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I • A purge rate should be selected as to stabilize drawdown. If the well is able to sustain a 0.5 gallon per minute (gpm) purge rate, then once temperature, pH, and specific conductance " parameters have stabilized, as listed above, well purging is considered complete. All purge V rates and volumes removed will be recorded on Groundwater Sampling Logs. • If the well is unable to sustain a 0.5 gpm purge rate and the well is pumped dry, then ! groundwater samples will be collected once the well has recovered a sufficient amount of it water to bail. A disposable or properly decontaminated TeflonTM bailer should be used to ` sample. If the well is purged dry a note will be recorded on the Groundwater Sampling Log. Techniques for conventional / modified well purging include: • Acceptable purge/sampling devices for this project shall be submersible positive- displacement type pumps, bailers, and bladder pumps for purging and sampling. It is recommended to purge and sample at similar rates. • Purging should be accomplished with as minimal disturbance to the surrounding formation as possible. ! • Purge water is containerized on-site and stored as directed by the Project Manager. The following formula may be used to determine the volume of any well: V = 5. 875xC2xH where: V = volume in gallons C = casing diameter, in feet H = height of water column, in feet Using this formula, the volume per linear foot of well casing of common casing sizes is listed below: Casing Diameter Volume per inches Linear Foot (gallons) 1 . 5 " 0.092 2 . 0 " 0.163 4 . 0 " 0.563 6 . 0 " 1 .469 Well Sampling After purging has been completed groundwater samples should be collected either directly from the new or properly decontaminated pump tubing or from a disposable or properly decontaminated TeflonTM bailer equipped with a bottorrremptying device. Appropriate 2597A LDGD Page 3 of 4 December 2004