Question
Last month, we did a major overhaul on our back yard, which is about 8,000 s.f. Previouly we had zosia grass, which is not suited to the cooler weather in New Jersey, and also, the terrain was uneven, making it hard to walk on. The landscaper removed all the existing growth, at which point we had a sprinkler system installed. Next he brought in many truckloads of topsoil, distributed it with a Bobcat, then hand raked it before spreading seed and blue spongy material to hold moisture and keep it in place. It looked somewhat okay until we used the sprinkler, which was only twice since the new seeding, and we also had a heavy rainfall last week. After that I noticed a lot of puddling and small streams of water that look like washout in those areas, and possibly an overconcentration of seed in other areas. Is this normal? Or did he not smooth the terrain enough before applying seed? I'm concerned that once the grass comes in, it will be patchy and have uneven little hills and valleys, no different than our old lawn. We are holding back the last payment to the landscaper, who will probably say that it's okay because he wants his money, but I want a second opinion. If there anything that can be done to smooth out the uneven surface? If so, would it be possible to fix it now, before the grass gets established, or wait until spring?

Answer
My opinion is - wait until you have a clear picture of the possible problems and how to fix them.
To begin with, if you are on a slope and you have had runoff (from either rainfall and / or irrigation) you will get some "relocation" of the grass seed. There will be areas of profuse germination and areas that will be sparse.
And until there has been a drying out of the ground, and good establishment of the seedlings, more harm (trampling) than good will be the result of any attempt to re-seed and / or re-grade.
If the grass can propagate by runners or stolons, you might not need to do anything. Even if it does neither, it may tiller aggressively and fill in.
Spring for spring!