Over 30 years ago, Arnold Associates developed an innovative planting technique for urban trees

Since its founding in 1990, the Fund for a Better Waterfront (FBW) has recognized the importance of trees as a unifying theme for Hoboken’s waterfront park. Trees that mature into a canopy, similar to what exists at the South Waterfront from Newark to Fourth Streets, provide a model for the Sinatra Drive Project as well as a new park at Union Dry Dock. Last spring, FBW hired Arnold Associates to propose a landscape plan for Sinatra Drive. In July, Stephen Lederach of Arnold Associates presented this plan to the City’s Sinatra Drive Project team.

The Sinatra Drive Project began a year ago, funded by several state and federal grants plus municipal bonding. From Fourth to Eleventh Streets, the project will repave this waterfront roadway with two-way, narrower traffic lanes and a 12-foot protected bicycle pathway. The City’s recent acquisition of the Union Dry Dock property has added a 700-foot long, 25-foot wide strip to the Sinatra Drive Project, providing room for additional trees as well as on-street parking.

On the Arnold Associates website, it states, “An obstacle to making cities more sustainable with shade trees is inappropriate planting details resulting in short-lived trees in urban conditions. The average length of survival of a new street tree in New York City is seven years.” For the Sinatra Drive landscape plan to be successful, Mr. Lederach has stressed two key elements: proper soil volumes to support each tree and the use of a specially formulated structural soil mix.

Soil Volumes

Canopy trees each require 1,000 cubic feet of soil volume and understory trees require 750 cubic feet in order to live long, healthy lives. These same standards are stipulated by the Hoboken Shade Tree Commission. Although the engineering firm working on the Sinatra Drive Project acknowledged these requirements, Arnold Associates reviewed the 90 percent landscape plan and calculated the actual volumes to be substantially less. FBW has communicated this finding in recent memos and in a meeting with the Sinatra Drive Team.

Air-Entrained Structural Soil

Over 30 years ago, Arnold Associates developed a planting method, utilizing a structural soil mix, termed “air-entrained soil,” that results in healthy, long-lived urban trees. Stephen Lederach and Henry Arnold (now retired) have successfully employed this soil mix in over a hundred national and international projects, including the Hoboken South Waterfront, Metrotech Center in Brooklyn and the Korean War Veterans Memorial in Washington, D.C.

The leaves of trees absorb carbon dioxide during photosynthesis. The tree roots, on the other hand, need oxygen. When soils become compacted, roots are deprived of air and water, often forcing the roots to grow upward, buckling pavements and compromising the health and longevity of the tree. Air-entrained soil solves this problem.