What We Know Now: Green Infrastructure Design, Implementation, and Maintenance in Portland, Maine

By Barry Sheff

Green Infrastructure or Green Stormwater Infrastructure (GI) is an important part of achieving water quality goals and flood management. It can also be highly visible and provide value as street beautification. Much is known about how to design effective GI, but as these investments have been made, it has become clear that the operations and maintenance (O&M) of GI is at least as important as the design.

To address combined sewer overflows and water quality goals, the City of Portland, Maine began making significant investments in GI in the early 2000s. Portland, a coastal city of 66,000 residents in southern Maine, had incorporated GI into an Environmental Policy Guide within its comprehensive vision, called Portland’s Plan 2030. The City’s Stormwater User Fee, which it uses to fund regulatory programs, capital projects, and O&M also makes specific reference to GI in its Credit Program. Today, the city owns and operates a network of nearly 150 GI features like subsurface wetland systems, porous pavements, and filtration and box filters.

Portland was proactive in developing GI but effective maintenance procedures lagged. Initially, O&M was handled by the Public Works Department drain and sewer teams. While these teams were skilled, they were not as effective in this new role because maintaining GI is different. It requires different skills and knowledge—staff who manage pipes may not be good gardeners.

As Portland installed more GI and the need to manage landscaping elements became clear, O&M was transferred to the Parks Department. This team had the skills but was stretched thin and could not keep up with the work. This led to a second important learning: management of GI requires significant effort and adaptability. To succeed, managers and staff need to tailor their approach to the specific challenges of the infrastructure, the local climate, and the concerns of the community.

Understanding the level of effort, the frequency of maintenance visits, and the different kinds of maintenance each feature requires is critical, so in 2014, the City decided to change course, hiring a consultant to evaluate specific maintenance needs, develop standard maintenance procedures, and estimate labor needed for future maintenance.

This helped define the scope of the need, but several other factors also influence the effort needed for GI maintenance. Busy streets may collect more litter and require more frequent visits simply for aesthetic reasons. A filter system that is full of wrappers and coffee cups performs worse and can damage public perception of GI. In residential neighborhoods, residents may park on filter zones, damaging them. Portland’s early designs often focused on native landscaping elements with bioretention, but without sufficient upkeep, plantings quickly deteriorated.

And in Portland, winters are long and varied, featuring freezing rain and sleet on top of significant snow accumulations. GI design needs to consider snow removal. Bioretention filters along streets are often buried in tons of snow and ice, creating driving and plow hazards, blocking inlets, and making winter rain events difficult to manage.

After the evaluation of GI assets, the City began hiring contractors for O&M. Over several requests for proposals (RFPs), Portland adapted their approach to feedback from their contractors to get more accurate bids. The most recent RFP contains detailed descriptions of each type of GI, a description of the system and subsystem types, and explicit inspection requirements and numbers of inspections for each type of system. It also includes maps and photos for all systems to be inspected and maintained.

The City is now requiring monthly inspections and maintenance on most of its filtration types of GI. Other more traditional stormwater controls have less frequent inspection and maintenance. The latest contract also contains a requirement for the contractor to record all inspection and maintenance work in the city’s computerized maintenance and management software program.

The increasing specificity of Portland’s RFPs shows the evolution of their understanding of O&M requirements in the contractor community. With more experience in the level of maintenance required for different installations, Portland can be more precise in describing its needs. And as the City’s GI program has developed, changes in the contracting community have taken place, resulting in the rise of stormwater-specific contractors with the skills and capacity to do the work. GI is different than traditional infrastructure and understanding its unique maintenance requirements is essential to retaining its performance.

Barry Sheff is a Senior Project Manager and Client Strategist with Woodard & Curran and the chair of the American Public Works Association Water Resources Management Committee.