Due to the impact dewatering can have on the design of a project, we recommend conducting pump tests prior to finalizing the dewatering scheme design. Pump tests are the preferred method of reliably assessing the hydraulic behavior of a well and determining the hydraulic properties of an aquifer, ensuring that the most relevant information regarding the water well, water quality and aquifer are available for consideration through design stage. A typical pump test consists of a number of stages:

 

 

• Step Drawdown Test

• Constant Discharge Test

• Constant Drawdown Test

• Recovery Test

 

Step Drawdown Test

The step drawdown test is conducted to establish short term yield versus draw-down data. The test involves pumping the well in a series of 4 - 5 steps, each step with an incrementally higher discharge rate. The final step tends to be operated at the maximum flow rate to establish the maximum yield of the well. Each step should be equal in duration (60-100min for operational and data analysis). On completion of the test water levels are allowed to recover before starting the constant rate test.

 

Constant Discharge Test

Based on the results of the Step Drawdown test, the well is pumped at a constant rate over a period of time, typically 1 – 7 days. The objective of a constant rate pumping test is to gather data on the characteristics of an aquifer within the radius of influence of the pumped well.

 

Constant Drawdown Test

.

 

Recovery Test

The recovery test is carried out on completion of the Step Drawdown and/or the constant pumping rate test providing a useful check on transmissivity values.

 

We utilise Telemetry Measurement of the Piezometers and Flow Meters to increase the accuracy of the pumping test data by enabling us to record measurements at defined intervals for the period of the test. Manual measurement, by Dip Meter, is also performed to verify Transducer data.