Engineering

Project Overview 

The Mendota-Pheasant Branch Greenway is currently overrun with undesirable and fallen trees that City maintenance crews cannot access and remove. Undesirable trees shade the channel banks, killing grasses and shrubs whose roots hold soil and prevent erosion. This erosion degrades water quality and causes more trees to fall, putting private property at risk and clogging channel outlets, which can lead to flooding.

The design goals for this greenway include:

• Convey flow without flooding

• Stabilize slopes to prevent erosion
• Provide access for maintenance and safety purposes
• Improve water quality
• Improve aesthetics
• Create habitat for wildlife

The proposed design creates a small ditch, similar to the existing channel with a 10’ wide access path alongside the channel. The proposed location of the new, low-flow channel and maintenance path was designed to coincide with a dense swath of undesirable trees, to minimize quality tree removal.  Slopes will be stabilized by restoring native vegetation and planting desirable tree species.

Tree Loss

The City-owned greenway has 189 trees.  Trees within the greenway that meet one or more of the following criteria will be removed:

• Conflicts with construction
• Unhealthy trees (branches fall, clogging outlets; entire tree falls, clogging the channel)
• Risk to private property/safety
• Opportunistic species removed to regrade and stabilize southern slope. This will also help to protect new homeless housing development from potential flooding

Approximately 70 trees will be left, most of which are silver maples. This will be a drastic change in screening for adjacent residents; however, the City encourages residents to keep in mind that both the neighborhood and City want the greenway to be well-vegetated. The City plans to plant additional trees and grasses that will provide screening. However, trees that flourish in wetlands and prevent erosion tend to grow slowly. It will take a number of years for the greenway to completely establish itself.

Restoration

The City will hire a native restoration specialist to plant and manage the new, native vegetation restoration within greenway in the spring, following construction.  This will allow for more diverse and dense plantings of shrubs, trees, and vegetation.  Many more trees will be kept, and added, than in the upstream section of greenway.

Construction

Construction will begin Sept. 30, 2019 and will terminate by Dec. 30, 2019.