Karst Aquifer Well Rehabilitation Project
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Transcript of Karst Aquifer Well Rehabilitation Project
EAWA Well #7 EAWA Well #7 RehabilitationRehabilitation
Municipal Groundwater Supply Municipal Groundwater Supply Corrective ActionCorrective Action
December 2008 – January 2009December 2008 – January 2009
BackgroundBackground
400-foot deep karst limestone well drilled in 1995400-foot deep karst limestone well drilled in 1995
Permitted at 400 gpmPermitted at 400 gpm
Permitted rate limited by turbidityPermitted rate limited by turbidity
High turbidity event in November 2008High turbidity event in November 2008
Well shut down by PaDEPWell shut down by PaDEP
Testing for surface influence by PaDEP in December Testing for surface influence by PaDEP in December 2008 (negative result)2008 (negative result)
Pre-Rehabilitation TeleviewingPre-Rehabilitation Televiewing
Well #7 and nearby Well #6 were televiewed December Well #7 and nearby Well #6 were televiewed December 8, 2008 before rehabilitation8, 2008 before rehabilitation
Cloudy water and significant silt and clay material in Cloudy water and significant silt and clay material in water-bearing zoneswater-bearing zones
Bottom 130 feet of well bore full of debrisBottom 130 feet of well bore full of debris
Review of 1995 report suggested that the well was not Review of 1995 report suggested that the well was not
adequately developed initiallyadequately developed initially
RehabilitationRehabilitation
Rehabilitation by air development with drill rig Rehabilitation by air development with drill rig occurred in December 2008occurred in December 2008
RehabilitationRehabilitation
Large volumes of muddy water, clay and rock Large volumes of muddy water, clay and rock debris removed from well during several days of debris removed from well during several days of air developmentair development
Rehabilitation ProcedureRehabilitation Procedure
Water-bearing zones were surged numerous Water-bearing zones were surged numerous times over several days times over several days
Well air developed by raising and lowering air Well air developed by raising and lowering air source over entire borehole length numerous source over entire borehole length numerous times during rehab periodtimes during rehab period
Surfactant used to clean up entire bore and Surfactant used to clean up entire bore and karstic water-bearing zoneskarstic water-bearing zones
RehabilitationRehabilitation
Dramatic improvement to water condition Dramatic improvement to water condition after several days of developmentafter several days of development
ComparisonComparison
Before:Before:
cloudy discharge w/ debris and 400 gpm limitcloudy discharge w/ debris and 400 gpm limit
ComparisonComparison
After:After:
cleaner discharge and increased yieldcleaner discharge and increased yield
RehabilitationRehabilitation
Rehabilitation resulted in a dramatic increase in Rehabilitation resulted in a dramatic increase in well yield - >1,000 gpmwell yield - >1,000 gpm
Blown yieldBlown yield
measured with weirmeasured with weir
Post-Rehabilitation TeleviewingPost-Rehabilitation Televiewing
Well was televiewed on Dec. 23, 2008Well was televiewed on Dec. 23, 2008
Well bore was clean and open to bottomWell bore was clean and open to bottom
Water-bearing zones were clean and openWater-bearing zones were clean and open
Smaller water-bearing zones seen below Smaller water-bearing zones seen below primary zone at 66 feetprimary zone at 66 feet
Post-Rehabilitation TeleviewingPost-Rehabilitation Televiewing
Post-Rehabilitation TestingPost-Rehabilitation Testing
Step-drawdown pumping test was conducted on Step-drawdown pumping test was conducted on Jan. 12, 2009Jan. 12, 2009
Pumping rates of 300, 400, 500, 600, and 620 Pumping rates of 300, 400, 500, 600, and 620 gpm (pump limit)gpm (pump limit)
Turbidity checked periodically and was below 1 Turbidity checked periodically and was below 1 NTU for duration of testNTU for duration of test
Post-Rehabilitation TestingPost-Rehabilitation Testing
Step-drawdown test results:Step-drawdown test results:
Post-Rehabilitation TestingPost-Rehabilitation Testing
Total drawdown after 60 minutes at 620 gpm - Total drawdown after 60 minutes at 620 gpm - 2.2 feet2.2 feet
45 feet45 feet
of availableof available
drawdowndrawdown
remainingremaining
Post-Rehabilitation TestingPost-Rehabilitation Testing
620 gpm drawdown extrapolated to 1.9 years resulted in 620 gpm drawdown extrapolated to 1.9 years resulted in about 14 feet of drawdownabout 14 feet of drawdown
(assuming(assumingno rechargeno rechargeand continuousand continuouspumping)pumping)
33 feet of33 feet ofdrawdowndrawdownremainingremaining
SummarySummary
Rehabilitation of Well 7 resulted in a significant Rehabilitation of Well 7 resulted in a significant improvement in water clarityimprovement in water clarity
Rehabilitation resulted in cleaner and more stable karstic Rehabilitation resulted in cleaner and more stable karstic water-bearing zoneswater-bearing zones
Rehabilitation resulted in a dramatic improvement in the Rehabilitation resulted in a dramatic improvement in the yield and performance of the wellyield and performance of the well
Step-test data suggests pumping yield of well may Step-test data suggests pumping yield of well may exceed 1,500 gpmexceed 1,500 gpm
LimitationsLimitations
Wellhead protection zone regulations limit the Wellhead protection zone regulations limit the pumping rate of the well to 600 gpm because of pumping rate of the well to 600 gpm because of the 175 feet of separation between the wellhead the 175 feet of separation between the wellhead and the nearby public roadand the nearby public road
Well bore diameter of 10-inches would limit the Well bore diameter of 10-inches would limit the pump size and therefore the maximum pumping pump size and therefore the maximum pumping rate of the well. rate of the well.