Medidas para fomentar un uso eficiente y sostenible del agua

The DOI regulation [43 CFR Section 11.61 (a)(1)] requires the Trustees to determine:

“whether an injury to one or more of the natural resources has occurred;

and that the injury resulted from the discharge of oil or release of a hazardous substance based upon the exposure pathway and the nature of the injury.”

Injury determination for the Assessment Area focused on aquatic-dependent resources. Aquatic-dependent resources are the non-living resources of Twelvemile Creek and Lake Hartwell (i.e., surface water resources, including sediment) and living ecological resources (i.e., biota) that are directly and indirectly dependent on Twelvemile Creek and Lake Hartwell. Examples of ecological resources that are directly dependent on Twelvemile Creek and Lake Hartwell are fish and benthic macroinvertebrates (e.g., aquatic insects). Examples of ecological resources that are indirectly dependent on Twelvemile Creek and Lake Hartwell include piscivorous birds and mammals.

3.1.1 Definition of Injury

During the injury determination phase of a damage assessment, the Trustees determine whether an injury has occurred to natural resources, based on definitions

provided at 43 CFR Section 11.62. The definitions as applied to ecological service losses in the Twelvemile Creek/Lake Hartwell NRDA are summarized below.

3.1.1.1 Surface Water Resources

The DOI regulation [43 CFR Section 11.62(b)] describes the circumstances that result in a determination of injury to a surface water resource from the release of a hazardous substance. The following circumstances are paraphrased from 43 CFR Section 11.62(b) (the reader should refer to the regulations for the complete definitions). Injury to surface water has occurred when:

• The release has resulted in concentrations and duration of substances in excess of standards for the protection of aquatic life as established by the Clean Water Act (CWA) if such concentrations were below the respective standards before the release [43 CFR Section 11.62(b)(iii)].

• The release has resulted in concentrations and duration of substances sufficient to have caused injury to biological resources, when exposed to surface water, suspended sediments, or bed, bank, or shoreline sediments [43 CFR Section 11.62(b)(v)].

3.1.1.2 Sediment

Injury to sediment is defined as a component of injury to surface water resources and geological resources. In essence, injury to sediment as a surface water resource has occurred if concentrations and duration of substances:

“[in sediment are] sufficient to have caused injury … to ground water, air, geologic, or biological resources, when exposed to surface water, suspended sediments, or bed, bank, or shoreline sediments” [43 CFR Section 11.62(b)(1)(v)].

Injury to sediment as a geologic resource has occurred if:

“concentrations of substances [in sediment] have caused injury …to surface water, ground water, air, or biological resources when exposed to the substances” [43 CFR Section 11.62 (e)(11)].

3.1.1.3 Biological Resources

An injury to a biological resource has resulted from the release of a hazardous substance if the concentration of the substance is sufficient to:

“Cause the biological resource or its offspring to have undergone at least one of the following adverse changes in viability: death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions (including malfunctions in reproduction), or physical deformations” [43 CFR Section 11.62(f)(1)(i)].

The DOI regulation details numerous biological responses (e.g., death, disease, behavioral abnormalities, and reproduction malfunction) that can be evaluated in determining whether an injury to biological resources has occurred [43 CFR Section 11.62(f)(4)].

3.1.2 Determination of Injury

Determination of injury consists of documentation that there is 1) a viable pathway for the substance released from the point of release to a point at which natural resources are exposed to the released substance, and that 2) injury of site-related resources has occurred as defined in 43 CFR Section 11.62.

3.1.2.1 Pathways

The DOI regulation [43 CFR Section 11.14(dd)] defines pathway as:

“the route or medium through which… a hazardous substance is or was transported from the source of the discharge or release to the injured resource.”

The principal pathway of exposure of natural resources to PCBs released from the Sangamo-Weston plant was the plant’s process water discharge to Town Creek.

The chemical properties of PCBs determine how they partition in the environment. PCBs have very low solubilities in water, but are fairly soluble in organic carriers. Thus, PCBs are said to be hydrophobic. For these reasons, once PCBs were discharged to the Town Creek/ Twelvemile Creek system, it is expected that the PCBs rapidly became more closely associated with particulate material than with water.

Particulate matter may be suspended in the water column or on the creek bottom (bed sediment). Suspended particulate matter settles out of the water column as a function of particle size, mass, current velocity, and turbulence. Thus, as Twelvemile Creek enters the more quiescent waters of Lake Hartwell, heavier particles tend to settle out closest to the mouth of the creek, and finer, lighter particles tend to settle out farther from the mouth of the creek. The concentration of PCBs thus declines with distance from the mouth of Twelvemile Creek as a function of the mass and grain size composition of sediment originating from the Twelvemile Creek drainage and the decrease in current velocity as the creek enters Lake Hartwell.

In addition to being hydrophobic, PCBs are lipophilic and can be readily accumulated by organisms. PCBs enter the food web principally through the direct or incidental ingestion of contaminated organic matter, sediment, and water, and ingestion of contaminated prey.

In summary, existing information indicates that there is a pathway from the release to trust natural resources. Documentation of the presence of PCBs in surface water of Twelvemile Creek and sediment of Twelvemile Creek, the Seneca River Arm, and Lake Hartwell indicate that there is a pathway linking the release at the Sangamo-Weston plant to surface water resources of the Assessment Area. Documentation of the presence of PCBs in biota (fish, Corbicula, seston, and mayflies) indicates there is a pathway linking the release at the Sangamo-Weston plant to selected biological resources of the Assessment Area.

3.1.2.2 Injury

Table 1 presents a summary of the data relied upon for the injury determination in the Assessment Area, the regulatory basis for determining that injury has occurred, and a description of relevant thresholds for injury determination. Site-specific information is available and sufficient to document injury from releases of PCBs from the Sangamo-Weston plant to surface water, sediment, and selected biological resources in the Assessment Area as described below:

• Surface Water Resources⎯Surface water resources include the surface waters and sediment of Twelvemile Creek and Lake Hartwell.

Although there has been extensive sampling of surface water in the Assessment Area, PCBs were detected in only a few high volume water samples from Twelvemile Creek (Battelle 2002). Analysis of these samples documented PCB concentrations at several locations to be greater than the ambient water quality criterion for the protection of aquatic life. Existing data for Lake Hartwell, however, are inconclusive for establishing injury to surface water based strictly on comparison of concentrations in water to the appropriate criteria, because detection limits are higher than the criteria. Data are sufficient to establish injury to sediment. PCBs have been documented in sediment in all segments of the Assessment Area at concentrations that are within the range of injury thresholds for biological resources.

• Biological Resources⎯Data are sufficient to establish injury to selected biological resources. In particular, PCBs in sediment have been documented at concentrations that are within the range of injury thresholds for benthic macroinvertebrates, and concentrations of PCBs in fish have exceeded levels that are associated with adverse effects in the scientific literature.