Design, Bidding, and Construction Oversight – Seattle, WA
CRETE led the design of a cleanup action at the former Time Oil Company brownfield site located on the south shore of Salmon Bay on the Lake Washington Ship Canal in Seattle, Washington.
The property included a bulk petroleum storage facility which distributed petroleum products via ships, rail, and truck with operations dating back to 1941.
Contamination present in soil and groundwater at the site included: total petroleum hydrocarbons (TPH) gasoline-, diesel-, and oil- range organics, arsenic, benzene, trichloroethene (TCE), vinyl chloride (VC), and pentachlorophenol.
Work was completed under a Washington Department of Ecology Prospective Purchaser Consent Decree.
The selected remedy involved:
- In‐situ groundwater treatment, incorporating a permeable reactive barrier (PRB) with granular zerovalent iron (gZVI) media and oxygen release compound (ORC) amendments
- In-situ soil solidification (ISS) of ~28,000 cy
- Excavation and off‐site disposal of 16,000 cy of NAPL impacted soil and capping of residual soil impacts
Work Performed
- Field investigation and analysis
- Regulatory negotiations – Washington Department of Ecology
- Construction oversight
- Reviewed RI/FS work and summarized data gaps for remedial design; prepared reporting memorandums summarizing data gaps
- Developed the Engineering Design Report, bid drawings and specifications, and supported bidding and construction oversight.
- Developed long-term soil, vapor and groundwater monitoring plans for the site
- Prepared a groundwater flow model to predict post remedial action flow conditions
- Conducted a Tier 3 VI assessment to support design for proposed commercial development
- Prepared design and permit documents, supported contractor procurement, provided CQA/CM support, and developed long-term performance monitoring and site management plans.
Value Added
- Successfully avoided expensive pilot testing by conducting bench-scale program during EDR and verification test cells at construction start.
- Incorporated ORC into remedy to reduce the extent of soil excavation within the City ROW
- Designed innovative shoring approach for deep excavations adjacent to active roadway
- Avoided expensive dewatering and TESC measures along the shoreline by sequencing shoreline excavation to overlap with low water levels in Salmon Bay where seasonal water levels are controlled by the USACE
- Developed confirmation sampling approach to minimize over-excavation and dewatering requirements
- Substantive compliance and permitting was completed to address City of Seattle, King County, and Ecology Water quality requirements.
- Beneficially reused ISS-treated soil to support site development grading requirements
- Developed strategic implementation approach to accommodate complex multi-faceted remedy within a highly constrained site.
