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Drainage Maintenance

When it rains or when snow melts, the water accumulates and flows across roads, parking lots, land etc. In rural environments, soil absorbs a significant portion of the runoff, but in urban, built-up areas, the increased hard-scaping (roads, sidewalks, driveways, roof-tops, parking lots etc.) reduces what can be absorbed by the soil. To decrease flooding risks, runoff is directed to the Town’s drainage system through catch basins, culverts, ditches, storm sewers and storm ponds.  Each of these elements is critical to ensure efficiency and effectiveness of the Town’s drainage system.

 Our drainage system consists of:

Catch basins are usually found at the sides of urban roads and are designed to drain excess rain and ground water from paved streets, parking lots, sidewalks into storm sewers, storm ponds and nearby natural drainage courses.


What We Do

  • Conduct routine patrols to assess the conditions of catch basins;
  • Repair / replace catch basins as required; and
  • Maintain catch basins that are damaged or plugged with surface debris.


How You Can Help

  • Remove privately generated leaves, lawn cuttings and other debris blocking catch basins;
  • Recycle and safely dispose of hazardous waste such as used oil, paint, paint thinners and batteries; and
  • DO NOT pour household liquids, paints or any hazardous wastes into catch basins as they are not filtered and lead directly into nearby storm ponds and/or directly into natural watercourses.

Culverts are typically short pipes that provide connection points and facilitate drainage between ditches, storm sewers, ponds or other drainage outlets.  Culverts are typically under driveways, roadways etc. They are required should a driveway / entrance cross a drainage ditch.


What We Do

  • Identify where culverts are required, at the property owner’s expense, through the Town’s Entrance Permit application process;
  • Replace damaged culverts; and
  • Maintain culverts that are plugged with debris, caved in or frozen (causing flooding).


*Note: If the property owner chooses to pave their driveway, the Town will NOT be responsible for replacement pavement and any hard surfaced landscaping in the event that a repair or replacement of the culvert is required due to frost heaving or as a result of construction.


How You Can Help

  • Remove privately generated leaves, lawn cuttings and other debris as it accumulates; and
  • DO NOT alter the ditch, culvert or drainage system in any way.

Ditches are inspected on a regular basis throughout the year to identify required maintenance. Ditches are located on the sides of roads and are specifically meant to drain water from adjacent lands / roadways.


Ditches hold water and, based on their design, control how fast the water enters the drainage system (i.e. storm sewers and ponds). Some ditches allow water to flow into the groundwater table, minimizing the amount of water discharged to natural watercourses.


What We Do

  • Maintain roadside ditches;
  • Remove leaves and debris, as it accumulates; and
  • Monitor the drainage efficiency of ditches.


How You Can Help

  • Remove leaves, privately generated lawn cuttings and other debris as it accumulates;
  • DO NOT alter the ditch, culvert or drainage system in any way; and
  • DO NOT pour household liquids, paints or any hazardous wastes into ditches as they lead directly into nearby storm ponds and/or directly into natural watercourses.


*Note: Property owners do not have the absolute right to outlet to roadside ditches. The Town reserves the right to remove or restrict any outlets to ditches that cause operational issues or damage to the drainage system.

The main purpose of the storm sewer system is to convey surface water and prevent flooding. The storm sewer system collects surface water into underground pipes and conveys the (untreated) water to surface watercourses such as lakes, rivers, storm ponds. Because water conveyed in this system is untreated, it is not permitted pour hazardous substances in any component of the Town’s drainage system.


Storm drains are designed to keep some pollutants from entering the environment, by installing infrastructure such as oil and grit separators. To ensure the storm sewer system works as intended, storm drains need to be maintained and the debris removed so that it doesn’t block the pipes which potentially can cause flooding in the streets and nearby residents and businesses.


What We Do

  • Remove debris from culverts, catch basins, ditches;
  • Clean-out of oil grit separators and catch basins;
  • Inspect sewer lines using Closed Circuit Television (CCTV) to identify areas that need to for repair / replacement; and
  • Conduct sewer flushing to clear the sewer of debris and to ensure adequate capacity and flow.


