SUGGESTIONS FOR REDUCTION
OF ANALYTICAL COSTS BY
ELIMINATION OF UNNECESSARY
FIELD BLANKS
by Douglas M. Chatham
Senior Chemist
SUMMARY
Many field blanks could be eliminated from environmental investigations
by relating the usefulness of the blanks to the project objectives.
If the purpose of the project is to discover the presence of contaminants
and/or measure the total amount of contaminants in a plume, the
blanks are needed to show that the contaminants are sample-related
and not introduced from other sources during the process of sampling.
If the purpose of the project is to demonstrate that cleanup levels,
ARARs, or MCLs have been met, field blanks are not necessary.
Elimination of excessive blanks from one project allowed a reduction
in analytical costs from $53,500 to $45,700 (14.5%).
RECOMMENDATIONS
Any and all QC which contributes to the quality of the data
or are required for other reasons should be included regardless
of arguments presented in this paper. For each blank sample proposed,
Project Managers (PMs) and Quality Assurance Project Officers
(QAPOs) should ask what that determination contributes to the
quality of the data and whether it helps meet the project DQOs.
If a blank sample contributes nothing toward the DQOs, an argument
should be made against incurring the cost for that sample.
For sampling efforts undertaken to demonstrate that ARARs, MCLs,
or cleanup levels have been met, eliminate all field
blanks.
For projects which require blanks, use the following criteria
for determining the frequency and type of blanks to take:
Ambient blanks - Collect only in the event that the field team
observes nearby activities that could contaminate VOC samples.
Equipment blanks - Collect rinseates on bailers used to collect
groundwater samples. Collect equipment rinseates for each decontamination
event. Do not collect rinseate blanks for soil or sediment samples.
Combine blanks (Equipment Rinseate, Ambient, and Trip Blanks)
wherever possible. When equipment rinseate or ambient blanks are
taken, eliminate trip blanks and ship all sample VOCs in the same
cooler as the equipment rinsate blank.
If sampling of multiple types of blanks cannot be avoided, analyze
only the equipment rinseate. If a problem is found, then analyze
the remainder of the blanks.
If corrective actions are possible, submit source blanks as needed
to implement those corrective actions. During long-term programs,
submit source water blanks from water purification systems either
to a fixed base laboratory or to an on-site chemist to maintain
quality control of that system.
DISCUSSION
The field blanks collected at a site could include trip blanks,
ambient blanks, bottle blanks, source water blanks, and equipment
rinseate blanks. The reason for analyzing different types of blanks
is to be able to trace the origin of contamination in order to
take corrective action. This requires that the results be available
as field work is being conducted. Generally, blank results are
not available before the sample results are reported, which can
be many weeks after the field effort is completed. A multiplicity
of blanks may be justified, but the project manager should develop
good reasons for them. Long-term programs involving numerous separate
projects could benefit from different types of blanks, since corrective
action can be taken between projects. If on-site analytical equipment
is available, analysis of blanks on-site would allow corrective
action to be taken rapidly and these are generally much less expensive
than fixed-base laboratory analyses. On-site analysis of blanks
must be conducted with methods which are analyte-specific, have
quantitation limits lower than the action levels, and documented
calibrations and detection limits. Many of the blanks submitted
to laboratories for analysis are probably not necessary.
In many cases, two or more blanks could be combined; e.g., an
equipment rinseate blank taken to the sampling site serves as
an ambient blank and a bottle blank, and if this blank is shipped
in a cooler with VOA analyses, it also serves as a trip blank.
Another approach might be to collect a full set of field blanks
and analyze only the most comprehensive (the equipment rinsate).
As stated by Dr. Keith (1), "Sample analysis is often expensive.
Sometimes it is prudent to collect a full suite of blanks but
only analyze the field blanks. If the field blanks indicate no
problems, the other blanks may be discarded or stored as necessary.
If a problem is discovered, the individual blanks can be analyzed
to determine its source. Resampling will still likely be necessary."
Data validation guidelines (2) state that if a compound is found
in any blank, positive sample results greater than the quantitation
limit and less than five times the blank concentration are qualified
as not detected (U or ND) at a quantitation limit (QL) equal to
the sample result. If this adjusted QL is above the action level,
it cannot be used to demonstrate a concentration below the action
level. There is no difference between a positive sample result
greater than an action level and a blank qualified result with
a quantitation limit greater than the action level when the purpose
is to demonstrate a concentration below the action level. Thus,
if the purpose of sampling is to demonstrate that ARARs, MCLs,
or cleanup levels have been met, or for monitoring remediation
efforts, there may be no reason to take any field blanks. Since
the resulting corrective action (i.e., resampling) based on a
sample result above the action level is the same with or without
blanks, the blanks probably are not necessary. Elimination of
excessive blanks and duplicates from one proposal has allowed
a reduction in analytical costs from $53,500 to $45,700 (14.5%).
