Laserfiche WebLink
COLORADO LEGACY LAND <br /> ATTACHMENT B SUMMARY TABLE OF GROUNDWATER WELL PURGING FIELD MEASUREMENT STABILITY CRITERIA FROM VARIOUS LITERATURE SOURCES _-a <br /> Oxidation No. Minimum <br /> Specific Dissolved Reduction Maximum Purge Screen Length <br /> pH Conductivity Oxygen Potential Temperature Turbidity Consecutive Frequency Purge Volume Volume or time Alternate Criteria Comments Applicability Reference <br /> (ORP or Eh) Readings or time <br /> Applicable to low-flow Mixed <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% ± 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 /> 0.25 well purging were greater than errors Barcelona and <br /> ± 10% ± 10% ±10% ± 10% Not Specified Not Specified Not Specified None 2 ft. <br /> volumes associated with sampling Helfrich(1986) <br /> mechanism or well casing effects. <br /> Criteria apply to"most wells" <br /> ± 10% ± 10% ± 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 /> a priori due to variability in <br /> ± 10µS/cm "Over consecutive <0.5 well Barcelona et al. <br /> ± 0.1 when<1,000 ± 0.2 mg/L ±0.1°C Not Specified bore volumes" volume 2 well volumes None aquifer properties. s 5 ft. (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 mV2 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 /> /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 m"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 la sampling needs". <br /> dissolved oxygen <br /> ± 10%when Specific to"Well-Volume <br /> ± 0.1 ±3% ± 0.3 mg/L ± 10 mV 3 Each well volume Not Specified Not Specified NoneApproach" Not Specified USEPA(2002) <br /> >10 NTU <br /> Specific to standard fixed volume <br /> purging. <br /> ±5%when s ±0.2°C <br /> 100µS/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 ±0.5°C 100 NTU 5 purging rate. (mandatory) Not Specified None the time over which field Not Specified USGS(2005) <br /> ±3%when> (liquid-in- measurements stabilize,using <br /> 100 RS/cm 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." number of well Fixed Volume Combined with <br /> PAGE 23 OF 24 <br />