When the city that I live in put in curb & gutter and widened the street, they dug up part of my yard. Once they were finished, the city contracted a company to replace the boulevard area with sod. The sod was a lower-grade sod as it was mainly weeds. It is so bad that if I were to treat the weeds, I'd be left with only dirt. I am wanting to put down topsoil and plant grass seed to match my existing yard, but I'm unsure of how deep the layer of topsoil should be. If there are any preparations that I need to do before putting the topsoil down, please include your suggestions as I've never done this before. The area needing to be dealt with is approximately 6' wide and approximately 150' long. I haven't applied any fertilizer to that area of the yard as of yet, nor purchased the topsoil. Thank you for any advice/tips that you can give me. As always, I truly appreciate you taking the time to help out people like me.