Project Location: Renton, Washington

Client: PACCAR Inc.

Construction Cost: In excess of $15 million

Wilder’s Role: Prime

Construction Period: 8/90 – 3/99

Wilder was the prime contractor for remediation and civil construction work associated with PACCAR Inc. on its 82-acre National Priorities List (NPL) Site from 1990 through 1999. The phased project involved voluntary cleanup of property contaminated by activities associated with a foundry and heavy industrial operations. Contamination at the site included heavy metals, polynuclear aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPHs) and polychlorinated biphenyls (PCBs). Five phases were planned, four of which were performed by Wilder Construction. In addition to those four phases, Wilder Construction was awarded contracts to perform the site work for the new Kenworth Truck Plant, to design and build a truck decking facility, to perform site work for an alignment building and to install a high-volume storm water line (in lieu of another on-site detention basin) downstream from the site.

Initial investigation and field study work was conducted in 1990 to evaluate bioremediation feasibility. Wilder excavated approximately 7,000 CY of contaminated soil and placed it into bioremediation cells. Landfarming and aerated pile methods were used to conduct full-scale treatability tests.

Phase I and II project work (1991 - 1992) were performed by Wilder in contaminated soil on the north half of the site in preparation for construction of the Kenworth Truck Plant. Wilder placed a 100,000 CY preload. Major remediation and construction efforts included demolition of asphalt and concrete paving; building demolition; excavation of PCB-contaminated soil; excavation, screening and stockpiling heavy metal and organic contaminant materials exceeding cleanup standards for future on-site treatment; and civil construction and site work for a new truck plant.

Utility installation performed in contaminated soils required deep excavations (to 22 feet below grade) and extensive dewatering and shoring, particularly because groundwater was encountered as shallow as three feet below grade. Wilder performed dewatering using a well point system to control groundwater along 2,000 feet of trench. The dewatering system generated more than four million gallons of contaminated water requiring on-site processing by Wilder before release to the publicly owned treatment works.

As part of Phase IV, Wilder demolished slab and concrete to provide fill materials; excavated 64,000 CY of soil exceeding organic contaminant cleanup levels; constructed 256,000 SF of lined land treatment units; biotreated 92,000 CY of petroleum-contaminated soil; cement stabilized 15,000 CY of heavy metal-contaminated soil; and filled, graded, placed clean cap, top soil and hydroseed on 40 acres.

Hydrocarbon contaminant concentrations for bioremediation were as high as 89,000 parts per million (ppm), with heavy metal concentration levels for stabilization as high as 19,000 ppm. Based on past experience, Wilder proposed an alternate, more cost-effective soil stabilization technique. Wilder bioremediated 106,000 CY of soil and stabilized over 15,000 CY of soil for on-site use.

On Phase V, Wilder demolished four acres of concrete building foundations and slabs and excavated over 23,000 CY of TPH contaminated soils for on-site bioremediation. Simultaneous to these efforts, Wilder performed site work for facility construction to return the site to industrial use.

Wilder demobilized from the site in 1998 after nine years of working closely with the owner, engineer, city and WA DOE. In late 1998, PACCAR requested Wilder remobilize to the site to perform all excavation associated with several Kenworth Truck Plant expansion projects. PACCAR required all bidders on the expansion projects use Wilder to perform the excavation work.