Cascade Natural Gas

The Cascade Natural Gas (CNG) Site in the retail center of Sunnyside and is currently occupied by a Cascade Natural Gas office building.  
 
Beginning around 1936, several underground storage tanks (USTs) were located on this Site.  Yakima County operated the property as a county shop and installed and operated at least two, and perhaps three, of these USTs, one for gasoline and one or two for diesel fuel; the County's ownership and operation of these USTs continued until 1956.  From 1956 to 1969 two automobile sales and service operations occupied the Site.
 
From the mid-1950s until the mid-1960s, some of the USTs may have been used to store fuel to heat the buildings located on the property.  In 1960, a fourth UST, for gasoline, was installed near the three older USTs.  By the mid-1960s, all USTs except for the newest gasoline UST were out of service, but all remained at the Site.  In the mid-to-late 1960s the Site was covered with asphalt, leaving only the dispenser for the newest gasoline UST visible.
 
In 1969 CNG began leasing the Site. Then in 1979 CNG purchased the Site.  CNG staff have submitted statements that diesel fuel was not used at the Site during their occupancy.  CNG did use the new gasoline UST from 1969 until 1988. 

The Site is currently on Ecology’s Hazardous Sites List with a ranking of “1”.  Sites on the Hazardous Sites List are a priority for Ecology, and have completed a Site Hazard Assessment (SHA).  A SHA provides information about the environmental risk of the Site. Risk is based on the amount of contaminants, how toxic they are, and how easily they can come in contact with people and the environment.  Sites are ranked relative to each other on a scale of “1” to “5”; with a rank of “5” being the lowest.

In 1990, to comply with Washington's new UST regulations, CNG retained a contractor to excavate the known 550-gallon gasoline UST at the Site.  During excavation, CNG discovered the remaining three other USTs.  During tank removal activities, petroleum contaminated soil (PCS) was encountered around each of the USTs.  PCS with visual and odor indicators of contamination was excavated and stockpiled at the Site in two phases.  Following the initial excavation, three monitoring wells were installed at the Site to evaluate potential impacts to groundwater.  Samples collected from these wells contained TPH-G, TPH-D, BTEX, and 1,2-dichloroethane (EDC) were detected at concentrations exceeding MTCA Method A cleanup levels. 
 
In April 1994, CNG entered into Agreed Order No. DE 94TC-C165, which ordered the performance of a Remedial Investigation/Feasibility Study (RI/FS) at the Site.  In 1995 CNG completed a RI/FS at the Site in order to assess potential threats attributable to the contamination. The conclusion, of the RI/FS, was that long-term groundwater monitoring and natural attenuation and degradation would be sufficient to protect human health and the environment, and was the preferred alternative for cleanup.
 
In May 1998, Ecology entered into Consent Decree (CD) No. 98-2-01173-3 with CNG with the purpose of providing for remedial action at the Site.  This CD required CNG to conduct the remedial action detailed in a Cleanup Action Plan negotiated with Ecology.  The Cleanup technology selected for the Site was intrinsic bioremediation in conjunction with institutional controls and monitoring of the groundwater. This technology was chosen because, due to Site-specific conditions, it provided an overall protectiveness of human health and the environment.

Periodic reviews are conducted every 5 years by Ecology for sites that have Environmental Covenants and/or Institutional Controls. The review is intended to examine the effectiveness of cleanup activities and to assure the continued protection of human health and the environment.

Periodic Review Results

The Site remains occupied by Cascade Natural Gas and is used for commercial purposes.  There have been no changes in current or projected future Site or resource uses. 

Based on this periodic review, the Department of Ecology has determined that the remedial actions at the Site fail to be protective of human health and the environment.  The requirements of the Restrictive Covenant are being met at the Site; however additional remedial actions may be required by the property owner to meet Site cleanup levels within a reasonable restoration timeframe.  It is the property owner’s responsibility to continue to inspect the Site to assure that the requirements of the Restrictive Covenant are being met.