Transcript No Slide Title

Water Wells for Yield and
Health
By
Michael L. Vaught
EGIS PA
441 Northside Dr
Ground Water Atlas of the
United States
Map Segment 6
Geographical provinces
Types of aquifers
Map Segment 11
capp.water.usgs.gov/gwa/gwa.htm
http://mapping.usgs.gov/mac/isb/pubs/boo
klets/usgsmaps/atlas.html
Ground Water Atlas of the United States
Segment 11
Rock Type
Sedimentary, Metamorphic, and
Igneous rocks.
Hard to crystalline rock verses
unconsolidated granular aquifers.
Reference the Ground Water Atlas of
the United States and the Geological
Surveys Maps.
Water Wells for Yield
Depth
Diameter
Screens
Test yield
Depth & Diameter
Geographic or Physiographic location
Coastal Plain
Piedmont
Mountains
Type of Well
shallow or deep
large or small diameter
cased or “open hole”
Well Depth & Diameter
Hard to crystalline rock
Charles Daniel III, 1989, Geological
Survey Water-Supply Paper 2341-A.
Wells below 400’
Large stress release fractures
12” wells have 4 times yield of 6” wells
Well Depth & Diameter
unconsolidated granular aquifers
Ralph Heath, 1983, Geological Survey
Water-Supply Paper 2220.
Depth depends on lowest zone tapped
Aquifer Thickness & Composition
Diameter has little effect on yield
Limits pump size
Ratio of Yields by diameter
4inch
1.oo
6
8
10
12
1.05
1.09
1.13
1.16
1.oo
1.04
1.07
1.10
1.oo
1.03
1.06
1.oo
1.03
Pump Size by well diameter
Well Yield
Pump Size
Casing Size
>100 GPM
4
6
75 – 175
5
8
150 – 400
6
10
350 - 650
8
12

Well Screens
Sizes
Types of material
Test Yield
Required yield
EPA 570/9-91-004
Homeowner per resident 50-75 gpd
Campgrounds per camper 15 gpd
Cottages seasonal per resident 50 gpd
Restaurants per patron 7 - 10 gpd
Test Yield
Codes and regulations.
Well Capacity
Domestic (not public, industrial, irrigation)
Max continuous quantity for 1 hour
Note static and pumping WL’s and GPM
Test Yield
Specific Capacity
Static Level
Pumping Level
Drawdown
Pumping Rate
Pump Depth
Recharge Rates
Static Head
Test Yield
Specific Capacity

