[en] Mercury TMDLs (Total Maximum Daily Loads) are a regulatory instrument designed to reduce the amount of mercury entering a water body and ultimately to control the bioaccumulation of mercury in fish. TMDLs are based on a BAF (bioaccumulation factor), which is the ratio of methyl mercury in fish to dissolved methyl mercury in water. Analysis of fish tissue and aqueous methyl mercury samples collected at a number of locations and over several seasons in a 118 km reach of the Savannah River demonstrated that species specific BAFs varied by factors of three to eight. Factors contributing to BAF variability were location, habitat and season related differences in fish muscle tissue mercury levels and seasonal differences in dissolved methyl mercury levels. Overall (all locations, habitats, and seasons) average BAFs were 3.7 x 106 for largemouth bass, 1.4 x 106 for sunfishes, and 2.5 x 106 for white catfish. Inaccurate and imprecise BAFs can result in unnecessary economic impact or insufficient protection of human health. Determination of representative and precise BAFs for mercury in fish FR-om large rivers necessitates collecting large and approximately equal numbers of fish and aqueous methyl mercury samples over a seasonal cycle FR-om the entire area and all habitats to be represented by the TMDL

[en] This report concerns mitigation options for reducing or eliminating the fish kills that occur in L Lake and Pond C as a result of reactor operations. These kills occur when fish that have entered the discharge areas during outages are killed by the rapid rises in temperature that follow reactor re-starts. Factors that have been observed to influence the severity of the kills include the length of the outage, season during which the outage occurs, reactor power level, and size of the fish in the discharge area. Without mitigation, fish kills can be expected to occur in Pond C with approximately the same frequency and severity as in the past. Even in the absence of mitigation, however, it is unlikely that future fish kills in L Lake will be as severe as the large kill that occurred in December 1986. Fish abundance in Region 2 of L Lake (where severe kills occurred in the past) has declined over 90% since 1986, largely due to a reduction in the abundance of juvenile sunfish (which constituted approximately 99% of past kills). There are basically three categories of mitigation options: changes in reactor operations, methods to exclude fish from time discharge areas, and methods to promote the escapement of fish from the discharge area. These options vary in approach, scope, and anticipated expense. Most would need to be researched in greater depth before it would be possible to predict their effectiveness more definitively. While the options have the potential to greatly reduce mortalities, none can totally eliminate mortalities. The only way of ensuring the elimination of all mortalities is to reduce effluent temperatures to sublethal levels with properly designed and operated cooling technology. 18 refs., 2 figs., 1 tab

[en] This paper summarizes information previously presented in an article published in Health Physics and additional information collected more recently concerning the continuance of trends noted in the first paper

[en] Entrainment (i.e., withdrawal of fish larvae and eggs in cooling water) at the SRS Savannah River intakes is greatest when periods of high river water usage coincide with low river dischargeduring the spawning season. American shad and striped bass are the two species of greatest concern because of their recreational and/or commercial importance and because they produce drifting eggs and larvae vulnerable to entrainment. In the mid-reaches of the Savannah River, American shad and striped bass spawn primarily during April and May. An analysis of Savannah River discharge during April and May 1973--1989 indicated the potential for entrainment of 4--18% of the American shad and striped bass larvae and eggs that drifted past the SRS. This analysis assumed the concurrent operation of L-, K-, and P-Reactors. Additional scenarios investigated were: (1) shutting down L- and P-Reactors, and operating K-Reactor with a recycle cooling tower; and (2) shutting down L- and P-Reactors, eliminating minimum flows to Steel Creek, and operating K-Reactor with a recycle cooling tower. The former scenario reduced potential entrainment to 0.7--3.3%, and the latter scenario reduced potential entrainment to 0.20.8%. Thus, the currently favored scenario of operating K-Reactor with a cooling tower and not operating L- and P-Reactors represents a significant lessening of the impact of SRS operations

[en] The K Reactor at the Savannah River Site (SRS) began operation in 1954. The K-Reactor pumped secondary cooling water from the Savannah River and discharged directly to the Indian Grave Branch, a tributary of Pen Branch which flows to the Savannah River. During earlier operations, the temperature and discharge rates of cooling water from the K-reactor were up to approximately 70 degree C and 400 cfs, substantially altering the thermal and flow regimes of this stream. These discharges resulted in adverse impacts to the receiving stream and wetlands along the receiving stream. As a component of a Consent Order (84-4-W as amended) with the South Carolina Department of Health and Environmental Control, the Department of Energy (DOE) evaluated the alternatives for cooling thermal effluents from K Reactor and concluded that a natural draft recirculating cooling tower should be constructed. The cooling tower will mitigate thermal and flow factors that resulted in the previous impacts to the Indian Grave/Pen Branch ecosystem. The purpose of the proposed biological monitoring program is to provide information that will support a Section 316(a) Demonstration for Indian Grave Branch and Pen Branch when K-Reactor is operated with the recirculating cooling tower. The data will be used to determine that Indian Grave Branch and Pen Branch support Balanced Indigenous Communities when K-Reactor is operated with a recirculating cooling tower. 4 refs., 1 fig. 1 tab

[en] Four Mile Creek was electrofished during June 26--July 2, 1990 to assess the impacts of outcropping ground water form the F- and H-Area Seepage Basins on fish abundance and distribution. Number of fish species and total catch were comparable at sample stations upstream from and downstream from the outcropping zone in Four Mile Creek. Species number and composition downstream from the outcropping zone in Four Mile Creek were similar to species number and composition in unimpacted portions of Pen Branch, Steel Creek, and Meyers Branch. These findings indicate that seepage basin outcropping was not adversely affecting the Four Mile Creek fish community. 5 refs., 3 figs., 4 tabs

