NIH has a good resource for overlap you can reference here:
Potential overlaps should be identified in your current/pending document, and you should provide an explanation on how they may be resolved. This may involve adjusting the scope of work, revising the budget, and/or modifying your time commitments.
Note that if there is an overlap, it should be addressed with the sponsor and resolved before a new award can be accepted. Otherwise, you may not be able to accept the new award. Addressing overlap may be done at the pre-award or post-award stage. You'll also need to discuss any project changes for any grants as part of your annual progress reporting process for those grants. Be transparent, comprehensive, and discuss any concerns with your chair/dean/ORSP before contacting the sponsor.