Category: Sediment

Lake Washington Brownfield

Former Wood-Treating Plant – Renton, WA

CRETE principals led the investigation and project_sports-fields-aerialcleanup of this brownfield redevelopment project at a former wood-treating site on Lake Washington. CRETE principals completed the RI/FS, Cleanup Action Plan, Consent Decree, Engineering Design Report, and design plans and specification for cleanup of the property. Remediation on the property consisted of:

  • In situ soil mixing of source area soil and NAPLs with cement and bentonite
  • Sediment removal from a cove and restoration of a forested wetland
  • Soil capping that was fully integrated with site redevelopment
  • Relocation of a salmon-bearing stream
  • Development of site-wide stormwater management program

In situ soil mixing was implemented because geotechnical constraints at the site made excavation impractical. A cement-bentonite additive was designed to reduce the hydraulic conductivity of the impacted soil, thus restricting contaminant transport to the lake. The additive was also formulated such that the soil-additive mixture exhibited strength similar to that of the native soil. Matching native soil strength allowed flexibility in the use of foundation piles for future site redevelopment. The mixed soil was reused on-site to reduce cleanup costs.

Extensive areas of peat and other organic debris generated methane at the site. Methane mitigation systems were designed and installed in the headquarters building, indoor practice facility, and maintenance building.

CRETE principals managed the sediment remediation and wetland restoration of the cove. A one-acre emergent marsh on Lake Washington was restored to provided resident turtle habitat.

The Engineering Design Report provided adequate flexibility in schedule and cap design scenarios for the final redevelopment design to be regularly adjusted while complying with Washington State Department of Ecology requirements. The capping options included asphalt parking areas, pile-supported structures, football fields constructed of natural and artificial turf, and support areas for maintenance, emergency response, and public viewing.

CRETE principals worked with other design team members to develop a stormwater management system consistent with the 2005 King County Surface Water Design Manual. The design efficiently utilized the limited land space by infiltrating rain water through 18 inches of sand in the football field subgrade, thus satisfying the enhanced treatment requirement for discharge to the lake without using land space for a separate enhanced treatment facility. An integrated pest management plan outlines best management practices for the selection and application of turf amendments to minimize the off-site transport of pesticides and fertilizers. The design also included the use of grassy swales around the parking lot sand filters to satisfy the pretreatment requirement. The stormwater outfalls were also designed to avoid the need for USACE permitting. CRETE principals also provided construction oversight including construction stormwater collection and treatment with carbon dioxide and chitosan prior to discharge to the sanitary sewer.

The final phase of the cleanup action (environmental capping and institutional controls) was completed in 2008 in conjunction with redevelopment activities.

Work Performed

  • Property transaction due diligence
  • Regulatory negotiations – MTCA
  • Upland and sediment RI/FS
  • Permitting – in-water cleanup, wetlands, stream relocation, construction stormwater, Metro discharge
  • Sediment cleanupSeahawksSoilMixingOverview
  • Wetland restoration
  • Shoreline site cleanup and development coordination
  • Methane mitigation systems
  • Construction plans and specifications
  • Construction stormwater treatment
  • Construction oversight
  • Stormwater system design

Value Added

  • Negotiated that RCRA F-waste listings did not apply to soil and groundwater
  • Used physical criteria to minimize the volume of K001 listed waste
  • Negotiated a flexible cleanup schedule to allow coordination with development
  • Created a menu of environmental cap designs to allow multiple site development scenarios
  • Developed the CAP to allow grading and reuse of contaminated soil on site
  • Designed in situ soil mixing of source soil and NAPLs to contain source material due to geotechnical constraints
  • Designed the in situ soil mix to provide a final mix strength similar to that of soil to maximize flexibility in the use of foundation piles for various redevelopment scenarios
  • Integrated enhanced stormwater treatment features, including sand filters and pretreatment, within the environmental caps to maximize the development footprint
Posted in Design & Cleanup, Projects, Sediment, Site Assessment, Stormwater | Leave a comment

Cleanup of Rural Town

Former Railroad Fueling Facility – Skykomish, WA

sky aerial croppedCRETE principals provided project management and environmental and civil design services for one of the largest petroleum cleanups in Washington State. The site is impacted by diesel and Bunker C dissolved in and floating on groundwater resulting from decades of locomotive fueling operations. Contamination had impacted soil and groundwater below a small town in the Cascade foothills and seeped into an adjacent river and wetland.

The comprehensive cleanup of river sediments, upland residential and commercial areas, wetlands, and the industrial facility included:

  • Excavation below Town including relocating and replacing structures and infrastructureSky dozer and bldg
  • Excavation and replacement of a vital flood control levee and nearby river sediment
  • Excavation and restoration of wetlands
  • in situ biological treatment of diesel-impacted soil and groundwater
  • Installation of a funnel-and-gate hydraulic containment system with reactive media
  • Treatment of groundwater and floating product using an integrated and fully automated product skimming/collection, and groundwater treatment system

The cleanup project occurred over a five-year active construction period.

