Herbicide-Impacted Sediment Remediation. II: Field Operations and Optimization

Abstract

This paper is the second in a series on the Tyco Fire Products LP Sediment Removal Project, Marinette, Wisconsin, describing the dredging, stabilization and solidification (S/S) treatment, and nonhazardous disposal of arsenic (As)–impacted sediments. The high spatial variability of the As effects drove the need to develop a screening program to assess the environmental quality of sediments in scows within their 6-h decanting period before off-loading for purposes of reagent dose optimization, versus a default dose of 25% by weight ferric sulfate (60% aqueous) plus 10% by weight portland cement ($78.82/t). Portable X-ray fluorescence (XRF) and 3-h mini–toxicity characteristic leaching procedure (TCLP) techniques calibrated to wet sediments (plus moisture content) were shown to be a quick, reliable means of assessing sediment quality (10 samples per scow) to enable reagent dose optimization on a scow-by-scow basis. The maximum measured XRF As and TCLP As values were 76,981 mg/kg and 195 mg/L, respectively, well above the sediment surrogates tested in the S/S treatability study. For 330 dredged scows (198 S/S-treatment bins) during the 2013 season (May 5 to November 23) processed at a typical daily rate of 1,600–3,000 t/day, only four bins required retreatment, for an overall 2% failure rate on bins processed. In total, 348,000 t of S/S-treated sediments were transported to nonhazardous landfill.