SMC lab intercalibration completed to ensure high-quality chemistry analyses for stormwater monitoring

The Southern California Stormwater Monitoring Coalition (SMC) has completed the fourth iteration of a periodic intercalibration exercise originally started in 2003 to ensure that laboratories performing routine chemistry analyses on stormwater samples are capable of generating comparable, high-quality monitoring data.

The intercalibration exercise, described in a SCCWRP technical report published in June, evaluated eight laboratories’ ability to measure five different classes of chemical contaminants in wet- and dry-weather runoff during three intercalibration rounds. The five classes were total and dissolved trace metals, nutrients, new and legacy pesticides, polynuclear aromatic hydrocarbons (PAHs), and general chemistry such as total suspended solids.

Laboratories received scores and letter grades based on accuracy and precision, and needed a minimum score of 70% or a “C” letter grade in each class of chemicals to pass. Overall, all but two laboratories that voluntarily opted not to participate in the final round of the intercalibration received passing grades for all five classes of chemicals.

The intercalibrations are used by stormwater managers for selecting high-quality contract laboratories for ongoing monitoring requirements, and ensure their data are comparable to other agencies enabling the SMC to compile databases to address regional scale questions.