Home expansion requires septic tank conversion?

[Chunkster]

I spoke with a contractor today about a 240 square foot addition to our house. He told me that the additional living space would trigger the new septic tank regulations to require us to decommission our cesspool and replace it with a septic tank. Total additional cost would be about $13,000 which would be a dramatic cost increase. Anyone know if his interpretation of the rules is correct?