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.