Which of the following products is not generally approved for filling tanks for disposal in place?

Heavy brine is not generally approved for filling tanks for disposal in place due to environmental and regulatory concerns. The use of heavy brine can pose significant risks to the surrounding soil and groundwater. Its chemical properties can be harmful, leading to potential contamination issues if it were to leak or escape the tank.

In contrast, materials such as sand fill, polyurethane type foams, and a combination of sand and Earth fill are typically considered more suitable for tank stabilization. These materials are often utilized because they can provide structural integrity, minimize the risk of groundwater contamination, and comply with environmental guidelines for disposal. Sand and Earth lessen the risk of voids that might lead to subsidence, while polyurethane foams can help in filling voids effectively without contributing to contamination.