. … He estimates $300 million of investment has been wasted, …
“In the Menaka region of Mali, 80% of wells are dysfunctional,” …“In northern Ghana, 58% require repair.” Key problems, he says, are bad design and poor construction. ….” NewScientist.com article dated 7/14/2009
WHY… cont.
‘Hand dug or excavated wells pose significant concern for the safety of those constructing, maintaining and using such wells.
In addition, the difficulty of constructing and maintaining a sanitary supply using the dug well technique argue against the practice…’
EVOLUTION of GUIDELINES
2008 NGWA DCIG presentations
2009-10 1st, 2nd, 3rd drafts
◦ Panama, WaTER, NOLA, AWRA, LV, email etc
◦ Circulated to 1000’s; 100’s of suggestions included
2011 4th draft & First Edition @ WaTER
2012 Second Edition – CBA added. EWB regional conference @ Cal Poly
2013 Swahili translation ½ day workshop @ WEDC – Kenya
KNOWN GUIDELINE USES Course text –
◦ US universities / academia
◦ International academia (latest in Afganistan)
Other International uses
◦ Field crews – Drillers/Hydrogeologists
◦ NGOs
◦ Government regulatory agencies (create stds)
◦ Government aid agencies
Reference resource
◦ WEDC - UK
◦ RWSN - Swiss
COMING SOON
Third & ??? editions ◦ Filter pack selection and design
◦ Well design considerations
◦ Shale trap application
◦ Drilling method comparison
◦ Sealant selection / application
Translations ◦ French
◦ Spanish
◦ Chinese
◦ Dari
Workshops?
SOME COMPONENTS
Location, location, location ◦ Set backs
Documentation – well logs ◦ Facilitates O&M
◦ Used by drillers, hydrogeologists Locate other well locations
Design other wells
Facilitate drilling plans for other wells
Aquifer characterization
Reposited & accessible
Annular seal ◦ Mandatory
◦ Chip bentonite
◦ Commingling
BENEFITS–PROMPTED BY BIG Q
Shouldn’t a well be constructed asap, even if resources aren’t available to properly build it, in order to get some immediate result e.g. lives saved?
Related concept: Wells should be constructed today even knowing that the resultant water supply has a high probability of containing a pathogen or harmful chemical or of wasting or contaminating groundwater?
or…
Will more people’s lives be compromised with inferior construction? Water quality, longevity of usefulness and safety are all factors.
e.g. If safety incident happens on your watch, will you be able to forgive yourself?
RISKS / THOUGHTS re: BIG Qs
Inferior wells require decommissioning or repair at some time in future: ◦ $$$ to properly decommission / repair
◦ Safety (open boreholes)
Contamination from GW creates negative perception of GW source ◦ One chance to make first impression
Long term aquifer damage ◦ GW becomes a problem, not a solution
Short term solutions are available ◦ e.g. pots
COST BENEFIT ANALYSIS
June 2012 – OSU
Jaynie Whinnery, BSME
October 2012
PDF on web – also spreadsheet
CBA Revelations
Almost 40x more benefit than cost
◦ If properly constructed, operated, maintained
~5X increase in net value with O&M
Unacceptable: Building wells that will
likely produce localized poor water
quality – negative NPV (B:C ratio <1)
3x to infinity more NPV: Proper well v
Inferior well
CBA Presumption (not specifically analyzed)
UNACCEPTABLE: Well that results in GW
contamination or aquifer damage - e.g.:
◦ Commingling
◦ Uncontrolled artesian
NEGATIVE IMPACTS:
◦ Reduced large-scale benefits
◦ Added cost of remediation / mitigation
Such impacts will most certainly result in negative NPV
CBA – Customizable Spreadsheet
Number of wells
Number of users per well
Construction costs
Discount rate
Percent of income used for water
Local GNI-PPP
Morbidity value
Mortality value