Site-Specific Health and Safety Plan (HASP) - Laschools.org

Screening data and definitive data quality levels will be used as indicated below:
• Screening analyses will be used for screening air in worker breathing zones for
health and safety purposes. This category may also be used to select sample
portions for further analysis. For example, soil sample headspace may be screened
to determine if laboratory analyses are required.
• Definitive analyses will be used to satisfy the requirements for site
characterization. Definitive data acquired during the investigation will be used to
evaluate COPCs.
2.2 DATA QUALITY ASSESSMENT CRITERIA
DQA criteria will be used to evaluate the quality of the field sampling efforts, field
screening results, and fixed-base laboratory results for compliance with project DQOs.
The DQA criteria are expressed in terms of analytical precision, accuracy,
representativeness, completeness, and comparability (PARCC). Procedures used to
assess data accuracy and precision are in accordance with USEPA's (1996) Test Methods
for Evaluating Solid Waste: Physical/Chemical Methods, SW-846.
2.2.1 Precision
Precision is the measure of variability among individual sample measurements under
prescribed conditions. The relative percent difference (RPD) between primary and field
duplicate samples, laboratory sample duplicate (SD) pairs, and matrix spike/matrix spike
duplicate (MS/MSD) sample results demonstrate the precision of the sampling and/or the
analysis within the batch of samples. When the laboratory control sample (LCS) results
meet the accuracy criteria (USEPA, 1996), results are also believed to be precise, and
represent the historical precision among the sample batches of the laboratory,
independent from the sample matrix. This is based on the LCS being within control
limits in comparison to LCS results from previous analytical batches of the same methods
and matrices. Precision will be expressed in terms of RPD between the values resulting
from primary and duplicate sample analyses. RPD is calculated as follows:
where:
RPD = [(x1 - x2)/X][100]
x1 = analyte concentration in the primary sample,
x2 = analyte concentration in the duplicate sample, and
X = average analyte concentration of the primary and the
duplicate sample = (x1 + x2)/2
Acceptable levels of precision will vary according to the sample matrix, the specific
analytical method, and the analytical concentration relative to the method detection limit
(MDL). For field duplicate samples, the target RPDs are ≤ 70 percent for soil samples
and ≤ 35 percent for groundwater samples. If the concentration of either duplicate is less
than five times the practical quantitation limit (PQL), a control limit of ± 2xPQL will be
compared against the range of the duplicate pair. The laboratory shall have procedures in
place for establishing and updating precision control limits. Typical control limits for
2-2
K:\Depts\Dept48\LAUSD\MSA WORK\QAPP\Draft Final QAPP to DTSC\QAPP for OU 1 RAP.DOC
287