--- title: the lachine rapids are not a pipe canonical_url: https://ensurance.app/guide/the-lachine-rapids-are-not-a-pipe markdown_url: https://ensurance.app/guide/the-lachine-rapids-are-not-a-pipe.md subtitle: "a channel, a drop, and a shore are a living reach. a retention tank is not." category: ecosystem-services --- # the lachine rapids are not a pipe *a channel, a drop, and a shore are a living reach. a retention tank is not.* The Lachine Rapids are a drop in a river, not a fitting in a pipe. Southwest of the island, the fluvial St. Lawrence falls over rock, and the harbour downstream of that drop is a channel ships still have to make. Calling all of that "water" is how a tank gets mistaken for a shore. Montreal stands in that reach. The island depends on the drop, the channel, and the shore remaining a living edge. The port, the plant, and the neighbourhoods depend on the island not replacing that edge with a single concrete answer and calling the job finished. :::johnson **a rapid is a living drop. a retention tank is storage.** The river around the island is the subject. The tanks and the ozone plant are tools the city already uses on the way to that river. ::: ## what the drop is The **Lachine Rapids** are the southwest drop of the fluvial St. Lawrence at this island. Lac Saint-Louis sits upstream of that turbulence. The harbour and the seaway locks are how ships pass a river that, at this point, is not a canal by nature. The rapids are habitat and current. They are also the reason the port's channel is an engineered courtesy inside a river that still has a mind. Nothing in these notes prices that drop. A view of the rapids is not a valuation, and a valuation is not the point of this page. The point is to keep the living reach distinct from the hardware built beside it. The shore continues downstream of the island's core. The port's 2024 notes describe continuing work toward a **National Wildlife Area** at **Îles-de-Boucherville**, with Environment and Climate Change Canada, and they mention reforestation at Contrecœur. Those are shoreline facts. Hectares were not researched. A page that invents them would be inventing the habitat. The map name for the forest region around this island is the eastern Great Lakes lowland. The ecoregion agent is a map, at [eastern great lakes lowland forests](/eastern-great-lakes-lowland-forests.ecoregion?from=guide). It is not a new place, and it is not the rapids. ## what the tanks are The city builds underground **retention structures** so that wastewater is not discharged to the waterways when the sewers surcharge. When capacity returns, the stored volume goes to Jean-R.-Marcotte. The city says the existing network can capture nearly **49 million litres**. The **Rockfield** basin in LaSalle, described as the largest once completed, holds up to **45,000 cubic metres**. The **Lavigne** basin is described as **20,000 square metres**. That unit is area, not volume. Adding litres to cubic metres to square metres produces a number nobody operates. Those structures are gray storage. They are useful. They are not a rapid, not a wetland, and not a shore. A tank holds what the interceptor could not take in that hour. The river is what receives whatever the tank does not hold, and what the plant discharges after treatment. Both of those are the living system. The concrete is the city's tool. This distinction is the whole page. [Nature-based solutions for urban flooding](/guide/urban-flooding-nature-based-solutions?from=guide) is the general argument that concrete fails as a complete answer. Here the concrete has a local name, a local volume, and a local river. The general argument does not need to be repeated. The local one does. ## what the plant is Jean-R.-Marcotte is the island's wastewater plant. It discharges to the St. Lawrence. A 16 March 2022 executive-committee deck put the revised disinfection budget at **$696.2 million**, the design flow at **40 cubic metres per second**, and ozone production at **57 tonnes a day**, with commissioning aimed at mid-2025. The city page updated **27 March 2026** says construction of the ozonation unit continues through **December 2028**, phases 4 through 6 having started in November 2024. Both documents stand. Neither one is a percent-complete. The English project page says overflows are still expected when it rains hard or when snow melts, including during periods when treatment capacity was reduced for the works. Ozonation is disinfection of what the plant already receives. It is gray treatment. It does not turn the rapids into a pipe, and it does not replace the shore. The English city page also says the plant treats **45%** of Québec's wastewater, and in the same breath gives an average daily volume that these notes refuse to use, because the volume sentence is not usable. The 45% claim is the city's, with that caveat. It is not a basis for a premium. Ensurance, if it ever funds anything on this reach, sits on the retention landscapes and on the receiving river. It does not sit on a second disinfection technology. That sentence is a boundary. It is not an offer, and it is not