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Mr. James C. Stevens January 30, 1998 Page 2 addition, all monitoring wells were measured for depth to water to determine the groundwater gradient and flow direction. Prior to sampling, each well was purged of a minimum of three well volumes of water or until the well was dry and allowed to recharge. On-site measurements of electric conductivity, pH, and temperature were recorded to ensure that the well stabilized so that a representative sample of the aquifer was collected. Copies of the field activity forms are attached. The bailer used to develop the wells was decontaminated with aphosphate-free detergent and distilled water between each well. Samples were collected with a Teflon disposable bailer and placed on ice until delivery to the laboratory for analyses. The samples analyzed for metals, nitrates+nitrites, fluoride, chloride, total dissolved solids (TDS), and pH were filtered in the field (.45 microns). Chain-of-custody forms accompanied the samples throughout the shipment and are included with the attached analytical report. The month indicated on the chain-of-custody form, originally indicating November, was in error and was corrected by the laboratory. Laboratory results indicate that samples obtained from well MWS were below the permit limits for all the required parameters and the landfill is in compliance. The permit limits were established by using the Human Health Standards and Secondary Drinking Water Standards tables contained in The Basic Standards for Ground Water or are at the method reporting limit of the Laboratory. The aldrin, alpha-BHC and 2,4-D detected in the previous quarterly monitoring event were not detected above the permit limits on the December 18, 1997 sampling event. Analytical results, Human Health Standards, Secondary Drinking Water Standards, TDS Standard, and the Groundwater Organic Chemical Standards are surnmarized in Tables 2 3, 4, and 5, respectively. Copies of the laboratory report and chain-of-custody form are attached. Greystone appreciates the assistance of the Division of Minerals and Geology with this project. If you have any questions, please contact me at (303) 550-0930. Greystone will conduct the next quarterly sampling event for the "shortiist" of analytical parameters in March 1998. Sincerely, ~~~~~~ Nick Mathis, C.P.G. Geologist Enclosures cc: Mr. Robert Vasquez, Costilla County 0125.1u~4&il1/30/9B