Particle Size Analysis of Green Bay Cell 4 Samples

Table 3

Particle Size Analysis of Green Bay Cell 4 Samples

Volume, %

C4P2

C4P4

C4P6

C4B

< 5 m

< 75 m

67.2

> 75 m

32.8

Bulk sediment chemistry. The C4B1, C4B2, and C4B3 samples were

homogenized, and two samples were then taken for bulk chemical analysis. The

average concentrations for the composite are reported in Table 4. The analysis

revealed the existence of some PAHs and metals, and concentrations of 3,755

and 39 g/kg, respectively, for PCB 1242 and PCB 1260.

Water content analysis. The water content of the C4P2, C4P4, and C4P6

samples was measured in duplicate by oven drying. The water contents averaged

59, 36, and 27 percent, respectively, for the three samples.

Fractionation testing. Although a full size and density separation was

desired on the Cell 4 material, due to time constraints the most important

separation to evaluate initially was the sand/silt separation at 75 m. This

separation was achieved by wet sieving a subsample of the material through a

75-m sieve. The sand fraction was washed off the sieve, and the wash water

was then drained off the sand. The sand sample was analyzed with the Coulter

LS100 Particle Size Analyzer and was found to contain only 5.5 percent <75 m

and 1.1 percent < 5 m by volume, indicating a relatively clean separation. Half

the fines slurry was flocculated using Hychem, Inc., CP626 cationic polymer.

Two (duplicate) samples from both the dewatered sand and flocculated fines

(silt/clay) samples were analyzed for chemical constituents as summarized in

Table 4. The other half of the fines fraction was reserved for further

fractionation testing. The unflocculated silt and clay fractions were separated

using a 50-mm (2-in.) hydrocyclone and the fractions analyzed for PCBs and

indicator analytes. The silt and clay fractions were analyzed on the Coulter to

evaluate effectiveness of the hydrocyclone separation. Approximately

5.7 percent of the silt fraction was greater than 75 :m, and approximately

14 percent less than 3 :m. The presence of particles greater than 75 :m in the

silt fraction can be attributed to oblong particles that pass through the #200 sieve,

and agglomeration of particles, which the Coulter may read as a single, larger

particle. The clay fraction was less clean, with a mean particle size of 15.24 :m,

and a median particle size of 6.39 :m. Approximately 90 percent of the clay

fraction was less than 36 :m, and 50 percent less than 6.4 :m. Only 25 percent

was less than 2.7 :m. The silt and clay fractions were also subsequently

analyzed for chemical constituents (Table 4).

Unlike the Cell 5 analysis, the Cell 4 data follow the expected trends, with

greater concentrations of the contaminants associated with the fines than with the

sand. Concentrations of metals in the silt/clay fraction are almost all one to two

orders of magnitude higher than in the sand. PCBs are an order of magnitude

higher in the silt/clay fraction than in the sand. Differences in concentrations

Chapter 2 Project Description