Chain of Custody and Laboratory Documentation

What Is Chain of Custody?

Chain of custody (COC) is the unbroken, documented record of every person who collected, handled, transferred, or analyzed a water or wastewater sample. From the moment you dip a bottle into a stream or effluent channel to the moment the laboratory reports a result, every handoff must be recorded in writing. If that record has gaps, the sample data can be challenged or thrown out in a regulatory proceeding—even if the laboratory analysis was perfect.

For water and wastewater operators, this matters because your discharge monitoring reports (DMRs), compliance sampling, and permit-required tests are legal documents. State environmental agencies, EPA inspectors, and courts rely on COC records to confirm that the sample analyzed is truly the sample you collected.

Why COC Has Legal Weight

State water and wastewater operator licenses exist because the public's health depends on accurate data. Permit limits under the Clean Water Act and Safe Drinking Water Act are enforced based on analytical results. If a facility appears to violate a limit, the regulatory agency must be confident the sample was properly collected, stored, and analyzed—and that no one tampered with it or substituted another sample. An unbroken COC is the primary evidence of sample integrity. A broken chain can result in a notice of violation being dismissed, or conversely, it can prevent a facility from defending itself against a false positive result.

Fields on a COC Form

Every COC form—whether your state uses its own format or an ELAP-style (Environmental Laboratory Accreditation Program) form—contains the same core fields:

• Station or site ID and location description – exactly where the sample was collected, tied to your permit or monitoring plan.
• Sample ID / bottle ID – a unique number linking the field sample to the lab's internal tracking system. IDs must match on the bottle label and the COC; a mismatch invalidates the record.
• Sample type – grab, composite, or duplicate.
• Date and time of collection – record in 24-hour format and specify time zone (for example, 09:45 PST). Recording Pacific time on a form submitted to a lab in Mountain time without noting the zone creates an apparent holding-time violation.
• Parameters requested – the specific analytes (e.g., total coliform, BOD, TSS, nitrate). Unlisted parameters will not be analyzed.
• Preservative and container type – confirms the correct preservation was used at collection.
• Number of containers – allows the lab receiver to verify nothing was lost in transit.
• Sampler signature and printed name – the collector takes legal responsibility for sample condition at the time of collection.
• Transfer/receipt signatures with date and time – every person who takes possession signs here. Multiple transfers each require a new entry.
• Sample condition on receipt – the lab receiver notes temperature, seal integrity, and any visible problems.
• Custody seal notation – if a seal is intact, note it; if a seal is broken, document it immediately with an explanation. Ignoring a broken seal is a documentation error with potential regulatory consequences.

Common Documentation Errors and Their Consequences

1. Missing signature – No legal transfer occurred; the sample's custody is broken and results may be inadmissible.

2. Incorrect or missing holding time – Analytes degrade after collection. If collection time is wrong or missing, the lab cannot confirm results are valid within regulatory holding times.

3. Mismatched sample ID – The bottle analyzed may not be the bottle collected. Results cannot be tied to the sampling location.

4. Broken seal noted but not documented – Suggests possible tampering; the sample cannot be defended as uncompromised.

5. Time recorded in wrong time zone – Creates an apparent holding-time violation that did not actually occur, or conceals one that did.

Handling and Safety During Sample Transfer

Samples collected for regulatory analysis often contain pathogens or chemical hazards. Always wear nitrile gloves when handling sample bottles. If samples contain suspected biohazards (wastewater, biosolids-contact water), a face shield or safety glasses and a lab coat or coveralls are appropriate. Place bottles in sealed plastic bags inside coolers to contain any leaks. Follow your facility's bloodborne-pathogen and chemical hygiene plan. When in doubt, treat all wastewater samples as potentially infectious.

Keep custody seals in a dry, clean location. Apply them so that the seal bridges the cap and bottle neck; any tampering will visibly break the seal.

Completing the COC: A Step-by-Step Approach

1. Label each sample bottle in the field before collection—never after.

2. Fill out the COC form completely in waterproof ink at the point of collection.

3. Note time zone explicitly every time you record a time.

4. Place custody seals on each bottle; photograph if your protocol allows.

5. Pack bottles in a cooler with ice; record cooler temperature at packing.

6. Keep the COC inside a waterproof sleeve in the cooler or with the samples at all times.

7. At lab receipt, the receiver inspects seals, temperature, and bottle condition before signing. Any discrepancy is written on the form—not corrected by erasing.

Never erase an entry on a COC. Draw a single line through an error, write the correction beside it, and initial and date the correction. This preserves the original entry and shows it was changed honestly.