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Download Appendix A - Horry County Stormwater
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SOP No.: 406 Page 8 of 9 Environmental Quality Lab Chemistry Procedures Rev. 3 3-15-09 Table 1. Quality Control Requirements for Turbidity by Hach 2100N Turbidimeter QC Sample or Activity Minimum Frequency Acceptance Criteria Capability demonstration Four (4) prepared samples analyzed prior to any customer sample analyses Criteria for duplicate precision 4-Point calibration plus deionized water blank At least quarterly 90-110% R (measured value of primary standards when analyzed as samples within 10% of expected values) Assign values to permanent transfer standards using formazin primary standards At least quarterly Measurement after acceptable 4-point calibration and values within 10% of previous established values Daily calibration check Immediately prior to and after sample analysis GELEX Secondary Turbidity Standards should read within 10% of assigned values Method blank Daily prior to sample analysis <1.0 NTU (i.e., < RL) Sample analysis For all sample analyses Direct sample reading within acceptable measurement range (i.e., 1.00 NTU to 4000 NTU) Sample duplicate One (1) per preparation batch RPD < 25% Internal PE sample Blind PE sample LCS = MB = MDL = MS = PE = Samples and frequency determined by Lab QA Officer Samples and frequency determined by accrediting agencies and projects laboratory control sample method blank method detection limit matrix spike performance evaluation QC = %R = RL = RPD = Corrective Action Repeat until acceptable Investigate problem. Correct any obvious problems. Repeat calibration until acceptable. Investigate problem. Correct any obvious problems including replacing transfer standards if necessary. Repeat until acceptable. Investigate problem. Correct any obvious problems. If necessary reassignment of GELEX values and reanalyze samples. Repeat calibration check until acceptable. Clean analytical system and repeat MB analysis. Identify and eliminate source of contamination. If reading below range report result as < RL. If result above range dilute sample. Investigate problem. If system precision is in control, qualify results. If system precision is out of control, reanalyze entire batch. 75-125% R RPD < 25% Investigate all unacceptable results. Determined by PE provider Investigate all unacceptable results. quality control percent recovery reporting limit relative percent difference
