Question

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

Explanation:

Groundwater contamination is a severe environmental issue. If hazardous waste migrates to groundwater sources, it can pollute water supplies, harm ecosystems, and pose risks to human health. Monitoring over time (while important) is more of a management aspect. Surface space (for setting up) and high - cost drilling are more logistical or economic challenges compared to the environmental catastrophe of groundwater pollution.

Answer:

ensuring the waste does not migrate to groundwater sources