1.0 Test Description

The goal of the test was to attempt to recreate the hydraulics that existed for the testing done in the summer 2001, to again pump the well and determine if the PCBs in the withdrawal water were again high. This was attempted by using packers to close off the lower portions of the well and the two new wells nearby.

Video logs of MW-4I were reviewed to determine where an inflatable sewer plug could be installed to close off the lower part of the borehole. The video showed a smooth-walled portion of the borehole existing from 82' to 84.5' below top of casing. It was decided to set the top of the six inch long plug at 83' below top of casing (elevation 803' amsl). The bottom of the pump was about six inches above the top of the plug. It was assumed the same bed of limestone was at the same elevation in well MW-20 and MW-21. No video logs exist of these wells. The tops of inflatable plugs were set at the same 803' elevation in these two wells. There is no way of knowing how complete any of the seals were. Two packers in MW-21 were apparently cut by sharp rock before the third plug seemed to seat. The seal was tested by pulling up on the airline and no movement of the plug was assumed to indicate a seal.

A tap was set on the 1 1/4" plastic discharge line for taking the water samples and a flow meter was installed after the tap. A water level recording logger was set in MW-21 about a foot above the plug and the recording interval set to five minutes. The recording logger in MW-6 was also set to five minutes. Initial hand water levels were taken in MW-4I, MW-21, MW-6, and KK-112.

Initial pumping began at 10:45 hours at approximately 10 gpm. The well pumped dry within one minute, however. The pumping rate was reduced to less than 2 gpm by use of an in-line valve. Pumping was re-started at 13:05 hours and continued until 15:13 hours with five interruptions that are noted in Table 1 - Pump Test Monitoring, the record sheet for the test. The pumping rate was between 1.5 and 2 gpm. The longest continuous pump cycle was 34 minutes.

The well would pump dry; the pump would be shut off for one minute and then restarted. Approximately 205 gallons were pumped from the well.

Samples for PCBs were taken at one minute intervals after pumping started and thereafter every fifteen minutes. Temperature and conductivity were measured with the samples. Hand water level measurements were taken in MW-4I and MW-21 during pumping and those results are shown in Table 1. Wells MW-6 and KK-112 were measured before the test and once just before the pump was turned off and those results are also listed in Table 1.

2.0 Test Results

2.1 Aquifer Hydraulics

During the two earlier pump tests well MW-4I was pumped at a rate of 10- 12 gpm, but sustained 4-5 feet of drawdown. It was thought that the highly transmissive zone at the 795-800' elevation was blocked by bentonite. However, after blocking off the 795-800' zone in well MW-4I as well as MW-20 and MW-21 the well was only able to sustain a pumping rate less than 2 gpm. This is more comparable to the pump test conducted on well MW4s on February 7,2002. Well MW-4s is open to the formation at elevations 804.53' to 817.53', and would not sustain a pumping rate over 2 gpm. It seems likely that during the two earlier pump tests of MW-4I water was withdrawn partially from the 795-800' zone.

Based on the hand measurements of wells MW-6 and KK-112, no drawdown was induced in these wells. As shown in Table 1, the initial depth to water in MW-6 was 48.25' and the measurement at 15:04 hours was 48.23'. Similarly, in KK- 112 the initial reading was 38.48' and the final was 38.45 at 14:55 hours.

Figure 1 shows the datalogger data for wells MW-6 and MW-21 on a five minute frequency. It is apparent no drawdown was induced in well MW-21. Whether this is due to a lack of connection in the formation above the packer or the frequent pumping interruptions is difficult to say. The segment of water level data for MW-6 shown on Figure 1 might give the impression that a slight amount of drawdown was induced. Figure 2 shows a longer segment of the data from which it is apparent that the levels are on a sinusoidal decline from the last rain event. The pumping of MW-4s on February 7 did induce drawdown in distant phreatic wells, including MW-6. However, based on the results of this test, the question is raised whether that drawdown was the result of cross-connection to the 795-800' zone between MW4s and MW-21.

2.2 PCB Levels

3.0 Conclusions

• The probability that during the two earlier tests only partial blockage of the 795-800' zone was occurring due to the bentonite plug.
• The similarities in pumping rates between this test and the February 7 MW-4s test reflect the transmissivity of the formation above the 803' elevation.
• The fact that drawdown was induced in other phreatic wells during the February 7 MW-4s test and no drawdown was induced in this test raises the question whether there was interconnection to the 795-880' zone occurring between MW-21 and MW-4s.

• High levels of PCBs do not exist near the 4-series wells in either the 795- 800' zone or the phreatic zone above it in non-storm conditions.
• The high PCBs noted in the July 12 and August 1, 2001 samplings were probably a transient event.