The water level in Lake Washington dropped an average of nine feet in 1916, when the complete set of canals and locks for increased shipping were completed. Much more land around the edges of Union Bay was then exposed, all of it soft and boggy. The City of Seattle had long used the low spots in various parks as dump sites, which is why artifacts are often found in low areas throughout Washington Park Arboretum. As the population grew, the area of the Arboretum which is now home to the SR520 ramps as well as plant collections including the Lindens became larger dump sites. Early photographs show the “islands” in and around Foster Island were really mounds of dredgings, changing form every few years. Foster Island was originally two acres in area, but it grew to ten acres after the water level dropped. After years of shoreline erosion due to fishermen, canoers, waterfowl, and visitors, much of it was unstable.
The Seattle Department of Parks and Recreation commissioned Anchor Environmental, L.L.C. (now Anchor QEA), as the prime consultant for a shoreline restoration project to restore and improve the waterfront park and habitat in 2004. It was funded by mitigation money from the expansion of the West Point treatment plant. The following information was taken from a report published when the project was completed.
“The Arboretum’s shoreline is located on Lake Washington’s Union Bay and contains one of the largest and most significant wetlands on the lake. The area is critical habitat for federally listed species such as Chinook salmon and nesting bald eagles. This wetland is also part of a very popular canoe route, and has a heavily used pathway system along the 1,700 linear feet of shoreline. The general intent of the project was to restore the eroded shoreline as fish and wildlife habitat, while providing access and views for recreation. Access for the disabled was also an important aspect of the trail improvements, which include relocating and rebuilding pathways, and replacing a major pedestrian bridge to Foster Island. As a result, carefully located viewpoints and water access points are designed to focus human use in appropriate locations. The habitat improvement component of the project was located on a former landfill and marsh. As a result, the design included structural elements and earthwork features that required geotechnical engineering analysis of a bridge as well as shoreline and pedestrian trail regrading. This project was an element of the Washington Park Arboretum’s Master Plan in 2001.”
Today, thirteen years later, the then newly planted vegetation has grown to stabilize the shoreline, and all types of creatures have returned to flourish in and around the water edges. School children can safely access the water edges and canoers can safely access the water. You can catch glimpses of all types of waterfowl, turtles, and even night-time bats.