The Ultra-Pure Drinking Water Blog

There are several basic causes of well problems.

• Improper well design and construction
• Incomplete well development
• Borehole stability problems
• Incrustation buildup
• Biofouling
• Corrosion
• Aquifer problems
• Overpumping.

The first two causes relate to the expertise and performance of the drilling contractor. Borehole stability problems, incrustation, corrosion and aquifer problems are related to characteristics of the aquifer. The last cause, overpumping, is caused by well users.

Improper well design and construction
When designing a well, the drilling contractor must match the type of well construction with the characteristics of the producing aquifer. A well screen is a slotted column beneath the well casing that blocks fine sand particles from traveling with the water through the pump. Decisions must be made about:

• Perforated well casing/liner vs. well screen (see Figure 1, Perforated Well Liner and Well Screen)
• Slot size of well screen
• Placement of well screen or perforated liner
• Size and amount of sand pack around the well screen (if required)
• Location of the pump in the well.

If poor choices are made, you may experience problems with sediment in your water or reduced well yield. Provincial regulations require that a well must be completed to ensure no damage will be incurred to the pumping system, plumbing or fixtures due to sediment in the water. For more information on well design and construction, see Module 3 “Design and Construction of Water Wells.”

Incomplete well development
During drilling, mud and bore hole cuttings can partially plug the aquifer. This material must be fully removed by the drilling contractor to allow water to freely enter the well. This procedure is part of well development. If the well has not been fully developed, you may experience problems with sediment in your water or low well yield.

Borehole stability problems
Borehole stability problems can result from damaged casing and screens, borehole wall collapse, corrosion or excessive water velocities into the well. High water velocity can cause formation particles, like sand, to flow into the well, causing eventual collapse of the borehole wall.
It is essential that the proper materials be selected and installed to avoid such problems. A combination of poor materials, improperly placed screens and a poor well seal make it uneconomical to maintain and restore such a well. Often the most cost effective solution is to drill a new well that is properly designed and constructed.

Figure 1: Perforated Well Liner and Well Screen

Mineral incrustation
Mineral incrustation is a common problem in some shallow water table type aquifers where there is an abundance of dissolved minerals including calcium, magnesium and iron, as well as iron bacteria. When water is pumped from the well, changes in pressure and temperature occur. This creates ideal conditions for minerals to precipitate or settle out, causing scale formation on the casing, liner and screens. Although incrustation or scale formation occurs mostly in the screen or slotted casing, it can also affect the formation around the well.

A combination of good preventive maintenance and good management practices can minimize the effect of incrustation. Management practices that reduce water pumping rates can reduce the effects of mineral incrustation. A strategy of reduced pumping rate with longer pumping intervals helps prevent incrustation of screens and perforated liners.

Biofouling
Installing and pumping a well increases the level of oxygen and nutrients in the well and in the surrounding aquifer. Bacteria, such as iron bacteria, may thrive under these conditions. They can form a gel-like slime or biofilm that captures chemicals, minerals and other particles such as sand, clays and silts. Minerals, such as iron, oxidize and get trapped in the biofilm. “Biofouling” occurs where biofilm accumulations are sufficient to reduce water flow. This can mean reduced well yield and water quality.

Regular shock chlorination can reduce the buildup of biofilms.

Corrosion
Chemical substances found in water can eat away or corrode metal well casings. To avoid corrosion, the drilling contractor must choose a casing material that is suitable for the water supply. For example, drilling contractors usually select plastic casing liners and stainless steel well screens for corrosive water.

Aquifer problems
While most well problems are related to the construction, development or operation of the well, the formation can also be a source of problems. Sulfate-reducing bacteria can also cause corrosion. Shock chlorination can keep these bacteria in check.

Reduced aquifer yield can be caused by lack of recharge. For example, the amount of water withdrawn can exceed the recharge from rain and snow melt. This is referred to as “mining the aquifer.” Sometimes the decline in water level is seasonal. Typically water levels are higher in spring and lower in the fall. Extended dry periods can also impact water levels, especially in shallow water table type aquifers.

Checking the water level in your well is an important maintenance procedure. You will be able to identify water level trends and identify well problems or aquifer depletion before the problem becomes serious.

Overpumping
A well is overpumped if water is withdrawn at a faster rate than the well was designed for or the aquifer is able to produce. Overpumping is the most common well problem that leads to premature well failure. Overpumping not only depletes the groundwater aquifer (or source), but it rapidly increases the rate of corrosion, incrustation and biofouling related problems. Overpumping also increases the rate of sediment particles moving toward the well, causing plugging of the perforated area where water flows into the well. It can also cause the aquifer to settle and compact which further restricts water flow to the well.
If you are pumping water at a rate close to the well’s capacity, excessive pump cycling can increase the problem of biofouling.

