Quality Assurance and Quality Control of Water Quality Data
DEC's Division of Water (DOW) is committed to transparency and standardization of data that reflects the quality of New York's waters. The methods used to generate and analyze water quality data must be reproducible and correct. Consistency in environmental information operations allow DOW to compare water quality data across time periods and/or locations, determine patterns, and understand water quality issues.
To ensure the scientific integrity of its work, DOW requires a description of quality for all water quality data and information it uses.
Data quality is described with measures known as Data Quality Indicators (DQIs). DQIs are used to define the minimum data requirements needed to meet project goals.
The six standard DQIs are:
- Precision: How close are multiple measurements from the same location?
- Accuracy: How close is an observed measurement to a known value?
- Bias: Are there underlying factors (e.g., sample collection method) leading to a consistent misrepresentation of results?
- Sensitivity: Does a measurement method (e.g., laboratory analysis) provide the resolution or level of detail necessary to meet project goals?
- Comparability: Can data collected at multiple locations be compared to one another?
- Representativeness: Does the collected data correctly portray the characteristics of interest (e.g., the ambient water quality of a lake)?
- Completeness: Was enough valid data (data determined to meet other DQI project requirements) available to meet project goals?
For more information on DQIs, please see Section B.1.A6, in EPA’s IT/IM Directive Standard: Quality Assurance Project Plan Standard (CIO 2015-S-02.1, August 2023). DQIs provide DOW with the necessary Quality Assurance (QA) information to determine how to use data appropriately and responsibly.
DQIs are described before work begins in a standard written document, known as a Quality Assurance Project Plan (QAPP). After the completion of work for DOW projects, a Data Usability Assessment Report (DUAR) is written to describe how these minimum requirements were met.
The majority of quality assurance documents are developed by the DEC’s water monitoring programs. Visit the DEC website for more information about DEC’s water quality monitoring programs.
Environmental Information Requirements
The environmental information DOW uses to implement its regulatory programs must adhere to the following requirements:
- QAPP based on guidance provided by the EPA IT/IM Directive Standard: Quality Assurance Project Plan Standard (CIO 2105-S-02.1, April 2024). The fulfillment of the data verification, validation, and usability component of the QAPP is to be documented in a Data Usability Assessment Report (DUAR).
- Adhere to approved test procedure methodologies defined in 40 CFR Part 136, as appropriate.
- Use laboratories certified by the New York State Department of Health (DOH) under the Environmental Laboratory Approval Program (ELAP) pursuant to Section 502 of the NYS Public Health Law. This requirement does not apply to specific parameters where DOH ELAP has not issued a certificate for the specific parameter.
To find ELAP approved methods, visit the Requirements for Laboratory Certification page on the DOH website.
- Item No. 180.1 details approved methods for Drinking (Potable) Water.
- Item No. 180.2 details approved methods for Non-Potable Water.
Quality Assurance Documents
SOP
A Standard Operating Procedure, (SOP), is a document that details the step-by-step process of a recurring activity. For example, how to calibrate and use a multi-parameter probe. SOPs can be useful to reference when developing a QAPP, but only of value when they are developed correctly and followed. For guidance on SOPs, please review the EPA Guidance for Preparing Standard Operating Procedures (QA/G-6, April 2007); the appendices of this guidance document provide excellent example SOPs for a variety of procedures. The templates below contain the standard content and formatting of DOW SOPs.
QAPP
A Quality Assurance Project Plan, (QAPP), is a formal document created prior to the start of a project that outlines how environmental information operations will be planned, implemented, documented, and assessed. QAPPs are reviewed and approved by the Quality Assurance Officer, (QAO), in accordance with EPA Quality Assurance Project Plan Standard. For guidance on QAPPs, please review the EPA IT/IM Directive Standard: Quality Assurance Project Plan Standard (CIO 2105-S-02.1, April 2024). The templates below contain the standard content and formatting DOW QAPPs must include.
DUAR
A Data Usability Assessment Report, (DUAR), is a document created at the end of a project to describe how well the QAPP was followed and if data met the quality control requirements defined in the QAPP. For guidance on DUARs, please review the EPA Guidance on Environmental Data Verification and Data Validation (QA/G-8, November 2022) and EPA Guidance for Data Quality Assessment: Practicl Methods for Data Analysis (QA/G-9, July 2000). The template below contains the standard content and formatting DOW DUARs must include.
QAMP
A Quality Assurance Management Plan, (QAMP), is a document created for an organization to describe and document their quality program. All non-EPA organizations performing environmental information operations on behalf of EPA, i.e. funded by the EPA, are required to develop a QAMP. The DOW Quality Assurance Management Plan (PDF) outlines the roles, responsibilities, and procedures for carrying out our quality system. Developing quality assurance documents for projects conducted and funded by the NYSDEC DOW is an important aspect in the DOW QAMP and quality system. For additional guidance on QAMPs, please review the EPA IT/IM Directive Standard: Quality Management Plan Standard (CIO 2105-S-01.1, March 20, 2024). The template below contains the standard content and formatting DOW QAMPs must include.
