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Frontier Transportation B23502.01A January 2, 1996 Page A4 free of sediment, and the values of pH, temperature, and specific electrical conductance (EC) have stabilized. Well development data will be recorded on the Sampling/Well Development Log (Attachment A). Purged water will be containerized in Department of Transportation-approved drums, and stored on site in an area inaccessible to the general public. The purged water is typically characterized either by sampling, or on the basis of the groundwater sample analytical results. Twining can recommend an appropriate method for disposition of the purged water. Disposal will be the responsibility of the client. A4 Standard Operating Procedures for Groundwater Monitoring Well Sampling Standard operating procedures (SOPS) used by The Twining Laboratories, Inc. (Twining) when sampling groundwater monitoring wells are presented below. Twining observes these procedures in order to obtain consistent, reliable data. Groundwater sampling will be performed a minimum of 24 hours following development, or when the post-development water level in the well has returned to the static level. before purging and sampling is performed, the depth to water and the total well depth will be measured. If floating hydrocarbons are suspected, a bottom-filling clear bailer, or _ hydrocarbon-detecting paste bailer, or interface probe may be used to record floating hydrocarbon thickness. Depth to water will be measured with an electric sounder, according to. Twining's "Standard Operating Procedures for Measuring Depths to Water and Calculating Groundwater Elevations". Prior to sampling a monitoring well, a minimum of 3 well casing volumes will be purged using a clean, stainless steel submersible pump or a disposable bailer equipped with a length of new rope. Disposable bailers and rope lengths will be used once, and discarded. After 3 casing_ volumes of water have been removed from the well, purging will continue until measured field parameters (pH, specific electrical conductivity, and temperature) have stabilized. Purging data will be recorded on the Well Sampling log. Some monitoring wells are expected to be evacuated to dryness after removing fewer than three casing volumes. These low-yield monitoring wells will be allowed to recharge for as long as 24 hours. Samples will be collected as soon as the monitoring wells have recharged sufficiently to allow sample collection. If insufficient water has recharged after 24 hours, the monitoring well will be recorded as "dry" for the sampling event. Purged water will be containerized in Department of Transportation-approved drums, and stored on site in an area inaccessible to the general public. The purged water is typically characterized either by sampling, or on the basis of the groundwater sample analytical results. Twining can recommend an appropriate method for disposition of the purged water. Disposal will be the responsibility of the client.