EP 1110-1-27
27 Jan 00
observation well outside the influence of the pumping well or static water levels obtained when the well is
not pumped.
d. Effects on Q/s calculations. Static and pumping water levels can be affected by oscillations
caused by the pump, cascading water, the water level probe becoming entangled in wiring and pump
column, and operator error.
(1) Many problems can be avoided by installing a stilling (drawdown) tube in the well. Also,
clearly establishing the "measuring point" (MP) of the well from which all measurement are taken and
informing all personnel who will be collecting data of the MP will avoid many problems. The discharge
rate can vary in response to system back-pressure and changes in pump performance, and therefore cannot
be assumed to be constant. It should be measured along with water levels when determining Q/s. The
flow meter used to measure the discharge rate is also subject to error as it wears or clogs.
(2) It is desirable that a baseline Q/s be determined at the intended discharge rate when a well is
constructed (assuming the efficiency of the well is acceptable). Subsequent measurements of the
drawdown in the well and discharge rate and recalculation of Q/s will provide an indication of the
ongoing performance of the well (Borch , Smith, and Noble, 1993; Howsam, P., Misstears, B., and Jones,
C. 1995). See Chapters 4 and 5.
2-4. Development Data
a. Purposes of development. In well construction, development has three purposes:
Repair damage done to the aquifer during drilling.
Set the filter pack.
Increase the permeability of the aquifer in the vicinity of the well.
b. Redevelopment. Later, development activities may be a component of a maintenance program
to further the original development effort, or applied as a component of a maintenance program to
maintain or restore a well's performance. In this use, the processes are termed "redevelopment."
c. Development process description and importance. Detailed descriptions of development and
redevelopment processes can be found in Australian Drilling Industry Training Committee Limited
(ADITC) (1997), Driscoll (1986), NGWA (1998), and ASTM D 5521 (in the context of monitoring
wells).
(1) Drilling method influence. The drilling method will, to some degree, modify or damage the
aquifer material in the process of drilling the hole. One must know what damage or modifications are
likely to have occurred in the aquifer material to judge the applicability or effectiveness of the develop-
ment effort. This information is usually recorded on the drilling field log maintained by qualified
oversight personnel. Each lithologic material will be uniquely vulnerable to the drilling process and may
require specific development methods. Also, future performance problems may be related to aquifer
lithology. Different well construction methods will require different methods of development and the
construction of the well will determine what methods are applied in future activities. Additionally, the
type of drilling method used tends to influence the method of development (if cable tool: surge blocks and
bailers, if rotary: air compressors and pumps).
(2) Development methods. Well development includes as components many tools and methods
and the development data should include descriptions of the tools and methods utilized. For example:
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