TagWalker Creek Basin Plan(12)

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.