Pilot‐scale demonstration of in situ capping of PCB‐containing sediments in the lower Grasse River

Abstract

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 It should be recognized that, based on the observation made in the spring of 2003, some of these conclusions are no longer valid for the pilot study area.The occurrence of ice jams in the lower Grasse River and their importance on sediments and PCBs within the system are currently under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 Wiley Periodicals, Inc.

Contaminated Sediments

“…Simulations indicated that the depth of bio-irrigation in the sediment and the release from mineral dissolution are major factors controlling the distribution of dissolved Arsenic in the sediment column. A pilot study using various combinations of capping materials in a seven acre portion of Lower Grasse River was conducted followed by a long-term monitoring program (Quadrini, et al, 2003). Optimal results were obtained with a 1:1 sand/topsoil mixture released from a clamshell bucket either just above or several feet below the water surface.…”

Model‐supported decision‐making at a contaminated sediment site: Post‐audit and site closure

“…Clearly, there is a need for retrospective studies of the accuracy of model predictions, that is, post‐audits, to evaluate the utility of models in supporting decision‐making (USEPA, 2009). There are a few post‐audits of contaminated sediment site models (Farley & Thomann, 1995; Greenberg et al, 2019; Kreis et al, 2011; Magar et al, 2009; Mossman & Schnoor, 1989; Quadrini et al, 2017; Reidy et al, 2019; Stivers & Patmont, 2015; see Supporting Information Section S1 for brief summaries). Some of these studies include projections of natural recovery in the absence of active remediation, and some incorporate the impacts of local remedial actions.…”

Field Measurements and Modeling of Ebullition-Facilitated Flux of Heavy Metals and Polycyclic Aromatic Hydrocarbons from Sediments to the Water Column

“…Ebullition has also been investigated due to its potentially negative impact on remedial capping integrity. Several remedial capping projects have recently been implemented as an alternative to dredging, including the Anacostia River in Washington, DC, 4 the McCormick and Baxter Creosote Superfund Site in Portland, OR, 5 the Grasse River in Massena, NY, 6 and Stryker Bay in Duluth, MN. 7 Capping was recently implemented to reduce dredging volume in the Grand Calumet River (IN, USA).…”