Inspection and maintenance

Overview

Integration of Low Impact Development (LID) best management practices (BMPs) into stormwater management (SWM) systems is widely advocated to better address the potential stormwater-related impacts of urbanization on the health of receiving waters. A substantial amount of guidance is available on the planning and design of LID BMPs (CVC & TRCA, 2010) and their construction (CVC, 2012) and some municipalities and conservation authorities commonly require them to be a part of new SWM systems.

However, even with sound design, LID BMPs may not provide the intended level of treatment if they are not installed properly or protected from damage during construction. Experiences with early applications have shown that failures are often due to:

• Practices not being constructed as designed or with specified materials
• Lack of erosion and sediment controls (ESCs) during construction; and/or
• Lack of rigorous inspection prior to assumption.

A 2009 survey of stormwater BMPs in the James River watershed (Virginia) by the Center for Watershed Protection found approximately half (47%) of the 72 BMPs deviated in one or more ways from the original design, or were receiving inadequate maintenance (CWP, 2009). Similar results have been revealed from surveys of stormwater detention ponds in Ontario (Drake et al., 2008; LSRCA, 2011), highlighting the need for thorough inspections of BMPs prior to assumption and a proactive approach to stormwater infrastructure operation and maintenance. Therefore, it is important to conduct timely inspections during construction and detailed inspection and testing prior to assumption to ensure that LID BMPs are:

• Built according to approved plans and specifications
• Installed at an appropriate time during overall site construction and with protective measures to minimize risk of siltation or damage; and
• Fully operational and not in need of maintenance or repair at the time of assumption by the property owner or manager.

Like all stormwater BMPs, LID practices are designed to retain pollutants carried by urban runoff and all have a finite capacity to perform this function in the absence of maintenance, until their treatment performance declines or they no longer function as intended. Their functional and treatment performance will only be sustained over the long term if they are adequately inspected and maintained. Under the Ontario Water Resources Act, provincial approvals for SWM facilities and BMPs (i.e., Ontario Ministry of the Environment and Climate Change’s Environmental Compliance Approvals process) typically make the property owner responsible for all inspection and maintenance tasks and associated record keeping (Zizzo et al., 2014). A proactive, routine inspection and maintenance program will also:

• Identify maintenance issues before they significantly affect the function of the BMP
• Help to optimize the use of program resources by providing the feedback needed to determine when structural repairs are needed and to adjust the frequency of routine inspection and maintenance tasks where it is warranted; and
• Help to improve BMP design guidance and develop standards.

Unlike conventional SWM systems that centralize treatment facilities in few locations on publicly owned land (e.g., detention ponds) an LID design approach involves smaller scale practices distributed throughout the drainage area, potentially on both public and private land. Implementing an LID approach to system design has major implications on municipalities and property managers with respect to operating the stormwater infrastructure they are responsible for, as it increases the number and types of BMPs to be tracked, inspected and maintained.

This Inspection and Maintenance (I&M) page is intended to assist users (municipalities, consultants and property managers) with developing their capacity to integrate LID SWM BMPs into their projects and/or larger infrastructure asset management programs. Sections below provide:

• Guidance on designing an effective LID BMP inspection and maintenance program
  • Based on experiences and advice from jurisdictions in Canada and the United States, and adapted to an Ontario context.

• Recommended standard protocols for inspection, testing and maintenance of the following types of structural LID BMPs:
  • Bioretention and dry swales
  • Enhanced swales
  • Vegetated filter strips and soil amendment areas
  • Permeable pavements
  • Underground infiltration systems
  • Green roofs; and
  • Rainwater cisterns

• Guidance on recommended inspection, testing and maintenance tasks specific to each BMP type
• A summarization of staff skills and equipment required to complete them
• sampling and testing procedures and protocols
• Estimated costs over a 50 year BMP life cycle.

Drawing upon the information provided on this; and its subsequent page(s) municipalities and property managers will be better able to design or adapt their infrastructure asset management programs to include LID BMPs effectively, and understand the tasks, procedures and estimated costs associated in adequately inspecting and maintaining them.

