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ti 7 ry n GROUND-WATER MONITO:•'ING AND SAMPLING PROCEDI3RES Prior to sampling, the depth to water was maasured in all monitoring wells using an electronic immersion probe. All measurements were read to the nearest 0.0I foot. If free product was present, the depth to free product and the depth to water were measured using an interface probe and an observation sample was collected with a clear teflon bailer for confirmation. No analytical samples were collected from monitoring wells containing more than 0.25 inch of free product. The monitoring wells were sampled on February 12 and 13, 1991. Prior to purging, each well was checked with a clear teflon bailer in order to observe the possible presence of floating hydrocarbons. _ Purging was accomplished using a stainless steel or teflon bailer. The bailer was thoroughly cleaned prior to each sampling using a trisodium phosphate(TSP)solution followed by a 10%methyl alcohol solution,and then rinsed twice with potable water. The wells were purged prior to sampling until pH, conductivity,and temperature values stabilized. Generally,this resulted in the removal of appruximately 3 to 5 well volumes of ground water from each weU during the purging process. The water obtained from purging was placed in labeled 55-gallon drums and stored on-site. The bailer rope was replaced after each sampling, Samples recovered from each weU were decanted into two appropriately prepared - and labeled 40-m1 volatile organic analysis(VOA)bottles. A travclank (numbered as MW-A)was also submitted for quality assurance. One travel blank per site ruin be analyzed. Duplicate samples will 1 only be analyzed by the laboratory when directed by Du Pont Environmental Remediation Services. I 'he sample bottles were immediately placed in an ice chest and maintained at 4'C until delivery to a State of California licensed laboratory. Routine chain-of-custody procedures were employed. 2. 4 t-^ j r � f A- 1 - f f