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March 2000 On-Post Quarterly Groundwater Monitoring Report

Section 2 - Sampling Methodology

The wells sampled as part of CSSA�s groundwater monitoring program include Wells 1, 2, 9, 10, 11, 16, D, G, H, I, MW1, and MW2. Wells 3 and 4 have not typically been sampled during various sampling events due to their proximity to Well 2. AFCEE, CSSA, and Parsons ES reached this consensus during the Technical Interchange Meeting (TIM) on February 13, 1997. No analytical results are available for Wells D, G, and H for this sampling event. A sample cannot be taken from Well H at this time because the sucker rods are not functioning and the water level is currently too low to collect a sample from Wells D and G.

Wells 9, and 10 are connected to the water distribution system at CSSA; thus, they are equipped with dedicated high capacity pumps through which groundwater samples can be collected. These dedicated pumps in the water-supply wells are often in use during weekdays and are typically turned off during weekends. Wells 1 and 11 are also sampled through dedicated high-capacity pumps although they have been taken off the CSSA water distribution system.�Wells G and I are agricultural-supply wells equipped with sucker rods and are powered by a gasoline engine and a windmill, respectively. Well I will be pumping any time there is sufficient wind energy. Dedicated slow-purge/low-flow QED bladder pumps have been installed in Wells 2, 16, D, MW1, and MW2. Information regarding pump depths and types as of March 2000 is included in Table 1.

Table 1 - Well Pump Information, March 2000

The first step of the quarterly groundwater sampling procedure is to measure the static water level in every available well with an electronic water level indicator. The only exception is Well 10, which is measured by the air-line method. Water levels were measured on the morning of March 20, 2000 before any groundwater samples were collected. Well 10 was being pumped at that time, affecting the water level recorded in this well and also likely influencing water levels recorded nearby in Wells 9 and 11. Well 10 was, however, the only well being pumped at that time. The pumps in Wells 1 and 9 had been turned off for at least 48 hours prior to measuring water levels.

In order to ensure that groundwater samples accurately reflect in situ groundwater conditions, several steps were taken at each well prior to filling the appropriate bottles with groundwater. The first of these actions was to evacuate any water within the pump system by purging several gallons from the well. Next, groundwater pH, conductivity, and temperature were monitored and samples were not collected until these parameter values had stabilized.

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