Laserfiche WebLink
i <br /> Intcrested Parties-Use Of Non-Purge Sampling Method <br /> April 23, 1997 <br /> Page 3 <br /> 3 In fine grained seduaents (predominately clayey/silty materials) where the <br /> groundwater gradient is relatively flat and wells are slow to recover (i e, <br /> groundwater monitonng wells roututcly become dry pnor to evacuating minimum <br /> purge volumes) These wells can be sampled after groundwater in the monitoring <br /> well r=overs to a iutnimum of 90% of the original groundwater elevation or 24 <br /> hours, whichever is less <br /> 4 The groundwater monitoring well is in use for air sparging and/or vapor <br /> extraction. <br /> If a leaking UST case is evaluated by Regional Bsard staff as a law-n--k sin: or if a responsible <br /> party requests site closure, Regional Board staff may require that a final purged groundwater <br /> samples) be taken from monitonng wells <br /> In areas where municipal supply wells have been impacted by gasoline and/or gasoline additives, <br /> purging of groundwater monitoring wells may be required <br /> Groundwater wells with measurable free product should be on a regular program of free product <br /> removal If a monitoring wells is determined to contain free product at the time monitoring is <br /> atticipated, it should be bailed to remove any standing free product, purged to remove minimum <br /> well volumes (4-10 casing volumes), allowed to equilibrate back to pre-purged levels, then free <br /> proauc, thicl.ness measured and reported <br /> All reports containing the results of gmundwatcr sampling and Nesting must adbere to QAIQC <br /> protocols and be submitted on this Regional Board's Laboratory Report Forms <br /> As new or updated information becomes available regarding the use and ciff6otiveness of the non- <br /> purge method of groundwater sampling, changes and/or updates to thus document will be made <br /> If you have any generalaquestions please contact Mr Jay Huang at (213)266-7608, or contact the <br /> Regional Board staff assigned to your UST case at (213) 266-7500 <br /> LAWRENCE P. KO//LB <br /> Acting Executive Officer <br /> cc Regional Board Members <br /> Allan Patton, Underground Storage Tank Program, SWRCB <br /> Regional Board UST Program Managers <br /> Ventura County Local Oversight Program <br /> Local Implementing Agencies <br /> Raeriwd PapW Ow fiW& a to 0 Amain aaQ""MM rM rrabry of camm"I Wwrmmrsre.+� <br /> *mom a-"RMD M ria wwr"AfFA o/pWi0a aae&M ft 9. bw <br />