REVIEW OF LOW-FLOW BLADDER PUMP AND HIGH-VOLUME AIRPISTON PUMP GROUNDWATER SAMPLING SYSTEMS AT SANDIANATIONAL LABORATORIES, NEW MEXICO

摘要

Since 1996, Sandia National Laboratories, New Mexico (SNL/NM) has run both aportable high-volume air-piston pump system and a dedicated, low-flow bladder pumpsystem to collect groundwater samples. The groundwater contaminants of concern atSNL/NM are nitrate and the volatile organic compounds trichloroethylene (TCE) andtetrachloethene (PCE). Regulatory acceptance is more common for the high-volume airpiston pump system, especially for programs like SNL/NM’s, which are regulated underthe Resource Conservation and Recovery Act (RCRA). This paper describes logisticaland analytical results of the groundwater sampling systems used at SNL/NM.With two modifications to the off-the-shelf low-flow bladder pump, SNL/NMconsistently operates the dedicated low-flow system at depths greater than 450 feet belowground surface. As such, the low-flow sampling system requires fewer personnel, lesstime and materials, and generates less purge and decontamination water than does thehigh-volume system. However, the bladder pump cannot work in wells with less than 4feet of water.A review of turbidity and laboratory analytical results for TCE, PCE, and chromium (Cr)from six wells highlight the affect or lack of affects the sampling systems have ongroundwater samples. In the PVC wells, turbidity typically remained < 5 nephelometricturbidity units (NTU) regardless of the sampling system. In the wells with a stainlesssteel screen, turbidity typically remained < 5 NTU only with the low-flow system. Whenthe high-volume system was used, the turbidity and Cr concentration typically increasedan order of magnitude. TCE concentrations at two wells did not appear to be sensitive tothe sampling method used. However, PCE and TCE concentrations dropped an order ofmagnitude when the high-volume system was used at two other wells.This paper recommends that SNL/NM collaborate with other facilities with similargroundwater depths, continue to pursue regulatory approval for using dedicated the low-flowsystem, and review data for sample system affects on nitrate concentrations.