Decew Falls Water Treatment Plant - 2025 Annual Water Quality Report
This annual water quality report summarizes the quality of drinking water from the Decew Falls Water Treatment Plant, drinking water system number 220002066, from Jan. 1 to Dec. 31, 2025.
This report satisfies the requirements of Ontario Regulation 170/03 - Drinking Water Systems.
Description of drinking water system
A conventional surface water treatment plant incorporates the following steps in its purification process:
- Zebra mussel control
- Travelling screens
- Coagulation
- Flocculation
- Sedimentation
- Filtration
- Disinfection
The plant consists of three separate treatment trains; referred to as Plant 1, Plant 2 and Plant 3, with a combined rated capacity of 227,300 m3/day. Primary disinfection is achieved utilizing sodium hypochlorite with ultraviolet light as enhancement.
The Decew Falls Water Treatment Plant supplies drinking water to the City of St. Catharines (260003279), City of Thorold (260004313), Town of Niagara-on-the-Lake (260001380) and sections of the Town of Lincoln (260004306) in Niagara. The water treatment plant is located at 2700 Decew Rd. in St. Catharines.
The water treatment chemicals used over this reporting period are:
- Sodium hypochlorite
- Aluminum sulphate
Water treatment plant infrastructure / system infrastructure
Monetary expenses
To ensure safe and efficient operations, the following major repairs or upgrade projects took place:
- Plant 3 contract 1 - $15,930,290
- Plant 3 contract 2 - $6,008,589
- York Road watermain replacement - $5,042,679
- Intake building rehabilitation - $125,919
- Brock high lift pumping station upgrades and valve replacement - $86,405.74
- High lift refurbishment - $80,623.63
- Upgrades to reservoir - $56,017.66
- St. David's chlorination facility upgrades - $40,856.64
- Victoria Avenue watermain replacement - $32,072.26
- Queenston pressure reducing valve chamber rehabilitation - $16,521.05
Summary of adverse water quality incidents
The following table summarizes the notices of adverse water quality incidents submitted in accordance with the Safe Drinking Water Act. Adverse water quality incidents are reported to the Spills Action Centre and the Medical Officer of Health.
Where there have been no adverse water quality incidents for the reporting period, the table will show "NIL".
| Incident date | Adverse condition | Corrective action | Notice of issue resolution |
|---|---|---|---|
| NIL | NIL | NIL | NIL |
Water quality test results
Reported results that are shown with "ND" (non-detect) instead of a numerical value indicates that the sample result is below the lowest possible detection limit for the parameter.
Microbiological testing
Microbiological testing carried out under Schedule 10 of Ontario Regulation 170/03 - Drinking Water systems, during this reporting period.
| Location | Number of samples | Range of E.coli results (minimum number) - (maximum number) | Range of total coliform results (minimum number) - (maximum number) | Prescribed standard* | Unit of measure |
|---|---|---|---|---|---|
| Raw | 52 | 0 - 21 | 0 - 12,000 | Not applicable | CFU/100 ml |
| Treated | 156 | 0 | 0 | Not detectable | CFU/100 ml |
| Distribution | 260 | 0 | 0 | Not detectable | CFU/100 ml |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards.
Heterotrophic plate count testing
Heterotrophic plate count testing (HPC) is conducted on some treated and distribution system samples. The heterotrophic plate count test is used as a tool to monitor overall quality, but the results are not indicators of water safety. There is no prescribed standard for heterotrophic plate count.
| Location | Number of samples | Range of HPC results (minimum number) - (maximum number) | Unit of measure |
|---|---|---|---|
| Treated | 156 | 0 - 4 | CFU/ml |
| Distribution | 260 | 0 - 9 | CFU/ml |
Operational testing
Operational testing carried out under Schedule 7 of Ontario Regulation 170/03 - Drinking Water Systems, during this reporting period. An analyzer continuously monitors the water treatment process and records results on a predetermined frequency. Where continuous monitors are used, 8,760 is reflected as the number of samples.
| Parameter | Number of samples | Range of results (minimum number) - (maximum number) | Unit of measure |
|---|---|---|---|
| Filter turbidity | 8,760 | 0.019 - 0.354 | NTU* |
| Treated chlorine | 8,760 | 0.25 - 2 | mg/l |
*NTU (nephelometric turbidity units) is a unit that measures the lack of water clarity.