65 GPM Withdrawal


15’
Static WL

100GPM Withdrawal


15’
Static WL


45’
Pumping WL


65’
Pumping WL



100gpm / (45-15)ft
= specific capacity of
3.3 gpm/ft of drawdown



65gpm / (65-15)ft
= specific capacity of
1.3 gpm/ft of drawdown

Specific Capacity of a
newer well

Specific Capacity
after 15 years
Water Wells for Health
Well Health and Safety
Casing
Sealing the Annulus
Wellhead Protection
Air quality, drainage, and recharge
Well Maintenance
Flushing and circulation
Sealing the Annulus
 Administrative codes and regulations
Minimum of 20’
Bentonite, Cement, Concrete, Mixtures
Wellhead Protection
Wellhead Protection
Wellhead Protection Guidebooks
WHPA Delineation Methods
Arbitrary fixed or calculated fixed radius method
Landscape so surface water drains away from
the wellhead
Well Maintenance
Homeowner
Campgrounds
Cottages
Non-community & Public Systems
Well Maintenance
Pump Depth
Exercise (water usage)
Chlorination
>200 ppm, 6 pH
Record keeping
Annual Testing for Bacteria
Chlorination not recommended for coliform
Set pump intake As Shallow As Possible (ASAP).
 Pumping influences motion within the borehole column
 Pumping oxygenates the well water from the top down.
 Pumping draws shallow water downward.
 Pumping utilizes water from two sources; Well Storage
and Well Flow.
Well Storage
 Stored water lies above the intake and the above the
highest water zone
 Well Storage- Zone of the water column within or
draining to the borehole that is both above the pump and
above the most shallow production zone,( called the “
Storage Cell”).
 In Storage Type Wells the pumping water level
continuously falls during the stress test.
Well Flow
 Flowing water moves between the production zones and
the pump intake.
 Well Flow – Zone of the water column between the pump
and any contributing production zone (called the
“Flowing Cell”).
 In Flowing Type Wells the water level stabilizes during
the stress test.
Flowing type wells generally remain cleaner.
 Flowing type wells minimize the borehole Storage and
maximize the Flowing Cells by the correct pumping
depth.
 Flowing Cells remain cleaner because of the borehole
turbulence and lack of enrichment.
 Flowing type wells = Long term reliability + controlled
biofouling.
Storage type wells require periodic maintenance.
 Typically Storage Cells become enriched and biofouled
in the top of a water well.
 Storage type wells must be exercised regularly to flush
biofilm and enriched water from the cell.
 Storage type wells = Short term maintenance + rapid
biofouling.
Minimize Storage and Enlarge Flow Cells
 Excess Storage generates uncontrolled growth of
naturally occuring biofilms within the well.
 Enrichment of the excess or recycled Storage accelerates
biofouling from the top down.
 Set the pumping depth in a well based on Actual
Maximum Demand.
 Set the pumping depth no more than twenty feet below
the actual maximum demand level in the average
Domestic size water well.
Set pump intake depth for actual
maximum demand.
 Actual Maximum Demand Water Level – Depth to water
within the well during one hour of continuous pumping
while hooked to the system under simulated intense
usage.
 Set the pumping depth no more than twenty feet below
the actual maximum demand level in the average
Domestic size water well.
Rehabilitating biofouled wells means controlled
biofilms.
 Recondition homeowners dirty wells by cleaning the
biofouling and repositioning the pump (ASAP).
 Repairs eliminate shallow water.
 Borehole flow diverters change the Flowing Cells to
eliminate turbidity.
Shallow Pump with Flow
Sleeve
Top of Casing
Ground Level
Grout
P
U
M
P
71.5’ Shallow water zone. 7 gpm
160’. Water producing
zone from video record.
Six inch open rock borehole.
Bottom of 6.25” Casing
Flow sleeve or flow pipe
176’. Documented by video.
Water producing zone.
300’ submersible pump with flow sleeve
500’. Bottom of the well from downhole video.
Deeper Pump with Flow
Sleeve
Top of Casing
Ground Level
Grout
42’ Bottom of 6.25” Casing
Six inch open rock borehole.
45.4’ Water Level. Static or full level
50’Shallow water zone.1gpm
160’. Water producing
zone from video record.
P
U
M
P
176’. Documented by video.
Water producing zone.
300’ submersible pump with flow sleeve
500’. Bottom of the well from downhole video.
Liner with Flow Sleeve
Liner pipe
Ground Level
Grout
42’ Bottom of leaky well casing
Six inch borehole.
Packer or seal to hold grout
50’Shallow water zone.1gpm
160’. Water producing
zone from video record.
P
U
M
P
Flow sleeve or flow pipe
500’. Bottom of the well from downhole video.
Well Abandonment
Disinfecting
Sealing
Decommissioning
Responsibility for Well
Abandonment
Codes and Regulations
Well owner
Well contractor
Pump installer
Forms ______
Abandonment of Bored Wells
Large diameter, 18-36 inches
Remove plumbing or obstructions
Disinfect with calcium hypochlorite
Remove well casing (3’ BGL)
Fill with cement, concrete, bentonite, dry
clay, natural material.
Cap with 1’ cement plug extending 1’.
Abandonment of Drilled Wells
Gravel packed, screened, unconsolidated
Remove or grout the casing
Determine well depth
Disinfect with calcium hypochlorite
Fill with neat cement or Bentonite grout
Cased open hole
Same as above except……...
Fill to 10’ below TOR or 5’ below CSG with
cement, bentonite, sand, gravel, or cuttings.
Fill to surface
Summary
 Well characterization is essential for sustained quantity and quality.
It is the first step in configuring a water supply system for long-term
yields of consistent water.” “Use-it-or-loose-it”, if the well is set up to
supply more water than is routinely needed, maintenance must
include maximum demand pumping either quarterly or monthly.
“Private Water Systems Handbook” says; “A home water system
must be able to supply the peak use rate continuously for one hour.”
 When the pump depth is set to maximize the well yield, the well may
accumulate enriched water above the pump. Pump depth should be
sufficient to allow only 10 to 20 feet of water above the pump during
peak demand intervals. Adequate drawdown can stop oxygen
enrichment and prevent biofouling.
References
Web sites (yahoo search - water well drawdown)
Books and Supplier Materials
Professional Organizations
 American Groundwater Trust
 Groundwater Associations
 Water Systems Council
Government
 EPA, USDA, USGS
 State Agencies
 Extension Service