During the July 1986 survey, triplicate sediment samples 
were collected at the center of each of the five disposal mounds 
(Figure 2-4) and at the Reference station using collection and 
handling methods described above. However, the top 2 cm of six 
cores were bagged separately to determine whether the surface 
sediment was relatively more or less contaminated than the deeper 
sediment due to the desorption of contaminants or the deposition 
of cleaner material. Parameters measured included grain size, 
trace metals, and several organic constituents. 
Sediment analyses were conducted using methods described 
by the U.S. Environmental Protection Agency (Plumb, 1981). Mercury 
analysis was performed using acid digestion and cold vapor atomic 
absorption spectrophotometry; arsenic analysis was accomplished 
using acid digestion and gaseous anhydride atomic absorption 
spectrophotometry. The other trace metals (Pb, Zn, Cr, Cu, Cd, and 
Ni) were analyzed using acid digestion and flame atomic absorption 
spectrophotometry. 
Carbon, hydrogen, and nitrogen analyses were conducted 
with an autoanalyzer using a combustion technique. Oil and grease 
measurements were made by extracting the sediment with freon and 
then analyzing the freon by infrared spectrophotometry. PCBs were 
extracted with hexane and also analyzed by electron capture gas 
chromatography. 
25 Benthic Community Analysis 
Quantitative benthic samples were obtained at the newly 
selected NL-85 disposal point prior to disposal in July 1985 and 
after disposal in July 1986. Benthic samples were also collected 
at the Reference station on both occasions. 
Five sediment samples were collected for benthic 
community analysis at each station and sieved onboard the research 
vessel through nested 2 mm and 0.5 mm mesh screens. The material 
retained in the sieves from each grab sample was preserved with 
buffered formalin for later sorting and identification in the 
laboratory. Two of the five samples were archived for future 
reference. A small subsample of each sediment grab was collected 
with a 3 cm inner diameter core tube for grain size analysis by the 
NED laboratory. A visual description of each sediment grab was 
recorded prior to sieving. In the laboratory, samples were stained 
with 0.2% rose bengal and sieved on 1.0 and 0.5 mm screens immersed 
in water. Many ampeliscid amphipods were removed by skimming them 
from the water surface after they were caught by surface tension. 
Small amphipod tubes and most organisms were separated from sand 
and gravel by repeated suspension and decantation. The coarse 
washed gravel was sorted in glass trays with a white background. 
All other fractions were examined with a binocular microscope. 
9 
