Environmental Engineering Reference
In-Depth Information
TABLE 4.2
Summary of Results for 1,4-Dioxane: No-Purge Sampler Demonstration Study,
McClellan Air Force Base
Number
of Trials
Median
RPD
Slope of
X
-
Y
Scatter Plot
a
Regression
Error (
R
2
)
b
Sampler B
Sampler A
Sampler B
Sampler A
Low-l ow
3-Volume
7
−1.5
1.41
0.97
Low l ow
=
3-volume
Low-l ow
Hydrasleeve
®
3
0.0
1.11
1.00
Low l ow
HSleeve
=
Low-l ow
PSMS
4
7.7
0.94
0.99
Low l ow
PSMS
=
Low-l ow
RCS
3
1.11
1.00
Low l ow
RCS
−7.4
<
Low-l ow
RPPS
7
6.1
0.92
0.99
Low l ow
RPPS
=
Low-l ow
Snap™
3
20.7
1.26
1.00
Low l ow
Snap
<
3-Volume
Hydrasleeve
®
3
1.05
1.00
3-Volume
HSleeve
−5.4
=
3-Volume
PSMS
4
5.2
0.90
0.99
3-Volume
PSMS
=
3-Volume
RCS
3
30.3
0.74
0.99
3-Volume
RCS
=
3-Volume
RPPS
7
28.6
0.64
0.99
3-Volume
RPPS
>
3-Volume
Snap
3
17.1
0.84
0.99
3-Volume
Snap
=
Hydrasleeve
®
PSMS
6
27.6
0.83
1.00
HSleeve
PSMS
>
Hydrasleeve
®
RPPS
7
25.0
0.69
0.99
HSleeve
RPPS
>
PSMS
RPPS
9
0.0
0.85
0.97
PSMS
RPPS
=
PSMS
Snap
3
1.20
n.a.
PSMS
Snap
−27.3
<
RCS
RPPS
9
0.0
0.90
0.95
RCS
RPPS
=
RCS
Snap
6
21.8
1.35
0.86
RCS
Snap
<
RPPS
Snap
9
28.6
1.50
0.95
RPPS
<
Snap
Source:
Parsons, 2005, Results report for the demonstration of no-purge groundwater sampling devices at former McClellan
Air Force Base, CA. Army Corps of Engineers, Omaha, Nebraska.
http://www.geoinsightonline.com/resources/
mcclellan_report_cover.html
(accessed October 12, 2006).
Notes:
AFCEE = Air Force Center for Environmental Excellence; RPD = relative percent difference; n.a. = not applicable (too
few data points were available for statistical signii cance). Low-l ow sampling removes a small volume of water at a low
l ow rate from a small portion of the screened interval of a well without mixing water among vertical zones. The
3-volume sampling method rapidly removes 3-5 well-casing volumes from the well to evacuate stagnant water within
the well casing and in the surrounding well i lter pack. Theoretically, “stagnant” water is replaced with “fresh” ground-
water from the surrounding formation with minimal mixing. Hydrasleeve
®
(abbreviated as HSleeve) is a l at-lying
30 × 2.75-inch polyethylene sleeve, sealed at one end, with a polyethylene reed-valve at the other end and a capacity of
2 L. The 2 × 2-inch polysulfone membrane sampler (PSMS) has 0.2 μm pore size and 108 mL capacity. The 13 × 1-inch
regenerated cellulose sampler (RCS) has 0.0018 μm pore size and 400 mL capacity. The 6 × 1.5-inch rigid porous
polyethylene sampler (RPPS) has 6-15 μm pore size and 150 mL capacity. The 10 × 1.6-inch Snap Sampler is a spring-
loaded volatile organic analysis (VOA) holder that opens a 40 mL VOA or 125/350 mL Polypro bottle at depth.
a
Scatter-plot slopes between 0.90 and 1.10 indicate that the populations are similar. Slopes less than 0.90 typically indicate
that the concentration in sampler A was greater than the concentration in sampler B. Slopes greater than 1.10 typically
indicate that the concentration in sampler B was greater than the concentration in sampler A.
b
R
2
values less than 0.90 indicate a greater degree of scatter and a lower coni dence that the slope value is meaningful.
R
2
values greater than 0.90 indicate a lower degree of scatter and a higher coni dence that the slope value is meaningful.
communication, 2007). In a comprehensive comparison of low- or no-l ow sampling devices
conducted at McClellan Air Force Base near Sacramento, California, the Snap Sampler provided
higher recoveries of 1,4-dioxane than all other types of low- or no-l ow samplers. The Snap
Sampler™ results were comparable to but slightly lower than those of conventional sampling (Table
4.2). Comparisons of 1,4-dioxane results from different sampling approaches from the McClellan
Air Force Base No-Purge Sampler Demonstration Study are summarized in Table 4.2.
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