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Mountain House Storm Water Detention Basin Page 4 WKA No. 6504.05 October 7, 2005 ' 4.2.2 Monitoring Well Sampling and Analysis The monitoring wells were sampled on September 14, 2005. Prior to sampling, the depth-to- groundwater and depth-to-bottom were obtained with an electronic sounder with a tape graduated in 1/100ths of a foot. The depths were measured from the top-of-casing of each well to an accuracy of±0.01 feet. The data from these measurements was recorded on well development/purging logs and used to calculate the well volume. Sampling purge data sheets are included in Appendix C. ' Following monitoring, each of the wells was purged of approximately three casing volumes ' based on the measured water column in each well. During purging, turbidity, temperature, pH, conductivity and total dissolved solids measurements and/or observations were recorded for each ' monitoring well. Each well was purged using an electric submersible pump and samples were collected from the purge pump discharge. Following purging of the calculated well-purge volume, groundwater samples were collected in I-liter poly containers provided by the analytical ' laboratory. Samples were immediately placed in a chilled, thermally insulated ice-chest and submitted under Chain-of-Custody documentation to California Laboratory Services, Inc. of Rancho Cordova, California (a California Department of Health Services-certified laboratory) for analysis as follows: ' • Total alkalinity using EPA method 310.1 • Chloride, fluoride, nitrate, and sulfate using EPA method 300 ' • Specific conductance using EPA method 120.1 • Methylene blue active substances using EPA method 425.1 • Boron, calcium, magnesium, potassium, sodium, and hardness as CaCO3 using EPA method 200.7 • PH using EPA method 150.1 • Total dissolved solids using EPA method 160.1 Irl` t' WALLACE•KUHL itac nacd :::o, &ASSOCIATES INC.