Work Performed

  • Regulatory negotiations – MTCASky vault
  • Upland and waterfront RI/FS
  • Bench testing of surfactant/polymer enhanced flushing and chemical oxidation
  • Permitting – in-water cleanup, floodway, wetlands, historic landmarks, cultural resources, utilities, WSDOT
  • Petroleum upland and sediment cleanup
  • Shoreline design and cleanup
  • Construction plans and specifications
  • Wetland restoration
  • Construction oversight
  • Construction stormwater treatment

Value Added

  • Negotiated a soil protective of groundwater remediation level that was more than 150 times greater than the cleanup level
  • Demonstrated that organic acids were causing elevated TPH results
  • Designed a cofferdam to contain NAPLs and silt during nearshore excavation
  • Designed an innovative funnel-and-gate groundwater containment system with reactive media while protecting the railroad mainline
  • Managed a design team of 15 firms and over 35 engineers and construction managers
  • Integrated mechanically stabilized earth walls during backfill to provide a near vertical face for the next year’s excavation and to protect newly constructed improvements
  • Managed uncovered cultural resources during mass soil excavation
  • Documented and protected historic structures within the project footprint
Posted in Design & Cleanup, Projects, Sediment, Site Assessment | Leave a comment

CERCLA Removal Action

Lower Duwamish Waterway – Seattle, WA

T117 Historical AerialTerminal 117 is the site of a former asphalt roofing materials manufacturing facility that operated from 1937 to 1993. PCB, petroleum, dioxin/furan, and PAH impacts in soil and sediment triggered EPA to designate the site an Early Action Area of the Lower Duwamish Waterway (LDW) Superfund site. CRETE successfully worked with the Port of Seattle and City of Seattle during several phases of the project, including: 1) design and oversight of a 2006 time-critical removal action in the Upland Area; 2) preparation of an Engineering Evaluation/Cost Analysis; 3) design of a non-time-critical removal action (NTCRA) in the Upland and Sediment Areas; and, 4) NTCRA bidding and construction support.

Key elements of the NTCRA included:

  • Pre-design and pre-confirmation soil, sediment, and geotechnical sampling
  • Removal of 46,000 cubic yards of soil and sediment in an Environmental Justice neighborhood
  • Special approval by permitting agency to conduct in-water and riverbank work outside of the standard in-water work window established for protection of salmonids
  • Deconstruction and diversion for re-use of existing site building materials
  • Utilized adjacent commercial facilities for construction haul roads and storage to minimize impacts on the residential community
  • Integrated the design with planned right-of-way cleanup activities by the City of Seattle
  • Performed a Cultural Resource Assessment with reporting to the Tribes and the State Historical Preservation Office
  • Prepared the technical bid documents for public bid, including the Port of Seattle’s first use of responsibility criteria

Upland construction was completed in the summer of 2014. The majority of the in-water work was completed in the winter of 2014 and the remainder was completed during the 2014/15 in-water work window.

Work Performed

  • Regulatory negotiations – CERCLA/MTCAT117 Completed Bank
  • Permitting – TSCA risk-based disposal approval, EPA off-site rule, ESA Section 7 biological assessment, cultural resource assessment
  • Sediment and upland cleanup design and bid documents
  • Construction oversight
  • Upland and sediment EE/CA
  • Insurance cost recovery
  • Groundwater-surface water fate and transport
  • Dioxin forensics

Value Added

  • Implemented project within an Environmental Justice residential area with intensive stakeholder involvement
  • Designed the cleanup to integrate with adjacent cleanups, utility improvements, and future site development of a habitat mitigation site
  • Obtained a non-potability determination for site groundwater
  • Negotiated cleanup levels incorporating groundwater-surface water attenuation due to tidal influence
  • Participated in a dioxin forensics work group that concluded that the site was likely not a significant contributor of dioxins to the neighborhood
Posted in Design & Cleanup, Projects, Sediment, Site Assessment, Stormwater | Leave a comment

Sediment Source Control Action

Lower Willamette River – Portland, OR

Soil riverbank cleanup

CRETE prepared the design and bid documents for the removal, capping, and stabilization of 1,700 lineal feet of riverbank fronting an active steel mill on the eastern bank of the Lower Willamette River within the Portland Harbor Superfund Site. Work was conducted through a Voluntary Remedial Investigation Source Control Measures Agreement between Oregon Department of Environmental Quality and the Owner. Bank and beach material was impacted with PCBs and metals, with contamination extending landward of the river beneath the active steel mill. Complete removal of bank and beach material was restricted by the facility and in these areas the design included capping and stabilization. Excavation and disposal included about 17,000 cubic yards of contaminated material.

The design required a balance between a more robust rock armor stabilization that is necessary given the site geometry and the desire to adequately stabilize impacted soil in place, and providing a habitat benefit to the design. Critical plant operational facilities are in close proximity to the riverbank which restricted the ability to flatten or change the relatively steep slopes. Extensive geotechnical, seismic, and erosion analysis were conducted to ensure that the design would remain in place under dynamic conditions. The design required less conventional ways to provide habitat benefits. Elements such as minimizing the footprint of rock armor by making it as steep as practical, providing higher value habitat as close to the uphill and beach extents of the armor as practical and providing habitat enhancements to fringe areas of the site work. A large portion of the work was below ordinary high water which triggered extensive permitting and restrictions on the timing of construction activities. Construction associated with the remedial action began in July 2015 and was completed in early 2016.

Work PerformedEVRAZ riverbank backfill

  • Regulatory negotiations – Oregon DEQ
  • Permitting – in-water cleanup, construction stormwater
  • Shoreline and sediment cleanup
  • Construction plans and specifications
  • Construction oversight

Value Added

  • Negotiated and designed a shoreline cleanup that protected critical plant operations
  • Negotiated a self-mitigating cleanup


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