Union Station

The Union Station Site includes three tax parcels that span six city blocks in the International District of Seattle, King County, Washington.  A coal gasification plant operated on the Site, beginning in 1874.  Around the turn of the century, Vulcan Iron Works manufactured iron, brass, and steel on the Site.  Union Station was constructed in 1911 and served passengers until 1971.  The Site was dormant until it was purchased by a private developer in 1997. 

Ecology and Union Station Associates entered into a Prospective Purchaser Consent Decree in 1997.  The cleanup remedy selected included paving, construction soil excavation, groundwater monitoring, contingent groundwater remediation, and institutional controls.    Subsequent to the purchase, soil contamination associated with the former site uses was cleaned up, Union Station was refurbished, office buildings were constructed south of Union Station, and groundwater monitoring began.  A Restrictive Covenant implementing the required institutional controls was recorded in 1997.  Groundwater remediation was never conducted.

The Periodic Review concluded:

 ·         Groundwater concentrations of acenaphthene, benzene, arsenic, benzo(a)anthracene, chrysene, diesel-range total petroleum hydrocarbons (TPH), and gasoline-range TPH exceed cleanup levels at the conditional point of compliance (the western property boundary) and this contaminated groundwater appears to be migrating off-property.  Therefore, the remedy is not protective of groundwater and marine surface water located downgradient of the property.  Based on this, the Site failed the periodic review. 

 ·         Required contingency actions are outlined in the Cleanup Action Plan (CAP).  According to the CAP, if any sample exceeds cleanup levels, another sample is to be collected one quarter later.  If the second sample exceeds cleanup levels, quarterly monitoring for one year is to commence.  Further contingency actions based on those findings (such as monitoring frequency changes or groundwater treatment), as well as the appropriate methods of analyzing the monitoring data, are described in the CAP.

 ·         Vapor intrusion does not appear to have been evaluated at the Site. For example, groundwater concentrations of benzene and naphthalene exceed the groundwater screening levels for vapor intrusion. A vapor intrusion assessment should be completed for the Site to determine if vapor intrusion from any of the contaminants of concern is a risk to building occupants.

 ·         Additional details can be found in the  2021 Periodic Review report.