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� COLORADO LEGACY LAND <br /> GROUNDWATER WELL PURGING FIELD MEASUREMENT STABILITY CRITERIA FROM VARIOUS LITERATURE SOURCES <br /> Oxidation- No Minimum <br /> pH Specific Dissolved Reduction Temperature Turbidity Consecutive Frequency Purge Volume Maximum Purge Alternate Criteria Comments Screen Length Reference <br /> Conductivity Oxygen Potential Readings or time Volume or time Applicability <br /> ORP or Eh <br /> Applicable to low-flow fixed <br /> volume purging <br /> Purge volumes and pumping rates <br /> should be evaluated on a case-by- <br /> 10%of calculated case basis. <br /> ± 10%, ± 101yo ---------- ±10% ±10% ---------- Not Specified purge 2 well volumes Not Specified None Not Specified USEPA(1985) <br /> requirement Rule of thumb guidelines for <br /> purge volumes should be avoided. <br /> No.of well volumes required for <br /> purging should be verified using <br /> indicator parameters. <br /> Variations in water chemistry on <br /> ± 10% ± 10% --------- +10% + ° 0.25 well purging were greater than errors Barcelona and <br /> _10/o Not Specified Not Specified volumes Not Specified None associated with sampling 2 ft. Helfrich(1986) <br /> mechanism or well casing effects. <br /> Criteria apply to"most wells" <br /> ± 10% _10/o _10% 2 3 minutes Not Specified Not Specified None Low flow rates are"ideal" Not Specified USEPA(1992) <br /> Wide range of opinion regarding <br /> proper purging procedures. <br /> Study applies to VOCs. <br /> Stabilization criteria cannot be set <br /> ±10 VS/cm "Over consecutive <0.5 well a priori due to variability in Barcelona et al. <br /> g/ --------------- ±0.1°C ----------------- Not Specified 2 well volumes None aquifer properties. <_5 ft. <br /> ±0'1 when<1,000 ±0.2 m L bore volumes" volume (1994) <br /> Dissolved oxygen and specific <br /> conductivity are the best <br /> indicators. <br /> ±5 PS/cm Specific to low-flow sampling. <br /> when<1,000 Purge until Turbidity optional if samples are <br /> ±30 mV 2 minutes or'fz readings are± filtered for metals analysis. <br /> ±0.1 ±0.2 mg/L ±0.1°C <5 NTU 3 4 well volumes Not Specified Not Specified Karklins(1996) <br /> ±10 µS/cm (Optional) casing volume 10%for each <br /> when>1,000 parameter Stability ranges for indicator <br /> parameters maybe adjusted <br /> based on site-specific conditions. <br /> Minimum <br /> parameters are pH, Specific to low-flow sampling. <1 in"for high <br /> ± 0.1 ±3% ±10% ±10 mV ------------------ ±10% 3 3 to 5 minutes Not Specified Not Specified conductivity,and resolution USEPA(1996) <br /> turbidity DI sampling needs". <br /> dissolved oxygen <br /> +10%when Specific to"Well-Volume <br /> ±0.1 ±3% ±0.3 mg/L ±10 mv ----------------- >10 NTU 3 Each well volume Not Specified Not Specified None Approach" Not Specified USEPA(2002) <br /> Specific to standard fixed volume <br /> ±5%when<_ ±0.2°C purging. <br /> 100 VS/cm (thermistor) "The number of well volumes to <br /> ±10%when< Dependent on 1 well volume be removed relies on confirming <br /> ±0.1 ±0.3 mg/L ----------- z 5 Not Specified None Not Specified USGS(2005) <br /> ±3%when> ±0.5°C 100 NTU purging rate. (mandatory) the time over which field <br /> 100 PS/cm (liquid-in- measurements stabilize,using <br /> glass) knowledge of the well and aquifer <br /> hydraulics". <br /> Not Not Specified Not Specified Not Specified Not Specified Not Specified Not Specified "Should be based A minimum Not Specified None Method D-Purging Based on Not Specified ASTM (2012) <br /> S ecified on purging rate." number of well Fixed Volume Combined with <br /> PAGE 21 OF 22 <br />