Eliminating Cross-Contamination in Surface Water Sampling: Best Practices for Accurate Data

Presented by Kamie Stecher, CTEH
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ABSTRACT

Accurate and reliable environmental data from surface water samples is crucial for environmental assessment and regulatory compliance. Preventing cross-contamination during sample collection is paramount to ensuring data integrity. This presentation focuses on best practices for eliminating crosscontamination in surface water sampling, drawing from fundamental environmental sampling principles and procedures outlined in environmental field work guidelines.

A foundational understanding of surface water sampling processes written into Sampling and Analysis Plans (SAP) is critical for minimizing contamination risks. SAP detail specific criteria for selecting appropriate sampling locations and identifying and address potential contamination sources. Proper data collection and documentation, including meticulous field notes are vital to maintain the traceability and integrity of surface water samples.

The presentation will emphasize the importance of selecting of appropriate sampling locations. While SAPs may specify sampling points, onsite evaluation is necessary to assess nearby potential sources of contamination, such as industrial discharges, agricultural runoff, waste disposal areas, or other activities that could impact water quality. Observations such as site conditions, noting odors, detailed description of the area, weather, recent rainfall provide context for impacts on water quality and should be thoroughly documented.

Key areas and sources of cross-contamination during sampling will be examined, including improper use or inadequate decontamination of reusable equipment such as dippers or Kemmerer samplers. Attendees
will learn about the correct selection and handling of containers (e.g., amber or clear, plastic or glass) and the proper use of preservatives (e.g., nitric acid, sulfuric acid, hydrochloric acid) all while following proper glove and PPE protocols. The session will highlight the importance sampling progression (i.e., collection activities) - from the least to most suspected contaminated areas to reduce the risk of sample compromise.

Furthermore, the critical role of quality assurance/quality control (QA/QC) samples in identifying and preventing contamination will be examined. This includes the strategic use of field blanks to assess ambient conditions, rinsate blanks to evaluate the decontamination effectiveness, and trip blanks to monitor for transport-related contamination, particularly those for Volatile Organic Analysis (VOAs). Adherence to surface water sampling best practices, such as proper grab sampling techniques, ensuring VOA vials are filled without air bubbles, and carefully considering the sample location relative to potential contamination sources, will be covered.

Attendees will gain practical guidance of implementing reliable surface water sampling procedures, including the thoughRul selection of sampling locations, diligent observation of potential contamination sources, and processes to reducing contamination risks. This presentation aims to enhance the knowledge and practices of state, federal, auditing, and lab experts in the collection of representative and uncontaminated surface water samples for robust and defensible data.