36.12.121 AQUIFER TESTING REQUIREMENTS
(1) Aquifer testing must follow standard procedures that are discussed in hydrogeology textbooks and professional literature. A hydrogeologist, hydrologist, or engineer familiar with aquifer testing procedures must supervise the aquifer test; however, the supervisor does not need to be on site.
(a) Applicants are encouraged to confer with department staff prior to designing an aquifer test to ensure that the test will not have to be repeated, which may require additional expense.
(b) Department staff will provide guidance on testing procedures, monitoring, and reporting, but will not provide technical support or assistance. Requests for variance from testing requirements must be submitted to the appropriate regional office manager.
(2) Minimum information that must be submitted with applications:
(a) a topographic map with labeled location of production and observation wells and water discharge point;
(b) if available, a geologic map, stratigraphic, geomorphic, or lithologic descriptions, and drilling logs;
(c) distances between the pumping well and the observation well, and depths, dimensions, and perforated intervals of each well as specified on Form No. 633;
(d) wellhead elevation, surveyed elevations if available;
(e) a description of testing methods; and
(f) Form 633, in electronic format, with all information and data provided.
(3) Minimum testing procedures are as follows.
(a) Pumping must be maintained at a constant discharge rate.
(b) The discharge rate must be equal to or greater than the proposed rate for the entire duration of the test if the application is for one well or if the total proposed rate for multiple wells can be obtained from a single well. The discharge rate may be less than the proposed rate if the application is for multiple wells and the total proposed rate cannot be obtained from a single well, so long as the remainder can be demonstrated from the remaining wells under (f).
(c) Discharge rate must be measured with a reliable measuring device and recorded with clock time according to the schedule on Form 633.
(d) Minimum duration of pumping during an aquifer test must be 24 hours for a proposed use or discharge of 150 gpm or less and a proposed volume of 50 acre-feet or less.
(e) Minimum duration of pumping during an aquifer test must be 72 hours for a proposed use or discharge of greater than 150 gpm and proposed volume greater than 50 acre-feet.
(f) Eight-hour duration drawdown and yield tests must be conducted on additional production wells.
(g) Discharged water must be conveyed a sufficient distance from the production and observation wells to prevent recharge to the aquifer during the test. Adequate water conveyance devices include pipe, large-diameter hose (e.g., fire hose), lined ditch or canal, or an existing irrigation system.
(h) One or more observation wells must be completed in the same water-bearing zone(s) or aquifer as the proposed production well and close enough to the production well so that drawdown is measurable and far enough that well hydraulics do not affect the observation well. If existing wells are monitored they must not be pumped, or if pumped should be monitored at a frequency necessary to separate the effects of the pumping.
(i) Electronic pressure transducer/data logger instrumentation, electric well probes, pressure gauges on turbine pumped wells, or graduated steel tapes are acceptable methods of measuring groundwater levels.
(j) Groundwater levels in the production well and observation well(s) must be monitored at frequent intervals for at least two days prior to beginning the aquifer test to evaluate background water-level trends. An applicant must evaluate and correct for background water-level trends.
(k) Water levels in the production well and observation well(s) must be measured with 0.01-foot precision according to the schedule specified on Form No. 633.
History: 85-2-113, 85-2-370, MCA; IMP, 85-2-302, 85-2-311, 85-2-330, 85-2-337, 85-2-341, 85-2-343, 85-2-344, 85-2-360, 85-2-361, 85-2-362, 85-2-402, 85-2-506, 85-2-508, MCA; NEW, 2004 MAR p. 3036, Eff. 1/1/05; AMD, 2012 MAR p. 2071, Eff. 10/12/12; AMD, 2018 MAR p. 451, Eff. 2/24/18.