Washington Manufactured Gas Plant Sites


Environmental Assessment
Expert Testimony & Litigation Support

Problem Nature and Extent

Aries was retained by the Joint Defense Group consisting of three insurance companies to provide litigation technical support and expert witness work for several Washington State manufactured gas plants (MGPs) including Gas Works Park in Seattle with contaminated soil and groundwater.


  • Aries investigated the cause and origin of tar and tarry waste releases at various MGPs. Our investigation involved researching the historical operations for information that would indicate leaks, spills, dumping, or waste discharges to surface water, soils and sediments. 
  • Aries studied the methods that were used to abandon or dismantle the MGPs as a potential for causing tar and tarry waste releases to the environment.
  • Investigation revealed that the observed site contaminants, including tars, oils, aromatic hydrocarbons, polycyclic aromatic hydrocarbons, cyanide, arsenic, and sulfur, were consistent with MGP wastes. 
  • Numerous leaks, spills and releases including some violations for discharges of MGP wastewaters to adjacent surface water bodies were documented in the available records.  Aries’ expert opined that environmental and historical records indicated observed site soil and groundwater contamination resulted from identified leaks, spills, and/or releases, and that the gas company would have been aware of the contamination.
  • Aries’ expert testified in depositions and provided litigation technical assistance which helped the Joint Defense Group provide technical information and clearly present it to the gas company which assisted in settling the dispute with the gas company outside of the court room.

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