The trail will run from Lake Washington Boulevard and 31st Avenue East, to Foster Island Drive and Arboretum Drive. The city said it should be complete by December 2017.
The city is seeking bids by Aug. 19 from contractors, according to a notice in the July 29 DJC.
A site inspection will be held at 10 a.m. Aug. 13.
The arboretum master plan adopted in 2000 identified the trail as a way to bring more people through the collection.
The city said the loop trail will provide a safe way for people to walk and bike through the arboretum, and increase accessibility to new areas.
The trail will have a curving path, benches, pedestrian bridges and wayfinding signage.
Berger Partnership is lead consultant for the trail. Subconsultants are Anchor QEA, KPFF Consulting Engineers, Hoshide Wanzer Williams, Lehrman Cameron Studio, Swenson Say Faget and Toole Design Group.
Seattle Parks and Recreation will maintain the trail. The University of Washington will use it to maintain the collection.