Floyd|Snider designed and implemented the remediation of petroleum-contaminated soil and groundwater on two waterfront-adjacent properties within the footprint of Seattle’s Alaskan Way, Promenade, and Overlook Walk redevelopment project. Data from the previous Phase II Environmental Site Investigation was used to strategize a focused soil investigation to delineate the contaminated soil source and subsequently prepare a Remediation Action Work Plan in compliance with MTCA and Ecology Toxics Cleanup Program’s model remedies for petroleum contaminated sites. In 2019, Floyd|Snider staff oversaw the cleanup action, which included removal of 2,150 cubic yards of contaminated soil as well as two underground storage tanks. Floyd|Snider also used pre-construction soil data to identify clean overburden and performed field screening and verification sampling during construction to segregate clean overburden for reuse. Due to the small site footprint, just over 17,000 square feet, the excavation was completed and backfilled in sections to allow space for overburden stockpiling and adequate movement of equipment and trucks. Contaminated groundwater was managed by pumping out accumulated water daily with offsite discharge, mixing dry and wet contaminated soils for disposal, and using quarry spalls to stabilize the base of excavation, which eliminated the need for large and costly temporary groundwater treatment on site.

Following the remediation, Floyd|Snider prepared a Remedial Action Completion Report and Long-Term Compliance Monitoring Plan. Groundwater monitoring was coordinated closely with SDOT staff to schedule around the ongoing site development and groundwater was determined to be in compliance with cleanup standards 18 months after the remedial action was completed. The site is now beneath the Seattle Aquarium Ocean Pavilion and Overlook Walk, key features of Seattle’s waterfront improvement project near Pier 62.

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