York-Durham Regional Environmental Laboratory

Once water samples have been collected from Lake Ontario, they are submitted for analysis to the York-Durham Regional Environmental Laboratory.


The York-Durham Regional Environmental Laboratory has commercial quality testing services specializing in analytical testing to meet the requirements of:

  • Safe Drinking Water Act
  • New Mains
  • Certificates of Approval
  • Waste Water Regulations
  • Sewer Use By-Law
  • Landfill Monitoring

***The results from the York-Durham Regional Environmental Laboratory are ADMISSIBLE IN A COURT OF LAW***


The York-Durham Regional Environmental Laboratory has been accredited by two organizations:

  • CALA (Canadian Association for Laboratory Accreditation) accredited against the International Organization for Standards 17025 (ISO 17025) which requires an on-site assessment every two years
  • Licensed by the Ontario Ministry of the Environment, Conservation and Parks (MECP) for analyzing drinking water quality which requires an on-site inspection two times per year


To receive and maintain accreditation, lab practices and results are validated internally as well as by both CALA and the MECP. Validation is achieved through:

  • Blind Proficiency Testing of samples from an accredited source
  • Blind Round Robin samples from the Ontario Ministry of the Environment and Toronto and Region Conservation Authority (TRCA)
  • Internal lab quality control, running standards, surrogates, duplicates, spikes, and blanks
  • Audits by CALA and MECP at scheduled intervals

Other Clients

Analytical services are provided to a wide variety of clients including:

  • Large Municipalities
  • Conservation Authorities
  • School Boards
  • Industries
  • Engineering Consultants
  • Small Waterworks

Lab Strengths

The York-Durham Regional Environmental Laboratory has an excellent customer service record with competent scientists who excel at:

  • Short lab turnaround times
  • Following a Chain of Custody protocol (results are admissible in a Court of Law)
  • Follow-up support to clients after samples have been analyzed
  • LIMS (Lab Information Management System)
  • Troubleshooting
  • Full-scale analytical services (including Microbiology, Inorganic Chemistry, and Organic Chemistry)
  • Specialized testing (e.g. Cryptosporidium and Giardia, Algal Toxins such as Microcystins, Taste and Odour compounds such as Geosmin and MIB, Algae monitoring, Molds, etc.)

Lab Challenges

There are analytical challenges involved with all types of chemical analyses. Since different gradients in water quality are observed between different sampling locations such as landfill sites, marshes, storm drains, lakes and drinking water, we need to be capable of analyzing a wide range of values.

Challenges that the lab may encounter include:

  • Ways to sample the chemical to be analyzed
  • Ways to separate the chemical from the matrix for analysis
  • Achieving low level detection limits

Non-Detect Samples

Sometimes samples analyzed fall below the minimum reportable level of the lab. They can be below a method detection limit (MDL) or below a reporting detection limit (RDL).

A reporting detection limit is the limit of detection after adjustments have been made for dilutions. A method detection limit or MDL is lower than the RL and is a statistical calculation.

If samples fall below a RDL or MDL they are called “non-detects” and are classified as being present at a concentration below the minimum reportable level.

For example, if the lab detection limit was 2 mg/L and the water sample had a lower concentration than 2 mg/L, the sample concentration would be reported as < 2 mg/L.

Over time, the York-Durham Regional Environmental Laboratory has improved their analytical techniques to achieve lower MDLs and RDLs for water quality nutrients such as total phosphorus (current TP Reporting limit = 2 µg/L), soluble reactive phosphorus (current SRP Reporting limit = 0.5 µg/L), nitrite (current NO2 Reporting limit = 2 µg/L), and ammonia (current NH3 Reporting limit = 13 µg/L). Sometimes our samples fall even below these limits.

Depending on the distance from shore and whether the samples were taken from the top or the bottom of the lake, many samples fall below the detection limit of commercial labs.

Of all the lake samples analyzed in this project between 2006 and 2020, the percentage of non-detects was high for ammonia (24%), E coli (38%), soluble reactive phosphorus (64%), and suspended solids (62%).

Of all the samples taken, many of the sites with concentrations below detection were located at distances greater than 1 km from the shore in the spring and fall, especially at the bottom of the lake. However, concentrations at sites less than 1 km from the shore were also below detection limits.

The University of Waterloo completed a study in 2008 using the same sampling locations as TRCA and generally taking samples within one day of when TRCA sampled. University Labs are extremely specialized and able to reach very low phosphorus detection limits, even lower than commercial labs.

If we assume that there are no major differences between the nutrient inputs, the climate, and the physical features in the lake between the day that the University sampled and the day when TRCA sampled, we can narrow down the concentration range of our non-detects at that time.

For example, at sites where TRCA had soluble reactive phosphorus non-detects, approximately 60% of the University of Waterloo samples were between 1 and 2 µg/L.

In 2016, the York-Durham Regional Environmental Laboratory reduced their soluble reactive phosphorus detection limit from 2 µg/L to 0.5 µg/L. This is comparable to government labs. At this limit, we still have a lot of non-detect SRP samples in the nearshore (25%)!

Chain of Custody and Analyzing Samples

The following image illustrates the chain of events that occurs between sample collection and receiving the water quality results from the lab.

Lake Ontario Waterfront nearshore monitoring York Durham Regional Environmental Library

Lab Data

Once we receive the data from the lab, the data undergoes Quality Assurance prior to being georeferenced, analyzed, and shared, the process is shown below:

Lake Ontario Waterfront nearshore monitoring York Durham Regional Environmental Laboratory