Dames & Moore, 1999 - USDA Forest Service

appropriate metric for protection of earthworm populations. However. as described below. several of the
default assumptions may not be true.
it is not clear that many of the sampling locations provide adequate habitat for earthworms. because of the
physical qualities of the substrate. This is particularly true of tailings piles which are typically devoid of
the organic matter that earthworms feed upon. Organic matter also enhances moisture holding capacity
that is needed for earthworm survival. Earthworms are unlikely to inhabit such soils even if no metals
were present. Therefore, although metals concentrations in these areas may exceed the earthworm TRVs.
it is unlikely that there is a complete exposure pathway for these organisms or their predators.
In Holden Village soils, only copper presents a potential risk to earthworms (Table 7.2.4-7A and B).
However, Janssen et al. (1997a; 1997b) have recently shown that the uptake of metals by earthworms is
governed by soil pH, amorphous iron content, organic carbon content, and temperature (Marinussen et al.
1997). Therefore, the degree of risk is likely to be lower in soils containing high levels of amorphous iron
and/or organic matter, and higher where pH is low. Therefore, since these soils come from lawns and
gardens that have been amended with organic matter, the actual risk is likely to be less than the predicted
risk, which was already relatively low.
Mule Deer
Hazard quotients for mule deer (Table 7.2.4-8) were calculated by dividing the doses estimated in Table
7.2.3-12 by the TRVs in Table 7.2.3-4B.
The default assumptions were:
mule deer fed only on plants from locations where soil samples were collected
mule deer fed only on plants growing in the UCL metal concentrations areas
mule deer consumed soil equivalent to 2 percent of their plant ingestion rate
deer drink only the UCL concentrations from Railroad Creek
the modeled plant metal concentrations were accurate
Table 7.2.4-8 shows that there is no risk to mule deer from the consumption of plants growing at even the
worst case locations. Therefore, there is no need to conduct further analyses of risk to this ROC.
Seeps contained higher concentrations of metals than the creek. If it was assumed that mule deer might
consume the highest median of the seep water as 1 percent of their daily water intake, this had no effect on
the estimated risk.
Deer Mice
Hazard quotients for deer mice (Table 7.2.4-9) were calculated by dividing the doses estimated in Table
7.2.3- 13 by the TRVs in Table 7.2.3-4B.
The default assumptions were:
, deer mice fed only on plants from locations where soil samples were collected
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