[en] Ecological half-lives (T_e's) were estimated for ¹³⁷Cs in largemouth bass, sunfishes, and bullheads from two reservoirs and three streams on the Savannah River Site, a nuclear weapons material production facility in South Carolina. Ecological half-life is the time required for a given contaminant concentration to decrease by 50% as a result of physical, chemical, and/or biological processes that remove it from an ecosystem or render it biologically unavailable. T_e's were estimated from whole-fish ¹³⁷Cs concentrations in samples collected during 1972--1996, following radionuclide releases that occurred primarily during the 1960's and early 1970's. T_e's ranged from 3.2 to 16.7 y, and all were shorter than expected from the half-life for radioactive decay (T_p = 30.2 y) alone. Fish taxa from the same locations differed in mean ¹³⁷Cs concentrations (highest in largemouth bass and lowest in sunfishes) but, in most cases, exhibited similar ¹³⁷Cs T_e's. Rates of ¹³⁷Cs removal in fishes were strongly correlated with rates of ¹³⁷Cs removal in water. The shortest T_e's occurred in the upper portions of the streams. T_e's in lower portions of the streams were longer, as were T_e's in one of the reservoirs. T_e's in the second reservoir, which had a much shorter water residence time, were nearly comparable to those in the upper portions of the streams until 1991. At that time, ¹³⁷Cs concentrations in fishes began to increase following drainage and refilling of the reservoir, which apparently resuspended ¹³⁷Cs buried in the sediments

[en] Sediment and small mammal samples were collected from the exposed sediments of Par Pond in early 1995, shortly before the reservoir was refilled after a 4-year drawdown. Sampling was confined to elevations between 58 and 61 meters (190 and 200 feet) above mean sea level, which includes the sediments likely to be exposed if the Par Pond water level is permitted to fluctuate naturally. Both soil and small mammal samples were analyzed for a number of radionuclides and metals. Some of the soil samples were also analyzed for organic contaminants. The objective of the study was to determine if contaminant levels in the Par Pond sediments were high enough to cause deleterious ecological effects

[en] During the operational history of the Savannah River Site (SRS), many different radionuclides have been released from site facilities into the SRS environment. However, only a relatively small number of pathways, most importantly "1"3"7Cs in fish and deer, have contributed significantly to doses and risks to the public. The “effective” half-lives (T_e) of "1"3"7Cs (which include both physical decay and environmental dispersion) in Savannah River floodplain soil and vegetation and in fish and white-tailed deer from the SRS were estimated using long-term monitoring data. For 1974–2011, the T_es of "1"3"7Cs in Savannah River floodplain soil and vegetation were 17.0 years (95% CI = 14.2–19.9) and 13.4 years (95% CI = 10.8–16.0), respectively. These T_es were greater than in a previous study that used data collected only through 2005 as a likely result of changes in the flood regime of the Savannah River. Field analyses of "1"3"7Cs concentrations in deer collected during yearly controlled hunts at the SRS indicated an overall T_e of 15.9 years (95% CI = 12.3–19.6) for 1965–2011; however, the T_e for 1990–2011 was significantly shorter (11.8 years, 95% CI = 4.8–18.8) due to an increase in the rate of "1"3"7Cs removal. The shortest T_es were for fish in SRS streams and the Savannah River (3.5–9.0 years), where dilution and dispersal resulted in rapid "1"3"7Cs removal. Long-term data show that T_es are significantly shorter than the physical half-life of "1"3"7Cs in the SRS environment but that they can change over time. Therefore, it is desirable have a long period of record for calculating T_es and risky to extrapolate T_es beyond this period unless the processes governing "1"3"7Cs removal are clearly understood. - Highlights: • "1"3"7Cs T_es in SRS floodplain soil, floodplain vegetation, and deer were 13–17 years. • "1"3"7Cs T_es in fish from SRS streams were 4–7 years due to washout and sedimentation. • "1"3"7Cs T_es in SRS ecosystems were generally comparable to those at other sites. • "1"3"7Cs T_es at the SRS changed over time due to natural and anthropogenic factors. • "1"3"7Cs T_es should not be extrapolated unless "1"3"7Cs removal processes are understood

[en] Objectives: - Determine whether a Zone of Influence (ZOI) develops in contaminated sediment deposited over active caps; - Evaluate the effects of bioturbation on development of the ZOI; - Improve understanding of the relationships among surface sediment recontamination, remediated contaminated sediments, and biological receptors. Hypothesis: A Zone of Influence (ZOI) will develop in contaminated sediment deposited over active caps and bioturbation will enhance the remedial effectiveness. The effectiveness of the caps will be assessed by evaluating the spatial extent and chemical characteristics of the ZOI that develops in the sediment that accumulates over the caps. Bioturbation may be important in ZOI development by mixing accumulating sediments with cap materials. This study will include mesocosms both with and without bioturbating organisms. Biouptake in caged organisms within the mesocosms will be compared with results from diffusive gradients in thin films (DGT) probes, which have the unique ability to detect fine vertical gradients in metal availability and speciation. Key Points: - Asian Clams were selected to create bioturbation in the experiment; - California Blackworms were selected to test toxicity and bioavailability; - Each mesocosm will receive 0.5 mL/min of synthetic fresh water; - Properties of the synthetic fresh water were measured and compared to Nanopure DI water; - Contaminated sediment will be added to each mesocosm throughout the experiment to determine whether a ZOI develops between the sediment and active cap; - Metal bioavailability and ZOI formation will be compared between mesocosms with and without bioturbation