Protecting Public Health and the Environment.

Canyon Owyhee School Services Agency (COSSA) Parking Lot - Wilder

Site Background

The redevelopment site was originally part of a 40-acre homestead and farm founded in 1913. The property included six structures: two family dwellings, a garage, and three sheds. Various land use practices associated with the homestead and agricultural activities resulted in the potential for contamination at the site.

The property had four aboveground storage tanks (ASTs) that held diesel, gasoline, and heating oil. Vehicle maintenance was performed on the property, and used oil was spread on the ground to deter weed growth. These practices likely occurred from 1961 through the 1990s.

Herbicides were stored and mixed on-site for application to the various crops, including onions, wheat, sugar beets, and seed alfalfa. Small releases of herbicide would occur during mixing and transfer, and the spills soaked into the ground.

Numerous empty and partially full containers of hydraulic fluid, motor oil, gasoline, diesel, and fertilizer were found.

The property was sold to the Wilder School District in 1996, and the Wilder School District quit-claimed the deed to the Canyon Owyhee School Services Agency (COSSA) for expansion of its Regional Technology and Education Center campus in 2009. Before development could occur, the site had to be assessed for environmental contamination.

A Phase I environmental site assessment (ESA) was performed by Materials Testing and Inspection (MTI) in 2009. MTI also removed a diesel AST and approximately 350 tons of petroleum contaminated soil.

In 2011, the site buildings were razed during a practice burn by the Wilder Fire District; remnant concrete foundations and slabs from the farmstead structures and two water wells were all that remained.

View of equipment shed (Jon Kruck, 2009, MTI)

Site Investigation Process

DEQ’s Brownfields Program became involved with the project in 2013. DEQ retained STRATA to perform a Phase I ESA at the request of COSSA to identify potential recognized environmental conditions (RECs) and a Limited Phase II ESA to assess building debris and site conditions.

The Phase I ESA identified potential chemicals of concern (COCs) related to the site’s former use as a farmstead, including volatile organic compounds (VOCs), semi-volatile organic compounds, and herbicides and pesticides. Additionally, the farmstead structures may have contained asbestos and lead-based paint.

The primary objective of the Limited Phase II ESA, conducted in January 2014, was to collect subsurface soil samples, composite soil stockpile samples, ground water samples, and building debris waste characterization samples to evaluate whether historic use impacted the site.

Ground water monitoring wells were installed and samples were collected for soil, ground water, asbestos, and leachable and total lead.

The Limited Phase II ESA led to the following conclusions:

  • VOC and polyaromatic hydrocarbon (PAH) impacts to soils were present in the area of the former diesel AST remedial action, but detected values did not exceed the residential use screening levels (RUSLs).
  • VOC and PAH soil impacts were found around the former equipment shed. The detected concentrations of all but one compound were below the RUSLs/initial default target levels (IDTLs).
  • Two pesticides were found above their IDTLs near the former equipment shed foundation.
  • One herbicide exceeded its IDTL in the soil stockpile.
  • VOC and PAH impacts to ground water were observed in the three monitoring wells, but detected values did not exceed the IDTLs or RUSLs.
  • Building debris did not contain asbestos or leachable lead greater than the regulatory standard but did contain total lead exceeding the regulatory level.

Based on those conclusions, the following recommendations were made:

  • A risk evaluation should be conducted appropriate for exposure possible through the planned redevelopment of a parking lot.
  • Soil in the former location of the 1,000-gasoline AST should be sampled for additional compounds.
  • The soil stockpile should be resampled.
  • Soil surrounding the existing building foundation remnants should be sampled for total lead.
  • Soil and ground water should be resampled for one of the pesticides.
  • Building debris may be disposed of as demolition debris at a local landfill with demolition workers informed that the debris contains lead.

An additional Limited Phase II ESA was completed in September 2014 to collect necessary data to address these recommendations. This additional ESA recommended that soils removed from the site during construction activities should be disposed of at a facility licensed to receive the waste.

Total assessment funds expended: Phase I, Limited Phase II, Additional Limited Phase II = $44,000

Acreage assessed: 15 acres (Phase I), 2 acres (Phase II)


COSSA’s Regional Technology and Education Center annually serves over 1,375 students. Approximately 28 “at risk” students graduate from the COSSA Academy each year. COSSA is an official Idaho “Go On” school with a diverse student base:

  • 800 special education students
  • 200 alternative education students
  • 200 professional-technical students
  • 125 gifted/talented students

COSSA struggles to accommodate parking for students and staff. By turning the 2-acre parcel into a gravel parking lot, they were able to address these needs.

Before the site was redeveloped, it was an eyesore that was overgrown with weeds and accumulating trash. COSSA spent about $15,000 to clear and redevelop the parking lot. The project employed five people. The parking lot was completed by the end of March 2016.

Visit the COSSA website for more information.

Finished parking lot (September 13, 2016)

Staff Contacts

Brownfields Program Coordinator
Eric Traynor
DEQ State Office
Waste Management and Remediation Division
1410 N. Hilton
Boise, ID 83706
(208) 373-0565

Related Pages

Brownfields Assessment Program

Brownfields Grants

Voluntary Cleanup Program

Brownfields Success Stories