Sediment Trend Analysis of the Hylebos Waterway: Implications for Liability Allocations
Notice bibliographique
Résumé
Sediment trend analysis (STA) is a technique that determines the net patterns of sediment movement and their dynamic behavior or stability. The data required are the complete particle size distributions obtained from bottom grab samples collected in a regular grid over the area of interest. Appendix 1 provides the particular details of how STA is undertaken. Because many contaminants are known to associate with the natural particles contained in sedimentary deposits, STA can provide additional weight-of-evidence in ecological risk assessment, remedial investigation, remediation itself, and litigation issues. The STA was applied to 242 sediment samples collected from the Hylebos Waterway, Tacoma, Washington, USA, in support of remedial action planning, contaminant source identification, and ultimately allocation of legal liability for contamination. The Waterway itself comprises a narrow shipping channel extending 3 miles from Commencement Bay (Puget Sound) where it ends in a dredged turning basin (Upper Turning Basin). A 2nd dredged turning basin (Lower Turning Basin) is located about three-quarters of the distance down its length. Both sides of the channel are home to an extensive industrial complex associated with significant contaminant releases into the water. The area was declared a Superfund Site in the early 1980s. The results of the STA showed a consistent pattern of sediment transport directed from the mouth of the Waterway to the turning basin at its head. Divided into 5 separate transport environments (TEs), the sediments within the Waterway progress from transport in Dynamic Equilibrium near the mouth, to Total Deposition (type 1) in the vicinity of the Lower Turning Basin, followed by Total Deposition (type 2) in the Upper Turning Basin. Assuming that contaminants associate preferentially with the finer, rather than the coarser, components of the grain size distributions, a probable behavior of contaminants that can be contained in the sediments is proposed for each TE. Maps showing the spatial distributions of existing contaminant data appear to conform very well to the patterns that might be expected from the STA results. This evidence was primarily used to demonstrate that potentially responsible parties (PRPs) located at the head of the Waterway could not be responsible for contaminated sediments toward its mouth. The findings, for example, effectively dismissed the assumption by the Natural Resource Damage Trustee agencies that contaminated sediments from a particular source would be as likely to migrate down the Waterway as up the Waterway. As a result, major documented sources of contamination near the mouth should be expected to bear a larger share of the total cleanup compared with sources farther toward the head. Furthermore, the STA provided explanations for apparent anomalies such as how hot spots of polychlorinated biphenyls (PCBs) could be located near a property where PCBs had never been released into the environment. If sediment gradient pattern analysis alone were used to allocate liability among PRPs, those located near such hot spots would receive a disproportionate share of liability.
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Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».