Question

which of the following is the largest environmental challenge in using underground injection wells for hazardous waste disposal? covering the high cost required for the drilling of the wells ensuring the waste does not migrate to groundwater sources requiring a large amount of surface space to set the well up needing to monitor the waste consistently over extended time

Explanation:

The most critical environmental concern with hazardous - waste disposal in underground injection wells is preventing contamination of groundwater, which is a vital resource for drinking water and ecosystems. Costs, space requirements, and monitoring are important but secondary to the risk of groundwater pollution.

Answer:

ensuring the waste does not migrate to groundwater sources