Maintenance of Stormwater Practices

Stormwater treatment practices (STPs) are engineered systems that require consistent, long-term maintenance to perform as designed. While proper design and construction are critical first steps, the ultimate success of an STP in protecting water quality and managing runoff volume is determined by its ongoing upkeep. A neglected practice will eventually fail to provide its intended benefits, representing a squandered investment and a potential threat to downstream resources. The proliferation of STPs under regulations such as the NPDES Phase II program has made the establishment of robust, comprehensive maintenance programs more critical than ever for local governments.

An effective maintenance program is built on a foundation of legal authority, clear assignment of responsibility, systematic tracking, and diligent inspection and enforcement. It provides the framework to ensure that the hundreds or thousands of individual facilities spread across a municipality function collectively as a cohesive stormwater management system. This section outlines the key components of a successful maintenance program, from the legal agreements that ensure accountability to the practical tasks required to keep STPs operational.

Why stormwater practices fail without maintenance

Without a proactive maintenance program, STPs are susceptible to a range of problems that degrade their performance and can lead to complete failure. The consequences of neglect extend beyond the loss of water quality treatment and can create public nuisances, safety hazards, and significant financial liabilities.

Common failure modes resulting from inadequate maintenance include:

• Sediment Accumulation: The primary function of many STPs is to capture sediment. Over time, this accumulated sediment reduces the permanent pool or detention storage volume, diminishing the practice’s capacity to treat runoff and control peak flows as specified in the original sizing criteria.
• Clogged Inlets and Outlets: Debris, trash, and vegetative growth can easily obstruct inlet pipes, riser structures, and outlet channels. Clogs can cause localized flooding, prevent the practice from dewatering properly, and create stagnant water conditions that are ideal for mosquito breeding.
• Erosion: Unchecked erosion on embankments, side slopes, or around outfalls can compromise the structural integrity of a practice. Embankment failure is a serious public safety risk.
• Vegetation Issues: While managed vegetation is integral to many STPs, neglect can lead to problems. Unwanted woody growth on dam embankments can threaten their stability, while invasive species can outcompete desirable native plants in wetlands and bioretention areas. Overgrown grass can impede sheet flow into swales and filter strips.
• Structural Decay: Components like risers, pipes, and trash racks made of metal or concrete can corrode or spall over time. Timely repairs are essential to prevent more significant structural failures.
• Loss of Infiltration Capacity: Infiltration trenches and basins can lose their ability to drain water if the surface becomes clogged with fine sediment and organic matter.

These physical failures translate into environmental and financial costs. A failing STP no longer removes pollutants, control flows, or recharges groundwater. Eventually, it will require extensive and costly rehabilitation, often far exceeding the cumulative cost of years of routine maintenance.

Maintenance agreements

A stormwater maintenance agreement is a legally binding contract between a local government and a property owner. It is a critical tool for ensuring the long-term maintenance of STPs on private property. The agreement formally assigns the responsibility for upkeep to the property owner in exchange for the municipality’s approval of a development plan. To be effective, the agreement must be recorded with the property deed, ensuring that the maintenance obligation transfers to all future owners of the land in perpetuity.

A comprehensive maintenance agreement clearly defines the roles, responsibilities, and remedies for all parties. While specific language varies by jurisdiction, a robust agreement typically includes the following core components.

Duties of the Property Owner

The agreement specifies the owner’s obligations to inspect, maintain, and repair the stormwater facilities. This includes performing all work in accordance with established standards, such as those found in a municipal stormwater design and construction specifications manual. The owner is required to conduct regular inspections, typically at least annually, and perform any necessary maintenance or repairs within a specified timeframe. The agreement also establishes that the property owner is responsible for all costs associated with these activities.

Rights of the Municipality

The agreement grants the local government specific rights to ensure compliance. A key provision is the right of ingress and egress, allowing municipal staff or authorized agents to enter the property to inspect the STP. This right is often formalized through separate maintenance easements. If an inspection reveals deficiencies, the municipality has the right to issue a written notice to the owner detailing the required repairs and providing a reasonable deadline for completion.

Failure to Maintain

A critical enforcement component of the agreement addresses the owner’s failure to maintain the facilities. If the owner does not complete the required work within the specified timeframe, the agreement authorizes the municipality to perform the maintenance or repairs itself. It further stipulates that the owner must reimburse the municipality for all costs incurred. To secure this obligation, the agreement may grant the municipality the right to place a lien against the property for the cost of the work plus interest if the owner fails to pay.

If the City or its authorized agent performs the required maintenance and/or repairs to the Stormwater Facilities, Grantor(s) shall reimburse the City all its costs incurred in completing the maintenance and/or repairs within thirty (30) calendar days of Grantor’s receipt of the City’s invoice for that work. Overdue payments shall accrue interest at the rate of twelve percent (12%) per annum.