How You Can Help

  • DO NOT pour household liquids, paints or any hazardous wastes into catch basins, ditches as they are not filtered and lead directly into nearby storm ponds and/or directly into natural watercourses.

About Stormwater Management Ponds

​After rain or snowfall, the water left behind on roads, sidewalks, grass and pathways is called “stormwater.” This is ordinarily absorbed into the ground by plants and soil. However, pavement and other hard surfaces — such as driveways, sidewalks and roofs (especially in urban areas) — can interfere with this absorption. This can lead to water pooling or even flooding.

To help take care of this, stormwater management ponds typically exist in urban developments. They are human-made areas created to gather and retain rainfall and surface water runoff. These ponds are usually found in neighbourhoods where stormwater can easily be collected. 

Stormwater management ponds can be either wet or dry and they are designed to maintain a permanent body of water within the pond area.

A dry pond is designed to remain dry until a rain event occurs which may temporarily retain stormwater within the pond area. A wet pond holds water all the time and is designed to collect and store runoff from rain and melted snow. These wet ponds collect sediment so only clean water is released back into rivers and creeks.

How Stormwater Ponds Work

Stormwater ponds have at least one inlet that allows water to flow from the storm sewer system into the pond. Once the stormwater drains into the stormwater pond, any of the sand, dirt and other sediments that pollutants attach themselves to settle to the bottom of the pond. The pond's outlet releases water from the pond into a nearby river or lake system at a controlled rate. This process helps make the water cleaner when it leaves the pond and back into lakes and rivers. Without stormwater ponds, large amounts of water would enter a stream all at once, causing flooding and eroding soil from the stream banks.

Benefits of Stormwater Ponds

  • Reduces flooding
  • Protects the natural environment from contaminants and erosion
  • Protects rivers and lakes by trapping pollutants such as oil, pesticides, bacteria and trash
  • Establishes a human-made habitat for wildlife
  • Encourages a naturalized space for walking and bird watching

Staying safe in the winter

Stormwater management ponds may look safe to walk and skate on, but they are extremely dangerous due to water constantly flowing in and out of the pond underneath. These ever-changing water levels make the thickness of the ice highly unpredictable. This is a serious safety hazard and one of many reasons to stay off the ice.

Staying safe in the summer

Swimming, boating and fishing are not safe in stormwater management ponds due to the constant flow of water in and out of the pond, multiple pollutants and unpredictable water levels. The bottom of stormwater management ponds is very soft and anyone, including pets, who enter may quickly become stuck.

Prohibited Activities

  • Skating, Swimming, Fishing, Planting
  • Planting gardens or cutting grass on pond property
  • Storing yard materials on pond property
  • Installing gates to access pond property from fenced yards
  • Disposing of grass clippings, yard waste or garbage on pond property or into the pond
  • Disturbing plants and vegetation around the pond
  • Disposing of pet fish in the pond
  • Disposing of swimming pool water and chemicals on pond property or in the pond

Maintenance of Stormwater Ponds

Each of these ponds need to be properly maintained to control the flow of water. Year-round, routine maintenance includes removal of debris in and around the pond, removal of invasive vegetation; maintenance of structures such as inlets and outlets, and maintenance of surrounding vegetation and plants.

Reporting an issue

Notice a stormwater pond that requires attention? Report issues, including any odours, beaver activity (damming) or high-water levels at here!

Individuals found dumping their household garbage are subject to a maximum fine of $5,000 per offence. If you witness illegal dumping or littering at a stormwater pond, please report it to Town of Gravenhurst at 705.687.3412 or

Did you Know?

Over time, sediment will accumulate in the pond reducing the pond’s ability to improve water quality. The Town, as required, will clean out ponds to restore the water quality function.

The Town appreciates all inquiries relative to drainage concerns, including blocked culverts, damaged or blocked catch basins and / or plugged ditches.

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