Client: Conrail
Project Location: Eastern Illinois
Project Cost: $350,000
PROBLEM:
A railroad tank car containing 20,000 gallons of diphenylmethane diisocyanate (MDI) derailed and released the tank car's contents. One thousand linear feet of railroad ballast under a railroad siding were contaminated. The liquid product underwent gradual polymerization and made product recovery an unacceptable option.
The remedial action plan consisted of l) contain and stabilize the site, 2) investigate the extent of contamination, 3) design and implement a remedial action program, and 4) document site decontamination.
SOLUTION:
MDI was contained using bentonite berms in the drainage path. Runoff diversionary structures were constructed and a polyethylene cover prepared in the event of rain. Treatability investigations were conducted to determine the most technically sound and cost-effective ultimate disposition of the contaminated ballast. It was determined that product incineration would be cost-prohibitive and potentially dangerous because of the continuous product polymerization.
Polymerization Operations
Various media including ground corn, ground clay and sand were investigated to determine the appropriate polymerization catalyst. Field tests confirmed that sand produced a solidified polyurea, sandstone-like material which was considered nonhazardous and would facilitate hauling in bulk. Initial negotiations with state regulatory authorities had required that the contaminated ballast be containerized and hauled in sealed containers. Subsequent negotiations facilitated bulk hauling, and resulted in a cost savings of over $1 million to the client.
Fifteen-hundred cubic yards of solidified ballast and sub-ballast were removed and transported to a licensed special waste facility. Nineteen-hundred linear feet of contaminated rail were sandblasted and decontaminated, utilizing a field designed sandblast booth with a HEPA particulate filtration system. Compaction testing was conducted on backfilled subgrade and ballast to insure soil stability. Two miles of access road were repaired along the railroad right-of-way, and an engineering report was prepared on project completion.