Publications

Review of low-flow bladder pump and high-volume air piston pump groundwater sampling systems at Sandia National Laboratories, New Mexico

Collins, Sue S.; Collins, Sue S.; Bailey, Gary A.; Jackson, Timmie O.

Since 1996, Sandia National Laboratories, New Mexico (SNL/NM) has run both a portable high-volume air-piston pump system and a dedicated, low-flow bladder pump system to collect groundwater samples. The groundwater contaminants of concern at SNL/NM are nitrate and the volatile organic compounds trichloroethylene (TCE) and tetrachloethene (PCE). Regulatory acceptance is more common for the high-volume air piston pump system, especially for programs like SNL/NM's, which are regulated under the Resource Conservation and Recovery Act (RCRA). This paper describes logistical and analytical results of the groundwater sampling systems used at SNL/NM. With two modifications to the off-the-shelf low-flow bladder pump, SNL/NM consistently operates the dedicated low-flow system at depths greater than 450 feet below ground surface. As such, the low-flow sampling system requires fewer personnel, less time and materials, and generates less purge and decontamination water than does the high-volume system. However, the bladder pump cannot work in wells with less than 4 feet 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 on groundwater samples. In the PVC wells, turbidity typically remained < 5 nephelometric turbidity units (NTU) regardless of the sampling system. In the wells with a stainless steel screen, turbidity typically remained < 5 NTU only with the low-flow system. When the high-volume system was used, the turbidity and Cr concentration typically increased an order of magnitude. TCE concentrations at two wells did not appear to be sensitive to the sampling method used. However, PCE and TCE concentrations dropped an order of magnitude when the high-volume system was used at two other wells. This paper recommends that SNL/NM collaborate with other facilities with similar groundwater depths, continue to pursue regulatory approval for using dedicated the lowflow system, and review data for sample system affects on nitrate concentrations.