What requirement is indicated for soil analysis?

Soil analysis is a critical component in managing heating oil tanks, especially when assessing potential contamination due to leaks or spills. The requirement that only methods approved by the Department of Environmental Quality (DEQ) must be used ensures that the analysis adheres to established standards and protocols. These approved methods are specifically designed to provide reliable and accurate data regarding soil contamination. Given the potential environmental impacts associated with heating oil leaks, it is essential that the methods employed are scientifically validated and recognized by regulatory bodies. This not only helps in making informed remediation decisions but also ensures compliance with state regulations aimed at protecting public health and the environment. The other options suggest using unverified or less rigorous methodologies, which could lead to inadequate assessments and potentially compromise safety and regulatory compliance.