Additional testing
Summary of additional testing and sampling carried out in accordance with the requirement of an approval, order or other legal instrument.
| Date of legal instrument issued | Location: parameter | Date sampled | Result value or range (minimum number) - (maximum number) | Requirement | Unit of measure |
|---|---|---|---|---|---|
| Municipal Drinking Water Licence Issue 14 Dec. 16, 2024 | Environmental discharge: free chlorine residual | Weekly (January to December) | 0 - 0.01 | < 0.02 | mg/L |
| Municipal Drinking Water Licence Issue 14 Dec. 16, 2024 | Environmental discharge: total suspended solids | Weekly (January to December) | < 3 - 240 | 25 (running annual average) | mg/L |
| Municipal Drinking Water Licence Issue 14 Dec. 16, 2024 | Raw: microcystin | Weekly (June to October) | ND | 0.0015* | mg/L |
| Municipal Drinking Water Licence Issue 14 Dec. 16, 2024 | Treated: microcystin | Weekly (June to October) | ND | 0.0015* | mg/L |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards.
Inorganic testing
Inorganic parameter testing carried out under Schedule 13 of Ontario Regulation 170/03 - Drinking Water Systems, during this reporting period. Inorganic substances include heavy metals and dissolved minerals that may be present in treated drinking water.
| Parameter | Number of samples | Last sample date | Range of results (minimum number) - (maximum number) | Prescribed standard* | Unit of measure | Exceedance |
|---|---|---|---|---|---|---|
| Antimony | 4 | Nov. 12 | ND |
0.006 | mg/L | No |
| Arsenic | 4 | Nov. 12 | ND - 0.0006 | 0.01 | mg/L | No |
| Barium | 4 | Nov. 12 | 0.018 - 0.021 | 1 | mg/L | No |
| Boron | 4 | Nov. 12 | 0.016 - 0.021 | 5 | mg/L | No |
| Cadmium | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| Chromium | 4 | Nov. 12 | ND - 0.001 | 0.05 | mg/L | No |
| Fluoride | 12 | Nov. 12 | ND - 0.06 | 1.5 | mg/L | No |
| Mercury | 4 | Nov. 12 | ND | 0.001 | mg/L | No |
| Nitrate | 12 | Nov. 12 | ND - 0.3 | 10 | mg/L | No |
| Nitrite | 12 | Nov. 12 | ND | 1 | mg/L | No |
| Selenium | 4 | Nov. 12 | ND - 0.0006 | 0.05 | mg/L | No |
| Sodium | 4 | Nov. 12 | 12.3 - 13.3 | 20 | mg/L | No |
| Uranium | 4 | Nov. 12 | ND | 0.02 | mg/L | No |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards. The prescribed standard for sodium is copied from Ontario Regulation 170/03 - Drinking Water Systems.
Lead testing
Lead testing carried out under Schedule 15.1 of Ontario Regulation 170/03 - Drinking Water Systems, during this reporting period.
| Location type | Number of samples | Last sample date | Range of lead results (minimum number) - (maximum number) | Prescribed standard* | Unit of measure | Exceedance |
|---|---|---|---|---|---|---|
| Treated | 4 | Nov. 12 | ND | 0.01 | mg/L | No |
| Distribution | 4 | Nov. 12 | ND | 0.01 | mg/L | No |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards.
Organic testing
Organic parameter testing carried out under Schedule 13 of Ontario Regulation 170/03 - Drinking Water Systems, during this reporting period. Trace organic test parameters include: volatile organic substances, pesticides, solvents, dioxins, PCBs and disinfection by-products.
