Project Merit: Remediation

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WSP Parsons Brinckerhoff (Herndan, Va.) for a minimally intrusive and cost effective clean-up that kept a manufacturing facility operational, saving 75 jobs in a 500-person rural Kansas town. Remediation involved chromium-affected soils underlying the facility to a depth of approximately 30 feet below ground surface, just above unaffected groundwater. The remediation strategy was based on in situ reduction and fixation of hexavalent chromium using the chemical reductant. Bench-scale testing of site soils determined an appropriate reductant dose, demonstrated stability of the resulting trivalent chromium across a wide range of potential geochemical conditions, and showed that significant off-gassing would not occur. The initial phase involved installing a chemical reductant-based passive horizontal barrier between the affected soil and groundwater. The barrier was designed to treat any chromium mobilized during treatment via chemical reductant flooding of surface infiltration galleries. Confirmation sampling showed the remedy was successful in achieving regulatory criteria, and the facility remains in operation.

AECOM (Los Angeles) for completing remediation and restoration in the wake of the Lac Mégantic, Quebec oil train derailment disaster of 2013. The accident caused explosions and fire that destroyed a portion of downtown, killed 47 residents and created a major environmental disaster. Spilled Bakken Crude oil impacted 38 buildings and municipal infrastructure, soils, and nearby surface water and sediments. Sitewide remediation started December 2013 was completed October 2015. Activity in 2015 included demolition of 32 buildings and a water treatment facility, contaminated soils removal, backfilling with hydroseeded clean materials, rebuilding urban infrastructure, and preparing the site for redevelopment. Soil requiring removal and treatment exceeded 400,000 tonnes; remediated demolition materials were reused; and surface groundwater trenching and recovery wells collected and transferred impacted water to a carbon-based treatment system. AECOM served as program manager and prime contractor to the Town of Lac-Mégantic and Québec Ministry of Sustainable Development, Environment and Climate Change.

Parsons (Syracuse, N.Y.) for its role in the Onondaga Lake cleanup, one of the largest environmental remediation projects in New York State's history. The Geddes Brook/Ninemile Creek site (part of the larger Onondaga Lake site) had been impacted over the past century by industrial contamination, relocated and channelized by road and bridge construction, and its floodplain habitats degraded by non-native invasive plant species. Parsons remediated and restored 36 acres of streams, wetlands, and floodplains. Over 90,000 plants from 120 native species were planted and over 200 plant species documented, including three state-listed threatened or endangered species. Biodiversity has subsequently increased, including the return of more than 70 fish and wildlife species, notably several rare species categorized as threatened or of special interest by the state.