How cities can use education, planning and cooperation to ensure low impact design guidelines are followed and implemented properly
Too often, Low Impact Design and Green Infrastructure (LID/GI) projects meet with internal municipal barriers. Conflicts can arise between various city departments – usually due to lack of knowledge about why LID/GI is being used and how it works. In my last blog about Low Impact Design, I talked about five facts you need to know about LID/GI. In this blog, let’s look at how municipalities can overcome the common internal obstacles that may get in the way.
Internal barriers can take many forms. There’s a learning curve that comes with implementing LID and GI projects and their new technology. Many municipal staff simply don’t have the time required to learn the ropes. Often, the internal processes required to approve and inspect these LID/GI facilities are not in place, and existing budgets and staff are fully used. There is also a perception that operations and maintenance of LID/GI is much more challenging, time consuming, and costly than traditional infrastructure.
By following the steps I outline below, your municipality will reduce internal barriers to LID/GI and address concerns and perceived, or potential, conflicts. All of this enables your municipality to smoothly implement LID and GI infrastructure.
- Bylaw Review: Review your municipal bylaws and guidance documents for barriers to LID/GI. Check drainage, sewer, watercourse, development, and zoning bylaws for trouble clauses that would prohibit or hinder LID/GI projects. Changes to bylaws and guidance documents take time and effort and may require both public consultation and council approval.
- Review and Approvals Process: LID projects are planned and designed differently than conventional stormwater management facilities. As such, they often require multi-disciplinary teams with an understanding of runoff hydraulics, soil, and plant material, as well as other factors that determine how the LID/GI will function. The municipal review team should also embrace a multi-disciplinary review and approvals approach. This may require improved communication and coordination between city departments, but it will result in a better understanding of the reasons for using LID/GI and should significantly decrease approval times for LID projects.
- Design Standards and Standard Drawings: Most municipalities do not have existing design standards or standard drawings for LID/GI facilities, but will have to create these documents to assist developers and engineers to submit acceptable designs. Municipalities may also create their own LID design guidance documents. Some things to consider while developing these new standards include:
- Distance of infiltration measures from building foundations. This value typically ranges from two to five meters.
- Infiltration facility drain time. How quickly should the facility drain to be ready for the next storm? This value reflects local rainfall conditions and is typically 24-48 hours in Ontario.
- Surface ponding. Will surface ponding in bioretention facilities be acceptable? If so, for how long and at what depth? Typically, bioretention facilities will be allowed to pond 20-30 cm, for up to 24 hours. Allowing ponding increases the amount of runoff that filters though the soil and gets treated by the facility.
- What LID/GI Practices the Municipality Will Accept: Each municipality has different drivers and needs when it comes to LID/GI. Some will be more concerned with volume control and groundwater recharge. Others will concentrate on water quality and nutrient removal. Each driver (volume, retention, treatment) impacts how LID/GI will be designed for a site. So each municipality must decide which parts of the LID/GI toolbox to accept and approve based on the needs of the community and watershed. Municipalities should also consider their policies regarding downsizing downstream infrastructure due to volume retention in LID/GI. Can infrastructure be downsized and, if so, by how much? This needs to balance the risk of failure of the LID/GI facilities and the additional cost of requiring two full sized systems (LID and traditional). Remember, in most cases where there are poor soils, LID will not completely eliminate the need for a downstream detention facility; but they will provided water quality treatment and volume capture, allowing for smaller (or no) forebays while shrinking pond volumes.
- Maintenance: Maintaining LID/GI systems is not as onerous as many think! Creating a maintenance guide and determining what maintenance and records are required will ensure your LID/GI project works properly. Remember, many LID facilities simply replace similar landscapes. Grass swales can be mowed the same as traditional grassed areas and vegetated LID facilities are often planted with low maintenance plants requiring little additional maintenance. LID facilities with more aesthetically pleasing (high value) plantings like flowers and shrubs are often located where similar high value gardens would have been placed and require essentially the same level of maintenance. Make sure to consult operations and maintenance staff during this process. It is also important to ensure the O&M staff know where all LID/GI are located to ensure they are treated properly. If staff doesn’t know where facilities are, or how to maintain them, they may accidently cause a failure. Some municipalities deal with LID maintenance in boulevards using staff. But others use bylaws to entrust maintenance to property owners. Municipalities can also insist on a warranty period, typically of 2 to 3 years. The warranty period may include maintenance and monitoring to ensure that plantings are thriving and the LID facility is operating as designed.
- LID/GI on Private Property: LID/GI on private property can create challenges for municipalities; challenges like maintenance, operation, ownership, and removal of facilities. Generally, the maintenance, operation, and ownership of LID/GI on private property are the owner’s responsibility. There are several ways to ensure that maintenance is occurring and that the facility is not removed by property owners. Municipalities can pass a maintenance bylaw that requires property owners to submit maintenance records. This can be as simple as providing dated photos of the facility for single family residential lots, or it could call for a more complex report submitted to the city by larger industrial or commercial lots. Such a bylaw would ensure the facility remains intact and operational. Additionally, restrictive covenants can be registered against the titles of properties. A restrictive covenant is a clause registered on the property title that places limits on what owners can do with the property. In this case the owner would not be allowed to remove the LID facility and would be required to maintain it. Since the restricted covenant is registered on the title, it ‘follows the land’ and all future owners would be made aware of the conditions prior to purchase and be bounded by the conditions listed. Some municipalities do not allow LID/GI on private property. In this, case the municipality must develop policies to allow for ‘regional’, or multi lot LID/GI, on public property or within the right of way.
- Staff Training: It is essential that municipalities train staff on the function, design, and operation of LID/GI. Knowledgeable staff are equipped to review and comment on LID/GI facilities. As a result, they can ensure that the proposed measures are adequate to meet the municipal and provincial criteria. It is very important that operations and maintenance staff are included in the training and engaged in creating maintenance protocols to ensure they know how to deal with the various LID facilities. For example, if the salt or sand truck operator doesn’t know what pervious pavers are, the operator may mistake it for a traditional facility and treat it as such, applying salt or sand and causing damage to the facility.
While these efforts above may appear daunting, don’t forget that an engineering firm with experience in LID/GI, like Stantec, can assist your municipality in preparing for LID/GI.
About the AuthorMore Content by Jennifer Young