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C + <br /> %4 COLORADO LEGACY LAND <br /> ATTACHMENT B SUMMAR ' GING FIELD Y CRITERIA FR E SOURCES <br /> Oxidation- No. Minimum <br /> Specific Dissolved Reduction Maximum Purge Screen Length <br /> pH Temperature Turbidity Consecutive Frequency Purge Volume Alternate Criteria Comments Reference <br /> Conductivity Oxygen Potential Readings or time Volume or time Applicability <br /> ORP or Eh <br /> Applicable to low-flow_r 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% ± 10% - ± 100/0 ± 100/0 ---------- 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% + 101/ +10/o 0 +10/o 0 Not S 0.25 well purging were greater than errors 2 ft. Barcelona and <br /> _ _ Specified Not Specified volumes Not Specified None associated with sampling . Helfrich(1986) <br /> mechanism or well casing effects. <br /> Criteria apply to"most wells" <br /> _10% _10% _10/0 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 /> a priori due to variability in <br /> +0 1 ± 10[IS/cm +0.2 m L Over consecutive <0.5 well Barcelona et al. <br /> g/ --------------- ±0.1°C ----------------- Not Specified 2 well volumes None aquifer properties. <_5 ft. <br /> when<1,000 - bore volumes" volume (1994) <br /> Dissolved oxygen and specific <br /> conductivity are the best <br /> indicators. <br /> ±5 µS/cm Specific to low-flow sampling. <br /> when<1,000 Purge until Turbidity optional if samples are <br /> ±30 mV 2 minutes or Y2 readings are± filtered for metals analysis. <br /> ±0.1 ±0.2 mg/L ±0.1°C <5 NTU 3 4 well volumes Not Specified o Not Specified Karklins(1996) <br /> ±10[IS/cm (Optional) casing volume 10/o for each <br /> when>1,000 parameter Stability ranges for indicator <br /> parameters may be 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 pr 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 /> purging. <br /> ±5%when<_ ±0.2°C <br /> 100 µS/cm (thermistor) "The number of well volumes to <br /> _0.3 mg/L ±10%when< Dependent on 1 well volume p be removed relies on confirming p ( ) <br /> ±0.1 + ----------- >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 VS/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 /> Specified on purging rate." I number of well Fixed Volume Combined with <br /> PAGE 23 OF 24 <br />