well from which a sample is to be collected shall have been appropriately purged immediately prior to sampling. 4. Precautions shall be taken to minimize the potential for cross-contamination or contamination through preferential pathways. (2)  The qualified person shall ensure that the well development and purging referred to in paragraphs 2 and 3 of subsection (1) shall be documented by, (a) recording, (i) the date of the development or purging, (ii) the time the development or purging started and stopped, and (iii) the volume of fluid removed from the well during development or purging; (b) recording a rationale for concluding the development or purging was complete; and (c) recording a description of the measures taken to minimize cross contamination between wells when using non-dedicated equipment. Limitation on use of measurements taken by field screening equipment 10.  Measurements taken by field screening equipment shall not be used to demonstrate that the applicable site condition standard or standard specified in a risk assessment for a contaminant have been met on, in or under the phase two property. Following standard operating procedures 11.  (1)  The standard operating procedures referred to in subsection 3 (5) shall be followed during the field investigation. (2)  A qualified person or person supervised by a qualified person may deviate from standard operating procedures as appropriate, but the qualified person shall ensure that there is a professional rationale for any deviation. (3)  The qualified person shall ensure that the standard operating procedures and any deviations from them, with a