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s A completed Chain-of-Custody form, detailing the sample I.D., date and time collected, analyses requested, and other project information, accompanied each sample to the laboratory. The Chain-of-Custody forms were signed and dated by all personnel retaining custody of the samples (Appendix F). Field Equipment and Calibration Proper maintenance, calibration, and operation of each field instrument are the responsibility of the field personnel and the instrument technicians assigned to the project. All instruments and equipment used during the program will be maintained, calibrated, and operated according to the manufacturers'guidelines and recommendations. Field equipment are calibrated prior to use in the field as appropriate. The calibration procedures follow standard manufacturers' instructions to ensure that the equipment is functioning within established tolerances and as required by the project. A record of field calibration of analytical instruments is maintained in the calibration logbook by field personnel. Copies of the instrument manuals and other equipment calibration records (e.g., thermometers, sounders) are maintained. Any notes on unusual results, changing of standards, battery charging, and operation and maintenance of the field equipment are included in the calibration logbook. All instruments are stored, transported, and handled with care to preserve equipment accuracy. Damaged instruments will be taken out of service immediately and not used again until a qualified technician repairs and recalibrates the instruments. Calibration Procedures Equipment calibration is performed in accordance with the manufacturer's instructions, and calibration checks are performed each day prior to the start of work. Calibration of rental equipment will be performed by a qualified technician prior to shipment of the equipment. Calibration standards are used once. Spent calibration liquids are placed in plastic bottles and transported off-site for disposal. A brief summary of the calibration procedures for field measurement equipment is provided below: • LH: Calibration for pH is performed prior to commencement of sampling activities, using standard buffer solutions having pH values of 4, 7, and 10. Calibration checks for pH values using buffer solutions of 4, 7, and 10 is performed daily. If the reading varies more than 0.10 of a unit between calibration checks, the meter will be recalibrated. • Conductivity: Calibration for conductivity is performed prior to commencement of sampling activities, using potassium chloride (KCI) standard solutions with conductivity values of 1,000 and 10,000 microsiemens/cm. The meter must read within one percent of full-scale to be considered calibrated. A calibration check for conductivity is performed daily.