TagSR509(108)

An independent wetland scientist, writing on behalf of the Airport Communities Coalition, raised concerns with the US Army Corps of Engineers about potential mapping errors affecting Wetland 44a near the proposed SR509 Temporary Interchange for Sea-Tac Airport's Third Runway project. The letter warned that discrepancies between engineering drawings and actual field conditions could mean the wetland was closer to the construction zone than documented, risking illegal filling or sediment discharge into protected wetlands. The scientist urged the Corps to verify the wetland's true location and review erosion control measures before approving any construction permits.

STIA Construction Site Stormwater Monitoring reports dated 10/16/2000 and 10/20/2000, samplers JL/RS and JB/RS. AR017259–AR017261. Documents turbidity and pH measurements at multiple construction sites including Logistics Site Development (unnamed catch basin, Tyee Pond, IWS Lagoon 3), MWS Lagoon 3 Construction treatment facility, Airfield Improvement (construction staging area, SDS-7, SDS-6, SDS3-594), Dobbs Flight Kitchen Remodel (SDE4-611,

In August 2000, the Port of Seattle submitted a revised implementation plan to the Washington Department of Ecology for a flow augmentation facility on Des Moines Creek, near Seattle-Tacoma International Airport. The plan outlines two potential water sources — a Port-owned well used to irrigate the Tyce Valley Golf Course, or water purchased from Seattle Public Utilities — along with details on pipeline construction, dechlorination treatment options, and pump configurations. Construction of the facility was scheduled to begin in June 2002, with the well preferred as the lower-cost option pending resolution of water rights issues.

A fisheries biologist hired by the Airport Communities Coalition assessed the potential environmental impacts of a temporary SR-509 interchange construction project near Seattle-Tacoma International Airport, concluding that the project posed serious risks to fish and wetland resources in Walker Creek. The report found that proposed erosion control measures, such as silt fences and whattles, were grossly inadequate given the steep terrain (slopes of 40–60%) adjacent to Wetlands 43 and 44, and that sediment-laden stormwater runoff containing metals and polycyclic aromatic hydrocarbons would likely reach these sensitive areas. The biologist also criticized the Port of Seattle and its contractor, Parametrix, Inc., for failing to conduct fish species inventories and for providing little documentation to support their claim that no significant wetland impacts would occur.

A June 2000 letter from Azous Environmental Sciences to the US Army Corps of Engineers raises concerns about the incorrect mapping of Wetland 44a near the proposed SR509 temporary interchange in SeaTac, Washington. A field review found that the wetland may be 20 to 40 feet closer to the construction zone than shown in project plans prepared by HNTB Corporation, potentially exposing it to significant sediment runoff during construction. The letter also highlights an overlooked creek system connecting Wetland 44a to Walker Creek and Miller Creek, warning that construction impacts could affect a broader network of wetlands and waterways.

A professional wetland scientist reviewed the construction plans for a temporary SR509 interchange near Seattle-Tacoma International Airport and concluded that the project would cause harmful sediment-laden stormwater runoff to discharge into nearby Wetland 43. The report found that the wetland boundary was significantly closer to the construction zone than project documents indicated, and that the steep slopes and sparse vegetation of the construction site made sediment runoff unavoidable. The scientist determined that the planned temporary erosion control measures were inadequate to protect the wetland, particularly during unexpected storm events.