ARCHIVED REPORTS_1999 - Laserfiche WebLink

Home Browse Search

Appendix Aquifer Test Methods This section describes the field procedures employed to collect the aquifer test data. A total of ten of the existing monitoring wells and the two extraction wells were used to record changes in water levels in the ground water surface during each of the five aquifer test phases. The monitoring wells used in the test were MW-4,MW-6,MW-7,MW-8,MW-9,MW-10,MW-11, MW-12,MW-13 and MW-14,as shown in Figure 1-2. The well depths,screened intervals and other well completion information for these wells is shown in Table D-1. Lateral distances between the monitoring wells and each extraction well were calculated based on survey results are also shown _ on Table D-1. The lateral distance information was used prior to the test to determine which wells to include in the observation well network. A Theis analytical model was run for the proposed test and simulated drawdowns in each observation well were evaluated. Wells showing more than 0.1 feet of drawdown in the computer simulations were included in the ARL aquifer test, as listed above. Data Collection Methods Water level measurements were collected and recorded in each well using automated pressure transducer/data loggers,with periodic measurement made by hand using an electric water level indicator. The automated data recording devices,called Trolls,are manufactured by In Situ Inc. They consist of a pressure transducer which when submerged senses changes in the hydrostatic pressure(the water height above the transducer). The Troll converts hydrostatic pressure into changes in water level relative to an initial reference water level set by the user. The device then stores the measurements and the time they were made in an internal data logger. Water level changes as small as 0.002 feet were recorded by the Trolls. The data are retrieved directly into electronic files through the use an interface software program installed on a laptop computer and an external data communications cable. The Troll devices were installed in each of the ten monitoring wells used as aquifer test observation wells. Since the extraction system had been in constant operation for approximately a year,it was assumed that water levels were at their lowest at the start of this aquifer test. Accordingly,the Trolls were lowered to depths of between 5 and 15 feet below the existing water levels,based on hand measurements made at the time of installation. The estimated depth of submergence of each Troll was checked against its initial measurements to assure the equipment was operating properly. A laptop personal computer was used to program each Troll on when to begin and stop measurements and the frequency of data collection. For the pretest background monitoring phase and for all phases at well MW-12,measurements were collected at 30-minute intervals. Data recording measurements were collected on a logarithmic cycle during each of the pumping and recovery test phases,as discussed in Sections 2.3 and 2.4. The data collected by the Trolls were downloaded periodically to a laptop computer for subsequent analysis and were checked against manual water level measurements to verify proper functioning of the devices. CDM Camp Dresser&McKee D-1 CS 010848 W:IREPORTS\STOCKTOMARIPLUME.981APPD.WPD City of Stockton 190855-00%