Now go back to the exercise at the start of this module. Try to identify possible causes for each problem you identified.

Troubleshooting Guide

There are four common symptoms associated with most water well problems:

• Reduced well yield
• Sediment in the water
• Change in water quality
• Dissolved gas in the water.

The guide on the next four pages refers to these four symptoms. To use the guide, find the section that identifies the symptom you are experiencing. Look down the left hand column for possible causes of the problem. Beside each cause is listed some indicators you can check for and ways to correct the problem.

Be aware that in many cases the well problem can be the result of a combination of causes and therefore correction may be a combination of actions as well.

Symptom # 1 – Reduced Well Yield

Symptom #2 – Sediment in Water

Symptom #3 – Change in Water Quality

Symptom #4 Dissolved Gas in the Water

1. Shock chlorination is effective as a regular maintenance technique to kill bacteria and limit its ability to create biofilm. However, shock chlorination is not effective at penetrating biofilm. If biofilm buildup is suspected, the introduction of appropriate chemicals and physical agitation is required to remove the biological plugging material. Studies conducted as part of the Sustainable Water Well Initiative have shown that preventative maintenance should be applied before a biofouled well has lost about 20 percent of its original specific capacity and well rehabilitation should be conducted before the specific capacity has declined 40 percent. Also, once the specific capacity of a biofouled well has declined 60-80 percent from its orginal specific capacity, it becomes increasingly difficult to restore the well’s original specific capacity (City of North Battleford Well Treatment Evaluation report:http://www.agr.gc.ca/pfra/water/uab/nb00rpt.pdf; Town of Qu’Appelle Well Treatment Project: http://www.agr.gc.ca/pfra/water/swwi/qawell5.pdf).
2. The presence and aggressiveness of nuisance bacteria, such as iron-related (IRB), sulfate-reducing bacteria (SRB) and heterotrophic bacteria (HAB), can be determined by the use of Biological Activity Reaction Tests (BARTs). These bacteria are naturally present in most groundwater environments and can result in biofouling of the water well and associated infrastructure. Studies conducted as part of the Sustainable Water Well Initiative (SWWI) have shown that about 70 percent of wells in any given area may contain highly aggressive levels of these nuisance bacteria (Rural Municipality of Mount Hope #279 Water Well Inventory and Microbiological Assessment: http://www.agr.gc.ca/pfra/water/swwi/rmmh279.pdf; Biofouling and Water Wells in the M.D. of Kneehill, Alberta:http://www.agr.gc.ca/pfra/water/knee_e.htm; Microbiological Activity and the Deterioration of Water Well Environments on the Canadian Prairies:http://www.agr.gc.ca/pfra/water/swwi/iah2000t.pdf ). Another SWWI study indicated that wells with high levels of nutrients, such as dissolved organic carbon (DOC) and nitrates, in the source water are at a greater risk of biofouling than wells with low levels of nutrients (Sustaining Water Well Infrastructure in an Agricultural Setting – Rural Municipality of Mount Hope: http://www.agr.gc.ca/pfra/water/swwi/MountHope.pdf). The factors that cause or accelerate water well biofouling are not well understood and additional research is still required in this area. Well capture zone studies are recommended to investigate the factors that may contribute to biofouling.
3. In many cases, variations in water quality will not result in observable changes in odor, taste or color. For instance, in situations where nitrate levels are increasing, there may be no apparent change in the odor, taste or color of the water. In addition, an increase in nitrate levels may also signal the presence of coliform bacteria or other pathogenic bacteria. A SWWI field study indicates that wells with high levels of nitrates often have high levels of coliforms (Sustaining Water Well Infrastructure in an Agricultural Setting – Rural Municipality of Mount Hope: http://www.agr.gc.ca/pfra/water/swwi/MountHope.pdf). New technologies are available that permit rapid onsite testing of coliform bacteria. A SWWI study, conducted in partnership with Saskatchewan Health, evaluated a new and innovative technology that can be used to determine the presence of coliforms and E. coli in drinking water (Evaluation of the Aquasure Pro 3000 Single Test Precision Portable Incubator Technology: http://www.agr.gc.ca/pfra/water/swwi/aqua3000.pdf)

This information may not be reproduced without the permission of Alberta Agriculture and Rural Development – Home Study Program, 7000-113 St, Edmonton, AB T6H 5T6

The groundwater use information provided in this publication was written from a Canadian prairie perspective, specifically focusing on the resources available and legislation within the Province of Alberta as of August, 2000.

For more information on local conditions, people from other jurisdictions should contact appropriate agencies and water well experts in their area.