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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 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 oncethewell has recovered a sufficient amount of 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 = 5.875xCZxH where: V=volume in gallons C=casing diameter, in feet H=height of water column,in feet Using this formula,the volume per Iinear foot of well casing of common casing sizes is listed below: i Casing Diameter Volume per inches Linear Foot(gallons) 1.5" 0:092 2.0" '0:163 4A" 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 TeflonT9 bailer equipped with a bottom-emptying device. Appropriate gw sampling.SOP Page 3 of.5 February 2005 i I