Dames & Moore, 1999 - USDA Forest Service

Ratio of Shredder Functional Feeding Group and Total Number of Individuals Collected
Shedders typically feed on living vascular hydrophyte plant tissue and decomposing vascular plant tissue or
coarse particulate organic material (CPOM). Shredders are typically sensitive to riparian zone impacts and
are particularly good indicators of toxic effects when the toxicants involved are readily adsorbed to the
CPOM and either affect the microbial communities colonizing the CPOM or the shredders directly (Plafkin
et al., 1989). This index at the reference locations ranges fiom 0.05 (CoC-I) to 0.14 (SFAC-I) and from
0.15 (RC- 10) to 0.54 (RC-5a) at the location downstream from the Site.
Total Number of Organisms
Total number of organisms reflects the general productivity of a community. In general, the abundance of
organisms indicates the availability of food sources for fish. Productivity within the Railroad Creek
locations was lowest at locations RC-7, -5% and -10 with total number of organisms of 64, 52, and 75,
respectively. The reference locations exhibited considerably higher total numbers of organisms ranging
from 997 at BC- 1 to 1266 at CoC- I.
The substrate sampled for benthic macroinvertebrates was generally homogenous within a given sampling
station. Upstream from the Site (RC-6 and RC-I) and the remote reference stations (SFAC-I, BC-I and
CoC-1) were void of any visible precipitate or flocculent. Precipitate was most evident at stations located
adjacent to and immediately downstream from the tailings piles (RC-7 and RC-5a). Although present, the
precipitate was reduced downstream at RC- I0 and RC-3.
RC-9, immediately upstream from Copper Creek, presented a unique opportunity for observing the affects
of the precipitate with respect to benthic macroinvertebrates. RC-9 was located adjacent to a seep (SP-2)
that originated at tailings pile 1. Approximately two thirds of RC-9 exhibited a transition to substrate
covered with precipitate which appeared to be associated with one or more seeps originating from tailings
pile 1 (Figure 4.6-3). Of the eight replicate samples collected at this station, one sample (replicate A) was
collected upstream and along the opposite bank (north) from the precipitate, two samples (replicates B and
D) were collected immediately upstream from the where the precipitate became obvious but possibly within
the influence of the precipitate, two samples (replicates F and H) were collected along the bank opposite the
seep but within the precipitate, and three samples (replicates C, E, and G) were collected adjacent to the
seep and well within the influence of the precipitate.
The results of the individual replicates indicate probable influence from the precipitate assumed to originate
from the tailings pile I seep or seeps. The sample collected upstream frorn and opposite the seep or seeps
(and upstream from the precipitate ) resulted in 15 10 organisms per square meter which is much greater than
either of the Railroad Creek reference stations (RC-I and RC-6). Those samples collected immediately
upstream resulted in reduced densities (240 and 300 organisms per square meter) compared to the replicate
collected further upstream. The samples obtained along the bank opposite the seep or seeps (200 and 260
organisms per square meter) were similar to those collected immediately upstream frorn the precipitate. The
greatest affect from the precipitate is exhibited by the low numbers of organisms within the replicates
collected adjacent to the seep or seeps (10, 20, and 70 organisms per square meter). Species composition
also changed fiom upstream to downstream of the precipitate. In general, the number of organisms which
feed by collecting detrital materials in the stream substrate were reduced downstream from the precipitate.
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17693-00S-019Vuly 19. 1999:4:51 PM:DRAm FMAL RI REPORT