Dependent on what city your located in currently most cities require environmental consultants to sample suspect contaminated soils. At the most basic level in residential sampling, soils should be tested for the presence of Extracted Petroleum Hydrocarbons (EPH). If the EPH levels are over the legal limit of 1000 than the property is considered contaminated. In cases that legal action may be taken, it is highly recommended to additionally test for Poly Aromatic Hydrocarbons as well (PAH or LEPH/HEPH). If your property is a commercial job and/or the storage tank has contents other than furnace oil, there are many different types of samples that may need to be taken.
For examples, please visit our gallery and check out some pictures of sampling.