a claim that the city's ozone project is a mistake. The city is doing the gray work. The living reach is still unfunded as a named thing. ## the reach has more than one edge The rapids are the drop a reader can picture. They are not the whole living system. West of the island, Lac des Deux Montagnes is the wide water the 2017 flood used to enter the West Island. North, Rivière des Prairies is a river in its own right, not a ditch beside a suburb. The harbour channel is the engineered pass. Inland wetlands sit on the shoreline and the island edge, including the Boucherville process. Their acreage was not researched, so this page does not borrow a hectare from a different coast to sound precise. Mount Royal's forest is the city's other living mass. It belongs to shade and heat, not to this drop. Leaving it out of the pipe metaphor is deliberate. A tank underground in LaSalle and a woodland on the hill are both easy to call green. Only one of them is this series. The port's commercial clock is the season the channel can be run. Less ice, changing waves, and heat on workers and cargo sit in the Ouranos file as chronic pressure. About 67 percent of the infrastructure was judged adequate. The living shore is the part of that sentence the percent does not settle. A quay can be tall enough for a water level and still stand in a river whose edge is thinning. ## a name for the reach, not a product on a shelf The river around the island is already there whether or not a certificate exists. There is no live St. Lawrence basin agent. The parent that does exist is [rivers and lakes](/rivers-lakes.ensurance?from=guide). A line called **fluvial st lawrence** can be co-created under that agent, meaning this island's reach: Rivière des Prairies, Lac Saint-Louis, the Lachine Rapids, and the harbour channel. It does not mean the gulf, and it does not mean the Great Lakes. Co-create it with us. A person reviews the suggestion. The parent agent receives it. The door is [suggest a fluvial st. lawrence line](/specific/create?mode=suggest&agent=rivers-lakes.ensurance&name=fluvial%20st%20lawrence&from=guide). [Flood resilience](/flood-resilience.syndicate?from=guide) is the live syndicate for high water, and it is a shelf, not a Montreal policy. The person who already cares for the drop and the shore, in the facts we have, is the port authority's wildlife-area process and the city's choice to keep surcharge out of the river. The specific ask is to keep those two efforts pointed at the living reach, and to give that reach a name under the agent that already exists. It is not a request to protect a skyline. If you want the failure that reached kitchens and basements, that is the next page. If you want who already pays for the tanks, that is the last page. Neither one will invent a price for the rapids. ## frequently asked questions ### what are the lachine rapids? They are the southwest drop of the fluvial St. Lawrence at the island of Montreal, below Lac Saint-Louis. They are current and rock and shore. They are not a section of pipe, and they are not the wastewater plant. ### is a retention basin the same as a river? No. The city's network stores nearly 49 million litres so wastewater is not discharged when sewers surcharge. Rockfield holds up to 45,000 cubic metres. Lavigne is described as 20,000 square metres, which is area. The river is what lies outside those structures. ### can i fund the rapids directly today? You can co-create a line called fluvial st lawrence under the rivers-and-lakes agent. A person reviews it. There is no separate live St. Lawrence agent to send you to, and this page does not pretend there is. ## sources [City of Montréal, retention structures](https://montreal.ca/en/articles/retention-structures-limiting-wastewater-discharge-14459) — network volume, Rockfield, Lavigne. [City of Montréal, ozone disinfection at Jean-R.-Marcotte](https://montreal.ca/en/articles/ozone-disinfection-construction-jean-r-marcotte-water-treatment-station-27451) — overflows during rain and snowmelt, including during the works. [Executive committee deck, 16 March 2022](https://ville.montreal.qc.ca/documents/Adi_Public/CE/CE_DA_ORDI_2022-03-16_09h00_Presentation_Desinfection_station_epuration_-_Jean-R._Marcotte.pdf) — revised budget, design flow, ozone tonnes, commissioning aim. [City page, 27 March 2026](https://montreal.ca/articles/travaux-la-station-depuration-jean-r-marcotte-actualites-et-impacts-35019) — phases 4–6 through December 2028. [Ouranos, Port of Montreal infrastructure](https://www.ouranos.ca/en/projects-publications/resilience-montreal-infrastructure) — channel and shore as climate-exposed infrastructure. ## the series - [montreal stands in the river](/guide/what-montreal-stands-in?from=guide) - [who depends on the river at montreal](/guide/who-depends-on-the-river-at-montreal?from=guide) - [the lachine rapids are not a pipe](/guide/the-lachine-rapids-are-not-a-pipe?from=guide) - [the spring that reached montreal](/guide/the-spring-that-reached-montreal?from=guide) - [who already works the montreal overflow](/guide/who-already-works-the-montreal-overflow?from=guide)