Common Well Problems Basic Solutions for Common Problems

Geologic Map of North Carolina

Parts of a Drilled Rock Well Casing extends one foot above grade Grout extends to minimum depth of twenty feet Bottom of casing seated and sealed in consolidated rock Submersible pump moves the water out of the well

New Well – open borehole

New Well – water zone

New Well – bottom of the well

Common Problems • Total coliform / Fecal coliform • Grit / silt / rock cuttings • Nuisance bacteria – IRB – yellow to red color – SRB – “rotten egg” odor

• Intermittent iron, silt, or coliform bacteria

Classifying Problems • • • • •

Biological - bacteria Geological – local geology Hydraulic – water movement Physical – pump movement Combination – two or more

Sources of Problem Total coliform / Fecal coliform –Local geology –Improper well construction –Improper pump installation • Failure to use basic sanitation

Sources of Problem Grit / silt / rock cuttings –Improper / insufficient development of well –Local geology –Improper well construction –Improper pump installation

Sources of Problem Nuisance bacteria - IRB / SRB –Iron Related Bacteria • yellow to red color

–Sulfate Reducing Bacteria • “rotten egg” odor

Sources of Problem Intermittent iron, silt, or coliform bacteria –Local geology –Improper well construction –Hydrologic cycle

Solution Options • Packer / liner installation –Deeper is better

• Pump placement / installation –Keep the water moving

• Well disinfection –Do it right

• Water treatment

Packer/Liner in a Well • Existing casing was not sealed into rock, allowing near-surface water into well • Deeper water is good • Packer/liner is installed to seal-off undesirable water • Space between liner and existing casing is filled with grout • Well now draws water from deep zones

Pump Placement / Installation • Keep the water moving – Bottom to top / top to bottom – High yield means shallow pump placement – Low yield means deep pump placement

• Use a pump shroud, especially in soft formations

Set-up a Well - wrong • Unless the well is pumped at a high rate, there will be a dead zone at the top of the well. Bottom of well is also a dead zone • Rockcuttings and grit will flow from large fracture into pump intake

Set-up a Well - right • High placement of pump provides movement of water • Pump placement in casing prevents occurrence of grit

Well Needs a Pump Shroud • Proper “exercise” of well will prevent dead zone in middle of well • Water movement up and down walls may create a grit problem • A properly designed pump shroud works better for grit problems

Pump Shroud • Shroud is installed over submersible pump • 4” wellseal is placed just above pump to hold 4” PVC casing • Pump inlet is located mid-length of shroud • Casing prevents pump intake from directly contacting sidewall of well

How a Pump Shroud Works • Pump inlet is located mid-length of shroud • Water flows past outside of shroud at high velocity • High speed rock particles continue to fall • Water flowing upward inside shroud cools motor

4 C’s of Effective Disinfection • • • •

Clean well Concentration Contact Time Circulation

Guilford Mackintosh well

Huffine Mill well

Huffine Mill well

Fecal Coliform in MHP well

McLeansville – cable tool well

Indicators of Biological Problem

Slime on drop pipe and pump

Dewberry well - before rehab

Midkiff well

Cleaning Out Well Bottom

Cleaning and Rehabbing

Completed Rehab • Existing casing extended above grade • Liner pipe held with Riser Clamp • Completed wellhead with 4” wellseal • Complete grout at later date • MockRock will be installed over wellhead

Westfield well

Westfield well

Westfield well

Punctured Casing

Big Rockcuttings

Happy Hill - before

Happy Hill - before

Happy Hill - after

Happy Hill - after

Directional Flow Device • Tailpiece or directional flow device is installed on bottom of packer • Device protects pump from falling rock and keeps grit from impellers • Device routes water throughout well, preventing dead zones

Properly Installed Well Seal?

Shoreham well

April Lane well

Leaning Tree Well - Record Well Record – 138’ casing – ¾ hp pump @ 225’ – 5 gpm @ 300’ – 365’ total

Well has grit problem

Leaning Tree Well - Video Video Results – 139.75’ casing – ½ gpm @ 145.5’ – Soft metamorphic rock produces grit – Pump @ 225’

Leaning Tree Well - Adjusted Video Results – 139.75’ casing – ½ gpm @ 145.5’ – Soft metamorphic rock produces grit Pump now @ 300’

To Prevent Problems, …. • Drill it right – Seal the casing – Develop the well

• Pump placement / installation – Keep the water moving – Use a shroud

• Disinfect the well properly – Do it right the first time

If You Have Problems, …. • Packer / liner installation – Deeper is better

• Pump placement / installation – Keep the water moving – Use a shroud

• Disinfect the well properly – Remember the 4 Cs

• Rehab if needed

Questions ??

John Nykamp, R.S. Environmental Health Program Specialist Guilford County Public Health Department 400 W. Market St Greensboro, N.C. 27401 (336)641-4807 (336)641-7613 FAX (336)641-3730 [email protected]

Well Contractor Certification Commissioner http://www.ncwelldriller.org/