to the storm sewer system until the residual chlorine content drops to an acceptable
Well Maintenance and Rehabilitation
Cleaning Well Screens. A clogged well screen or a clogged aquifer near
the well bore are the most common causes of decreasing yield. If the specific capacity
has dropped to 60 percent of the new well value, then cleaning the well screen can
improve the yield. If the specific capacity has dropped to 40 percent of the new well
value, it is usually necessary to redevelop the well. Well screens on deep wells can be
cleaned in place using one of the methods described below. Well screens can also be
pulled for cleaning or for reuse.
Several well screen cleaning methods are listed below. Also listed are
the paragraph numbers corresponding to a full discussion of the cleaning processes.
Dry Ice Cleaning
Sonic Process Cleaning
Acid Treatment. Encrustation of screens is caused principally by
calcium carbonate deposits and occasionally by iron oxide and calcium sulfate
deposits. Corrosion may also cause encrustation. Acidizing with properly inhibited
muriatic acid or sulfamic acid cleans encrusted screens. Do not use uninhibited acids.
The following procedures apply:
Estimate the severity of encrustation from the records of
changes in yield, specific capacity, drawdown, etc.