A.57 Pine Street Canal, VT

A.57.1 Contacts

Mike Smith
Vermont Department of Environmental Conservation
802-249-5826
[email protected]

 

Karen Lumino
USEPA Region 1
617-918-1348
[email protected]

A.57.2 Summary

Environment:	Canal
Scale:	Full
Contaminants of Concern:	PAHs, VOCs, metals, coal tar NAPL
Final Remedy:	Sand capA covering over material (contaminated sediment) used to isolate the contaminants from the surrounding environment. and cap with organophilic clayClay minerals whose surfaces have been ion exchanged with a chemical to make them oil-sorbent. Bentonite and hectorite (plate-like clays) and attapulgite and sepiolite (rod-shaped clays) are treated with oil-wetting agents during manufacturing. Quaternary fatty-acid amine is applied to the clay. Amine may be applied to dry clay during grinding or it can be applied to clay dispersed in water. amendment

A.57.3 Site Description

Primary source(s): Plant wastewaters and residual oil and wood chips saturated with organic compounds were directly discharged or disposed of in the Pine Street Canal wetland. 

From 1908 to 1966 a coal gasification plant began operating on Pine Street, southeast of the canal. In the 1960s and 70s, an oily material was detected seeping from the wetland into the canal. 

A.57.4 Remedial Approach

Final selected remedy: Sand cap and cap with organophilic clay amendment

In 2002-2003, a nominal 3’ sand cap was initially placed over the coal tar contaminated sediments and sludges and over sunken barges that were deemed to be of archeological significance. During placement over the thickest layer of contaminated sludge (approximately 10-12 ft thickness of oily sludge), sediment waves formed and some of the sludge and NAPL was displaced through cribbing walls around the canal. Continued consolidation and gas ebullitionThe act, process, or state of bubbling up usually in a violent or sudden display. also led to NAPL release through the cap in this area.

In 2009, the sand cap was replaced with an amended cap in the high seepage area. The amended cap was composed of multiple layers of reactive core mat containing organophilic clays to absorb any NAPL that might be mobilized. The potential displacement of coal tar through the porous cribbing bounding the canal is being addressed by a 200-300 ft long vertical barrier and passive recovery wells installed during the 2012 field season. The sand cap throughout the rest of the canal was left in place and appears to be effective at containing the contaminants.

This site illustrated that mobile NAPL can penetrate a sand cap, particularly if hydraulic forces or gas migration encourage such penetration.

Why the remedy was selected: The organophilic clay mat was used to replace the original sand cap in areas where NAPL mobilization was occurring due to gas ebullition.

A.57.5 References

Pine Street Canal, Waste Site Cleanup and Reuse in New England, USEPA Region 1. http://yosemite.epa.gov/r1/npl_pad.nsf/31c4fec03a0762d285256bb80076489c/f8cfe11e53efa23c8525691f0063f6e8!OpenDocument.

Publication Date: August 2014