Final answer:
The best course of action for the auditor is to arrange a training session for the EHS staff with experts in wastewater legal issues. This will help address the control weakness of poor knowledge about legal issues related to wastewater discharge into municipal water sources. Additional procedures can be performed to determine the potential effects, but training is key in preventing violations.
Step-by-step explanation:
The best course of action for the auditor to take in this scenario is option C: Arrange for a training session for the EHS staff with experts in the field of wastewater legal issues. This action will help address the control weakness by providing the necessary knowledge and training to the department personnel, enabling them to better understand and comply with legal issues related to wastewater discharge into municipal water sources.
By arranging a training session with experts, the EHS staff will gain a better understanding of the legal requirements and potential consequences of their actions. This will help them make more informed decisions and take appropriate actions to avoid any violations. Training sessions can also provide an opportunity for the staff to ask questions and seek clarity on any legal issues they may be unsure about.
Performing additional procedures to determine the potential effects of the control weakness (option A) may be necessary, but it should be done in conjunction with providing training and addressing the root cause of the issue. Narrowing the scope of the engagement to examine wastewater discharge (option B) may not fully address the control weakness, as the issue lies in the lack of knowledge and understanding of legal issues rather than the specific act of wastewater discharge. Reporting possible violations to the regulatory authority (option D) should only be considered if the training and additional procedures reveal actual violations, as it should be used as a last resort when all other actions fail to address the control weakness.