2,216
edits
Changes
Jump to navigation
Jump to search
Line 119:
Line 119:
→Intake Protection Zones (IPZs)
====Intake Protection Zones (IPZs)====
====Intake Protection Zones (IPZs)====
An Intake Protection Zone (IPZ) is an area that includes both land and surface water around municipalities' intake pipes that lead to a water treatment plant (WTP) and contributes to the municipalities drinking water system and sources. An IPZ on a map delineates where surface water is originating from and how it end up in the municipal water supply. These zones are determined by how far away they are from the intake location and the time it would take to reach it. The resulting size and shape of each of the three (3) zones of a typical IPZ represents either this set distance around the intake or simply the length of time it would take water and potential contaminants from overland flow to reach the intake.
{{textbox|The 3 zones of IPZ are as follows:
'''IPZ‐1''': This is the area closest to a municipality's intake pipe and is a set distance which extends one kilometre (Km) upstream and 120 metres onto the shore. IPZ-1 is the most vulnerable to contamination as it is the closest to the intake and allows limited time for dilution to occur to help reduce the concentration of a contaminant released within the zone, this lack of time also doesn't allow municipal water system operators much time to react to this released contamination that is headed towards the municipal intake.
'''IPZ‐2''': This area is developed by utilizing both hydrodynamic modelling and a time-of-travel calculation within overland pathways (natural and human-made - i.e. rivers, creeks, swales, storm sewers, etc.) that ultimately lead to and discharge near the municipalities intake(s). Includes both the on and offshore areas where overland flowing water that may be polluted with a concentration of a given number of contaminants would be able to reach the municipal intake within approximately two (2) hours. The 2 hour mark is set as the minimum amount of time to allow municipal water system operators to address a potential contamination concern.
'''IPZ‐3''': This area lies outside of IPZ-1 and IPZ-2 and as such contaminants likely could only reach the intake pipe during and/or after a major rainfall/storm event. The size and shape of an IPZ-3 zone is based on associated lakes, streams and other humanmade conveyances that could contribute excess overland flow during an event.
''Six intake pipes deliver water to four treatment plants located along the shoreline from Oakville to Hamilton. Each pipe is surrounded by a protection zone that identifies where it takes surface water two hours or less to flow to the intake or where significant drinking water threats exist. The protection zones include areas of land adjacent to streams and storm sewers where runoff water can quickly reach the intake. These zones are vulnerable to contamination.
The area considered to be most vulnerable to contamination is the area closest to the intake. The reason for this vulnerability is due to an assumed lack of time for dilution to reduce the concentration of any contaminant released within the zone. Also, there is an assumed lack of time for the operator of the water system to react to the release. To protect this vulnerable area, a circle with one kilometre radius is drawn, centred on the intake and projected to the lake bottom. This zone is called “intake protection zone one” or IPZ-1. Where these circles intersect land the onshore extent is 120 metres.
The intake protection zone two, or IPZ-2, is delineated using a combination of hydrodynamic modelling within the lake and the calculation of time-of-travel within in-land pathways such as creeks and storm sewers that discharge near the lake intakes. Two hours has been set as the minimum amount of time needed for operators of the water treatment plant to react to a contamination concern.
Intake protection zone three, IPZ-3, is an area where modelling has demonstrated that contaminants released during an event may be transported to the intake and cause an adverse effect. The IPZ-3 lies outside of an IPZ-1 and IPZ-2.''
Vulnerability of the Intake’s Source Water
The vulnerability scores assigned to the IPZ-1 and IPZ-2 intake protection zones reflect the susceptibility of the intakes to contaminants and is determined based on local knowledge and professional judgment. The score is based on multiplying the following factors:
an area vulnerability factor, which is set at the maximum value for an IPZ-1 and considers the percentage of the IPZ-2 that is land, the land characteristics (cover, soil type, permeability, slope), and the hydrological and hydrogeological conditions
a source vulnerability factor, which considers the distance of the intake from shore, the depth of the intake from water surface, and the historical water quality concerns at the intake
A vulnerability score is not given to an IPZ-3.
===2) Identify Threats===
===2) Identify Threats===