Declaration of Stormwater Facility Maintenance Covenant, City of Kent, WA

Tracking systems

A municipality cannot manage what it does not measure. A systematic tracking system is essential for managing an inventory of STPs, scheduling and recording inspections, and documenting maintenance activities. Such a system serves as the administrative backbone of a maintenance program, providing the data needed for compliance, enforcement, and long-term planning.

The complexity of a tracking system can vary based on a community’s size and resources, but all effective systems share the goal of organizing critical information. Systems generally fall into one of three categories:

• Simple Database: For smaller communities, a spreadsheet or basic database program can be sufficient to track essential text-based information. This is the least expensive option but may require separate filing systems for documents like as-built plans and photographs.
• Database with Graphic Links: A more advanced system allows digital documents to be linked directly to an STP’s record. This gives inspectors easy access to as-built plans, photos from previous inspections, and scanned maintenance agreements, streamlining the inspection process.
• Geographically-Based System: The most sophisticated option integrates the database with a Geographic Information System (GIS). This allows staff to view STP locations on a map, query facilities by watershed, and optimize inspection routes. Planners can use such a system to identify potential retrofit opportunities and assess cumulative treatment within a drainage area.

Information to Track

Regardless of the platform, the tracking system should store comprehensive data for each STP. Key data fields include:

• Basic Information: A unique facility ID, project name, location (address and/or GPS coordinates), watershed, owner contact information, and links to legal documents like the maintenance agreement and as-built plans.
• Design and Structural Data: The STP type (e.g., wet pond, bioretention), drainage area, impervious cover treated, storage volumes, and details on key components like riser material, pipe sizes, and filter media type.
• Inspection and Maintenance History: A log of all inspections, including the date, inspector’s name, and findings. This should include a list of required repairs, deadlines for completion, the date repairs were verified, and the associated costs. Linking digital photographs is highly valuable for documenting conditions over time.

Inspection checklists and notifications

The inspection is the primary mechanism for assessing an STP’s condition and identifying maintenance needs. A structured inspection process ensures consistency, thoroughness, and clear communication with the property owner.

The Inspection Process

A professional inspection involves four main steps:

1. Notification: The property owner is formally notified in writing of an upcoming inspection. This letter informs the owner to expect an inspector on their property and may outline any pre-inspection actions they are required to take.
2. Preparation: The inspector gathers necessary background information, such as as-built plans, previous inspection reports, and photos. They also assemble the required safety and inspection equipment.
3. Field Inspection: The inspector conducts the on-site assessment using a detailed checklist specific to the STP type. The checklist guides a quantitative and objective evaluation of all components.
4. Follow-up: The inspector documents the findings and, if deficiencies are found, prepares a maintenance notification letter to be sent to the property owner.

Checklists and Notifications

Standardized checklists are essential for an effective inspection program. A good checklist is quantitative, using a rating system (e.g., a 0-4 scale) to prioritize problems rather than relying on subjective notes. It should be specific to the STP type, covering all key components from inflows and pretreatment to the primary treatment area and outlets. This structured data can be easily entered into the tracking system to monitor trends and prioritize maintenance across the community.

Following an inspection, clear communication with the property owner is paramount.

• A Maintenance Notification Letter is sent to the owner if repairs are needed. It details the specific deficiencies, provides a clear deadline for completion, and outlines the required repair process.
• If the owner fails to comply, the municipality can escalate to a more formal Notice of Violation. This letter references the legal authority under the local ordinance and maintenance agreement, restates the required repairs, and clearly states the consequences of continued non-compliance, such as municipal action to perform the work at the owner’s expense.

Common maintenance tasks by practice type

Maintenance needs vary significantly depending on the type of STP. While some tasks are universal, such as trash removal, others are specific to the function of a particular practice. The following table summarizes common routine tasks and typical frequencies.

Funding and responsibility models

The primary responsibility for funding and performing maintenance on private property lies with the property owner, as established in the maintenance agreement. However, municipalities must have a clear framework for oversight and enforcement to ensure this responsibility is met.

The most common model is direct, owner-funded maintenance. The property owner or homeowners’ association (HOA) pays for all routine upkeep and any necessary repairs. The municipality’s role is to inspect the facilities and enforce the terms of the maintenance agreement if the owner is delinquent.

To secure these obligations, municipalities can use several financial tools:

• Performance Bonds: A developer may be required to post performance bonds during construction and for a warranty period afterward. This bond can be used by the municipality to correct construction defects or perform initial maintenance if the developer defaults.
• Maintenance Escrow: Some jurisdictions may require the owner to fund an escrow account dedicated to long-term maintenance activities, particularly for major tasks like sediment dredging in a large pond.

Enforcement is the ultimate backstop of any maintenance program. The legal authority for enforcement comes from the signed maintenance agreement and the local model stormwater ordinance. When an owner fails to comply with a maintenance notice, the municipality can exercise its right to perform the work and recover the costs, ensuring that the public interest and environmental quality are protected.

Frequently Asked Questions