Chain of Custody Procedure
One of your industrial users under the Industrial Pretreatment Program is disputing your sampling results. They say they have never discharged the level of PCBs that you claim they have. They may even have lawyers involved and perhaps a court date to resolve this. You know that you took the samples properly and that there is no doubt about the accuracy of the results. Unfortunately you didn’t follow chain of custody procedures. Therefore, according to the law, you didn’t sample their effluent. Your results are worthless for legal purposes.
The chain of custody procedure incorporates a number of controls to assure the integrity of a sample. These procedures, along with the required written documentation, provide you with the necessary backing to defend the integrity of the sample in any litigation – whether it is to resolve an NPDES issue or an Industrial Pretreatment Program one.
The chain of custody procedure starts with sample collection and follows through to the destruction of the sample. The purpose of the procedure is to ensure that the sample has been in possession of, or secured by, a responsible person at all times. It should remove any doubt about sample identification or that the sample has been tampered with. While every laboratory’s procedures may be different, there are certain aspects that should be present to assure an adequate chain of custody procedure. Below are the most common aspects of a chain of custody program developed from a survey of Standard Methods…, the Sacramento series, WEF’s Manual of Practice series, and various EPA publications:
Sample Number. All samples must be assigned a sample number. This number will follow the sample through all the analyses to the final report. It should be used to identify the sample on the container, the chain-of-custody form, in all data sheets, in computer entry, and reports. In our lab for example, if we were to sample an industrial user named Bay Coast Services, on February 28, 2003, we would assign the composite sample an identification number of BCC022803. The first two letters, BC, are an abbreviation of the company’s name. The fourth letter will either be a C (for composite) or a G (for grab). The numbers represent the date the sample was collected. For grab samples we add the time to the end of the sample number. This is how we identify samples. Whatever way you choose to develop sample numbers, it must be consistent.
Sample Tag or Label. Attach to every sample container a tag or label with the following information written in waterproof ink: sample number, location where sample was taken, date and time of collection, what preservation is used, and your initials. Sample containers are often sealed with a tamperproof seal at this point.
Field Notebook. Record in your field notebook all the basic information such as sample number, location, times and dates of sampling, addresses, types of samples taken, volume of composite sample collected, and composite sample temperature. Also record anything about the sample and sampling event that you may need for future reference. These can include calculations, who you spoke to at the company you sampled, what processes they were running at the time of sampling, and anything else that relates to the sampling event. A recent example of where I needed to record information in my notebook happened while I was trying to sample for VOCs at a local industrial user. This company neutralizes their waste stream with carbon dioxide. So trying to take a VOC sample without gas bubbles in the vial was like trying to sample a can of ginger ale. Recording this information like this is not only important to help explain potential erroneous lab results, but to warn future samplers of what to expect at that sample location.
Chain of Custody (or Chain-of-Possession as some other sources suggest). This form is filled out at sample collection and follows the sample through every person involved in the chain of possession until it reaches the laboratory. It includes information such as sample number, location where sample was taken, preservative used in each container, type and size of container for each sample (1 L glass, 500 mL amber glass, 250 mL plastic, 40 mL VOC vials, etc), dates and times of collection, type of sample (water, soil, wastewater, etc), and the name of person collecting the sample. Every time the sample changes possession, the person relinquishing the sample and the person receiving it must sign and date/time the Chain-of-Custody form. For example, the sampler may relinquish the sample to a courier. At the transfer, both parties sign and date/time the form. Then the courier delivers the sample to the laboratory where now the courier and lab representative sign and date/time the form.
Log-in at Laboratory. All samples should be logged in at the laboratory where the integrity of the samples are checked (correct preservation was used, tamperproof seals are intact, the proper signatures are present, the holding times fall within the requirements, and so on). If you deliver to a contract lab, they may assign their own ID number at this point.
Chain-of-custody procedures seem like a lot of work. But considering the amount of time spent calibrating and cleaning equipment, the labor of placing samplers in manholes or at industrial users, and the time spent doing lab work or the cost of sending it out to a contract lab, then the little bit of extra paperwork to make this a "legal" sample is well worth the time.
The information in this article is very general. As usual, check your federal, state, and local regulations. You may have additional regulations or requirements that you must meet.
If you have any questions, suggestions, or comments, please contact NEWEA Lab Practices Committee Chair Phyllis Arnold Rand 207-782-0917 (email@example.com) or Tim Loftus at (508) 949-3865 (firstname.lastname@example.org).