Should 2,4-D be a concern for groundwater contamination?
No. The rapid breakdown of 2,4-D minimizes the potential for movement in soil, and greater than 90 – 95 percent dissipates in the top six inches of soil.

Eventually 2,4-D breaks down to CO2 and is integrated into other carbon compounds in the soil. Any findings of 2,4-D in ground water have been extremely rare. These have been attributed to spot contamination or spills near water wells or unique soil conditions with high rainfall or irrigation shortly following application.