What to Consider When Designing Green Stormwater Systems

This blog is the first in a series of three that focuses on maintenance for Green Infrastructure (GI) systems and includes design considerations for selecting and designing GI systems, developing O&M manuals, and training maintenance staff to maintain the installed GI facilities.

Conventional or grey stormwater infrastructure systems require maintenance in order to provide the services they were designed for (e.g. to manage flooding, control discharge, provide water quality, etc.). Nationwide, municipalities and private entities employ many thousands of maintenance hours to keep their stormwater systems operational. Leaf and litter debris is removed from catch basins, pipes are jet cleaned, pump stations are regularly inspected, and damaged pipes are rehabilitated or repaired. These maintenance protocols help ensure that stormwater infrastructure is functioning properly.

Providing maintenance for Green Infrastructure (GI) systems, as with conventional systems, is crucial to the operational efficacy of the system. Specific BMP based operations and maintenance (O&M) activities are necessary to keep GI systems working at managing flows, providing water quality, and conveyance. Without appropriate maintenance, the many benefits that GI facilities provide can be lost. And as with conventional stormwater controls, when GI systems fail, there can be serious and costly impacts.

That’s why it’s important for designers to consider O&M protocols when designing GI facilities. Early consideration of O&M can streamline feasibility assessment, refine the design, and reduce total costs.

Some elements may require specialized equipment such as this pervious pavement vacuum sweeper for moss removal (Credit: MIG|SvR)

Below are six O&M considerations when selecting and designing GI systems:

  • Funding: The most important first step is to establish a maintenance budget that is tailored to the specific BMPs that need to be maintained. There are resources available that outline the level and intensity of maintenance required for various installations. Communities that have working GI systems can also be a valued resource with a budget set to identify long term sources of funding like a stormwater utility fund or a local improvement district. The source of funding for labor, equipment, and materials should be in place prior to selecting and designing a GI system. Failure to establish funding sources can result in failed systems with costly and sometimes dangerous impacts.
  • Equipment: Designers should verify early in the design process what equipment is available for the care of infrastructure systems. This can include commonly-owned equipment from lawn mowers and power washers to specialty items such as weed burners or vacuum sweepers. Designers should not include types of facilities for which proper maintenance equipment is not or will not be available. Additionally, designers should strive to design systems that “fit” the equipment. A simple example of this approach can be found in the design of a roadway curb cut. A roadway curb cut is a depression in a roadside curb that allows for stormwater to flow from the roadway pavement surface, across the top of the depressed curb, and into an adjacent landscaped zone or bioretention facility. Curb cuts come in all shapes and sizes and designers must consider surface conditions, flow rates, and slopes. By also considering O&M, a designer may elect to widen the opening to fit a shovel or shape the curb to permit effective street sweeping. By speaking with maintenance personnel and familiarizing themselves with equipment, engineers can design more cost-effective GI solutions.
  • Materials: The availability of appropriate materials will have a significant impact on the function and lifecycle of GI facilities. Maintenance protocols will include the repair and replacement of materials impacted by utility cuts, damage, die-off etc. so designers should verify early in the design process the material sources available for the construction and care of infrastructure systems. These materials can include familiar supplies like bark mulch or specialty materials like bioretention soil or pervious concrete. Establishing material availability will ensure that maintenance personnel can perform their tasks to keep stormwater facilities in top shape.
  • Appropriate Staff: GI facilities perform multiple functions beyond those related to simply stormwater. These include serving as a landscaped buffer, a habitat, a transportation surface, a roof surface, or even a play or educational feature. Where traditional maintenance functions have included street sweeping by the roadway crews, catch basin cleaning by utility personnel, and planting maintenance by landscape crews, GI systems can overlap traditional trades. Determine early on which personnel have the authority and capability to maintain the proposed GI. There may be a need to hire additional staff in order to meet maintenance needs. This can include seasonal staff during the spring growing season or in the fall when leaf debris increases.
  • Aesthetic vs Function: When selecting GI facilities, designers must establish with owners the desired aesthetic and discuss the level of effort and maintenance protocol to maintain that aesthetic. Owners should be made aware of what the facility will look like when mature and what level of maintenance effort will be required to keep the facility looking that way. Part of maintenance protocols includes establishing a level of effort. This should be done with the owner early in the project as part of the vetting process to ensure that there are sufficient staff and funding.

By considering O&M protocols when designing GI facilities and having continuous and open conversations with owners and maintenance personnel, professionals can design and implement cost-effective and long-lasting GI solutions for stormwater control.

Our second blog in this series will cover O&M Manuals for maintaining GI facilities.

Image 1: Eric Fischer / CC BY 2.0

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