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SFPUC June 10, 2020 Page 13 Teflon-lined lid. The bottles should be acid-cleaned and confirmed by the lab to be mercury-free. "Ultra-clean" sampling protocols are not necessary for sediment samples, which are typically >1000-fold more concentrated than in water. Nonetheless, the sampler should wear gloves and collect samples using clean equipment. Sample bottles should be bagged, labeled and stored immediately on ice in a closed cooler. No preservation is needed for sediments other than refrigeration(<6°C). Sediment samples should be analyzed for total mercury content(USEPA Method EPA 7471A with a reporting limit of 0.02 mg/kg),particle size analysis (ASTM D4464M), and percent total volatile residue (SM 2540E with a reporting limit of 0.10%). Concentrations should be tracked over time to confirm levels are not increasing towards the threshold of interest(4 mg/kg). If sediment samples are determined to exceed the on-site threshold for industrial exposure (4 mg/kg), the sediment to be removed should be analyzed to confirm that it is not classified as hazardous (California Code of Regulations' Total Threshold Limit Concentration of 20 mg/kg) and thereby eligible for disposal at a municipal landfill. Documentation Procedures Sample documentation, described in this section, is important for maintaining a clear record for characterizing and tracking each sample collected. Field Logs Field measurements, samples and observations should be recorded on field logs. All entries should be made in indelible ink; errors should be corrected by one single line through the text being revised, and all such corrections should be initialed and dated. The date and time of sampling should be noted. Sample ID Conventions Sample bottles submitted for laboratory analyses should be labeled with the project name (Mercury Interception), site name (Tesla UV Building), analysis to be performed, date and time of sample, responsible sample collector and receiving lab. Chain of Custody Workers should collect samples and deliver them to the analytical laboratory following standard chain-of-custody (COC) protocols. Every sample should be recorded on a COC form that identifies how, where, when, for what analysis, and by whom it was collected. Each time sample containers are relinquished and received should be noted. Before relinquishing samples, each responsible individual will: • Sign and time-stamp the original COC form. • Retain one copy of the COC form. • Provide the original COC form to the receiver. Transport to Lab Water samples should be hand-delivered to the laboratory to meet the 48-hour hold time for total mercury. However, if preserved with HCl, the holding time is 90 days.