Pilot-scale demonstration of in situ capping of PCB-containing sediments in the lower Grasse River
A fish‐consumption advisory is currently in effect in a seven‐mile stretch of the Grasse River in Massena, New York, due to elevated levels of PCBs in fish tissue. One remedial approach that is being evaluated to reduce the PCB levels in fish from the river is in situ capping. An in‐river pilot stud...
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Veröffentlicht in: | Remediation (New York, N.Y.) N.Y.), 2003, Vol.14 (1), p.33-53 |
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Zusammenfassung: | A fish‐consumption advisory is currently in effect in a seven‐mile stretch of the Grasse River in Massena, New York, due to elevated
levels of PCBs in fish tissue. One remedial approach that is being evaluated to reduce the PCB levels in fish from the river is in situ
capping. An in‐river pilot study was conducted in the summer of 2001 to assess the feasibility of capping PCB‐containing sediments of the
river. The study consisted of the construction of a subaqueous cap in a seven‐acre portion of the river using various combinations of capping
materials and placement techniques. Optimal results were achieved with a 1:1 sand/topsoil mix released from a clamshell bucket either just above or
several feet below the water surface.
A longer‐term monitoring program of the capped area commenced in 2002. Results of this monitoring indicated: 1) the in‐place cap
has remained intact since installation; 2) no evidence of PCB migration into and through the cap; 3) groundwater advection through
the cap is not an important PCB transport mechanism; and 4) macroinvertebrate colonization of the in‐place cap is continuing.
Additional follow‐up monitoring in the spring of 2003 indicated that a significant portion of the cap and, in some cases, the underlying
sediments had been disturbed in the period following the conclusion of the 2002 monitoring work. An analysis of river conditions in the spring of 2003
indicated that a significant ice jam had formed in the river directly over the capping pilot study area, and that the resulting increase in river
velocities and turbulence in the area resulted in the movement of both cap materials and the underlying sediments. The pilot cap was not designed to
address ice jam–related forces on the cap, as the occurrence of ice jams in this section of the river had not been known prior to the observations
conducted in the spring of 2003. These findings will preclude implementation of the longer‐term monitoring program that had been envisioned for
the pilot study. The data collected immediately after cap construction in 2001 and through the first year of monitoring in 2002 serve as the basis for
the conclusions presented in this article. It should be recognized that, based on the observation made in the spring of 2003, some of these conclusions
are no longer valid for the pilot study area.The occurrence of ice jams in the lower Grasse River and their importance on sediments and PCBs within the
system are currently under investigation. © 2003 W |
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ISSN: | 1051-5658 1520-6831 |
DOI: | 10.1002/rem.10093 |