LID Practices' Inspection & Maintenance

• Inspection and Maintenance: Bioretention & Dry Swales

Inspection & Maintenance Terminology

Construction Inspections

Construction inspections should be a shared responsibility between the property owner or their project manager, the designers (i.e., engineer and landscape designer) and the construction contractors. Many municipalities already conduct some form of inspection of infrastructure they will eventually assume during its construction. Those that do not, might choose to work with internal departments (e.g., road or building inspectors, parks/landscaping inspectors) or other agencies (e.g., conservation authorities) that routinely conduct inspections at active construction sites. With adequate training and staff resources, it might be possible to integrate stormwater BMP inspection duties during construction into existing programs. If the workload or skill set needed is beyond what existing programs can handle, or the timing of other types of inspections do not coincide with critical timing of BMP construction inspections, hiring of trained contractors or allocation of dedicated stormwater infrastructure program staff may be necessary.

The frequency of Construction inspections may be determined by the municipal stormwater infrastructure program policy or may be general program targets (e.g., weekly, after large storm events, as triggered by construction milestones and hand-off points between different contractors). At a minimum, inspections should occur just prior to the onset of BMP construction to ensure compliance with erosion and sediment control plans and after any large storm event (e.g., 15 mm rainfall depth or greater) during the BMP construction period.

Feedback from Construction inspections should be used to correct any issues associated with BMP installation or Erosion Sediment Controls (ESCs) and to identify when changes to the installation procedures, ESCs or BMP design are needed due to site circumstances or complications encountered. In cases where the project proponent or property owner uses a formal bidding process to select a construction contractor, opportunities exist to include special provisions in tender documents or contracts that will help ensure that LID BMPs receive adequate inspection and maintenance during construction.

Special provisions in tender documents or construction contracts related to LID BMP installation that can be included to help ensure adequate inspection and maintenance during construction include the following (CVC, 2014):

1. Clearly outline the work required to install each type of BMP and list the activities involved
2. Detail the product and material specifications and whether approved equivalents are permissible
3. Outline installation procedures for each type of BMP and critical points in the sequence of activities when Construction inspections are required before proceeding further (e.g., checking elevations and grades of excavations and pipes prior to backfilling)
4. State any testing requirements or quality assurance documentation for construction materials that must be received and accepted prior to delivering the material to the site (e.g., filter media, aggregate material);
5. Specify maintenance tasks the contractor is responsible for, including procedures and conditions for when or how frequently they need to be done (e.g., sediment removal from BMP pretreatment devices and conveyance structures, maintenance of plantings over the warranty/establishment period).

For more detail and examples of how special provisions relating to LID BMPs can be used in construction tender documents and contracts refer to Credit Valley Conservation’s Grey to Green Retrofit Guides (CVC, 2014.)

Life Cycle and Inspection

- Copy of McMaster Training course and link to the course

Training Requirements

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Embedded Guide

This guide is focused on planning and design. In many places you will find tips to design structures with considerations for how to facilitate future maintenance.

But to get detailed information from STEP on the inspection and maintenance of LID practices, please see our complete guide here or embedded below:

Example of inspection and testing indicators framework and maintenance guide for bioretention and dry swales practices.

Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions.

A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.

State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls.

Stormwater Management

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

The changing of land cover and land uses from rural to urban; the growth of urban settlements.

Watercourses and Lake Ontario, to which Stormwater and Combined Sewer Overflows discharge.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

The temporary storage of stormwater to control discharge rates, and allow for sedimentation.

Lake Simcoe Region Conservation Authority

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer.

Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls.

The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.

A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades.

The practice of adding organic material, such as mulch or compost to topsoil to improve fertility, and tilling of the native soils to reverse compaction and restore its water retaining capacity.

Tank used to store rainwater (typically roof runoff) for later use.

Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls.

Credit Valley Conservation

Sustainable Technologies Evaluation Program

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

Toronto and Region Conservation Authority

Ground depression acting as a flow control and water treatment structure, that is normally dry.

A body of water smaller than a lake, often artificially formed.