A.34 Lavaca Bay Area, TX

A.34.1 Summary

Environment:	Marine
Scale:	Full
Contaminants of Concern:	Hg: SWAC 0.7 ppm PAHs: Max 137.4 ppm
Final Remedy:	Hydraulic Cutterhead dredge and MNR. Dewatering method was gravity settling. Contaminated sediment was taken to an off-site facility 2.8 miles away at Point Comfort, TX.

A.34.2 Site Description

Lavaca, Cox, and Western Matagorda bays

Cox Creek, Cox Cove, Cox Lake

400-acre artificial dredge spoils island

Year: 1999

Target volume: 184,000 yd³

Actual volume removed: 79,500 yd³ 

Contaminated sediment area: 80,000 acres

A.34.3 Remedial Objectives

Sediments in fringe marsh habitat: < 0.25 ppm, in open-water: < 0.5 ppm

A.34.4 Remedial Approach

Hydraulic cutter head dredge; monitored natural recovery to verify a drop in concentrations in biota.

A.34.5 Monitoring

Silt curtains were in place to contain suspended sediment. Turbidity monitoring was performed downstream to measure the success of silt curtains. Slightly elevated mercury levels were shown to occur periodically.

Two phases were done: partial implementation as part of a treatability study, followed by actual remediationThe act or process of abating, cleaning up, containing, or removing a substance (usually hazardous or infectious) from an environment..

A.34.6 References

EPA Superfund Record of Decision. Alcoa (Point Comfort)/Lavaca Bay EPA ID: TXD008123168 OU 01. Dec 2001. http://www.epa.gov/superfund/sites/rods/fulltext/r0602001.pdf.

Record of Decision. Alcoa (Point Comfort)/Lavaca Bay Site CERCLIS# TXD 008123168. Dec 2001. http://www.epa.gov/region6/6sf/pdffiles/alcoa_lavaca_final_rod.pdf.

Five-Year Review Report. Alcoa (Point Comfort)/Lavaca Bay Superfund Site EPA ID# TXD 008123168. June 2011. http://www.epa.gov/superfund/sites/fiveyear/f2011060004079.pdf.

Major Contaminated Sediment Sites Database; Sept. 2004 as updated 2008. http://www.smwg.org/MCSS_Database/MCSS_Database_Docs.html.

Publication Date: August 2014