36.21.664    TESTS FOR YIELD AND DRAWDOWN

(1) Every well shall be tested for yield and drawdown for a period of not less than 1 hour either by bailing, pumping, or air testing. During testing, discharge rate shall be as uniform as possible. The minimum data to be entered on the well log report form shall be:

(a) static water level immediately before testing begins;

(b) pump rate and means of discharge (i.e., bailing, airlift, pumping) ;

(c) pumping level after one hour;

(d) recovery level and time of recovery; and

(e) for public community, non-community public and multi-family water supply wells, the testing requirements set out in ARM Title 17, chapters 30, 36 and 38 shall apply.

(2) In the event that pump test data is required for 100 gpm or more or as required by the board, pump test data to be recorded on the well log report form shall be:

(a) static water level immediately before testing begins;

(b) depth at which pump is set for test;

(c) the pumping rate;

(d) the maximum drawdown during the test;

(e) the duration of the test, including both:

(i) the pumping time; and

(ii) recovery time;

(f) recovery water levels and the respective times after cessation of pumping that the recovery water level data was taken;

(g) All depth measurements shall be from the top of the well casing unless otherwise specified.

(3) Flowing wells must be flow tested at least one hour.

(4) Wells intended to yield 100 gpm or more shall be tested for a period of eight hours or more. The test shall follow development of the well, and shall be conducted continuously at a constant discharge which is at least as great as the intended appropriation.   As a minimum, water level data shall be collected and recorded on the schedule shown on the department's "well test data sheet". If possible, it is recommended that drawdown data instead be collected on a logarithmic schedule (see, for instance, Johnson's "Ground Water and Wells") throughout the test. The height above ground of the point from which water levels are measured shall also be recorded. The above information and any additional aquifer testing data shall be attached to the driller's log and submitted to the department.

History: 37-43-202(3), MCA; IMP, 37-43-202(3), MCA; NEW, 1986 MAR p. 1699, Eff. 10/17/86; AMD, 1997 MAR p. 65, Eff. 1/17/97; AMD, 2001 MAR p. 562, Eff. 4/6/01.