15A ncac 02c .0110       WELL TESTS FOR YIELD

(a)  Every domestic well shall be tested for capacity by one of the following methods:

(1)           Pump Method

(A)          select a permanent measuring point, such as the top of the casing;

(B)          measure and record the static water level below or above the measuring point prior to starting the pump;

(C)          measure and record the discharge rate at intervals of 10 minutes or less;

(D)          measure and record water levels using a steel or electric tape at intervals of 10 minutes or less;

(E)           continue the test for a period of at least one hour; and

(F)           make measurements within an accuracy of plus or minus one inch. 

(2)           Bailer Method

(A)          select a permanent measuring point, such as the top of the casing;

(B)          measure and record the static water level below or above the measuring point prior to starting the bailing procedure;

(C)          bail the water out of the well as rapidly as possible for a period of at least one hour; determine and record the bailing rate in gallons per minute at the end of the bailing period; and

(D)          measure and record the water level immediately after stopping bailing process.

(3)           Air Rotary Drill Method

(A)          measure and record the amount of water being injected into the well during drilling operations;

(B)          measure and record the discharge rate in gallons per minute at intervals of one hour or less during drilling operations;

(C)          after completion of the drilling, continue to blow the water out of the well for at least 30 minutes and measure and record the discharge rate in gallons per minute at intervals of 10 minutes or less during the period; and

(D)          measure and record the water level immediately after discharge ceases.

(4)           Air Lift Method. Measurements shall be made through a pipe placed in the well. The pipe shall have a minimum inside diameter of at least five‑tenths of an inch and shall extend from top of the well head to a point inside the well that is below the bottom of the air line.

(A)          Measure and record the static water level prior to starting the air compressor;

(B)          Measure and record the discharge rate at intervals of 10 minutes or less;

(C)          Measure and record the pumping level using a steel or electric tape at intervals of 10 minutes or less; and

(D)          Continue the test for a period of at least one hour.

(b)  Public, Industrial and Irrigation Wells.  Every industrial or irrigation well and, if required by rule adopted by the Commission for Public Health, every well serving a public water supply system upon completion, shall be tested for capacity by the following or equivalent method:

(1)           The water level in the well to be pumped and any observation wells shall be measured and recorded prior to starting the test.

(2)           The well shall be tested by a pump of sufficient size and lift capacity to test the yield of the well, consistent with the well diameter and purpose.

(3)           The pump shall be equipped with sufficient throttling devices to reduce the discharge rate to approximately 25 percent of the maximum capacity of the pump.

(4)           The test shall be conducted for a period of at least 24 hours without interruption and, except for wells constructed in Coastal Plain aquifers, shall be continued for a period of at least four hours after the pumping water level stabilizes (ceases to decline). If the total water requirements for wells not serving a public water supply system are less than 100,000 gpd, the well shall be tested for a period and in a manner to show the capacity of the well, or that the capacity of the well is sufficient to meet the intended purpose.

(5)           The pump discharge shall be set at a constant rate or rates that can be maintained throughout the testing period.  If the well is tested at two or more pumping rates (a step‑drawdown test), pumping at each pumping rate shall continue to the point that the pumping water level  declines no more than 0.1 feet per hour for a period of at least four hours for each pumping rate, except for wells constructed to Coastal Plain aquifers.  In wells constructed in Coastal Plain aquifers, pumping at each pumping rate shall continue for at least four hours.

(6)           The pump discharge rate shall be measured by an orifice meter, flowmeter, weir, or equivalent metering device.  The metering device shall have an accuracy within plus or minus five percent.

(7)           The discharge rate of the pump and time shall be measured and recorded at intervals of 10 minutes or less during the first two hours of the pumping period for each pumping rate.  If the pumping rate is relatively constant after the first two hours of pumping, discharge measurements and recording may be made at longer time intervals but not to exceed one hour.

(8)           The water level in each well and time shall be measured and recorded at intervals of five minutes or less during the first hour of pumping and at intervals of 10 minutes or less during the second hour of pumping.  After the second hour of pumping, the water level in each well shall be measured at such intervals that the lowering of the pumping water level does not exceed three inches between measurements.

(9)           A reference point for water level measurements (preferably the top of the casing) shall be selected and recorded for the pumping well and each observation well to be measured during the test.  All water level measurements shall be made from the selected reference points.

(10)         All water level measurements shall be made with a steel or electric tape or equivalent measuring device.

(11)         All water level measurements shall be made within an accuracy of plus or minus one inch.

(12)         After the completion of the pumping period, measurements of the water level recovery rate in the pumped well shall be made for a period of at least two hours in the same manner as the drawdown.

 

History Note:        Authority G.S. 87‑87; 87‑88;

Eff. February 1, 1976;

Amended Eff. September 1, 2009, April 1, 2001; December 1, 1992; September 1, 1984; April 20, 1978.