(a) General limitations. Until the authorized official has made the determination required in § 11.23 of this part to proceed with an assessment, field sampling of natural resources should be limited to the conditions identified in this section. All sampling and field work shall be subject to the provisions of § 11.17 of this part concerning safety and applicability of resource protection statutes.

(b) Early sampling and data collection. Field samples may be collected or site visits may be made before completing the preassessment screen to preserve data and materials that are likely to be lost if not collected at that time and that will be necessary to the natural resource damage assessment. Field sampling and data collection at this stage should be coordinated with the lead agency under the NCP to minimize duplication of sampling and data collection efforts. Such field sampling and data collection should be limited to:

(1) Samples necessary to preserve perishable materials considered likely to have been affected by, and contain evidence of, the oil or hazardous substance. These samples generally will be biological materials that are either dead or visibly injured and that evidence suggests have been injured by oil or a hazardous substance;

(2) Samples of other ephemeral conditions or material, such as surface water or soil containing or likely to contain oil or a hazardous substance, where those samples may be necessary for identification and for measurement of concentrations, and where necessary samples may be lost because of factors such as dilution, movement, decomposition, or leaching if not taken immediately; and

(3) Counts of dead or visibly injured organisms, which may not be possible to take if delayed because of factors such as decomposition, scavengers, or water movement. Such counts shall be subject to the provisions of § 11.71(l)(5)(iii) of this part.