EXH1123042490

Temporary Impacts to Wetlands during Third Runway Embankment Construction Introduction Construction of the Third Runway will require filling low areas west of the current airfield to raise the existing grade to approximately 400 feet MSL. This construction will require unavoidable placement of fill in existing wetlands. Temporary impacts to wetlands will result from facilities needed to meet water quality standards for construction runoff, construction dewatering, construction access, and construction staging. The facilities and activities that will result in temporary impacts to wetlands and streams are discussed below and summarized in Table 1. Temporary construction in some of the wetlands west of the toe of the runway embankment is unavoidable because certain construction activities must occur outside (west of), but in close proximity to the footprint of the embankment where wetlands are located.. Construction impacts to wetlands west of the embankment are considered temporary because following completion of construction, these impacts will be removed and the wetland areas restored to pre-construction conditions. Where feasible and consistent with FAA requirements regarding wildlife attractants, existing wetlands will be enhanced (i.e. wetlands dominated by non-native vegetation will be replanted with native species). Permanent facilities west of the runway embankment, such as storm water detention facilities, will generally be constructed outside of existing wetlands. Storm water runoff from construction areas requires water quality treatment facilities to prevent water quality impacts to Miller Creek due to potential sedimentation. The proposed storm water treatment facilities must be constructed in low areas (which are often wetlands) and parallel…

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PSCAA Advisory Council Meeting Agenda
Add to CalendarMWednesday Mar 11, 9:00am - 11:35am
1904 3rd Avenue, Suite 105, Seattle, WA 98101
Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]