Groundwater: Evaluating Your Well Problems & Maintenance Tips

Groundwater: Evaluating Your Well Problems & Maintenance Tips
by David Hanson



Summary: With so many causes potentially affecting the performance and upkeep of wells, the most important factor is gathering correct information before formulating solutions. The following article presents several steps in ensuring that a well is properly treated, tested and maintains its value to the owner for years to come.

There are all kinds of problems experienced in pumps and wells. Pump problems can be mechanical, electrical or system related, causing a reduction in yield or total breakdown. Well problems are often associated with: 1) a reduction in yield, caused by plugging of the screen or an open borehole from iron bacteria, slime bacteria, mineral scale, sand or silt infiltration, or debris in the well (Yields can also be affected by other pumping wells, or physical changes in the aquifer, i.e., a drop in static level or seismic activity.); 2) odors; 3) discoloration, and 4) corrosion caused by either water chemistry, galvanic activity, stray currents (AC or DC) or some forms of bacteria.

Problems arent often discovered in municipal or industrial wells until theyre well beyond minor repairs. The pump breaks suction or quits pumping water due to a mechanical problem. Theres air in the water lines, reddish water and/or odors. This often sets up an emergency condition and presents major problems. Any time you have an emergency it costs extra money. Theres little time to really understand the problem and design a proper and effective solution. Here are some basic steps to plan well maintenance.

Well information
Good information is paramount. Too many times, little information is available about well dimensions, well depths, screen lengths, aquifers (thickness and type), pumping data (gallons per minute -- gpm -- at a certain pumping time and pump setting), past performance of the pump (its different than well performance), water chemistry or biological identification/quantification. Information like this often is difficult to find, so its important well and pump records are kept fastidiously and readily available where possible.

File records according to well number. Separate well and pump information. Organize maintenance information for each file in chronological order. Construct an "as built" drawing or ask the contractor for that information. Its easier to understand. Put the well log and general pump information at the front page for easy reference.

Understanding problems
Pumping rate alone isnt a measurement for determining well problems. A pump impeller may be loose, or there may be a hole in the pump column pipe (can be either vertical turbine or submersible), which will cause a decline in recorded yield. Neither have anything to do with the well. The key to separating well and pump problems is understanding if the yield of the well is declining, which is done by calculating "specific capacity" or SC (see Figure 1).

Figure 1. Well calculations
First, record the "static water level" (SWL). Let the water level stabilize from pumping before these data are taken. Generally, 4-to-12 hours is sufficient, but if you monitor the static level and its stable, this level can be recorded. Keep in mind, nearby pumping wells may affect the static level in this well. Start the pump and record the "pumping water level" (PWL) at a consistent pumping time -- say 60 minutes for most small municipal wells -- along with the average gpm pumped. The recorded time of the PWL must be well beyond the casing storage (water in the casing minus the pump column) of the well. It generally takes 15-to-45 minutes (depending on well diameter to outer diameter -- OD -- of the pump column) to pump the casing storage out of a well before water enters the borehole from the aquifer.

Generally, the longer the test, the more accurate the information. What