| Parameter | Number of samples | Last sample date | Range of results (minimum number) - (maximum number) | Prescribed standard* | Unit of measure | Exceedance |
|---|---|---|---|---|---|---|
| 1,1-Dichloroethylene (vinylidene chloride) | 4 | Nov. 12 | ND | 0.014 | mg/L | No |
| 1,2-Dichlorobenzene | 4 | Nov. 12 | ND | 0.2 | mg/L | No |
| 1,2-Dichloroethane | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| 1,4-Dichlorobenzene | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| 2,3,4,6-Tetrachlorophenol | 4 | Nov. 12 | ND | 0.1 | mg/L | No |
| 2,4,6-Trichlorophenol | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| 2,4-Dichlorophenoxy acetic acid (2,4-D) | 4 | Nov. 12 | ND | 0.9 | mg/L | No |
| 2-4 Dichlorophenol | 4 | Nov. 12 | ND | 0.9 | mg/L | No |
| 2-Methyl-4-chlorophenoxyacetic acid (MCPA) | 4 | Nov. 12 | ND | 0.1 | mg/L | No |
| Alachlor | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| Atrazine + N-dealkylated metabolites | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| Azinphos-methyl | 4 | Nov. 12 | ND | 0.02 | mg/L | No |
| Benzene | 4 | Nov. 12 | ND | 0.001 | mg/L | No |
| Benzo(a)pyrene | 4 | Nov. 12 | ND | 0.00001 | mg/L | No |
| Bromoxynil | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| Carbaryl | 4 | Nov. 12 | ND | 0.09 | mg/L | No |
| Carbofuran | 4 | Nov. 12 | ND | 0.09 | mg/L | No |
| Carbon tetrachloride | 4 | Nov. 12 | ND | 0.002 | mg/L | No |
| Chlorpyrifos | 4 | Nov. 12 | ND | 0.09 | mg/L | No |
| Diazinon | 4 | Nov. 12 | ND | 0.02 | mg/L | No |
| Dicamba | 4 | Nov. 12 | ND | 0.12 | mg/L | No |
| Dichloromethane | 4 | Nov. 12 | ND | 0.05 | mg/L | No |
| Diclofop-methyl | 4 | Nov. 12 | ND | 0.009 | mg/L | No |
| Dimethoate | 4 | Nov. 12 | ND | 0.02 | mg/L | No |
| Diquat | 4 | Nov. 12 | ND | 0.07 | mg/L | No |
| Diuron | 4 | Nov. 12 | ND | 0.15 | mg/L | No |
| Glyphosate | 4 | Nov. 12 | ND | 0.28 | mg/L | No |
| HAA - Distribution (latest running annual average) | 12 | Dec. 15 | 0.026 | 0.080 (running annual average) | mg/L | No |
| Malathion | 4 | Nov. 12 | ND | 0.19 | mg/L | No |
| Metolachlor | 4 | Nov. 12 | ND | 0.05 | mg/L | No |
| Metribuzin | 4 | Nov. 12 | ND | 0.08 | mg/L | No |
| Monochlorobenzene | 4 | Nov. 12 | ND | 0.08 | mg/L | No |
| Paraquat | 4 | Nov. 12 | ND | 0.01 | mg/L | No |
| Pentachlorophenol | 4 | Nov. 12 | ND | 0.06 | mg/L | No |
| Phorate | 4 | Nov. 12 | ND | 0.002 | mg/L | No |
| Picloram | 4 | Nov. 12 | ND | 0.19 | mg/L | No |
| Polychlorinated Biphenyls (PCB) | 4 | Nov. 12 | ND | 0.003 | mg/L | No |
| Prometryne | 4 | Nov. 12 | ND | 0.001 | mg/L | No |
| Simazine | 4 | Nov. 12 | ND | 0.01 | mg/L | No |
| Terbufos | 4 | Nov. 12 | ND | 0.001 | mg/L | No |
| Tetrachloroethylene | 4 | Nov. 12 | ND | 0.01 | mg/L | No |
| THM - Distribution (latest running annual average) | 12 | Dec. 15 | 0.033 | 0.100 (running annual average) |
mg/L | No |
| Triallate | 4 | Nov. 12 | ND | 0.23 | mg/L | No |
| Trichloroethylene | 4 | Nov. 12 | ND | 0.005 | mg/L | No |
| Trifluralin | 4 | Nov. 12 | ND | 0.045 | mg/L | No |
| Vinyl Chloride | 4 | Nov. 12 | ND | 0.001 | mg/L | No |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards.
Parameters exceeding prescribed half-standard
Any inorganic or organic parameter(s) that exceeded half the standard prescribed in Schedule 2 of prescribed standards documented in Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards or prescribed standards documented within Ontario Regulation 170/03 - Drinking Water Systems for large municipal residential drinking water systems.
Sodium - prescribed standard is <=20*
| Result value or range (minimum number) - (maximum number) | Date of sample |
|---|---|
| 12.3 - 13.3 mg/L | Feb. 5 |
*Prescribed standards are copied from Ontario Regulation 169/03 - Ontario Drinking Water Quality Standards. The prescribed standard for sodium is copied from Ontario Regulation 170/03 - Drinking Water Systems.
© Niagara Region - 1815 Sir Isaac Brock Way, Thorold, ON, L2V 4T7 - Phone: 905-980-6000, Toll-free: 1-800-263-7215
