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using site samples which most likely have different characteristics than the Tracy pond
<br /> sediments, however, these data should be less uncertain than literature values and certainly more
<br /> defensible than modeled results. A copy of the table is attached.
<br /> Foraging times (i.e., site use factors) - The Army should examine the time spent on site for all
<br /> receptors, especially the mallard. The available information now being used for this risk
<br /> assessment suggests that the nesting mallard spends much if not all of its time on the site during
<br /> nesting, however, these mallards probably do not spend the entire year on site. The pond does
<br /> not have year round surface water, therefore suggesting that the receptors would not be exposed
<br /> for long periods of time. The site use factor should be adjusted accordingly.
<br /> Food resources - The Army is encouraged to discuss the likelihood of the receptors feeding on
<br /> food items other than those found exclusively in the pond. For instance, the great blue heron is
<br /> reported to have nearly 75%of its diet as fish,but it also eats small rodents, amphibians, snakes,
<br /> lizards, insects, crustaceans, and occasionally small birds (p32, California Wildlife, Vol II Birds,
<br /> 1990). The Army has stated that over the last three or four years, fish have not always been
<br /> observed in the pond resulting in a lower exposure to the great blue heron. This observation
<br /> should be incorporated into the discussion of exposure to the great blue heron. From the same
<br /> source cited above (p64, Ibid), the mallard is reported to have a diet of about 90%plant material;
<br /> mostly grains, seeds and leaves of aquatic plants, grasses, and other green vegetation. The
<br /> remaining diet is mostly aquatic insects,but includes snails, small crustaceans, earthworms,
<br /> tadpoles, and small fish; animal foods being especially important during breeding season.
<br /> Hatchlings feed mostly on insects, but shift to seeds by 6 weeks. The mallard tips up for food in
<br /> shallow water, skims and filters food from water and bottom, gleans insects and seeds in fields
<br /> and along shores,probes in mud and shallow water, and sometimes grazes, but rarely dives.
<br /> Navy TRVs - The correct reference for this information is: "US Navy (1997). Development of
<br /> Toxicity Reference Values as Part of a Regional Approach for Conducting Ecological Risk
<br /> Assessments at Naval Facilities in California. Draft Technical Memorandum, Department of the
<br /> Navy,Engineering Field Activities West Naval Facilities Engineering Command, San Bruno,
<br /> California."
<br /> p4-7, Section 4.1.2.4, EPA suggests that the comparison of gut length among carnivorous,
<br /> omnivorous and herbivorous birds as presented is not relevant to a discussion of the most
<br /> appropriate DDE TRV for the great blue heron. The statement is unsupported with data and
<br /> should be removed.
<br /> p4-7, Section 4.1.2.7, The suggestion that lead bioavailability may be affected by acid-volatile
<br /> sulfides (AVS) is well known (see ET&C, Vol 15, No. 12, 1996) as the author suggests in this
<br /> texts, however, it's not clear from the information presented that lead in the pond sediment at
<br /> Tracy would be the sulfide salt. The Army would have had to measure AVS and simultaneous
<br /> extracted metals (SEM) to determine if the sulfides in the sediments might have been related to
<br /> the sequestration of lead as would be suggested by the SEM/AVS ratio. Other information in
<br /> the section e.g., speciation and the respective bioavailability of the various forms of lead seem to
<br /> be relevant when used to describe the most likely form of lead at the site.
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