Types of Investigations
The CERCLA preliminary assessment (PA) and the RCRA facility
assessment (RFA) are used to identify any releases or migration
from a facility based on the existing information and apparent
visual evidence. The PA or RFA are typically the first step in
the CERCLA or RCRA process. Samples are not usually taken during
these assessments.
The CERCLA Site Investigation (SI) and the RCRA Confirmation Sampling
Process (CS) are used to confirm or disprove suspected releases
to an environmental medium based on information obtained during
the PA or RFA. The SI or CS process is generally limited in scope;
the goal is to gather sufficient data to confirm the presence
or absence of contamination at Potential Release Locations (PRLs),
and to provide a basis for the scope of the CERCLA Remedial Investigation
(RI) or the RCRA Facility Investigation (RFI) process or a No
Further Action decision. The data quality levels for SIs or CSs
are generally required to be Level IV (CLP) or Definitive data
(3) since the data is required to be litigation quality. These
investigations are usually the first ones conducted at most sites
and historical data will be limited or non-existent. The blanks
are needed to prove that the contamination found is from the site,
but multi-purpose blanks may be justified in many cases.
The CERCLA Remedial Investigation (RI) and the RCRA
Facility Investigation (RFI) are used to evaluate the nature and
extent of the releases of hazardous waste and hazardous constituents
and to gather sufficient data to support the preparation of a
risk assessment and Feasibility Study (FS) or Corrective Measures
Study (CMS). RI/RFI studies could be screening data with definitive
confirmation. These studies are much more extensive than SI/CS
investigations. The screening data could be on-site and/or Level
II fixed laboratory analyses with 10% Level III or CLP definitive
confirmations. Blanks should be based on quality control rather
than quality assessment considerations; e.g., monitoring an on-site
water purification system to prevent the use of a spent system.
The CERCLA Feasibility Study (FS) and the RCRA Corrective Measures
Study (CMS) are used to develop and evaluate a remediation plan
or corrective measures alternatives and to recommend the appropriate
corrective measure for the facility. FS/CMS studies could be screening
data with definitive confirmation. These studies can be as extensive
as RI/RFI investigations, but FS/CMS studies are much more focused.
The analyses are limited to the analytes of concern which have
been well documented in prior investigations. The screening data
could be on-site and/or Level II fixed laboratory analyses with
10% Level III or CLP definitive confirmations. Blanks should be
based on quality control rather than quality assessment considerations;
e.g., monitoring an on-site water purification system to prevent
the use of a spent system.
The CERCLA Remedial Design/Remedial Action (RD/RA) and the RCRA
Corrective Measures Implementation (CMI) are used to design, construct,
operate, maintain, and monitor the performance of the remedial
action or corrective measure selected. These studies can be as
extensive and focused as FS/CMS investigations. The analyses are
limited to the analytes of concern which have been well documented
in prior investigations. The screening data could be on-site and/or
Level II fixed laboratory analyses with 10% Level III or CLP definitive
confirmations. Blanks should be based on quality control rather
than quality assessment considerations; e.g., monitoring an on-site
water purification system to prevent the use of a spent system.
The basic purpose of cleanup verifications and long-term monitoring
is to demonstrate that the concentrations of contaminants are
below a mandated level. Blanks are not needed for quality assessment
of these studies. Blanks should be based on quality control rather
than quality assessment considerations; e.g., monitoring an on-site
water purification system to prevent the use of a spent system.
LIST OF REFERENCES
1. Keith, Lawrence H., Ph.D., Environmental Sampling and
Analysis, A Practical Guide, Lewis Publishers, Inc., 1992.
2. USEPA Contract Laboratory Program, National Functional Guidelines
for Organic Data Review, June, 1991.
3. EPA, Data Quality Objectives Process for Superfund, Interim
Final Guidance, p. 42, EPA540-R-93-071, September 1993.
4. EPA, Test Methods for Evaluating Solid Waste, Physical/Chemical
Methods, SW-846, 3rd Edition, Final Update 1, November 1990.
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