P. annua sprouts the fall before, so if the barrier wasn't up then, it had no problems. Even a good pre-emergent barrier is only about 90-95% effective, and in practice that's frequently lower. So although it would have taken care of 19 out of 20 sprouts (maximum), one out of twenty will still make it through.

KBG takes 2-3 weeks or more to germinate, fescue takes 1-2 weeks. Since you're seeding into an existing lawn, I say go for fescue or use your same mix if you have it. KBG will be outcompeted by the existing grass before it can get established. Next year if you want all KBG, plan to kill everything and fallow for a few weeks before planting. Back to Tenacity: if you find yourself running out of water part of the way, you can adjust the dosage per gallon, multiplying the .55 teaspoon by whatever percentage you covered with your practice try. It comes with a syringe to measure. Next year if you have poa annua despite pre-emergents you can use Tenacity at a lower dosage (2 oz per acre) for a few applications. The bottle doesn't say it controls mature poa annua but people have had success with it.

"Poa annua", or annual Bluegrass may be an annual or may be a perennial. If what you have is the annual sub species and you cut the grass before any seeds formed you should not see any new plants germinating. Corn Gluten Meal, applied in mid September, should give good control of any "Poa annua": annual seeds that try to germinate, and maybe stop germination any of the perennial that might grow, this fall. If your soil temperatures are below 70 degrees F you may still have time to apply CGM. Most any herbicide that might control "Poa annua" will also kill the grass you want to keep. kimm1q is kimmsr

I'm no help with the poa issue. As far south as I am it is not much of an issue. I see it in the lawn, but only for a few weeks (long enough to go to seed, though). Overseeding KBG? Why? Especially when it's as dense as yours seems to be? I think you're watering too frequently...unless your temps are running over 110 degrees F. Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall. There's a very small chance you have clay. Are there brick factories nearby? If not you probably don't have clay. It is much more likely you have a soil with an imbalance of salts like calcium, magnesium, sodium, and potassium. That can be corrected once you have a good soil test (Logan Labs $25 is the test you need). You can see for yourself whether you have clay by doing a jar test. Find a clear container, fill it half way with soil, fill it the rest of the way with water and a few drops of soap. Measure up the side with a ruler and take a picture to see how many inches of soil you have. Then screw the top on the jar and shake it like crazy. Set the jar down with the ruler next to it. At 2 minutes take another picture. At 2 hours take another picture. At 2 days take another picture. The material that has settled after 2 minutes is sand and gravel. After 2 hours you'll get the loam. At that point if you can see through the water on top so that you could read something held on the other side of the jar, then you have zero clay. Everything that will settle will settle by 2 days. Suspended clay particles will still cloud the water after 2 days. Then you can use the measurements of settled material in your pictures to determine the proportional content of your soil (sand versus loam versus clay). Zones are only used to select plants for winter hardiness. Once you pick a plant, then the zone is meaningless for care. For example I think Oregon has most of the zones except 9 and 10. But I would not think to grow bermuda there.